FLASH OVER INSIDE THE VSD BUT WHY ???

[sethar]

Hi there! I hope someone will be able to assist me about reasons & possible causes of flash over. I work at a Gas plant in Pakistan. Our plant commissioned just two year before in 2002 , there are many VSD installed but last week a ABB VSD to drive an induction motor 37 KW its service was Produce water disposal pump flash over found inside the VSD so due to flash main PCB ( we can say mother board ) found severe damaged. We are now trying to establish the cause for this. VSD mounted on the wall in the air conditioned switch room but not IP protected. On inspection / checking I found that the cooling air fan working normal. Do you have any ideas ? Thank you for your assistance.

[sethar]

In addition to above following actions are also taken:

 

1. We have been meggered the Motor & power cables found infinity.

2. PCB copper flashed l damaged.

3. No any capacitor found burst, physically these are in good condition.

4. The drive was on Auto.

5. On the outgoing IGBT single power terminal found severe spark but all the power terminal was very tight, no any loosness observed.

6. VSD incoming breaker was not tripped & power fuses found OK from switchgear.

[Guest]

Are the IGBTS mounted on the main PCB (What you call motherboard )

As you have stated that all the capacitors are healthy ( I believe ones on DC link and may be some on Power input filter section ), to cause a kind of severe damage on PCB as you state, only element left out is The IGBT it self .

In case of some problem in the firing sequence of IGBT, flash over may be caused . By the way which ABB drive do you use ,ACS ?

[GGOSS]

Hello sethar,

 

From your description of the fault it is difficult for anyone to give solid reason for the failure.

 

Are you able to post an image (jpg, gif etc) of the failure here?

 

If not please advise if you have identified any failed components.

 

Regards,

GGOSS

[marke]

Hello sethar

 

As GGOSS has already said, it is very hard for us to give a useful answer without a better idea of what has happened. A good photograph would certainly be a step in the right direction.

 

This sort of problem is usualy due to:

Moisture or water on the pcb - possibly condensation

Conductive or damp dust build up on the pcb - carbon is common

Ionised air passing through the drive - arcing elsewhere

High voltage high energy transients.

Component failure

This list is far from exhaustive, but it does cover the main causes.

 

Best regards,

[spkam]

Hello sethar

 

As GGOSS has already said, it is very hard for us to give a useful answer without a better idea of what has happened. A good photograph would certainly be a step in the right direction.

 

This sort of problem is usualy due to:

• Moisture or water on the pcb - possibly condensation

Conductive or damp dust build up on the pcb - carbon is common

Ionised air passing through the drive - arcing elsewhere

High voltage high energy transients.

Component failure

This list is far from exhaustive, but it does cover the main causes.

 

Best regards,

 

 

I also recommend you to check up for the following

 

1) IGBT failure can cause control card failure if directly wired ( ie without optical coupling)

2) Excessive pollution in the atmosphere , check for pollution classes G1,G2,G3,GX ????

3) Did any control voltage mix up happen?

[Carl]

If it is an IGBT failure...then it is not uncommon for the chopper section of the pcb to fail.......thats if it is not one of those smart power modules, which usually have the chopper section built in the power module.