11 ms·

ZF makes magnet-free electric motor uniquely compact and competitive

224 points by taubek 3y ago

matanyal 3y ago
[flagged]
FirmwareBurner 3y ago
Well, magnet-less separately exacted synchronous motors with the exact same architecture have existed since ... checks notes ... over 100 years, so it took me a while to digest the whole marketing fluff where they use an entire page to explain how an electric motor works, and see what's so special about this besides the claim that it's now "up to 90mm more compact axially". It seems like the big innovation here is that it doesn't use slip rings and brushes anymore, and the power to the rotor is now transferred via induction coils: "energy is transferred inductively, i.e. without mechanical contact, into the rotor, generating a magnetic field by means of coils. Thus, the I2SM does not require any brush elements or slip rings. Furthermore, there is no longer any need to keep this area dry by means of seals. As with permanently magnetized synchronous motor, the rotor is efficiently cooled by circulating oil." The good part is there's no more brushes to wear out and no dry seal needed so the motor can now be oil cooled from the inside as well, but to me it raises the big question about the power losses incurred by the energy that's transferred to the rotor via induction versus the previous direct contact via brushes and slip rings. Those coils seem to be quite far apart from one another, have a look at this moment in their video: https://press.zf.com/press/en/media/media_60352.html?kalturaStartTime=33 https://press.zf.com/press/en/media/media_60352.html?kaltura...
- Farmadupe 3y ago
  Out of interest, what could make such a design better than a traditional inductive motor? Such motors already suffer inductive losses, and do not need slip rings or brushes, and presumably do not an additional set of windings to transfer power to excite the stator? Just could the two sets of coils be optimized for their own purposes?
  - formerly_proven 3y ago
    Inductive coupling in an ASM is at the drive frequency (hundreds of Hz), inductive coupling in an inductive electrically excited SM can work at an arbitrary frequency, e.g. 100 kHz. You can also see in the ZF release how small the coils for transferring the excitation current are compared to the main windings, they are the small rings on the left side.
  - FirmwareBurner 3y ago
    >what could make such a design better than a traditional inductive motor Traditional induction motors, compared to these with wound rotors, are heavier and bigger in size for the same power output, and have less efficiency especially at starting/low-speeds.
    - sidewndr46 3y ago
      that is only true if you don't have a VFD. At that point you can basically get whatever you want out of them until they melt or blow out a bearing
      - Loughla 3y ago
        So then it comes down to cost? If this is cheaper than a motor and vfd, then it's still a win? Source: the one time I restored a massive JT Towsley jointer and had to get a vfd for the giant motor I had to put on it. In other words, I have no idea what I'm really talking about.
        sidewndr46 3y ago
        as others commented, this is not new tech. It's the result of the PR department needing to make a press release.
- userbinator 3y ago
  Brushless synchronous induction motors have also existed for a long time.
  - FirmwareBurner 3y ago
    Yes, but these ones with externally excited wound rotors have the advantage of more torque and efficiency at compact packages but have had the disadvantage of brushes that would wear out, create carbon dust and electrical noise.
- belter 3y ago
  To be fair, is practically on one of the first lines of the press release: "...In contrast to the magnet-free concepts of so-called separately excited synchronous motors (SESM) already available today..."
  - franciscop 3y ago
    That's the normal/traditional advantage of "brushed" motors vs synchronous motors, but the brushed motors have the massive disadvantage of having a mechanical contact (the brushes) that wear off, need to be sealed, etc. The advantage here is that it behaves like a brushed motor, but without the brushes!
- deleted 3y ago
  [deleted]
- rand0mx1 3y ago
  There will be large losses due to induction method.
  - WJW 3y ago
    "large" is meaningless unless you can compare it to the friction cost of the brushes they replace.
    - ilyt 3y ago
      Except you're competing with brushless motors using magnets, not other induction motors.
- londons_explore 3y ago
  The animation seems to show that the rotor has a DC (ie. constant) field. That is easy to do with slip-rings and a DC current source, but with any induction mechanism, there must be a rectification stage on the rotor. They don't show any of that.
  - MayeulC 3y ago
    I'm wondering if performance could be improved by controlling the polarity of the rotor coil fields, to push against the stator-induced ones. Since some semiconductor rectifiers are necessary in the stator, it doesn't sound much more complex to control the polarity. Part of the control logic could be handled before the inductive power transfer mechanism, by modulating the frequency, though it gets complex as you probably want to tune the resonant frequencies of the sender and receiver.
    - Animats 3y ago
      Wind turbines work that way. Early wind turbines had to mechanically rotate at a fixed speed to match the grid. With modern ones, the field is sometimes electrically rotated to adjust for rotor RPM. This can be done quickly as the wind changes. The range of control is not large, though. This is a quick adjustment made electronically until the blade pitch can slowly be changed by motors to re-tune the wind turbine for the current wind speed. Look up "doubly fed induction generator".
      - MayeulC 3y ago
        Interesting to know, thank you. They seem to mostly use this to adjust the frequency of the induced current in the stator, as they control the rotation speed of a "virtual rotor" (rotation of the rotor + rotation of the magnetic field around the rotor). That's indeed similar, but in the wind turbine use-case, the stator is passive. A direct application could be to tune the torque/speed response, or improve motor weight by reducing the number of coils on one of the elements.
  - Animats 3y ago
    Hm. Do they have diodes in the rotor? It's common for large, power station sized, generators to have that. The field windings are on the rotor, and the heavy power comes out from the stationary armature windings. To power the field windings, there's a smaller generator as part of the machine, but it's the other way round - stationary field, rotating armature producing power. The output of the smaller generator is rectified by diodes on the rotor to provide DC power for the main rotating field. No commutators or slip rings. No wear, no arcing. Did someone just scale this down for motors?
- franciscop 3y ago
  Oh I was just going to comment that those looked like some sort of brushes and thus that would negate other advantages, but after reading your comment and carefully reading the notice yeah that is definitely great! Induction coils instead of brushes for the rotor current def seems like a key advantage/development.
- baybal2 3y ago
  > The good part is there's no more brushes to wear out and no dry seal needed so the motor can now be oil cooled from the inside as well, but to me it raises the big question about the power losses incurred by the energy that's transferred to the rotor via induction versus the previous direct contact via brushes and slip rings. Slip ringed motors can be perfectly oil cooler as well. And you will need oil seals and drains in under any circumstances you use oil cooling.
- qwertox 3y ago
  So it's the `I2` from the `I2SM`-name which is the key part, referring to the induction of current into the outer coils, and then the magnetic induction to create the forces.
- twobitshifter 3y ago
  Brushes and slip rings seem like they would be more efficient, but they are adding friction and sparking that isn’t part of this, and as they wear become less efficient. BLDC showed that induction wins through one conversion, but this is making 2. Simple napkin math: If you compare BLDC to Brushed efficiency. Best BLDC is 90% efficiency and best brushed is 80%. Even if the inductive rotor loses as much energy as the complete BLDC motor, it would still perform on par with a brushed motor.
  - TaylorAlexander 3y ago
    Well, BLDC doesn’t really use induction at all. It just makes a magnetic field that pushes on magnets.
    - deleted 3y ago
      [deleted]
    - TaylorAlexander 3y ago
