How to not kill a tesla drive unit

[jrbe]

Since Tesla motors are three-phase asynchronous motors, a rolling vehicle should not be a problem after correct shutdown, as no current is produced. With leaf and Model3 it will be different.

I believe they would still make voltage when there is enough rpm because of the capacitor bank. I'm not sure how much rpm is enough. Just recently cutting power from the contactor would leave the capacitor charged as well. https://www.electricaleasy.com/2014/12/ ... rking.html

[mane2]

I've experienced contactors open while driving two times. Once during regen braking and once when just cruising 80km/h. During regen, one inverter power phase burned and had to get new motor. During cruising steady 80km/h, motor survived.

If there would have been 1 second delay for contactors opening on regen, I don't think that would have been enough. Should be something like 4-5 seconds.

[phillipschip]

I've experienced contactors open while driving two times. Once during regen braking and once when just cruising 80km/h. During regen, one inverter power phase burned and had to get new motor. During cruising steady 80km/h, motor survived.

If there would have been 1 second delay for contactors opening on regen, I don't think that would have been enough. Should be something like 4-5 seconds.

Any advice on what size capacitor to use for a 5 second delay?

[mane2]

I don’t know. Those obvious mistakes with wiring and bms configuration that I had, were fixed and car has been working perfectly since.

[muehlpower]

I assume the time scaling is seconds. Then it looks like the peak is less than a second. Maybe catphisch can confirm this.

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[phillipschip]

Anyone have any idea what size capacitor to use for a long enough delay? I can't quite make out the above graph-it's too low res.

[muehlpower]

[mane2]

I don't understand that graph, but with my 4-5 second duration I was referring for how long regen current could be generated (before full stop) if you're driving like 60-70km/h and all the sudden main contactor opens. But if you cut the 12V from motor/OI controller too at that point, it might go to neutral faster and does not regen for that long.

[phillipschip]

In my testing so far, a 50 watt 5 ohm resistor and a 62,000uf cap delay the off by about 2 sec.

[phillipschip]

I’m still trying to fully understand this and cover all my bases before testing. If I have “DC on” option, killing the contractor while driving should protect the inverter as long as it still has 12v? Like blowing a HV fuse etc? If so wouldn’t it be a good option in most builds to have a panic switch that immediately drops the main contractor(bypassing the capacitor if used) and if desired, a capacitor/resistor in the circuit in case of sudden loss of 12v to the inverter?

[mane2]

If your contactor opens (gets killed) during cruising, inverter might survive. If it opens during regen or heavy acceleration, it probably won’t. This has nothing to do with “DC on option” aka “trip mode” “All off”.

But if you configure your board limits low and exceed them, OI board commands contactors to open if trip mode is set to “all off”. So it’s recommended to use “keep DC switch closed” to avoid inverter damage.

[phillipschip]

Ok, yes. I forgot about the fact that dc on keeps the contractor closed. Duh. Would having regen off help at all?I need to watch that video again. For some reason I had it in my head that he used too small of a fuse for motor current while testing and it blew. Then said that it would have protected the inverter to have DC on…..

[mane2]

Yeah, disabling regen is good idea when doing initial testing.

[Mancini]

What caused the contractors to open?

[mane2]

What caused the contractors to open?

In my case, it was too low "charge limit" -setting in Orion BMS 2. It lifted the contactors during highest point of regen braking. After that incident I added a relay that does not allow BMS to control contactors when "ignition" is on.