We have a machine with one VFD which feeds a common bus to 10 high speed spindle motors, all operating at the same frequency - this bus is enabled continually, with individual relays operating as dictated by the plc outputs of the machine.
Occasionally this bus goes dead but the VFD reports that there are no errors, therefore the plc does not recognise a fault and the machine continues to operate, however the spindle motors do not spin and we have mechanical breakages as a result.

I would like to fit an indicator of some sort to the common bus to either indicate to the machine operator that all is good to continue, or fit a 'relay' to drop out if this bus goes dead. I could then wire the relay contacts to the VFD healthy circuit.

If you have any advice on this, I would be grateful.
Thank you
Chris

 

a voltage relay on the bus feed, or on each motor may prove useful.

 

a voltage relay on the bus feed, or on each motor may prove useful.

Yes, I thought this, but what can I use? I'm not sure a simple relay would work due to the complex nature of the output voltage.

 

A voltage sensing relay rather than a simple relay:
https://broycecontrol.com/product/lmcvr-500v/

 

Thats brilliant !
Thank you so much, I will give it a try.

 

Make sure the specifications of the voltage sensing relay is suitable for your application, check with relay supplier if unsure. The VSD will have a high frequency output, probably 4kHz