      I don’t understand why this is being downvoted? Is this a terminology thing? I design my own brushless motor controllers. A brushless motor operates by generating a magnetic field in fixed coils and using that magnetic field to directly act on magnets. Wikipedia defines magnetic induction thusly: “Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.” So basically using a changing magnetic field to create voltage in a conductor. While it is true that induction occurs in a brushless motor as a secondary effect (the rotating rotor induces back EMF on the stator coils), the primary mechanism of movement is a magnetic field physically acting on permanent magnets - no induction involved. This is distinct from an AC induction motor, about which Wikipedia says: “An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.” Basically in an induction motor, induction is a required effect for the operation of the motor, rather than a side effect as in a brushless motor. So while induction occurs in a brushless motor, if induction could be magically disabled the motor would still work. This is not true for an induction motor.
- fluxeb 3y ago
  It's more than that. A great write-up by Tesla (2007) [1] In an ideal brushless drive, the strength of the magnetic field produced by the permanent magnets would be adjustable. When maximum torque is required, especially at low speeds, the magnetic field strength (B) should be maximum – so that inverter and motor currents are maintained at their lowest possible values. This minimizes the I² R (current² resistance) losses and thereby optimizes efficiency. Likewise, when torque levels are low, the B field should be reduced such that eddy and hysteresis losses due to B are also reduced. Ideally, B should be adjusted such that the sum of the eddy, hysteresis, and I² losses is minimized. Unfortunately, there is no easy way of changing B with permanent magnets. Essentially, this new tech combines the best of Permanent Magnet Brushless DC and Induction motors. It allows you to change the magnetic field B without contact. The losses in the shaft coils are low when B is low so the gains in efficiency for an "eco mode" would be excellent as you modulate B for low torque and you would still retain the ability to crank up the power in a "sport mode" at the cost of efficiency. [1]https://www.tesla.com/blog/induction-versus-dc-brushless-motors https://www.tesla.com/blog/induction-versus-dc-brushless-mot...
  - sitkack 3y ago
    Exactly. The B field can be cranked up for short a duration to maximize torque. The rotor could also have much lower inertia. I sketched out this same topology, with inductively coupled coils for the rotor's magnetic field. If you don't need the fields to reverse (they wouldn't with a magnetic field). Then you could still have small PMs in the rotor with a coil to provide boost field for additional torque during acceleration.
  - addaon 3y ago
    > Unfortunately, there is no easy way of changing B with permanent magnets. There’s the old semi-permanent magnet trick, although this only allows a couple of discrete field strengths, not continuous tuning. Basically, a neodymium (or other hard) magnet and alnico (or other soft) magnet are put in parallel, surrounded by a pulse winding. A pulse can flip the magnetization of the alnico, but not neodymium, so you get field strengths of either neo + alnico or neo - alnico. (This is most often used sized for similar strengths to turn a “permanent” magnet on or off, but can be used in non-equal strengths as desired.)
userbinator 3y ago
It's just an inductively excited synchronous motor; this is a decades-old design being brought out again to satisfy the current trending buzzwords in the industry. https://patents.google.com/patent/US2969491A https://patents.google.com/patent/US2969491A https://patents.google.com/patent/US3034035A https://patents.google.com/patent/US3034035A https://patents.google.com/patent/US3667014 https://patents.google.com/patent/US3667014 (The most powerful motors have always been wound-field designs, since huge permanent magnets are extremely difficult to make and even more difficult to handle at all.)
- adrian_b 3y ago
  All the inductively excited synchronous motors described in those patents work due to including semiconductor rectifiers in the rotor. It is likely that today this concept from more than a half of century ago can be revived at a much higher level of performance, due to the present ability of making optimized designs and due to the fact that now much better rectifiers are available, e.g. silicon carbide Schottky diodes.
  - achr2 3y ago
    There might not be any diodes required if the driver uses a very high frequency DC chopper, the smoothing could be purely reactance + momentum.
    - ARob109 3y ago
      I suspect this ZF motor is like what is described in this paper [1]. An air gapped transformer is used to transmit power to the rotor and diodes rectify it. See Figure 1. This [2] appears to give a good summary of PSM vs ASM vs EESM and introduces iEESM (i is for inductive excitation instead of brushes, sounds like the ZF motor) at slide 14. [1] Design of Inductive Power Transmission into the Rotor of an Externally Excited Synchronous Machine https://mediatum.ub.tum.de/doc/1226682/1226682.pdf https://mediatum.ub.tum.de/doc/1226682/1226682.pdf [2] https://cdn.vector.com/cms/content/events/2018/vEMOB18/01_Inductive_Electric_Excited_Synchronous_Machine_Parspour.pdf https://cdn.vector.com/cms/content/events/2018/vEMOB18/01_In...
promiseofbeans 3y ago
I saw a video recently of Tesla bragging that they had a new motor with only 3(?) powerful magnets in it. This makes me think that less magnets is a good thing - can anyone explain to me the reason to use less magnets in motors? (To me it just seems that less magnets would make it harder to spin with a magnetic field, but I'm no engineer).
- moffkalast 3y ago
  I think it just dictates the number of poles the motor has? The fewer the poles the less torque it has, but higher RPM. Either way you have to gear it down for EV use, so I suppose it doesn't really matter much in the end, except if it makes the rotor less likely to explode. I would've expected very high pole counts to be more practical though, since a lower RPM is more manageable in terms of bearings wearing out. On the other hand, steppers have a high pole count and their efficiency is crap so maybe they can get more power out with fewer poles.
  - Farmadupe 3y ago
    Steppers are super optimized for being super precise and easy to controle while being (relatively) cheap to build. They have weird "trick" geometry that means you can move the rotor to many different angles (tens, hundreds) with far fewer stator windings. The cost of this is really low power and efficincy if you just want to spin them.
  - rawicki 3y ago
    Unless you want to chase Tesla with marketing numbers trading off torque for something else is almost always a good tradeoff. Modern electric motors are much stronger than most users need.
- mannykannot 3y ago
  If having fewer magnets means less rare earth consumption for the same performance, then that's a benefit in itself - the same one as is being claimed for this motor. https://news.ycombinator.com/item?id=37454238 https://news.ycombinator.com/item?id=37454238
moffkalast 3y ago
> In contrast to the magnet-free concepts of so-called separately excited synchronous motors (SESM) already available today, ZF’s I2SM (In-Rotor Inductive-Excited Synchronous Motor) transmits the energy for the magnetic field via an inductive exciter inside the rotor shaft. This makes the motor uniquely compact with maximum power and torque density. Permanent-magnet-free would be more accurate, this is sort of like a BLDC motor, except that if I understand this correctly they use some kind of wireless charging to power coils on the rotor? Doesn't wireless charging have only like 70% efficiency?
- raverbashing 3y ago
  This sounds like it's an induction motor where the inductors are on the spinning part (the rotor - or maybe in both?) People are downplaying this, but I'm not so sure (yes I know about synchronous motors, etc), but there sure it is covered in marketing fluff (which is not wrong per se - if tesla passes gas people would have been all over it)
- agumonkey 3y ago
  Maybe compensated a bit by the lack of friction and the overall lifespan of the device ?
- twobitshifter 3y ago
  https://m.youtube.com/watch?v=43JMIuwVrY4&pp=ygUOSW4gcnVubmVyIGJsZGM%3D https://m.youtube.com/watch?v=43JMIuwVrY4&pp=ygUOSW4gcnVubmV... A regular BLDC motor is already using induction. See this video. The 70% number you are referring to is for a flat coil through a much greater distance than would be needed here. For the new design, I imagine another set of coils inside and separated from the rotor, and the magnets on the rotor replaced by a simple ring. The induction coils would need to be offset to produce torque on the ring. Yes, it would be less efficient because you are using power to produce the magnetic field. However, no rare earth metals are required.
  - effie 3y ago
    There is EM induction happening in the stator coils, but it is not substantial to how the motor effect comes about. This effect is due to magnetic force of the coil poles acting on the permanent magnets, no induction is needed to create this effect (thus it exists even when instantaneously, EM induction in any one coil is zero).
Farmadupe 3y ago
