VSD and circuit breaker
VSD and circuit breaker
(OP)
Hi all.
If one has the following scenarion:
Supply network->VSD->transformer->cable->motor. Is it possible to utilise the VSD as a protection against short circuits? Or should one have the following solution:
Supply network->VSD->transformer->Circuit breaker->cable->motor
Help is appreciated.





RE: VSD and circuit breaker
Please note if you interrupt the wiring between the motor and VFD you can damage the VFD.
VFD's typically shut themselves down if they detect the motor wiring is open or shorted, but it's not a code-approved overcurrent device like a breaker.
VFD's also typically provide overload protection to protect motors from long periods of slightly (typically 125-140%) elevated current, but again this doesn't replace breakers.
RE: VSD and circuit breaker
Supply network feed->CB->VSD->transformer->Disconnector/earthing switch->cable->motor?
RE: VSD and circuit breaker
What voltages are we dealing with anyway? I am not sure how a drive would work with a transformer.
Typically I have seen just a safety disconnect at the motor, the drive providing the protection for the cable and motor. (and in this case the TX)
RE: VSD and circuit breaker
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RE: VSD and circuit breaker
Transformer->CB->VSD->Cable->Motor
The CB will protect 'upstream'. i.e. the transformer and the VSD should protect itself if the motor or motor cable encountered a short circuit.
RE: VSD and circuit breaker
The client has chosen this system. It confuses me too.
Supply network feed->CB->VSD->transformer->Disconnector/earthing switch->cable->motor
I have heard that the VSD should not be used as a protection of the cable, so how will this protection scheme be?
Could you also explain why the VSD will be damaged, if one closes the disconnector while the VSD is energized?