Axpert 5kw AC converter stage

[AndrewF]

Hi there, is there a way to test waveform signal to IGBT drivers without drivers installed , to confirm correct waveform etc to avoid damaging new IGBT drivers. There are 5 drivers, are they all part of the AC conversion circuit.

[Coulomb]

Do you mean drivers or devices?

As far as I know, if the new devices are not yet soldered in, you can't damage the drivers if the waveform out of the DSP is wrong. [ Edit: And it would be very unusual for that to happen. ]

Of course, if the devices are installed and soldered in, and the driver components are faulty , then you could damage the devices (IGBTs), which in turn could damage the driver components.

I don't have time to check right now, but I'm pretty sure I mention testing the driver outputs (gate signals) using multiple bench power supplies in the AEVA repair and update topic.

Edited April 23, 2023 by Coulomb
Reworded for clarity.

[AndrewF]

Hi ok so ive replaced the faulty opto isolators in the sine wave converter circuit, as well as the diodes linking the opto isolator outputs to the gates of drivers, I'm only getting sine wave on QA1 & QB2. 

Ant ideas  ??

[AndrewF]

oh and all gate drive 47ohm resistors replaced

[Coulomb]

6 hours ago, AndrewF said:

I'm only getting sine wave on QA1 & QB2. 

It's normal to see a 50 Hz square wave on the neutral IGBTs. The actives should see "rectified" 50 Hz sine wave envelope on 19 kHz square waves.

[AndrewF]

On 2023/04/29 at 6:41 PM, Coulomb said:

It's normal to see a 50 Hz square wave on the neutral IGBTs. The actives should see "rectified" 50 Hz sine wave envelope on 19 kHz square waves.

Hi Coulomb QC1 has the square wave, QD2 has nothing , the optos have been replaced(measured resistance between gates and pin 6 on optos & resistance/connection is ok, have you had similar issues like this .....

[AndrewF]

On 2023/04/29 at 6:41 PM, Coulomb said:

It's normal to see a 50 Hz square wave on the neutral IGBTs. The actives should see "rectified" 50 Hz sine wave envelope on 19 kHz square waves.

Hi Coulomb i cant find schematic showing the control board that sends sine wave(i assume) to main board, sine wave which passes all protection circuitry before reaching the gates of the drivers..., to trace where the signal is lost on QD2 

[BritishRacingGreen]

45 minutes ago, AndrewF said:

Hi Coulomb QC1 has the square wave, QD2 has nothing , the optos have been replaced(measured resistance between gates and pin 6 on optos & resistance/connection is ok, have you had similar issues like this .....

When you read nothing, do you mean nothing on logic side of the opto driver, or nothing on the igbt gate. If the latter, what is nothing, 0V or - 5V? . On the igbt there are 2 gate supplies 15V for turnon and - 5v for turnoff. 

[Coulomb]

11 hours ago, AndrewF said:

have you had similar issues like this .....

No, sorry.

10 hours ago, AndrewF said:

i cant find schematic showing the control board that sends sine wave(i assume) to main board,

That's one part of the inverters that I don't have a schematic trace for. I've started on it a few times, and run into problems with tracks running under big components and not being able to figure out where they go. There are mysterious D flip-flop chips involved, and I don't know what they do.

I note that all the outputs from the control board are open collector, so they will appear to have no output if you don't have a pull-up resistor, or any of the pull-up resistors on the main board are faulty (there are three involved for each PWM output; 2 x 500Ω, 1 x 1kΩ). If there is a problem on the control board, it pretty much has to be one of:

* The open collector driver, ULN2003 from memory

* The D flip-flops or associated diodes and resistors

* The DSP itself (pray that it's not that).

[AndrewF]

On 2023/04/29 at 6:41 PM, Coulomb said:

It's normal to see a 50 Hz square wave on the neutral IGBTs. The actives should see "rectified" 50 Hz sine wave envelope on 19 kHz square waves.

Hi Coulomb i cant find schematic showing the control board that sends sine wave(i assume) to main board, sine wave which passes all protection circuitry before reaching the gates of the drivers..., to trace where the signal is lost on QD2 

[AndrewF]

The DSP itself (pray that it's not that).

I plugged the processor board into another identical inverter and it works fine its something on the main board  but you have given me plenty to check and work on , thanks so much this far down the road......

 

[AndrewF]

On 2023/05/02 at 5:25 AM, Coulomb said:

I note that all the outputs from the control board are open collector, so they will appear to have no output if you don't have a pull-up resistor, or any of the pull-up resistors on the main board are faulty (there are three involved for each PWM output; 2 x 500Ω, 1 x 1kΩ). If there is a problem on the control board, it pretty much has to be one of:

Hi Coulomb, i cant find the resistors mentioned(there are three involved for each PWM output; 2 x 500Ω, 1 x 1kΩ) on  the main board are they in the area supplying signals to the optoisolaters in the AC conversion circuit.