I know press releases never describe anything that's actually novel, but it looks like they're just describing an asynchronous induction motor? I'm wondering if this release is implicitly pretending that some "low slip ratio" motor is "basically" synchronous Just guessing, does ZF mostly put out induction motors, and they need to make them look less unfashionable so that people choose them for new designs?
- westmeal 3y ago
  ZF is generally known for gearboxes, a huge amount of manufacturers use their transmissions in their cars. New corvette uses a zf 10 speed I think, same with vw and BMW.
finnjohnsen2 3y ago
Germany doing it's thing making the parts everyone needs.
- userbinator 3y ago
  Maybe their electric stuff will be better, but unfortunately my experiences with ZF transmissions have not been great.
  - scrlk 3y ago
    Out of interest, what issues did you have? Most of the time when I read a car review, they seem to praise the ZF 8HP 8-speed.
    - userbinator 3y ago
      This is about their automatics, but parts availability (especially aftermarket) and service information is relatively scarce and expensive compared to e.g. GM/Allison. Their bus/truck transmissions also shift quite roughly, almost like a manual. ZF is what I'd consider very stereotypically German engineering: optimised for efficiency and cost, at the expense of longevity and serviceability, with very little margin for overload.
      - ricardobeat 3y ago
        > stereotypically German engineering: optimised for efficiency and cost, at the expense of longevity I thought German engineering had the exact opposite image worldwide?
        Freestyler_3 3y ago
        Same here.
        seabird 3y ago
        There's a difference between what the layman has been led to believe by Big Deutschland, and the reality experienced by those who actually have to deal with German designs. A lot of them are interesting and "elegant" on paper, but the good experiences usually end there. It feels like the fun factor of the design process is what's prioritized most heavily, which is great for the designers (and I don't say this facetiously; the fun is the #1 reason to do it at all, and I'm glad they make a living off it), and not-so-great for the poor fucker that has to repair a VW. That's not to say that they always shit things up. I'll take Wago nuts over American style ones any day of the week. VW's VR6 engines are a simplification that would probably make my life a lot easier if I didn't have to buy them with the rest of the VW vehicle attached. There is so much more vision coming out of Germany in industrial controls than anywhere else it's outrageous. Life has its ups and downs, I guess.
adrian_b 3y ago
The most usual kind of motor with permanent magnets, is just a synchronous motor, where, in order to remove the power supply needed by the rotor windings, the rotor windings are replaced by permanent magnets. Here, in order to achieve the same brushless operation like when using permanent magnets, the rotor windings are kept, but the electrical current needed by them is transmitted to the rotor wirelessly. For this to work, I suppose that the rotor includes some kind of semiconductor rectifiers and the rotor current is induced at a frequency much higher than the rotation frequency. This should indeed have characteristics similar to the permanent magnet motors, except that it is not clear if the energy efficiency can be equally good. A permanent magnet rotor is equivalent with a rotor having superconducting windings, so it has no losses due to the electrical excitation currents (though it may have losses due to other causes, e.g. hysteresis and eddy currents). This motor will have extra losses in the copper windings of the rotor and in whatever kind of rectifiers it uses. Nevertheless, perhaps these extra losses are small, so the efficiency can be much higher than that of asynchronous motors (like initially used by Tesla) and only a little lower than that of the permanent magnet motors.
- londons_explore 3y ago
  > except that it is not clear if the energy efficiency can be equally good. There are potentially ways energy efficiency can be better... It's possible to produce stronger (ie. more flux density) magnetic fields with electrical currents than with neodymium magnets. Those stronger fields mean flux paths can be shortened and (for the same mass of copper), wires can be shortened and resistive losses reduced. However, I haven't done the math to see if those effects are of a significant enough magnitude.
  - effie 3y ago
    I don't see it. In a brushless DC magnet rotor, there is little energy loss, the magnets aren't very conductive. Here, we have additional current and newly introduced Joule losses in the rotor. It is not clear that these can be kept low enough so the result is as good. Stronger magnetic field due to high current in the rotor does not directly imply higher efficiency, it only directly implies higher torque, which gives the car higher acceleration. We don't need to increase this strength, current motors are plenty strong. This top torque mode of operation usually goes with decreased efficiency, due to high currents and high Joule losses. The best efficiency is likely to be achieved when ohmic and friction losses are kept low, thus currents as low as possible everywhere, induction coupling frequency dynamically governed to be at the optimal value dependent on the angular speed. The only obvious advantage of the marketed motor is smaller size and likely lower weight. I'm afraid price will be a disadvantage.
samtho 3y ago
This is not new, if you have a car with any fossil fuel motor, you likely already have a similar device: your alternator. By applying a voltage between 2 and 13 to the exciter coil, you can adjust how much is drawn from the primary winding.
- stephen_g 3y ago
  A car alternator uses brushes or slip rings to get power to the excitation coils, which is a big part of what the motor in the article has been designed not to use.
  - userbinator 3y ago
    There are brushless car alternators. https://www.delcoremy.com/alternators/find-by-model-family/35si https://www.delcoremy.com/alternators/find-by-model-family/3...
deleted 3y ago
[deleted]
KingOfCoders 3y ago
ZF stands for "Gear Factory" and is owned by the Zeppelin Foundation (yes, that Zeppelin) which is onwed by the city of Friedrichshafen.
- codethief 3y ago
  And (to my surprise) they are not exactly small: > The Consolidated ZF Group is represented with 168 production locations in 32 countries as well as 19 main development locations in nine countries. In fiscal 2022, ZF reported sales of €43.8 billion with approximately 165,000 employees worldwide. The company spent 7,8 percent of its sales on research and development in 2022. https://www.zf.com/mobile/en/company/company.html https://www.zf.com/mobile/en/company/company.html
  - slow_typist 3y ago
    Not as big as Bosch but still a first tier automotive supplier.
  - NovemberWhiskey 3y ago
    Every European car I've ever owned has had a ZF transmission.
    - windowsrookie 3y ago
      And all Zf transmissions had a major design fault up until the current 8 Speed. Now they are pretty good. Not only European cars use them, many Chrysler/Dodge/Jeep/Ram cars have ZF 8 speeds in them.
      - nomel 3y ago
        > And all Zf transmissions had a major design fault up until the current 8 Speed Any reference or hint? Google brings up nothing obvious.
        3y ago
weinzierl 3y ago
The commenters saying that this is old news and that magnet-free brushless motors have existed for a long time miss the main point. ZF claims to have one that is competitive with traditional designs utilizing rare earth materials. Even ten to fifteen years ago the effort German automakers put into saving a milligram Dysprosium here and there - not only in the drive motor but every electric motor in the vehicle - was insane. I'm out of automotive for a couple of years now, but I can only imagine that this pains must have increased dramatically. Because of all this effort, a motor without rare earth metals would only have to be nearly as good as the competition to still be a huge deal.
- deleted 3y ago
  [deleted]
- mschuster91 3y ago
  > Because of all this effort, a motor without rare earth metals would only have to be nearly as good as the competition to still be a huge deal. Even if it were not as good, getting rid of the dependency on rare-earth materials and their dirty supply chain is worth it.
  - hamburglar 3y ago
    Indeed. Dirty, expensive, and bottlenecked.
- specialist 3y ago
  IIRC, the proper KPI for (EV) vehicles is cost per km traveled. Right? Meaning balancing tradeoffs of performance, cost, weight, etc. (Not to mention mitigating risks, like sourcing and externalities.) It's fascinating to me, as a lurker, that misc EV OEMs are making different choices. Such exciting times. PS- Why'd you leave the automotive industry?
  - weinzierl 3y ago
    I always had a strong interest in security and that's the direction I developed even when still in automotive. When the opportunity came to work for a security company I switched.
londons_explore 3y ago
