400V 500A inverter

Cars have a short service life in hours, so there's a big difference in reliability requirement compared to say testgear or domestic electronics.

NT

In high voltage high current power electronics a fault usually propagates with arcing on the entire board rendering it useless

If it could be repaired, how do you guarantee that nothing else has been over stressed and will fail just after recommission?

Cheers

Klaus

Lasse Langwadt Christensen wrote in news: snipped-for-privacy@googlegroups.com:

It should still be a separate module/daughtercard. The designer should have put more consideration into serviceability.

They will be, after all, a likely weak link in the overall design. An MTBF analysis would find those elements at the top of the list. Motor windings, things like that last a long time. Overtaxed, constantly temperature cycled FETs not so much.

Klaus Kragelund wrote in news: snipped-for-privacy@googlegroups.com:

Some of the circuit segments need to be segregated from the main drive board. The output drivers, for one.

The weak use of small beads of encapsulant on HV segments is a failure waiting to happen too.

Those are only relative low power (up to 20 kW).

In a VFD those are for the full power.

The external Tesla V3 charger is capable of supplying the full power

250 kW at 400 Vdc.

Big switching transistors often have internal reverse polarized diodes between drain and source, which will rectify the braking current into the DC bus and in this case into the batteries. In other system, the breaking energy is directed via a transistor to a load resistor.

Each of the three phases is a half-bridge,** part of a three-phase "H-Bridge". Energy flow is bidirectional, controlled by whether switching phase leads or lags the motor coils, so deceleration puts energy back into the battery. In my Prius, I can start down a steep hill in Somerville, with the readout showing my battery gain as I go down, stop at a light at the bottom, then power my way up the next hill to the same elevation, with the battery returning almost exactly to its original state.

** Each phase has two SOT-24 isolated MOSFET driver ICs, STGAP1AS, including de-saturation diagnostic readback. Each driver has P and N-channel DPak MOSFETs to further beef up the gate-drive capability. HI-bus drive goes to four SiC MOSFET modules, each with a gate resistor. Four more identical LO-bus modules, makes up one phase. Three phases = 8 x 3 = 24 MOSFET modules. The 400V switched phase lines go straight to motor coils, no L-C filter. Hey, no RFI comes out of the metal case?

--
 Thanks, 
    - Win

I'm not sure about the modules. There may be four SiC MOSFETs mounted together in a plastic carrier, with a circuit board making some connections and providing pin alignment. There must be a rather thick something to conduct heat to the case, and thence to heat sinks in a coolant chamber underneath.

--
 Thanks, 
    - Win

Yes, as you watch the video, you can see light reflecting off the sealant coating on ICs, parts and PCB. (I often use a urethane spray for that purpose.) Some places have apparently been masked off from coating. Also, the entire assembly is in a bolted-up sealed housing with an O-ring.

--
 Thanks, 
    - Win

Interesting teardown. So the Chevy motor is an 8 pole 3-phase synchronous design rated for 8810 RPM max, which works out to 1175 Hz max inverter frequency, about the same as the 1200 Hz which Dr Cuk said was used by Tesla in one of his power conversion presentations a few years ago. The high speed is how they get so much power out of such a small motor, along with liquid cooling and low duty cycle.

Chevy tries to reduce the rare earths used in its motor designs as much as possible as they seem unconvinced of their forever-availability at reasonable prices for a traditionally US company.

Tesla doesn't seem to have the same concerns likely because if necessary their whole operation can simply be packed up and moved to China with few consequences as compared to Chevrolet which can't really do that.

That is to say Tesla figures its products have much broader global appeal than GM's do and they're probably right. They don't really care that much if Americans (who will likely remain very ambivalent about EVs for the foreseeable future) buy their products or not when all of Asia and Europe is waiting, if US don't like 'em f*ck 'em.

Ya, young Asian folks do like tossing stuff like that in sometimes to let the old white dudes have a laugh. Ha! me so solly, white man! Not know how do you language.

China finds it amusing that America traded 90% of her industry to them in exchange for jokes, lol. Me so solly!

or switch back to the induction motor they used in previous models

I wonder who does their PCB assembly and SMT etc ?

China ?? US ? Does Tesla use contract manufacturers for that or do they do it themselves ?

OR does

make Tesla's PCB assemblies ?

I am not sure if we disagree or is it just a question of terminology.

To my understanding in a H-bridge, both end of a winding are driven by a half-bridge. Thus, with 3 isolated windings, six half bridges or 12 transistors are required. Indeed, the peak-to-peak voltage is twice the DC-bus voltage.

However, if the windings are connected in delta, the half bridge connected to A feeds current into AB and AC windings, the half bridge connected to B feeds BC and BA winding and the half bridge connected to C feeds CA and CB windings. With some imagination you might see also H-bridges in this configuration. With sine wave connected to A, B and C terminals, the voltage across each winding is only 1.73 times the half bridge voltage, not twice the half bridge voltage as in real H-bridge..

Os the half bridge output supposed to be PWM sine wave or just square wave? At least feeing a square wave or other waveforms with lots of harmonics into an induction motor, will cause a lot of heat dissipation in the motor and also a lot of acoustic noise.

The whole world will eventually go from dirt poor to sort of middle class. Everybody wants electricity and clean running water and beds and windows in their houses. Most people want heat and eventually a/c. China and Africa getting better doesn't diminish us.

That progress will take a lot of energy.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

You think that was done on purpose?

I see a lot of expensive advertising that is such bad English that it must hurt sales; sometimes you can't tell what they are trying to sell. That would be an expensive joke.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com