[Coulomb]

26 minutes ago, AndrewF said:

i cant find the resistors mentioned

On the models I'm familiar with, they are like these (R2, R3, R5):

It must be the first part of the circuit that they designed, with the very low designation numbers (U1, Q1, R2, etc).

From this part of the traced schematic:

 

[AndrewF]

On 2023/05/02 at 5:25 AM, Coulomb said:

I note that all the outputs from the control board are open collector, so they will appear to have no output if you don't have a pull-up resistor, or any of the pull-up resistors on the main board are faulty (there are three involved for each PWM output; 2 x 500Ω, 1 x 1kΩ). If there is a problem on the control board, it pretty much has to be one of:

Hi Coulomb, i cant find the resistors mentioned(there are three involved for each PWM output; 2 x 500Ω, 1 x 1kΩ) on  the main board are they in the area supplying signals to the optoisolaters in the AC conversion circuit.

[AndrewF]

Coulomb top message an error

 

[AndrewF]

the opto isolators i used were TLP350 which has a fet and fet config , as apposed to transistor and fet config in T350, would this device be a problem.

[Coulomb]

6 hours ago, AndrewF said:

Coulomb top message an error

Sorry, I don't understand this.

6 hours ago, AndrewF said:

the opto isolators i used were TLP350 which has a fet and fet config , as apposed to transistor and fet config in T350, would this device be a problem?

It's possible that the bipolar transistor can source more current than the FET. Compare drive current specifications between the two data sheets.

[AndrewF]

Hi Coulomb, its strange how the cap across the opto isolator AT350v driving the IGBTs in the AC stage is 820nf in the model you made a circuit of and the model I'm busy tracing faults on the cap is 100nf 

[Coulomb]

11 hours ago, AndrewF said:

strange how the cap across the opto isolator AT350v driving the IGBTs in the AC stage is 820nF...

SMD capacitors are unmarked. That value will likely be from Maxo measuring it in-circuit, in which case all the parallel components will have affected the measurement. So those capacitor values are to be taken as a very rough guide only.

Also, the value of those bypass capacitors isn't critical. It's possible that they ran out of 100 nF capacitors and used 82 nF instead. The 820 nF may be a typo.

[AndrewF]

8 hours ago, Coulomb said:

SMD capacitors are unmarked. That value will likely be from Maxo measuring it in-circuit, in which case all the parallel components will have affected the measurement. So those capacitor values are to be taken as a very rough guide only.

Also, the value of those bypass capacitors isn't critical. It's possible that they ran out of 100 nF capacitors and used 82 nF instead. The 820 nF may be a typo.

yes a typo makes a lot of sense as 82nf is a realistic replacement/substitute, Thanks so much for your input and efforts BTW , much appreciated... 

[AndrewF]

On 2023/05/07 at 3:51 PM, Coulomb said:

On the models I'm familiar with, they are like these (R2, R3, R5):

It must be the first part of the circuit that they designed, with the very low designation numbers (U1, Q1, R2, etc).

From this part of the traced schematic:

 

Hi Coulomb, on these same opto's U1 & U3 , I have measured on a working unit , voltage @pin 8 is around pos15V and voltage @pin 5 is neg 5V, on the faulty unit U1 pin 8 is 20V instead of 15V and pin 5 is 0,4V instead of neg 5V,  and on U3 pin 8 is 4,8V and pin 5 is neg 15V.

what normally regulates these voltages at the output of the opto's.

many thanks again for all your assistance....

[Coulomb]

20 hours ago, AndrewF said:

what normally regulates these voltages at the output of the opto's.

It's just these zeners and resistor, smoothed / decoupled by the capacitors. The problem could in decreasing order of likelihood: ZD2, R10, or C39:

[AndrewF]

1 hour ago, Coulomb said:

It's just these zeners and resistor, smoothed / decoupled by the capacitors. The problem could in decreasing order of likelihood: ZD2, R10, or C39:

thanks Coulomb, ZD2 is cracked, what is the value of C39, possibly100n

[AndrewF]

2 hours ago, AndrewF said:

thanks Coulomb, ZD2 is cracked, what is the value of C39, possibly100n

Hi Coulomb the value of C39 ? 

[Coulomb]

12 hours ago, AndrewF said:

what is the value of C39, possibly100n

Hard to tell with those very high permittivity ceramic capacitors. I measured 1 μF on my spare board.