SDU: No udc voltage

Lood · Post by **Lood** » Sat Sep 30, 2023 5:58 pm

I am using a (front) SDU, I have had the drive unit working with 48V. Now I supplied 186V, the precharge contactor closes (udcsw=175V) but after five seconds it opens again. Error code "PRECHARGE". The inverter isn’t reading any voltage (udc around 2V). I measure 186V on the cables going to the inverter. I don’t understand why udc is not reading any voltage?

why there is no udc voltage?

Parameters used

Code: Select all

{
  "boost": 3800,
  "fweak": 230,
  "fweakstrt": 300,
  "fconst": 300,
  "udcnom": 300,
  "fslipmin": 1.5,
  "fslipmax": 3,
  "fslipconstmax": 4,
  "sincosofs": 2048,
  "fmax": 500,
  "dirchrpm": 100,
  "dirmode": 1,
  "ocurlim": 1200,
  "potmin": 16,
  "potmax": 450,
  "pot2min": 16,
  "pot2max": 450,
  "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,
  "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": 175,
  "udcswbuck": 540,
  "tripmode": 1,
  "bootprec": 0,
  "pwmfunc": 0,
  "pwmgain": 100,
  "pwmofs": 0,
  "canspeed": 1,
  "canperiod": 1,
  "nodeid": 1,
  "fslipspnt": 0,
  "ampnom": 0
}

Peter · Post by **Peter** » Sat Sep 30, 2023 9:04 pm

Hi Lood. Try lowering udcsw to say 160v and see if the precharge drops out again at 5 secs. I would also be monitoring the dc readout on the parameters to see if the dc voltage rises during the 5 secs. Whats your precharge resistance value? Need that info first

Pete

Lood · Post by **Lood** » Sat Sep 30, 2023 9:09 pm

Hi Peter,
Thanks for your reply. I will try tomorrow.
I am using a 50 ohm resistor

Peter · Post by **Peter** » Sat Sep 30, 2023 9:33 pm

Ok Lood. 50 ohm is fine. I am hoping you can monitor the udc voltage before the precharge drops out. Good luck.

Peter · Post by **Peter** » Sat Sep 30, 2023 10:07 pm

Also measure voltage across 50 ohm resistor during the precharge.

Lood · Post by **Lood** » Sun Oct 01, 2023 10:04 am

Changing the precharege voltage to 160V didn't make a difference. With the webinterface it is hard to measure udc at precharge. But is think it is reading udc= 1.96V all the time.
At precharge i meassure 1.93V across the resistor.

catphish · Post by **catphish** » Sun Oct 01, 2023 10:25 am

If you're definitely seeing 186V going into the inverter and at the same time, udc is showing near zero then one of two things must be wrong:
1) The udc measurement circuit is broken.
2) The udcgain parameter is wrong

I'm not sure if this helps you, but I can't think what else could be wrong here.

Peter · Post by **Peter** » Sun Oct 01, 2023 12:29 pm

You should see the voltage change across the resistor at start of precharge and at the end as the capacitors charge up.
Should be a high voltage across it at the initial start of precharge which reasonably quickly drops to a few volts after a second or two.
As another test put a load across the inverter cables and make sure your precharge contactor/resistor etc are actually allowing current to flow.
Suggest a 100w lamp (not LED) if you can find one

Lood · Post by **Lood** » Tue Oct 03, 2023 5:51 pm

Thanks for te response. I don't have a 100W lamp, but I will test (this weekend) the prechare system by pulling some current via the dc/dc (Tesla GEN2) converter. I am afried that i have to remove the inverter from the car for futher testing.

Lood · Post by **Lood** » Sat Dec 16, 2023 10:19 am

The precharge circuit is providing current, so this is not the issue.
With the inverter now removed from the car, I checked:

* IGBT (diode test) test results are OK;
* A visual inspection of the driver-board seems OK;
* HVIL circuit was not working (bad contact in DC- connector), So I disconnected the HVIL on the OI board (conn 2), no result;
* I tested the OI udc-read by simulating a voltage on pin 1 of the IGBT-drive connector, and then the UDC-value was reading something, so the IO board seems OK;
* I tried to measure the UDC directly from the driver-board (pin 1), but there was no voltage.

Conclusion, the UDC measurement of the driver-board is bad?
But it seems impossible to remove the driver-board, so I guess the only option is to look for a new inverter (or drive unit)...

jrbe · Post by **jrbe** » Sat Dec 16, 2023 12:08 pm

Could be a bad solder joint at a connector. It's probably worth reflowing the connectors first.

YouTube · Post by **johu** » Sat Dec 16, 2023 12:37 pm

When disconnting hvil remember to close the jumper on the oi board. Won't solve the udc issue though

Lood · Post by **Lood** » Tue Dec 19, 2023 2:01 pm

I have ordered another inverter, and I hope this one will work.
What I don't understand is why at first the inverter worked (@48V), then I connected 190V, and it stopped working (the UDC-measurement).

One thing I did wrong was that I connected the gas pedal potentiometer the wrong way to the OI-board. At full throttle (no HV connected), the OI-board switched off and on again. After connecting the potentiometer correctly, the OI-board worked normally again.

