Failure of control board in VSD

[maypot]

Hi,

We experienced a failure of one control board on our 700 A Ultradrive a few days after commissioning.There was a flash on the control card and one electrolytic capacitor appeared to be the cause of the flash. The control card is powered via the DC bus and the VSD is used to drive a fan.
The high inertia load of the fan means that the DC bus voltage is not constant due to the regenerative load. There is no brake chopper nor braking resistor installed on the VSD.
One of the cause of the failure of the control module could be a surge on the power line or the DC Bus.We did not monitor any fluctuation on either voltage or supply frequency.
It is also important to note that a similar drive, although on a diferent application , is operating well near the one which failed.
My belief is that the failure of the control card is due to a component failure and not the cause of outside parameters.
Any suggestion is welcomed.

Bob
If it is

 

[Skogsgurra]

Sounds more like regeneration due to too fast deceleration. That happens very often if you do not have a braking resistor and/or the deceleration ramp is fast.

There is also the possibility of wind-milling (fan being driven by air going up the duct). That also needs a braking resistor - or DC braking.

Gunnar Englund

http://www.gke.org

 

[sreid]

Fans may have a lot of inertia but also have a lot of drag. If the decel ramp is slow to moderate the fan is likely to continue to require power rather than generate it. The drive will also protect itself through an over-voltage fault if a high regen voltage should occur.

Ocams Razor; The simplist explanation that fits the evidence is preferred.

Most likely; Infant Mortality.

 

[jraef]

Maypot,
PDL had an internal grounding connection problem on certain sizes of Ultradrives some time back, and offered a retrofit kit to correct it. The symptom you describe sounds like what was happening. Contact your supplier and ask them for information on the "MkII notch kit". If they don't know, ask them to contact PDL and ask. It was in a service memo from late 2003 or early 2004.

If your VFD is newer than that it should have had that problem taken care of, but sometimes drives sit on the shelf for a while.

"Our virtues and our failings are inseparable, like force and matter. When they separate, man is no more."
Nikola Tesla

 

[maypot]

Thanks jraef for this valuable information. I will query the supplier.

Bob

 

[Hanter12]

I haven't had experience with PDL drives but I have encountered capacitor failures on control cards from other drive systems. Check the ripple on the DC bus. Usually
a 13 % ripple suggests a supply phase loss and could result in capacitor failures. Also, check the circuitry if there is a resistor circuit running in series with the DC BUS and control card. If so, check if this is faulty. As sreid mentioned the software would most likely have over-voltage protection so regenerative braking is unlikely the cause.