HELP! Robicon CSI Drive Problem... 'Over Voltage'... need troubleshooting advice...

Have an 800HP Robicon CSI drive (ID CSI 456980.00 fyi).. and when the drive runs at/above 44Hz I get over voltage faults. I've looked at the clamp voltage (at 43Hz ranged from 560s-910s). Last weekend changed all of the commutation caps, and clamp caps. (talk about joy! ).
Today we've replaced the power board.. same problem.

Symptoms.. at lower speeds (<=30Hz), the unit runs smoothly, though the clamp voltage fluctuates around 150vdc total range.
As the speed increases the beating becomes more pronounced... and by the upper 30s the drive essentially 'pulses'...


We've adjusted the ramp rates, and I/V gains (at different times). Still have the same issue...

Drive has run at similar speeds for years without incidence...


Any help would be greatly appreciated....


Russ

While the link was useful, I've been on the phone with Robicon/Siemens for days.. and have had their techs on site.
Since their techs/help have not been useful, I thought I would come here. I know there are many experienced techs here, who can offer assistance.
I'm waiting for them to reply.

There are others that could offer more probably but I will ask a few things and the offer some things.

I do not know this brand/model but since it uses CSI can I assume it is a current source inverter with regeneration? I assumed this partially from the comments you made about caps etc. CSI types are normally used for fan or pump applications, is that was is being done? I also assume this is using dual bridge IGBT's.

IF the above is true then I believe you could have a shorted diode OR a bad IGBT, the clamping will not work especially if an IGBT is faulty.

This link is about current source inverter and may offer assistance in troubleshooting, it would help if Robicon has a schematic and/or troubleshooting points for checking the diodes and IGBT's.
http://www.tf.uni-kiel.de/etech/LEA/dl-open/A22166_csiprotect_final.pdf

rsdoran said:

There are others that could offer more probably but I will ask a few things and the offer some things.

I do not know this brand/model but since it uses CSI can I assume it is a current source inverter with regeneration? I assumed this partially from the comments you made about caps etc. CSI types are normally used for fan or pump applications, is that was is being done? I also assume this is using dual bridge IGBT's.

IF the above is true then I believe you could have a shorted diode OR a bad IGBT, the clamping will not work especially if an IGBT is faulty.

This link is about current source inverter and may offer assistance in troubleshooting, it would help if Robicon has a schematic and/or troubleshooting points for checking the diodes and IGBT's.
http://www.tf.uni-kiel.de/etech/LEA/dl-open/A22166_csiprotect_final.pdf

Click to expand...

You're 90% correct in your assumptions. This is being used on a fan, and it is a current source inverter. But instead of IGBT's it uses SCR's. (The GTs use IGBT's which are much quieter...thankfully ).
From what I've seen, the incoming line power is solid (within 10% I/VAC). I've been wondering if an SCR could be failing ? Maybe a failing gate, or a reduced anode/cathode resistance? I'm not sure what could cause the clamp voltage to swing upwards of 300+VDC. It's a fascinating puzzle, and I look forward to finding the solution.
The motor sounds fine (except for the vfd pulsing that's coming through). The fan bearing temps are very low, and there have been no vibration issues.

I have a paper somewhere on SCR and technically I originally thought this may be an SCR unit from your original post. Now that you have stated that I would greatly suspect an SCR.

Technically the main difference between SCR and IGBT is switching capability, the principle is still the same.

The best guy I know of on Robicon current source drives is Lee Bates of Beverly Hills Michigan. His company name is AEM Inc. and the phone is 248.540.9500.

He has lived and worked with these drives for years and knows them backwards and forward.

I used to work for him 10+ years ago.

DickDV said:

The best guy I know of on Robicon current source drives is Lee Bates of Beverly Hills Michigan. His company name is AEM Inc. and the phone is 248.540.9500.

He has lived and worked with these drives for years and knows them backwards and forward.

I used to work for him 10+ years ago.

Click to expand...

AEM are good guys... and they've spent roughly 17hrs on site (so far).
After changing one of the scr banks (thanks for the recommendation) the drive can now run to 45Hz. This is an improvement.