Lood · Post by **Lood** » Sat Jan 13, 2024 3:12 pm

The inverter arrived, it passed the diode-test. Then I tested it with a bench power supply (max 30V), UDC reading was working.
Today I installed it in the drive-unit, applied 180V and the UDC reading is not working any more. (PRECHARGE error)

So bad luck again?!
Where do I find a working SDU-inverter?

jrbe · Post by **jrbe** » Sat Jan 13, 2024 5:36 pm

What hasn't changed between inverters and boards? The issue likely lies there or there is some error being copied over.
Do you have verified good grounds?

Lood · Post by **Lood** » Mon Jan 15, 2024 6:37 pm

First inverter:
* Test at 48V; everything is working OK; the motor is spinning.
* Test at 180V, no udc reading

Second inverter:
* Bench test of inverter at 30V power supply. UDC measurement is working.
* Test at 180V, no udc reading

I grounded the drive unit (via the grounding strap) to the car chassis.
What I didn't change:
* OI board (V8)
* HV-Battery, including precharge circuit
* HV-cable to drive unit
* drive unit

I did change the parameters with the precharge relay closed (HV connected via the precharge resistor). Can this be the issue?

The question for me is, did I do something wrong (twice) or did I have a bad inverter (twice)?
Why does the UDC measurement fail after supplying HV?

I think I will open 1 of the inverters, and have a look at the UDC circuit (viewtopic.php?t=2345)

YouTube · Post by **johu** » Mon Jan 15, 2024 7:12 pm

Does the udc measurement come back when you drop back to 48V? What is the voltage on pin 1 (UDC_HI) at various bus voltages?

Lood wrote: ↑Tue Dec 19, 2023 2:01 pm One thing I did wrong was that I connected the gas pedal potentiometer the wrong way to the OI-board. At full throttle (no HV connected), the OI-board switched off and on again. After connecting the potentiometer correctly, the OI-board worked normally again.

Haha, I did exactly that a long time ago. It shorts out the 5V supply. Might damage the pot but not the board.

Lood · Post by **Lood** » Thu Jan 18, 2024 5:57 pm

johu wrote: ↑Mon Jan 15, 2024 7:12 pm Does the udc measurement come back when you drop back to 48V? What is the voltage on pin 1 (UDC_HI) at various bus voltages?

No, It doesn't come back at any voltage.

jrbe · Post by **jrbe** » Thu Jan 18, 2024 11:45 pm

Do any of the other analog inputs work? ( Like throttle, temp, etc.)

Lood · Post by **Lood** » Fri Jan 19, 2024 8:24 am

jrbe wrote: ↑Thu Jan 18, 2024 11:45 pm Do any of the other analog inputs work? ( Like throttle, temp, etc.)

Yes, the OI board seems to be working fine. All inputs are working, and when applying a voltage on pin 1 of the power-stage connector, I get an udc reading in the web interface.

Lood · Post by **Lood** » Fri Jan 19, 2024 10:29 am

What I don't understand is that if the inverters were already broken when I got them (so they were broken at high voltage), why did they work at first (when I tested them) at a low voltage?

When I applied a high voltage, the inverters stopped working. But after that, the inverters didn't work at low voltage anymore...

I don't understate it, so that makes me doubt that I am doing something wrong (destroying the inverters).

jrbe · Post by **jrbe** » Fri Jan 19, 2024 1:11 pm

Do the inverters turn the motor after this event and it's just the udc signal that's bad?

Similar threads of testing ok at low voltage then failing at operating voltage.

viewtopic.php?p=36622&hilit=Tesla+fail+ ... age#p36622

viewtopic.php?p=63286&hilit=Tesla+low+h ... age#p63286

Looks like udc floats to about 209v if it's not connected. Seems something is shorting out the signal in your setup(s).
viewtopic.php?f=10&t=3397

Lood · Post by **Lood** » Fri Feb 02, 2024 5:35 pm

I got another (3th) inverter, this time with drive unit.
This one also passed the diode test, and with a bench power supply the udc reading is working.

But now I am a little afraid to hook it up to HV.
So first, I want to check if the parts I didn't change are OK:

OpenInverter Board:
I have a V8 board,
* The 3.3V circuit is at 3,297V but the 5V circuit is 4,90V. Is this a problem? (I read in some topics that it should be just over 5V?)
* The soldering looks OK by visual inspection
* The board draws approximately 250mA with nothing external connected
* version: 5.20.R-sine
* I have changed the parameters with HV attached (the positive contactor was always open, but the precharge contactor was closed)
* How do I properly turn off the inverter? First, switch off 12V to the inverter, and then switch off HV?

Drive Unit:
This has worked at 48V (first run in April), since then, nothing has changed with this unit.
But now I have a second drive unit, so maybe test this new one first.

Battery/Precharge
Tested the precharge circuit with a light bulb. It seems to work OK

YouTube · Post by **johu** » Mon Feb 05, 2024 8:49 am

I'm a bit reluctant for advise because it is so strange. The odds of two broken inverters seem low. It must be something with your setup. Maybe try bringing back HV with a super high resistor.