Does anyone have a raw materials cost breakdown of motors? Are the neodymium magnets actually a big chunk of the cost? Or is it more of a "we'll get government grants for inventing a type of motor that doesn't require a material that China has strategic control over".
- iancmceachern 3y ago
  They absolutely are, especially as the motors get bigger. See for yourself at k&j magnetics: https://www.kjmagnetics.com/?gclid=Cj0KCQjwmICoBhDxARIsABXkXlILq8MC5a5RR20bfP1afy1hQMQ_CRrdEa16nr6TNDLbujnwjEHBGEgaAuy0EALw_wcB https://www.kjmagnetics.com/?gclid=Cj0KCQjwmICoBhDxARIsABXkX... Small ones are a few dollars, bigger ones are hundreds or thousands
slow_typist 3y ago
Nice job, now magnet free generators for windmills please.
- mannykannot 3y ago
  The same technology should work for them, I believe.
  - slow_typist 3y ago
    Sure; the economic case might be trickier though.
    - mannykannot 3y ago
      The mismatch between a constrained rare earth supply and rising demand for motors and generators means that the case gets better as time passes.
amluto 3y ago
The obvious comparison is to an AC (asynchronous) induction motor, which also has no magnets and couples energy into the rotor inductively. These are widespread. I didn’t see anything on the website about how their design is better.
hoc 3y ago
Hm. Can I just buy two of them plus drivers or do I have to order a fully custom designed series?
chris222 3y ago
Here we have motors that don’t require rare earth metals. The largest battery maker CATL is making breakthrough leaps in LFP batteries (which have no cobalt). [1] Recycling large EV batteries is becoming cheaper and easier. [2] Are the EV FUDsters heads exploding yet? [1] https://www.catl.com/en/news/6091.html https://www.catl.com/en/news/6091.html [2] https://youtu.be/s2xrarUWVRQ?si=hBfD1lLd4dxEJI6b https://youtu.be/s2xrarUWVRQ?si=hBfD1lLd4dxEJI6b
- vbezhenar 3y ago
  I'm not EV fudster, but for me gasoline cars are better in every aspect. May be except maintenance (I'm not sure, but I expect that I don't have to change oil every year in an electric car). I don't have money to buy two cars, so I need one versatile enough car. I can bring 100L gasoline with me to add 1000 km range on top of existing 500 range. I can charge it within 5 minutes, not 5 hours. It does not get worse with every year, because there's no degrading battery which costs like half a car. Probably the only thing that's better about EV is that electricity is the same everywhere, I can't charge it with bad electricity mixed with water in the old station, LoL. Electric cars probably are the future, but I don't like this future. They don't have a soul.
  - mlyle 3y ago
    > I can bring 100L gasoline with me to add 1000 km range on top of existing 500 range This is the big advantage. > not 5 hours This one is mixed. You can charge the EV at home for ordinary use. That's better. For road trips, you can use DC fast charging to add a bunch of range in 30 minutes. This is worse, requiring combining charging and meal stops. PHEVs are a decent compromise, though: you can do basically all of your driving electrically, and then burn a little bit of gas on road trips. > It does not get worse with every year Sure gasoline vehicles become more maintenance heavy and terrible over time. EV degradation is probably around 10-15% range lost after 5 years typical today. > May be except maintenance Odds are you don't deal with brake pads anymore, and yes, no oil changes. The sheer torque of most models feels like a spaceship when you press down the gas pedal.
    - 3y ago
ouid 3y ago
[dead]
rootusrootus 3y ago
It still boggles my mind how much power a modern electric motor gets from such a small package. I'm so used to big engines weighing hundreds of pounds making maybe a couple hundred horsepower. Now we have electric motors making quite a lot more (and not to mention insane torque) that I could easily pick up with my hands.
- hinkley 3y ago
  There are motors with peak efficiency about 90%. The first one of those I ran into was fifteen years ago. Which means not only is it possible but the patents will have expired, if not now then soon. Power density has gone almost too far. There’s one pancake motor I’ve seen recently where the shape of the enclosure is dictated by mounting concerns. You have to be able to mount the motor to something it can’t tear apart. If they shrunk that motor another 20% then it would be half housing. I’m not sure where you go from there. Thinner? Motor per wheel?
  - travisporter 3y ago
    Motor per wheel sounds interesting. As I understand it’s not ideal for handling because of unsprung weight. Maybe that will change? Would be very excited about the prospect of converting cars to purv (somehow)
    - nomel 3y ago
      Motor per wheel doesn’t have to be in the wheel. Could be through a very compact axle, maybe with a fixed gear box to get the angle right.
      - hamburglar 3y ago
        What would be wild (and probably wildly impractical) is an inductive coupling between the motor (inboard, unsprung) and the wheel.
        3y ago
ipbrown 3y ago
The innovation here is in the packaging, fitting the brushless inductive power coupling for the field excitation inside the shaft. T he idea of using a high frequency rotating transformer or inductive coupler to transmit current to the field winding without using brushes and slip rings has been investigated by a number of companies, universities, and national labs. A good survey paper of excitation systems for wound field synchronous machines or electrically excited synchronous machines is. J. K. Nøland, S. Nuzzo, A. Tessarolo and E. F. Alves, "Excitation System Technologies for Wound-Field Synchronous Machines: Survey of Solutions and Evolving Trends," in IEEE Access, vol. 7, pp. 109699-109718, 2019, doi: 10.1109/ACCESS.2019.2933493. An example of a high frequency transformer or inductive coupling developed by General Motors is detailed for example in the following paper. C. Stancu, T. Ward, K. M. Rahman, R. Dawsey and P. Savagian, "Separately Excited Synchronous Motor With Rotary Transformer for Hybrid Vehicle Application," in IEEE Transactions on Industry Applications, vol. 54, no. 1, pp. 223-232, Jan.-Feb. 2018, doi: 10.1109/TIA.2017.2757019. Below is some work done by Oak Ridge National Lab on rotating high frequency transformers for field excitation. T. Raminosoa, R. H. Wiles and J. Wilkins, "Novel Rotary Transformer Topology With Improved Power Transfer Capability for High-Speed Applications," in IEEE Transactions on Industry Applications, vol. 56, no. 1, pp. 277-286, Jan.-Feb. 2020, doi: 10.1109/TIA.2019.2955050. The field excitation current is typically provided using a single phase high frequency transformer (20 to 100 kHz switching frequency) which is then rectified by a rotating full bridge rectifier. Just to clear up some of the misconceptions in the comments. In state-of-the-art electric vehicles there are basically three main machine topologies that are used for the main traction machine. - Interior permanent magnet synchronous machines (IPMSMs): A large number of OEMs and suppliers use/supply this motor topology, e.g., General motors, Tesla model 3, Ford, etc. - Induction machines (IMs): Also used by a large number of OEMs and suppliers, e.g., Tesla model S and X, G.M. for assist motors, etc. - Wound field synchronous machines (WFSMs) [in Europe more commonly known as electrically excited synchronous machines (EESMs) but they are the same thing] - Currently used in Renault and some BMW models. A large number of suppliers are developing them. Each of the machine topologies has tradeoffs compared to the others, cost, manufacturing CapEx, supply chain risk, drive cycle efficiency, difficulty of control, failure modes, cooling complexity, etc. WFSMs or EESMs have some potential advantages over IPMSMs or IMs for some applications. - They don't contain rare earth permanent magnets eliminating the supply chain and price volatility associated with them. - In terms of drive cycle efficiency generally they are more efficient than IMs and if the drive cycle is dominated by moderate torques and highspeeds they can exceed the drive cycle efficiencies of IPMSMs. - They are very easy to field weaken and theoretically can have an infinite constant power speed range. - The field excitation can be controlled to provide unity power factor potentially allowing the stator inverter to be downsized. The main negatives of WFSMs or EESMs compared to IPMSMs or IMs are: - The field excitation is more complicated and requires power electronics either for brushes and slip rings or inductive power transfer approaches. - The cooling of the field winding is difficult and typically spray/jet cooling of the end turns or at a minimum through shaft cooling. - The control of WFSMs or EESMs is considerably more complicated than IPMSMs or IMs.
larkinrichards 3y ago
What would be the impact of this style of motor on regenerative braking?
- effie 3y ago
  If designed well, this type of motor could do regenerative braking too. It's a matter of proper control of current in the stator and rotor and their phase difference, thus mostly electronics.

