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How electric trains work and why they make interesting sounds [video]
- hejira 2y agoFun and educational video!
- CraigJPerry 2y agoThat video turned out way more interesting than I first thought. I never really considered why the 380 makes that noise, i assumed it was a maintenance issue.
- mlok 2y agoIt's a mystery to me how the camera is mounted for the video at 7:55. https://youtu.be/IRJIJPTUXXE?t=474 https://youtu.be/IRJIJPTUXXE?t=474 A drone ? The camera follows the train so precisely that it seems it is mounted on the train, but it passes on the other side of some objects so it cannot be mounted on it.
- lainga 2y agoI believe this is an example of ludonarrative dissonance. The camera is simply at a fixed offset from the train model.
- sicross 2y agoThat’s not a real life video. Is a capture from a train simulator app. Like Microsoft Flight Simulator, but for trains. Example: https://www.trainsimworld.com/ https://www.trainsimworld.com/
- mjamesaustin 2y agoThe secret behind this camera is that it exists within a virtual world, and therefore can freely float anywhere ;) An easier giveaway might be the floating teal icons on the station platform.
- zdw 2y agoI think that's game footage, but not sure what game it is. The train game or sim genre has a bunch of folks who go incredibly deep and accurate in their representations of real trains. If you want an incredibly detailed 3 hour history of the genre: https://www.youtube.com/watch?v=5vwE_p9SCXw https://www.youtube.com/watch?v=5vwE_p9SCXw
- rootusrootus 2y agoSimulations have gotten quite good, apparently. It threw me for a loop for a moment, too, until I figured out what was going on.
- jkingsman 2y agoFascinating video! One of my favorite train vids is a Taurus starting up in frigid conditions. As the wheels slip and the PWM modulation on the individual motors varies to keep traction, it makes beautiful music. https://www.youtube.com/watch?v=Q_bF1Wb_pSE https://www.youtube.com/watch?v=Q_bF1Wb_pSE
- asciii 2y agoThat's really neat - it sounds like a violin. I can barely keep a tune so I'm wondering if anyone knows anything special about the melody
- gorlilla 2y agoThey sound just like stepper motors to me. Especially when they're operating to create a radius/arc in a 2-D plane.
- bmicraft 2y agoWell, those VVVF frequency converters were specifically tuned to have their "steps" on full notes/chords. It doesn't sound like that by accident.
- rob74 2y agoDetailed explanation (in German) here: https://de.wikipedia.org/wiki/Siemens_ES64U2#Ger%C3%A4uschentwicklung https://de.wikipedia.org/wiki/Siemens_ES64U2#Ger%C3%A4uschen... > Google translation: When switching on from a standing start, a noise can be heard that is reminiscent of playing through a scale on a tenor saxophone. It is created in the three-phase motors by controlling the power converters. The noise is twice the clock frequency of the pulse inverters, which is gradually increased. The frequency changes in whole and semitone steps over two octaves from d to d" in the tone pool of the root tones. It is a Dorian scale on the root D. Theoretically, it would be possible to program the locomotive in such a way that it emits completely different sounds. However, the manufacturer has opted for a scale because these sounds are perceived as pleasant by the human ear. This makes it possible for a four-voice tone to result when the wheelsets are spinning (for example due to wet rails). No wonder the Austrians (who have a reputation of being music lovers) have most of these engines...
- fotta 2y agoAnyone know what the BART FOTF trains use? I’m guessing it’s IGBTs but they sound more like fixed PWM switching to pattern mode with pulse drops.
- Animats 2y agoSome OBB locomotives have their PWM systems tuned so that when they change frequency, they're always on a standard musical note. There's one example of that in the video. It's a cute feature, people like it, and it's probably all in software.
- 0_____0 2y agoThey could easily have picked aharmonic intervals, and it would have even been a little easier. But given the opportunity, they chose to make something that added a little bit of color and magic to the world. I love that.
- fransje26 2y agoExplained with a bit of technical detail in an other comment on this post. [1] [1] https://news.ycombinator.com/item?id=41807522 https://news.ycombinator.com/item?id=41807522
- theideaofcoffee 2y agoAs much as I love the futuristic and sophisticated sounds that electric traction drives make as compared to their fossil-fueled counterparts, I do think that the driving and control systems that actually generate the PWM waveforms that are sent to the motors are even more interesting. Huge, massive IGBTs weighing a kilo+ each chopping up hundreds of thousands of joules/s of energy without destroying themselves, current transformers, contactors, it really tickles parts of my brain. He only spent a handful of seconds on those, would be interesting to hear a deeper dive.
