VSD output damage
VSD output damage
(OP)
We have the output damaged on a VSD driving a 1200kW cyclone pump on a mine. After three weeks of operation the drive did not restart after it was switched off. The power unit on the white phase had burn marks on and the fuses driving the power unit from the dc bus were open. Can this of been caused by back emf from the motor when stopped? The motor turns backward when stopped from the water header pressure that comes back down after the motor stopped. PS: There is no contactor between the output of the drive and the motor - only at the input.
Please help!!
Please help!!





RE: VSD output damage
I am assuming an induction motor and a standard PWM VFD. If you have a synchronous motor and some other VFD, there are other options to get the VFD damaged. A WRIM motor with a cascade control adds even more possibilities. Which type of motor and drive do you have?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VSD output damage
There is no check valve :/
Its a vacon drive (PWM) with teco motor (standard induction motor - 4pole)
The drive stop has been set to coasting stop - not ramped.
Kevin Bosch
Rainbow Technologies
RE: VSD output damage
So the pump is going to force the motor to turn continuously after the drive stops or just long enough to drain the pipe back down to zero head?
The DC bus fuses blew too.<sigh>
Can you slow the motor to the point that the flow thru it is not supported but the pump is still being driven. At some point the flow thru the pump would reverse and drain the pipe while still controlling the motor. Once there's no column left you should be able to zero the drive and shut it off.
Alternatively use a valve and bring the flow way down then manually turn off the valve as fast as you can and then zero the VFD.
You should really be using a check valve that you slow the pump down until the flow just stops and the check seats. Then you zero out.
Keith Cress
kcress - http://www.flaminsystems.com
RE: VSD output damage
Contactor on output of VFD would have this functionality:
1 On Estop would open up after ramp down of VFD.
2 During normal stop the contactor would open up after a predetermined amount of time after ramp down.
3 When the start button was pushed the contactor would be pulled in, then the enable to the drive would come on.
This assumes that the VFD is in ramp mode on stop. If doing this make sure that the ramp is long enough that there is no overvoltage on the VFD.
RE: VSD output damage
Keith Cress
kcress - http://www.flaminsystems.com
RE: VSD output damage
No ramp-to-stop either, the OP said it coasts down.
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If we learn from our mistakes I'm getting a great education!
RE: VSD output damage
Would a ramp down help the situation? We are getting new parts airfreighted and we would hate to fry them (and our jobs!!)
My understanding was that it could be the rapidly collapsing field on a coasted stop, or the "generating" action when the motor spins backwards. We cannot put a check valve on a slurry line.
Sigh.....
Kevin Bosch
Rainbow Technologies
RE: VSD output damage
I know a Vacon chap in Europe (if that is where you are, time zone indicates EU or Africa) that can help you out with the details. He is with Vacon Stockholm. I also have a very good contact in Vaasa, Finland (Vacon HQ).
But do not just fix it and blow it again. That would definitely be bad.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: VSD output damage
I would recommend what gunnar is saying braking resistors. It would dump all that excess energy during gen on the motor. Above is a manufacturer of braking resistors, excellent literature to know what you need, in the USA, but not available in europe. Might get you started in right direction. I would think ABB, Siemens, or some other manufacturer of VFD that you have can recommend a local source.
That way you get the right sizing on the braking resistor with the right resistance for the load that you want.
RE: VSD output damage
Slight aside: I picked up some info from a US resistor manufacturer called Mosebach a little while ago - any comments on their products anybody?
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If we learn from our mistakes I'm getting a great education!
RE: VSD output damage
" It would dump all that excess energy during gen on the motor"
Not sure if it is just your terminology but you don't dump it to the motor if brake resistors are connected to the brake chopper, the energy is 'dumped' into the resistors and dissipated in heat. If it is an active front end then the energy is returned back into the AC supply.
RE: VSD output damage
Looks like both sources given are in bed with each, claiming they are sister companies.
Cressall Power Resistors is out of the UK and is on this site, might get support out of them for braking resisters.
RE: VSD output damage
But leaving the VFD output on to decel (ramp down) and then providing someplace for the regen energy to go should solve the problem regardless.
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