224 points by taubek 3y ago

[flagged]

Well, magnet-less separately exacted synchronous motors with the exact same architecture have existed since ... checks notes ... over 100 years, so it took me a while to digest the whole marketing fluff where they use an entire page to explain how an electric motor works, and see what's so special about this besides the claim that it's now "up to 90mm more compact axially". It seems like the big innovation here is that it doesn't use slip rings and brushes anymore, and the power to the rotor is now transferred via induction coils: "energy is transferred inductively, i.e. without mechanical contact, into the rotor, generating a magnetic field by means of coils. Thus, the I2SM does not require any brush elements or slip rings. Furthermore, there is no longer any need to keep this area dry by means of seals. As with permanently magnetized synchronous motor, the rotor is efficiently cooled by circulating oil." The good part is there's no more brushes to wear out and no dry seal needed so the motor can now be oil cooled from the inside as well, but to me it raises the big question about the power losses incurred by the energy that's transferred to the rotor via induction versus the previous direct contact via brushes and slip rings. Those coils seem to be quite far apart from one another, have a look at this moment in their video: https://press.zf.com/press/en/media/media_60352.html?kalturaStartTime=33 https://press.zf.com/press/en/media/media_60352.html?kaltura...

Farmadupe 3y ago
Out of interest, what could make such a design better than a traditional inductive motor? Such motors already suffer inductive losses, and do not need slip rings or brushes, and presumably do not an additional set of windings to transfer power to excite the stator? Just could the two sets of coils be optimized for their own purposes?
- formerly_proven 3y ago
  Inductive coupling in an ASM is at the drive frequency (hundreds of Hz), inductive coupling in an inductive electrically excited SM can work at an arbitrary frequency, e.g. 100 kHz. You can also see in the ZF release how small the coils for transferring the excitation current are compared to the main windings, they are the small rings on the left side.
- FirmwareBurner 3y ago
  >what could make such a design better than a traditional inductive motor Traditional induction motors, compared to these with wound rotors, are heavier and bigger in size for the same power output, and have less efficiency especially at starting/low-speeds.
  - sidewndr46 3y ago
    that is only true if you don't have a VFD. At that point you can basically get whatever you want out of them until they melt or blow out a bearing
    - Loughla 3y ago
      So then it comes down to cost? If this is cheaper than a motor and vfd, then it's still a win? Source: the one time I restored a massive JT Towsley jointer and had to get a vfd for the giant motor I had to put on it. In other words, I have no idea what I'm really talking about.
      - sidewndr46 3y ago
        as others commented, this is not new tech. It's the result of the PR department needing to make a press release.
userbinator 3y ago
Brushless synchronous induction motors have also existed for a long time.
- FirmwareBurner 3y ago
  Yes, but these ones with externally excited wound rotors have the advantage of more torque and efficiency at compact packages but have had the disadvantage of brushes that would wear out, create carbon dust and electrical noise.
belter 3y ago
To be fair, is practically on one of the first lines of the press release: "...In contrast to the magnet-free concepts of so-called separately excited synchronous motors (SESM) already available today..."
- franciscop 3y ago
  That's the normal/traditional advantage of "brushed" motors vs synchronous motors, but the brushed motors have the massive disadvantage of having a mechanical contact (the brushes) that wear off, need to be sealed, etc. The advantage here is that it behaves like a brushed motor, but without the brushes!
deleted 3y ago
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rand0mx1 3y ago
There will be large losses due to induction method.
- WJW 3y ago
  "large" is meaningless unless you can compare it to the friction cost of the brushes they replace.
  - ilyt 3y ago
    Except you're competing with brushless motors using magnets, not other induction motors.
londons_explore 3y ago
The animation seems to show that the rotor has a DC (ie. constant) field. That is easy to do with slip-rings and a DC current source, but with any induction mechanism, there must be a rectification stage on the rotor. They don't show any of that.
- MayeulC 3y ago
  I'm wondering if performance could be improved by controlling the polarity of the rotor coil fields, to push against the stator-induced ones. Since some semiconductor rectifiers are necessary in the stator, it doesn't sound much more complex to control the polarity. Part of the control logic could be handled before the inductive power transfer mechanism, by modulating the frequency, though it gets complex as you probably want to tune the resonant frequencies of the sender and receiver.
  - Animats 3y ago
    Wind turbines work that way. Early wind turbines had to mechanically rotate at a fixed speed to match the grid. With modern ones, the field is sometimes electrically rotated to adjust for rotor RPM. This can be done quickly as the wind changes. The range of control is not large, though. This is a quick adjustment made electronically until the blade pitch can slowly be changed by motors to re-tune the wind turbine for the current wind speed. Look up "doubly fed induction generator".
    - MayeulC 3y ago
      Interesting to know, thank you. They seem to mostly use this to adjust the frequency of the induced current in the stator, as they control the rotation speed of a "virtual rotor" (rotation of the rotor + rotation of the magnetic field around the rotor). That's indeed similar, but in the wind turbine use-case, the stator is passive. A direct application could be to tune the torque/speed response, or improve motor weight by reducing the number of coils on one of the elements.
- Animats 3y ago
  Hm. Do they have diodes in the rotor? It's common for large, power station sized, generators to have that. The field windings are on the rotor, and the heavy power comes out from the stationary armature windings. To power the field windings, there's a smaller generator as part of the machine, but it's the other way round - stationary field, rotating armature producing power. The output of the smaller generator is rectified by diodes on the rotor to provide DC power for the main rotating field. No commutators or slip rings. No wear, no arcing. Did someone just scale this down for motors?
franciscop 3y ago
Oh I was just going to comment that those looked like some sort of brushes and thus that would negate other advantages, but after reading your comment and carefully reading the notice yeah that is definitely great! Induction coils instead of brushes for the rotor current def seems like a key advantage/development.
baybal2 3y ago
> The good part is there's no more brushes to wear out and no dry seal needed so the motor can now be oil cooled from the inside as well, but to me it raises the big question about the power losses incurred by the energy that's transferred to the rotor via induction versus the previous direct contact via brushes and slip rings. Slip ringed motors can be perfectly oil cooler as well. And you will need oil seals and drains in under any circumstances you use oil cooling.
qwertox 3y ago
So it's the `I2` from the `I2SM`-name which is the key part, referring to the induction of current into the outer coils, and then the magnetic induction to create the forces.
twobitshifter 3y ago
Brushes and slip rings seem like they would be more efficient, but they are adding friction and sparking that isn’t part of this, and as they wear become less efficient. BLDC showed that induction wins through one conversion, but this is making 2. Simple napkin math: If you compare BLDC to Brushed efficiency. Best BLDC is 90% efficiency and best brushed is 80%. Even if the inductive rotor loses as much energy as the complete BLDC motor, it would still perform on par with a brushed motor.
- TaylorAlexander 3y ago
  Well, BLDC doesn’t really use induction at all. It just makes a magnetic field that pushes on magnets.
  - deleted 3y ago
    [deleted]
  - TaylorAlexander 3y ago
    I don’t understand why this is being downvoted? Is this a terminology thing? I design my own brushless motor controllers. A brushless motor operates by generating a magnetic field in fixed coils and using that magnetic field to directly act on magnets. Wikipedia defines magnetic induction thusly: “Electromagnetic or magnetic induction is the production of an electromotive force (emf) across an electrical conductor in a changing magnetic field.” So basically using a changing magnetic field to create voltage in a conductor. While it is true that induction occurs in a brushless motor as a secondary effect (the rotating rotor induces back EMF on the stator coils), the primary mechanism of movement is a magnetic field physically acting on permanent magnets - no induction involved. This is distinct from an AC induction motor, about which Wikipedia says: “An induction motor or asynchronous motor is an AC electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.” Basically in an induction motor, induction is a required effect for the operation of the motor, rather than a side effect as in a brushless motor. So while induction occurs in a brushless motor, if induction could be magically disabled the motor would still work. This is not true for an induction motor.
fluxeb 3y ago
It's more than that. A great write-up by Tesla (2007) [1] In an ideal brushless drive, the strength of the magnetic field produced by the permanent magnets would be adjustable. When maximum torque is required, especially at low speeds, the magnetic field strength (B) should be maximum – so that inverter and motor currents are maintained at their lowest possible values. This minimizes the I² R (current² resistance) losses and thereby optimizes efficiency. Likewise, when torque levels are low, the B field should be reduced such that eddy and hysteresis losses due to B are also reduced. Ideally, B should be adjusted such that the sum of the eddy, hysteresis, and I² losses is minimized. Unfortunately, there is no easy way of changing B with permanent magnets. Essentially, this new tech combines the best of Permanent Magnet Brushless DC and Induction motors. It allows you to change the magnetic field B without contact. The losses in the shaft coils are low when B is low so the gains in efficiency for an "eco mode" would be excellent as you modulate B for low torque and you would still retain the ability to crank up the power in a "sport mode" at the cost of efficiency. [1]https://www.tesla.com/blog/induction-versus-dc-brushless-motors https://www.tesla.com/blog/induction-versus-dc-brushless-mot...
- sitkack 3y ago
  Exactly. The B field can be cranked up for short a duration to maximize torque. The rotor could also have much lower inertia. I sketched out this same topology, with inductively coupled coils for the rotor's magnetic field. If you don't need the fields to reverse (they wouldn't with a magnetic field). Then you could still have small PMs in the rotor with a coil to provide boost field for additional torque during acceleration.
- addaon 3y ago
  > Unfortunately, there is no easy way of changing B with permanent magnets. There’s the old semi-permanent magnet trick, although this only allows a couple of discrete field strengths, not continuous tuning. Basically, a neodymium (or other hard) magnet and alnico (or other soft) magnet are put in parallel, surrounded by a pulse winding. A pulse can flip the magnetization of the alnico, but not neodymium, so you get field strengths of either neo + alnico or neo - alnico. (This is most often used sized for similar strengths to turn a “permanent” magnet on or off, but can be used in non-equal strengths as desired.)