- itishappy 2y agoSame! That stuff is so freakin' interesting! The other deep dive I really want (pun intended) is submarine sonar transducer drivers, which as I understand do basically the same thing but bidirectional and with a LOT more waveform customization.
- rwmj 2y agoPhoto on Wikipedia: https://en.wikipedia.org/wiki/Insulated-gate_bipolar_transistor https://en.wikipedia.org/wiki/Insulated-gate_bipolar_transis... Are they manufactured using regular silicon lithography? You'd think when making something so large you could just mix up the chemicals instead.
- theideaofcoffee 2y agoFrom what I understand, mostly yes. They are still built up layer-by-layer with standard litho techniques, with pattern masks, ion implantation for the p- and n-type layers, etching, CVD to deposit insulation material (for the 'insulated gate' part of the device). Though they don't have to be nearly as precise, as I understand it as something more sophisticated, like a cpu, they still need to lean on those to make it chooch.
- bgnn 2y agoI don't thik they're produced with the same process as CMOS, but I bet some photolithography is involved.
- 2y ago
- amelius 2y agoCan't they filter out those sounds with some L's and C's?
- CarVac 2y agoThe motor is a bunch of big Ls, and the Cs are already used to feed the chopper.
- rcxdude 2y agoNot very easily. Firstly, the power involved in these systems is massive, making any inductor or capacitor you put in very expensive (and bulky). Secondly, filtering it out may reduce the sound, but still will have some part of the circuit switching at that frequency, and with the power involved, some part of the inductor will see that and vibrate accordingly. Modern power electronics generally avoids this problem primarily by pushing the switching frequency higher than human hearing (which also has other advantages, like reducing the inductance and capacitance involved). Generally the higher-power the device, the physically bigger it is, and the slower you can switch it without melting it, so bigger systems are stuck at lower frequencies (this is something that's improving as technology develops: so there's the other factor that most train stock is quite old and the designs older still, meaning they switch even slower than your new laptop, even taking everything else into account).
- jimmaswell 2y agoI still find it amusing that most fossil fuel trains only burn it to power a generator, with the wheels run by electric motors. It makes perfect sense with the massive startup torque a train requires, something electric motors are much better at.
- stackghost 2y agoThe term for that is a hybrid series powertrain. It allows one to optimize the generator to run at a single RPM, which leads to efficiency benefits.
- euroderf 2y agoFWIW back in the 80s Mother Earth News had plans for a car that used this principle.
- Loughla 2y agoI genuinely believe hybrid cars will be the path once we get the itch for electric cars out of our system. You get all the good parts of each engine type, with less of the bad parts of the other type.
- gambiting 2y agoI have a PHEV and I genuienly believe this is the best combination of both, it's so practical with upsides of both drivetrains, but also let's not kid ourselves - PHEVs are vastly more complicated than either just plain ICE or EV cars, you have a lot more stuff that can go wrong. I deal with it by just buying extended warranty for as long as they let me lol, but it's definitely a concern with them.
- Lwerewolf 2y agoThe Prius and other HSD cars (i.e anything with a power-split device of the Toyota variety - input-split PSD) are some of, if not flat out the most reliable and simple ICE cars. Permanent atkinson-cycle engine, no turbos because there's no exhaust gas pressure to drive them in the first place (and if there was, it'd be an inefficiency to be rooted out), bulletproof starter/generator especially since the ls600h (double-sided cooling of IGBTs >> no usual IGBT packaging degradation-related failure modes - this was NOT the setup on the 3rd gen prius), still a very efficient power transfer from the engine to the wheels (a big percent is still transferred mechanically), etc, etc. Adding a bigger battery to those isn't a whole lot of increased complexity. The only issue is making a PHEV that has the same performance characteristics in both EV and hybrid mode - not that it hasn't been done. Specifically on HSD cars, the two electric motors combined, or even just MG2 (the "motor") have way more power than you'd assume - they actually function as an AC-AC converter, converting a significant portion of the engine's output power from mechanical to electric and back to mechanical again. It's essentially the way the eCVT works. Therefore, with a battery (and buck-boost converter) that can support such a load, they can propel the car alone way more than adequately - with a speed limit to protect the "generator" from too high RPM, due to the way the HSD works. Anyways, it absolutely can be done and it absolutely can be way simpler. If it's a case of a typical modern ICE with a big battery and a motor thrown in somewhere that makes it "hybrid"-ish - i.e. all the ICE complexity + the EV "complexity" (minus the classic starter/alternator) - yeah, no thanks. IMO: Good examples - the Chrysler Pacifica PHEV. Bad examples - C63 AMG (the PHEV version).
