Continuity at the Inverter

[phillipschip]

Yesterday was a bit of a bad day. I was excited to finally get the motor spinning with HV after a successful run on 40v-(this was a while back). I tested the voltage at the motor contacts and the correct on/start sequence all seemed good to go. plugged it in and switching the IGN on was fine, but then when I hit the start button it was like I was firing off a bomb. I started testing stuff after I successfully put the fire out. The main contactor seems to be welded together, and I have continuity also at the inverter/motor connections. There aren't any errors when I hook it up, but I'm pretty sure this is back to the drawing board. I can't get the minus connection off the motor yet-it seems to be welded too.

[tom91]

What settings did you have in it?!?

did you change your UDCsw to the battery voltage one?

[phillipschip]

Yes. udscsw wouldn't have caused a fire though right?

[tom91]

Post you parameters.

Failing to precharge would cause your issue or reverse connected voltage

[uhi22]

Which kind of fuses have been in the circuit? Did they trip?

[phillipschip]

No the fuses didn’t trip. EV west 600a (website is down so can’t get a link). I’ll post parameters when I get home.

[phillipschip]

Here are the parameters-basically just copied the one of the tested versions from wiki:


{
"boost": 3000,
"fweak": 250,
"fweakstrt": 300,
"fconst": 500,
"udcnom": 400,
"fslipmin": 2,
"fslipmax": 3,
"fslipconstmax": 4,
"polepairs": 2,
"respolepairs": 1,
"sincosofs": 2048,
"encmode": 1,
"fmax": 500,
"numimp": 36,
"dirchrpm": 100,
"dirmode": 1,
"snsm": 12,
"pwmfrq": 0,
"pwmpol": 0,
"deadtime": 63,
"ocurlim": 1200,
"il1gain": 1.5,
"il2gain": 1.5,
"udcgain": 7.59,
"udcofs": 0,
"udclim": 450,
"snshs": 2,
"potmin": 0,
"potmax": 4095,
"pot2min": 4095,
"pot2max": 4095,
"potmode": 0,
"throtramp": 5,
"throtramprpm": 20000,
"ampmin": 3,
"slipstart": 50,
"brakeregen": 0,
"regenramp": 10,
"regentravel": 5,
"offthrotregen": 0,
"cruiseregen": 0,
"regenrampstr": 50,
"brklightout": -50,
"bmslimhigh": 50,
"bmslimlow": -1,
"udcmin": 0,
"udcmax": 450,
"idcmax": 650,
"idcmin": -300,
"idckp": 2,
"idcflt": 9,
"tmphsmax": 85,
"tmpmmax": 150,
"throtmax": 100,
"throtmin": -100,
"iacmax": 900,
"ifltrise": 10,
"ifltfall": 0,
"chargemode": 0,
"chargecur": 0,
"chargekp": 80,
"chargeki": 10,
"chargeflt": 8,
"chargepwmin": 0,
"chargepwmax": 90,
"idlespeed": -100,
"idlethrotlim": 50,
"idlemode": 3,
"holdkp": -0.25,
"speedkp": 0.25,
"speedflt": 5,
"cruisemode": 1,
"udcsw": 0,
"udcswbuck": 540,
"tripmode": 1,
"bootprec": 0,
"pwmfunc": 0,
"pwmgain": 100,
"pwmofs": 0,
"canspeed": 1,
"canperiod": 1,
"nodeid": 1,
"fslipspnt": 0,
"ampnom": 0
}

[tom91]

"udcsw": 0

Here you go buddy. No precharge, big inrush Blow up the capacitors and weld the contactors.

You probally superheated some bits under your plate.

600A fuse, why the heck did you pick that size?!? Even for a tesla LDU a 600A fuse is huge.

Cables would have to be like 120mm2 to handle 600A for anything near what the fuse is rated to.

[phillipschip]

I picked it based on the recommendation from the seller. I figured the SDU is rated to 600a peak for 10 sec or so, therefore it would be good? How would udcsw set to 0 cause this? Doesn't that just keep it from closing if batteries are too low?