userbinator 3y ago

It's just an inductively excited synchronous motor; this is a decades-old design being brought out again to satisfy the current trending buzzwords in the industry. https://patents.google.com/patent/US2969491A https://patents.google.com/patent/US2969491A https://patents.google.com/patent/US3034035A https://patents.google.com/patent/US3034035A https://patents.google.com/patent/US3667014 https://patents.google.com/patent/US3667014 (The most powerful motors have always been wound-field designs, since huge permanent magnets are extremely difficult to make and even more difficult to handle at all.)

adrian_b 3y ago
All the inductively excited synchronous motors described in those patents work due to including semiconductor rectifiers in the rotor. It is likely that today this concept from more than a half of century ago can be revived at a much higher level of performance, due to the present ability of making optimized designs and due to the fact that now much better rectifiers are available, e.g. silicon carbide Schottky diodes.
- achr2 3y ago
  There might not be any diodes required if the driver uses a very high frequency DC chopper, the smoothing could be purely reactance + momentum.
  - ARob109 3y ago
    I suspect this ZF motor is like what is described in this paper [1]. An air gapped transformer is used to transmit power to the rotor and diodes rectify it. See Figure 1. This [2] appears to give a good summary of PSM vs ASM vs EESM and introduces iEESM (i is for inductive excitation instead of brushes, sounds like the ZF motor) at slide 14. [1] Design of Inductive Power Transmission into the Rotor of an Externally Excited Synchronous Machine https://mediatum.ub.tum.de/doc/1226682/1226682.pdf https://mediatum.ub.tum.de/doc/1226682/1226682.pdf [2] https://cdn.vector.com/cms/content/events/2018/vEMOB18/01_Inductive_Electric_Excited_Synchronous_Machine_Parspour.pdf https://cdn.vector.com/cms/content/events/2018/vEMOB18/01_In...

promiseofbeans 3y ago

I saw a video recently of Tesla bragging that they had a new motor with only 3(?) powerful magnets in it. This makes me think that less magnets is a good thing - can anyone explain to me the reason to use less magnets in motors? (To me it just seems that less magnets would make it harder to spin with a magnetic field, but I'm no engineer).

moffkalast 3y ago
I think it just dictates the number of poles the motor has? The fewer the poles the less torque it has, but higher RPM. Either way you have to gear it down for EV use, so I suppose it doesn't really matter much in the end, except if it makes the rotor less likely to explode. I would've expected very high pole counts to be more practical though, since a lower RPM is more manageable in terms of bearings wearing out. On the other hand, steppers have a high pole count and their efficiency is crap so maybe they can get more power out with fewer poles.
- Farmadupe 3y ago
  Steppers are super optimized for being super precise and easy to controle while being (relatively) cheap to build. They have weird "trick" geometry that means you can move the rotor to many different angles (tens, hundreds) with far fewer stator windings. The cost of this is really low power and efficincy if you just want to spin them.
- rawicki 3y ago
  Unless you want to chase Tesla with marketing numbers trading off torque for something else is almost always a good tradeoff. Modern electric motors are much stronger than most users need.
mannykannot 3y ago
If having fewer magnets means less rare earth consumption for the same performance, then that's a benefit in itself - the same one as is being claimed for this motor. https://news.ycombinator.com/item?id=37454238 https://news.ycombinator.com/item?id=37454238

moffkalast 3y ago

> In contrast to the magnet-free concepts of so-called separately excited synchronous motors (SESM) already available today, ZF’s I2SM (In-Rotor Inductive-Excited Synchronous Motor) transmits the energy for the magnetic field via an inductive exciter inside the rotor shaft. This makes the motor uniquely compact with maximum power and torque density. Permanent-magnet-free would be more accurate, this is sort of like a BLDC motor, except that if I understand this correctly they use some kind of wireless charging to power coils on the rotor? Doesn't wireless charging have only like 70% efficiency?

raverbashing 3y ago
This sounds like it's an induction motor where the inductors are on the spinning part (the rotor - or maybe in both?) People are downplaying this, but I'm not so sure (yes I know about synchronous motors, etc), but there sure it is covered in marketing fluff (which is not wrong per se - if tesla passes gas people would have been all over it)
agumonkey 3y ago
Maybe compensated a bit by the lack of friction and the overall lifespan of the device ?
twobitshifter 3y ago
https://m.youtube.com/watch?v=43JMIuwVrY4&pp=ygUOSW4gcnVubmVyIGJsZGM%3D https://m.youtube.com/watch?v=43JMIuwVrY4&pp=ygUOSW4gcnVubmV... A regular BLDC motor is already using induction. See this video. The 70% number you are referring to is for a flat coil through a much greater distance than would be needed here. For the new design, I imagine another set of coils inside and separated from the rotor, and the magnets on the rotor replaced by a simple ring. The induction coils would need to be offset to produce torque on the ring. Yes, it would be less efficient because you are using power to produce the magnetic field. However, no rare earth metals are required.
- effie 3y ago
  There is EM induction happening in the stator coils, but it is not substantial to how the motor effect comes about. This effect is due to magnetic force of the coil poles acting on the permanent magnets, no induction is needed to create this effect (thus it exists even when instantaneously, EM induction in any one coil is zero).

