6 ms·
> A lot of Tesla fans claim that electric vehicles are inherently superior, because with fewer moving parts, they'll be able to stay on the road basically forev
by brandmeyer 11y ago
> A lot of Tesla fans claim that electric vehicles are inherently superior, because with fewer moving parts, they'll be able to stay on the road basically forever - no piston rings to wear, no transmissions to fail, no oil to change.
There are at least two major components that "wear out" in power electronics - capacitors and power transistors. Traditional vacuum-impregnated motor winding insulation also has a wear-out mechanism.
Electrolytic capacitors have both an electrolyte breakdown and dryout at extended temperatures and voltage. Film capacitors also have a (much slower) dielectric breakdown. Power transistors have two wear-out mechanisms: one that is based on thermal cycling of the wire bonds and one that is based on thermal cycling of the solder between the transistor and direct-copper-bonded substrate.
Datacenter-scale UPS addresses both of these with field-replaceable modules. The main AC and DC capacitor banks are replaceable in advance of failure, and power transistors are field replaceable in much larger power modules, typically only after a failure.
Vacuum-impregnated motor winding insulation is typically not completely void-free. The high dV/dt that a direct-connected inverter imposes on the windings causes large repetitive voltage spikes across the winding insulation. The voltage spikes trigger partial discharge in the voids, which in turn erodes the insulation.
IMO, long-lived electric cars should at least have capacitor banks that are schedule-replaced, and drive modules that are replaceable after failure. With the level of diagnostics and history monitoring available today, we should be able to replace both components in advance of failure as well.
Do electric cars have lower maintenance, longer life, and higher reliability than ICE cars? Definitely, probably, and probably, respectively. But "lower", "longer", and "higher" don't mean "zero", "forever", and "infinite".
- jacquesm 11y agoThose voids also allow the wiring of the windings to flex slightly under the changing magnetic flux leading to eventual insulation failure.
- B1FF_PSUVM 11y agoMost big-ass transformers also produce an audible hum, meaning something is moving enough to push air around.
- jacquesm 11y agoThat's a combination of those same gaps and gaps in the transformer laminations where the laminates don't line up perfectly around the edges (they flutter ever so slightly) and inside the stack if a sheet isn't pressed perfectly flat or the lacquer isn't applied evenly.
- brandmeyer 11y agoAlso, air-cooled transformer windings are installed such that there are deliberate air gaps between each coil layer. Spacers are inserted in between the gaps for some structural rigidity, but there is enough remaining flexibility to vibrate.
- georgefrick 11y agoI found your addition very interesting. But I think the "Tesla fans" referred to, are referring to something different. The Tesla vehicles are "missing" a lot of parts that rust, corrode, and cause engineering challenges. One of the main ones behind the exhaust system. Speak with a series of car mechanics and they'll invariably tell stories of cars that never received an oil change until something fails. There are videos, pictures, and documentation of Tesla being able to swap drive trains, etc. Put together, Tesla is able to better protect the frame and body from corrosion by separating it from the same parts that usually "Carry this along". That's a lot of text to say they reduce the surface area and mass of corrosion and failure prone parts. This isn't to say I agree, but I find the information all fascinating (as a car guy). The best way to make a car, in my mind; more serviceable is to increase the protections from rust and corrosion. Otherwise a simple brake pad ends up being an entire brake system upon repair attempt. In regards to electronics; they can go in sealed compartments and be easily serviced. How awesome. They can also just as easily be replaced by a superior implementation. Anyways, your post made me ramble a bit but I'm trying to determine if I agree with the original post or not.
- WalterBright 11y agoI have an 89 Ford. It has been parked outside in rainy Seattle for 20 some years. Other than the exhaust system, it is free of corrosion. I find this rather incredible. Ford has done a truly amazing job with corrosion protection, unlike my older car which rusts when a cloud passes by. I also have to compliment Ford on building a low maintenance vehicle that is also cheap and simple to repair when it does go wrong.
- tamana 11y agoHow many years (or electrons) is "long-lived"? There is a wide range of finite numbers, some are practically infinite, dominated by other factors (cumulative risk of totalling the car in a crash, change in road or passenger compartment design,...)