[tom91]

UDCsw is precharge end voltage. At this voltage the contactor closes, by having it zero (which you do when you manually precharge for testing) it closes right away no precharge. This is covered many many times in posts and videos.

SDU is rated to 600a peak for 10 sec or so. The fuse is rated for continuous of this, it is rated for 1000s of amps for 10s, you cables and other components are not. This is why you had a fire.

[phillipschip]

So is my motor a boat anchor?

[tom91]

So is my motor a boat anchor?

The inverter section yes, rest should be okay.

[uhi22]

Would be interesting to see, which components show which kind of damage, to understand what was happening. Cannot imagine that the IGBTs go short just by a "microseconds-super-fast-precharge-event". Reverse polarity is excluded?

[johu]

That's right, super fast precharge primarily welds contactors and might damage capacitors, not IGBTs. I've suscepted my Leaf inverter to multiple such events and it still runs fine. I suspect reverse polarity.

[catphish]

This does feel like the polarity was reversed at the inverter, or maybe you . Are you able to trace things through and determine if that's the case? If the current stopped, then presumably something in the circuit opened. If it wasn't the contactor, and it wasn't the fuse, then I can only assume the IGBTs are exploded. The purpose of UDCsw is to prevent the main contactor from closing before the precharge has finished successfully, and would have saved you here, but too late for anything but learning on that front.

Another possibility is that you accidentally crimped the shield of the high voltage cables. The shield of both cables in the SDU is connected to the chassis ground, so if you crimp them into the HV, things will explode, but I guess you'd have noticed this during the low voltage test.

Another possibility is that you just got extremely unlucky and got a bad SDU with multiple failed short-circuit IGBTs (they only go short circuit when high voltage is applied for the first time, I don't know why). I've never heard of this causing a catastropic failure but it's technically possible.

[phillipschip]

(feeling defeated). I don't know how polarity could be reversed. I checked, double checked. If it is that one wrong setting that sucks.

[phillipschip]

The negative at the inverter is welded. also, the negative at the battery is too.

[johu]

It's not a setting, it's how you hook it up or crimp it

[phillipschip]

Ok so the udcsw set to zero wasn’t necessarily the issue? It sure seems like reverse polarity to me too but I have double checked that. Wouldn’t a plus or minus reversed be pretty obvious?
I tested voltage at each box, and total voltage after pre charge and start before plugging in. Should I check the motor with low voltage and fuse/heating element? If there is a possibility it might spin that would be amazing.

[uhi22]

If you have continuity between phase outputs of the inverter (while the motor is disconnected) there are shortcuts in the IGBTs. It will not spin.
Using heater element the next time sounds like a good idea.

[tom91]

Ok so the udcsw set to zero wasn’t necessarily the issue?

This would be an issue. Maybe one of the many mistakes made.

Do you have pictures of what burned? And pictures of your HV contactor setup before?

[muehlpower]

Does not help a delay between ignition and start even if udcsw=0.

[phillipschip]

I didn’t change anything from when it worked perfect on 36v Confirmed precharge working with on switch, then main switching on/pchge off was confirmed. Then I tested HV at motor connectors. 390v correct polarity. Haven’t dug into that box yet. Bms shows all cell groups healthy except one. 59 healthy, one gone

[phillipschip]

My understanding of udcsw was that it was the minimum voltage the main contactor would be allowed to close “after precharge”. Thought the higher setting was just to prevent the driver from being able to take off with too low batteries. I had to lower it from 330 to below my testing battery voltage (36) otherwise precharge would happen but then just open without the main contactor also closing. Sorry im having such a hard time understanding this and thanks so much for trying to help and bearing with me!

[tom91]

udcsw was that it was the minimum voltage the main contactor would be allowed to close “after precharge”.

No it is the finishing point of Precharge, it is the following

If UDC > UDCsw close main contactor

So your UDCsw of 0 meant it immediately closed the main contactor, this is also why you have to change this to allow manual precharging for testing.