Farmadupe 3y ago

I know press releases never describe anything that's actually novel, but it looks like they're just describing an asynchronous induction motor? I'm wondering if this release is implicitly pretending that some "low slip ratio" motor is "basically" synchronous Just guessing, does ZF mostly put out induction motors, and they need to make them look less unfashionable so that people choose them for new designs?

westmeal 3y ago
ZF is generally known for gearboxes, a huge amount of manufacturers use their transmissions in their cars. New corvette uses a zf 10 speed I think, same with vw and BMW.

finnjohnsen2 3y ago

Germany doing it's thing making the parts everyone needs.

userbinator 3y ago
Maybe their electric stuff will be better, but unfortunately my experiences with ZF transmissions have not been great.
- scrlk 3y ago
  Out of interest, what issues did you have? Most of the time when I read a car review, they seem to praise the ZF 8HP 8-speed.
  - userbinator 3y ago
    This is about their automatics, but parts availability (especially aftermarket) and service information is relatively scarce and expensive compared to e.g. GM/Allison. Their bus/truck transmissions also shift quite roughly, almost like a manual. ZF is what I'd consider very stereotypically German engineering: optimised for efficiency and cost, at the expense of longevity and serviceability, with very little margin for overload.
    - ricardobeat 3y ago
      > stereotypically German engineering: optimised for efficiency and cost, at the expense of longevity I thought German engineering had the exact opposite image worldwide?
      - Freestyler_3 3y ago
        Same here.
      - seabird 3y ago
        There's a difference between what the layman has been led to believe by Big Deutschland, and the reality experienced by those who actually have to deal with German designs. A lot of them are interesting and "elegant" on paper, but the good experiences usually end there. It feels like the fun factor of the design process is what's prioritized most heavily, which is great for the designers (and I don't say this facetiously; the fun is the #1 reason to do it at all, and I'm glad they make a living off it), and not-so-great for the poor fucker that has to repair a VW. That's not to say that they always shit things up. I'll take Wago nuts over American style ones any day of the week. VW's VR6 engines are a simplification that would probably make my life a lot easier if I didn't have to buy them with the rest of the VW vehicle attached. There is so much more vision coming out of Germany in industrial controls than anywhere else it's outrageous. Life has its ups and downs, I guess.

adrian_b 3y ago

The most usual kind of motor with permanent magnets, is just a synchronous motor, where, in order to remove the power supply needed by the rotor windings, the rotor windings are replaced by permanent magnets. Here, in order to achieve the same brushless operation like when using permanent magnets, the rotor windings are kept, but the electrical current needed by them is transmitted to the rotor wirelessly. For this to work, I suppose that the rotor includes some kind of semiconductor rectifiers and the rotor current is induced at a frequency much higher than the rotation frequency. This should indeed have characteristics similar to the permanent magnet motors, except that it is not clear if the energy efficiency can be equally good. A permanent magnet rotor is equivalent with a rotor having superconducting windings, so it has no losses due to the electrical excitation currents (though it may have losses due to other causes, e.g. hysteresis and eddy currents). This motor will have extra losses in the copper windings of the rotor and in whatever kind of rectifiers it uses. Nevertheless, perhaps these extra losses are small, so the efficiency can be much higher than that of asynchronous motors (like initially used by Tesla) and only a little lower than that of the permanent magnet motors.

londons_explore 3y ago
> except that it is not clear if the energy efficiency can be equally good. There are potentially ways energy efficiency can be better... It's possible to produce stronger (ie. more flux density) magnetic fields with electrical currents than with neodymium magnets. Those stronger fields mean flux paths can be shortened and (for the same mass of copper), wires can be shortened and resistive losses reduced. However, I haven't done the math to see if those effects are of a significant enough magnitude.
- effie 3y ago
  I don't see it. In a brushless DC magnet rotor, there is little energy loss, the magnets aren't very conductive. Here, we have additional current and newly introduced Joule losses in the rotor. It is not clear that these can be kept low enough so the result is as good. Stronger magnetic field due to high current in the rotor does not directly imply higher efficiency, it only directly implies higher torque, which gives the car higher acceleration. We don't need to increase this strength, current motors are plenty strong. This top torque mode of operation usually goes with decreased efficiency, due to high currents and high Joule losses. The best efficiency is likely to be achieved when ohmic and friction losses are kept low, thus currents as low as possible everywhere, induction coupling frequency dynamically governed to be at the optimal value dependent on the angular speed. The only obvious advantage of the marketed motor is smaller size and likely lower weight. I'm afraid price will be a disadvantage.

samtho 3y ago

This is not new, if you have a car with any fossil fuel motor, you likely already have a similar device: your alternator. By applying a voltage between 2 and 13 to the exciter coil, you can adjust how much is drawn from the primary winding.

stephen_g 3y ago
A car alternator uses brushes or slip rings to get power to the excitation coils, which is a big part of what the motor in the article has been designed not to use.
- userbinator 3y ago
  There are brushless car alternators. https://www.delcoremy.com/alternators/find-by-model-family/35si https://www.delcoremy.com/alternators/find-by-model-family/3...

deleted 3y ago

[deleted]

KingOfCoders 3y ago

ZF stands for "Gear Factory" and is owned by the Zeppelin Foundation (yes, that Zeppelin) which is onwed by the city of Friedrichshafen.

codethief 3y ago
And (to my surprise) they are not exactly small: > The Consolidated ZF Group is represented with 168 production locations in 32 countries as well as 19 main development locations in nine countries. In fiscal 2022, ZF reported sales of €43.8 billion with approximately 165,000 employees worldwide. The company spent 7,8 percent of its sales on research and development in 2022. https://www.zf.com/mobile/en/company/company.html https://www.zf.com/mobile/en/company/company.html
- slow_typist 3y ago
  Not as big as Bosch but still a first tier automotive supplier.
- NovemberWhiskey 3y ago
  Every European car I've ever owned has had a ZF transmission.
  - windowsrookie 3y ago
    And all Zf transmissions had a major design fault up until the current 8 Speed. Now they are pretty good. Not only European cars use them, many Chrysler/Dodge/Jeep/Ram cars have ZF 8 speeds in them.
    - nomel 3y ago
      > And all Zf transmissions had a major design fault up until the current 8 Speed Any reference or hint? Google brings up nothing obvious.
      - 3y ago

weinzierl 3y ago

The commenters saying that this is old news and that magnet-free brushless motors have existed for a long time miss the main point. ZF claims to have one that is competitive with traditional designs utilizing rare earth materials. Even ten to fifteen years ago the effort German automakers put into saving a milligram Dysprosium here and there - not only in the drive motor but every electric motor in the vehicle - was insane. I'm out of automotive for a couple of years now, but I can only imagine that this pains must have increased dramatically. Because of all this effort, a motor without rare earth metals would only have to be nearly as good as the competition to still be a huge deal.

deleted 3y ago
[deleted]
mschuster91 3y ago
> Because of all this effort, a motor without rare earth metals would only have to be nearly as good as the competition to still be a huge deal. Even if it were not as good, getting rid of the dependency on rare-earth materials and their dirty supply chain is worth it.
- hamburglar 3y ago
  Indeed. Dirty, expensive, and bottlenecked.
specialist 3y ago
IIRC, the proper KPI for (EV) vehicles is cost per km traveled. Right? Meaning balancing tradeoffs of performance, cost, weight, etc. (Not to mention mitigating risks, like sourcing and externalities.) It's fascinating to me, as a lurker, that misc EV OEMs are making different choices. Such exciting times. PS- Why'd you leave the automotive industry?
- weinzierl 3y ago
  I always had a strong interest in security and that's the direction I developed even when still in automotive. When the opportunity came to work for a security company I switched.

londons_explore 3y ago

Does anyone have a raw materials cost breakdown of motors? Are the neodymium magnets actually a big chunk of the cost? Or is it more of a "we'll get government grants for inventing a type of motor that doesn't require a material that China has strategic control over".

