OT - Getting rid of induced voltage

[iant]

I understand that you have a single conduit with all cables in that conduit.
All VFD manufacturers recommend that the motor is shielded correctly.
Your supplier will be well aware of this. I would say they are trying to pull the wool over your eyes.
you need to either shield the control or the motor wiring.
Even install a second conduit.
Earthing the conduit is not a shield nor should it be.
the Relay is an Idea, as you need speed only use the Coil - not the contacts.

 

[vu2gmc2000]

induced voltages

thanks, will try it.

narayan

 

[Lancie1]

3. Used a shielded cable for the motor and put inside the conduit. The problem disappears.

Firstly, the inverter is part of the motor supply so I cannot use that as an excuse.

It seems you found the solution. Noise problems from inverter drives are well-known so this is NOT an excuse, but a reality that you have to work around. Like Okie says, use the special VFD-rated shielded cable if you can get it. It is designed to prevent the noisy VFD varying voltage from interfering with nearby cables and equipment.

PS: I wonder what Bob did about the original customer problem back in 2007? He mentioned the best solution in his first post - not using multi-core unshielded cables to power a bunch of 24 VDC motors.