submersible pumps on VFD
submersible pumps on VFD
(OP)
Our client specification calls for an isolation transformer on LV VFD output side. This VFD is for the submersible pump application. Don't understand what the reason behind it. Any input would be appreciated.





RE: submersible pumps on VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: submersible pumps on VFD
RE: submersible pumps on VFD
Use either transformer or VFD with sine output, aka sinus drive.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: submersible pumps on VFD
RE: submersible pumps on VFD
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RE: submersible pumps on VFD
I have seen this practice a few times.
I also agree with jraef. Boosting the volts the the VFD if the bore depth is long is a means to ensure you have the right volts reaching the motor. Most submersible pumps require you to fit a sinewave filter on the output of the VFD (the motors used often have low insulation quality and need a sinewave/low dvdt) and this output filter will drop the voltage by a few %. This can be critical if the cable is long.
RE: submersible pumps on VFD
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: submersible pumps on VFD
RE: submersible pumps on VFD
In my opinion it doesn't really matter what we think, speculate the need for, or what you think is reasonable. Your client specified an isolation transformer, so, you should provide one.
Failure to provide one is a good way to inherit all sorts of large legal bills.
Keith Cress
kcress - http://www.flaminsystems.com
RE: submersible pumps on VFD
RE: submersible pumps on VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: submersible pumps on VFD
RE: submersible pumps on VFD
Another possible advantage in this instance was that the transformer driven pumps used 3000 Volt motors rather than 600 Volt motors.
This client should also know which Voltage was most advantageous.
Bill
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"Why not the best?"
Jimmy Carter
RE: submersible pumps on VFD
I don't think HamidEle is saying the isolation transformer will be left out or is arguing against it, they just want to know the reason for it in this instance.
RE: submersible pumps on VFD
RE: submersible pumps on VFD
It does, my mistake. HamidEle: I suggest you take the advice given...
RE: submersible pumps on VFD
RE: submersible pumps on VFD
RE: submersible pumps on VFD
RE: submersible pumps on VFD
Keith Cress
kcress - http://www.flaminsystems.com
RE: submersible pumps on VFD
In the 'make sense' category:
For a residual current ground fault detection scheme as used on many VFDs, the ground fault is detected because the three phase output current supplied to the motor does not sum to zero. Specifically, all of the current leaving the VFD through the three phase motor leads is not returning to the VFD through the same leads (Kirkoff's Current Law).
The assumption is that the 'missing' current is returning to the VFD through a different path than the three phase motor leads. That path is assumed to be an unintentional ground circuit from a faulted motor winding back through the (grounded) wye connection of the secondary side of the transformer supplying the VFD.
If you have a residual ground fault detection device of any type in the circuit between the grounded motor and the power supply (in this case VFD), then the it will trip.
Application of an isolation transformer (delta-wye) between the residual ground fault relay (drive ground fault circuitry) and the faulted motor will isolate the fault from the ground fault relay and prevent a trip.
Because Hamidele has not provided information abot what this pump is used for I cannot judge if the ground fault isolation is a good thing or not.
RE: submersible pumps on VFD