- rootusrootus 2y agoGreat video, lots of nice details. Now I wonder what technology our local light rail train is using, because I've noticed the gear switch sound (though it just has a single switch at perhaps 10-15 mph or so). Apparently it's a Siemens S70 (there are several varieties of rolling stock, but this is the one that makes the most distinctive sounds).
- exabrial 2y agoI do not have perfect pitch (cool party trick), but I can identify all 8 'normal' equal temperament intervals by ear relative to a reference (If you couldn't guess, I play bass, which is a lame party trick). I was in Austria last year, and a bunch of the trains starting from a standstill had a "gradual acceleration" algorithm for their traction motors. As the drive frequency increased, you could hear the drive motor whine (or maybe it was the inverter?) along with the frequency. It was fascinating, because it played chords as it accelerated: root, 2nd minor, 4th major, 6th minor, octave, then it would pause at the octave and do it again after a few seconds until it reached max power I assume. Each chord had a very faint tritone added to it relative to the chord tonic, so you got this really harmonic pulsing. After the second course there was too much rail noise to hear what happened, but it was fascinating. I'll try to find a video, I know I recorded it. Power in Austria/Germany is delivered to trains via a really weird standard too: something like 25hz 27 kV. Leftover standard from 100 years ago.
- the_mitsuhiko 2y agoNormally it just plays the scale: https://www.youtube.com/watch?v=-SDYdHzT7Qw https://www.youtube.com/watch?v=-SDYdHzT7Qw But it can be configured to play other tunes. Here is a rare recording of it playing the Austrian anthem: https://www.youtube.com/watch?v=UkdQmDGU9AM https://www.youtube.com/watch?v=UkdQmDGU9AM (another recording: https://www.facebook.com/unsereOEBB/videos/290883783832057/ https://www.facebook.com/unsereOEBB/videos/290883783832057/)
- exabrial 2y agoThat was fascinating! That is different that what I remember hearing but that's exactly what I'm talking about! Just compared it to a midi player... first video starts on a G. It may not be equal temperament? Some of the scale degrees sound just slightly flat or sharp.
- bobthepanda 2y ago25kv 50/60Hz is the norm. The German standard you are thinking of is 15kv 16.7Hz.
- garaetjjte 2y agoSee also: https://www.youtube.com/@yuqquu/videos https://www.youtube.com/@yuqquu/videos
- grishka 2y agoSo it's more complicated than I thought it was. Now I'm curious about our Russian trains, especially in subways. They've never made any interesting sounds, it seems. The older (Soviet-era) ones don't make any noticeable sounds at all. The newer ones just make a high-pitched whine that varies in volume (but not frequency I think) when they accelerate or brake.
- forgot-im-old 2y ago[flagged]
- GavinGruesome 2y agoNerd knowledge. Btw nothing beats the sounds made by both steam- and opposing-piston diesel engines - you can feel the power. Sounds made by electric engines are mostly whining.
- fransje26 2y agoCould someone explain the difference between the PWM mode and the pattern mode? To me, the example of the PWM wave [1] looks like the VFD mode, but: - instead of varying between [-V..V], varying between [0..V] - instead of having a regular variation of pulse pattern to get a regular wave, having an irregular pattern. But that irregular pattern (or non-recurring pattern) only seems to be an illustrative example to match the brown wave shape, and I assume you wouldn't want to have irregular wave patterns to drive your engine? [1] https://youtu.be/IRJIJPTUXXE?feature=shared&t=406 https://youtu.be/IRJIJPTUXXE?feature=shared&t=406
- atahanacar 2y agoAs far as I can understand from the video, pattern is variable frequency PWM.
- fransje26 2y agoSo a PWM pattern with a fixed number of pulses that are relatively broadened/shrunk to have a variable wave frequency?
- lockedup 2y agoHttp://www.yahoo.com/news