iancmceachern 3y ago
They absolutely are, especially as the motors get bigger. See for yourself at k&j magnetics: https://www.kjmagnetics.com/?gclid=Cj0KCQjwmICoBhDxARIsABXkXlILq8MC5a5RR20bfP1afy1hQMQ_CRrdEa16nr6TNDLbujnwjEHBGEgaAuy0EALw_wcB https://www.kjmagnetics.com/?gclid=Cj0KCQjwmICoBhDxARIsABXkX... Small ones are a few dollars, bigger ones are hundreds or thousands

slow_typist 3y ago

Nice job, now magnet free generators for windmills please.

mannykannot 3y ago
The same technology should work for them, I believe.
- slow_typist 3y ago
  Sure; the economic case might be trickier though.
  - mannykannot 3y ago
    The mismatch between a constrained rare earth supply and rising demand for motors and generators means that the case gets better as time passes.

amluto 3y ago

The obvious comparison is to an AC (asynchronous) induction motor, which also has no magnets and couples energy into the rotor inductively. These are widespread. I didn’t see anything on the website about how their design is better.

hoc 3y ago

Hm. Can I just buy two of them plus drivers or do I have to order a fully custom designed series?

chris222 3y ago

Here we have motors that don’t require rare earth metals. The largest battery maker CATL is making breakthrough leaps in LFP batteries (which have no cobalt). [1] Recycling large EV batteries is becoming cheaper and easier. [2] Are the EV FUDsters heads exploding yet? [1] https://www.catl.com/en/news/6091.html https://www.catl.com/en/news/6091.html [2] https://youtu.be/s2xrarUWVRQ?si=hBfD1lLd4dxEJI6b https://youtu.be/s2xrarUWVRQ?si=hBfD1lLd4dxEJI6b

vbezhenar 3y ago
I'm not EV fudster, but for me gasoline cars are better in every aspect. May be except maintenance (I'm not sure, but I expect that I don't have to change oil every year in an electric car). I don't have money to buy two cars, so I need one versatile enough car. I can bring 100L gasoline with me to add 1000 km range on top of existing 500 range. I can charge it within 5 minutes, not 5 hours. It does not get worse with every year, because there's no degrading battery which costs like half a car. Probably the only thing that's better about EV is that electricity is the same everywhere, I can't charge it with bad electricity mixed with water in the old station, LoL. Electric cars probably are the future, but I don't like this future. They don't have a soul.
- mlyle 3y ago
  > I can bring 100L gasoline with me to add 1000 km range on top of existing 500 range This is the big advantage. > not 5 hours This one is mixed. You can charge the EV at home for ordinary use. That's better. For road trips, you can use DC fast charging to add a bunch of range in 30 minutes. This is worse, requiring combining charging and meal stops. PHEVs are a decent compromise, though: you can do basically all of your driving electrically, and then burn a little bit of gas on road trips. > It does not get worse with every year Sure gasoline vehicles become more maintenance heavy and terrible over time. EV degradation is probably around 10-15% range lost after 5 years typical today. > May be except maintenance Odds are you don't deal with brake pads anymore, and yes, no oil changes. The sheer torque of most models feels like a spaceship when you press down the gas pedal.
  - 3y ago

ouid 3y ago

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rootusrootus 3y ago

It still boggles my mind how much power a modern electric motor gets from such a small package. I'm so used to big engines weighing hundreds of pounds making maybe a couple hundred horsepower. Now we have electric motors making quite a lot more (and not to mention insane torque) that I could easily pick up with my hands.

hinkley 3y ago
There are motors with peak efficiency about 90%. The first one of those I ran into was fifteen years ago. Which means not only is it possible but the patents will have expired, if not now then soon. Power density has gone almost too far. There’s one pancake motor I’ve seen recently where the shape of the enclosure is dictated by mounting concerns. You have to be able to mount the motor to something it can’t tear apart. If they shrunk that motor another 20% then it would be half housing. I’m not sure where you go from there. Thinner? Motor per wheel?
- travisporter 3y ago
  Motor per wheel sounds interesting. As I understand it’s not ideal for handling because of unsprung weight. Maybe that will change? Would be very excited about the prospect of converting cars to purv (somehow)
  - nomel 3y ago
    Motor per wheel doesn’t have to be in the wheel. Could be through a very compact axle, maybe with a fixed gear box to get the angle right.
    - hamburglar 3y ago
      What would be wild (and probably wildly impractical) is an inductive coupling between the motor (inboard, unsprung) and the wheel.
      - 3y ago

ipbrown 3y ago

The innovation here is in the packaging, fitting the brushless inductive power coupling for the field excitation inside the shaft. T he idea of using a high frequency rotating transformer or inductive coupler to transmit current to the field winding without using brushes and slip rings has been investigated by a number of companies, universities, and national labs. A good survey paper of excitation systems for wound field synchronous machines or electrically excited synchronous machines is. J. K. Nøland, S. Nuzzo, A. Tessarolo and E. F. Alves, "Excitation System Technologies for Wound-Field Synchronous Machines: Survey of Solutions and Evolving Trends," in IEEE Access, vol. 7, pp. 109699-109718, 2019, doi: 10.1109/ACCESS.2019.2933493. An example of a high frequency transformer or inductive coupling developed by General Motors is detailed for example in the following paper. C. Stancu, T. Ward, K. M. Rahman, R. Dawsey and P. Savagian, "Separately Excited Synchronous Motor With Rotary Transformer for Hybrid Vehicle Application," in IEEE Transactions on Industry Applications, vol. 54, no. 1, pp. 223-232, Jan.-Feb. 2018, doi: 10.1109/TIA.2017.2757019. Below is some work done by Oak Ridge National Lab on rotating high frequency transformers for field excitation. T. Raminosoa, R. H. Wiles and J. Wilkins, "Novel Rotary Transformer Topology With Improved Power Transfer Capability for High-Speed Applications," in IEEE Transactions on Industry Applications, vol. 56, no. 1, pp. 277-286, Jan.-Feb. 2020, doi: 10.1109/TIA.2019.2955050. The field excitation current is typically provided using a single phase high frequency transformer (20 to 100 kHz switching frequency) which is then rectified by a rotating full bridge rectifier. Just to clear up some of the misconceptions in the comments. In state-of-the-art electric vehicles there are basically three main machine topologies that are used for the main traction machine. - Interior permanent magnet synchronous machines (IPMSMs): A large number of OEMs and suppliers use/supply this motor topology, e.g., General motors, Tesla model 3, Ford, etc. - Induction machines (IMs): Also used by a large number of OEMs and suppliers, e.g., Tesla model S and X, G.M. for assist motors, etc. - Wound field synchronous machines (WFSMs) [in Europe more commonly known as electrically excited synchronous machines (EESMs) but they are the same thing] - Currently used in Renault and some BMW models. A large number of suppliers are developing them. Each of the machine topologies has tradeoffs compared to the others, cost, manufacturing CapEx, supply chain risk, drive cycle efficiency, difficulty of control, failure modes, cooling complexity, etc. WFSMs or EESMs have some potential advantages over IPMSMs or IMs for some applications. - They don't contain rare earth permanent magnets eliminating the supply chain and price volatility associated with them. - In terms of drive cycle efficiency generally they are more efficient than IMs and if the drive cycle is dominated by moderate torques and highspeeds they can exceed the drive cycle efficiencies of IPMSMs. - They are very easy to field weaken and theoretically can have an infinite constant power speed range. - The field excitation can be controlled to provide unity power factor potentially allowing the stator inverter to be downsized. The main negatives of WFSMs or EESMs compared to IPMSMs or IMs are: - The field excitation is more complicated and requires power electronics either for brushes and slip rings or inductive power transfer approaches. - The cooling of the field winding is difficult and typically spray/jet cooling of the end turns or at a minimum through shaft cooling. - The control of WFSMs or EESMs is considerably more complicated than IPMSMs or IMs.

larkinrichards 3y ago

What would be the impact of this style of motor on regenerative braking?

effie 3y ago
If designed well, this type of motor could do regenerative braking too. It's a matter of proper control of current in the stator and rotor and their phase difference, thus mostly electronics.