400Hz Converter Repair

[tccotham]

Hi,
I've been asked to help fix a 400Hz converter that has been sitting unused for a couple years. Upon inspection I found several burnt resistors and damage to connected components. I'm looking for troubleshooting advice to find the cause and prevent burning up any new parts.

Other than the 6 burnt resistors I've found 2 shorted snubber capacitors. The large blue capacitors aren't giving any capacitance reading so I guess I'll need to replace them as well.

 

[Martaine2005]

I’m afraid your information means nothing.
We know it’s a 400Hz converter because you told us.
Is this aviation?
Pump or motor drive?
You’ll need to supply much more information.
Blue capacitors? Where?
Our crystal balls still have ‘social distancing’ and a mask. So are of no use.

Martin

 

[Martaine2005]

Apologies, you seem to have tried inserting an image.
One of the moderators may be able to find the picture via a link but it’s best to try again. Keep the image to approx 300kB as that seems to work on this forum.

Martin

 

[bertus]

Hello,

Your picture was way to large (2.6MB).
Pictures of about 300 kB are fine.
I have resized the picture:


Bertus

 

[tccotham]

I’m afraid your information means nothing.
We know it’s a 400Hz converter because you told us.
Is this aviation?
Pump or motor drive?
You’ll need to supply much more information.
Blue capacitors? Where?
Our crystal balls still have ‘social distancing’ and a mask. So are of no use.

Martin

 

[tccotham]

Yeah apologies, uploading pictures doesn't seem to be working from my phone. It converts facility power for testing aviation equipment.
Abacus controls part# CID 961022-12KW

 

[Martaine2005]

Thanks @bertus
Any info on actual image size for the forum?. Limits?.

 

[Martaine2005]

First of all, I have no knowledge of aviation equipment.
That said, it’s electronics, right?.
How have you identified a short on the blue caps? Have you disconnected them and tested out of circuit?.

Martin

 

[tccotham]

First of all, I have no knowledge of aviation equipment.
That said, it’s electronics, right?.
How have you identified a short on the blue caps? Have you disconnected them and tested out of circuit?.

Martin

No short on the caps. They are two 10k μF, 300V caps connected in parallel. They seem to be at the center of everything that blew up. Capacitance reading is OL and resistance builds up to 1 MΩ

 

[tccotham]

No short on the caps. They are two 10k μF, 300V caps connected in parallel. They seem to be at the center of everything that blew up. Capacitance reading is OL and resistance builds up to 1 MΩ

And yes that is out of circuit

 

[Martaine2005]

Those black duel diode boxes? have you checked?.
Not sure what they are. But if one or the other diode failed short circuit, you’d have a problem.
Can you give us clearer photos. They should check as diodes across the shown terminals.

Martin

 

[tccotham]

Those black duel diode boxes? have you checked?.
Not sure what they are. But if one or the other diode failed short circuit, you’d have a problem.
Can you give us clearer photos. They should check as diodes across the shown terminals.

Martin

 

[tccotham]

These came up as "snubber capacitors" when I looked up the part number. I tested all three out of circuit and the diodes do appear to be shorted for all of them. Just want sure if this was the original fail or a symptom.

 

[Martaine2005]

If they have failed (shorted), that is normally where you ask why.
Check for a short before , anything? If not, check upstream. Anything?.
Diodes and capacitors do cause 80% of problems.

Martin

 

[tccotham]

Alright will do. Probably won't make it over to that building until Monday but I appreciate the help.

 

[Martaine2005]

Also, don’t assume anything. A simple resistor can die shorted.
If possible, check all you can ‘out’ of circuit.
Ps. This isn’t for an airline? Please don’t do this at 35,000ft

Martin

 

[tccotham]

Haha no, this doesn't actually touch anything that goes in the air. If it did they certainly wouldn't let me try to fix it.

 

[Martaine2005]

Haha no, this doesn't actually touch anything that goes in the air. If it did they certainly wouldn't let me try to fix it.

You’d be surprised.