We have an 1800 kW electric motor equipped with a CT BOX (Current Transformer Box) mounted on it. If we plan to operate this motor through a VFD (Variable Frequency Drive), will these CTs still be used or will they become unused?

 

depends.....does the CT box (I'm guessing that it measures current, since you supply only very sparse information) measure true RMS?

 

depends.....does the CT box (I'm guessing that it measures current, since you supply only very sparse information) measure true RMS?

Inside the CT Box, there are only six terminals and nothing else.
One of my colleagues mentioned that since the motor will be controlled by a VFD, this box is no longer needed and can be shorted.
After all, the drive itself provides the necessary protection, so it seems that the CT Box is not required anymore.

 

is the CT box the connection terminals for the motors? Normally "CT" means current transformers.
What can be, is that you have a 2 speed motor (Dahlander windings). In that case you wire it in the high speed connection and just drive it with the VFD with a ramp up so the low speed windings are not used anymore.

 

is the CT box the connection terminals for the motors? Normally "CT" means current transformers.
What can be, is that you have a 2 speed motor (Dahlander windings). In that case you wire it in the high speed connection and just drive it with the VFD with a ramp up so the low speed windings are not used anymore.

No, it’s not the motor terminal box. It’s clearly labeled “CT BOX” on it.

 

so does that mean this box contains the current transformers for measuring the motor current?

 

Sounds like you need to contact the vendor to insure the warranty coverage

 

That was also my first idea. But for some kind of reason many people here on the forum are afraid of contacting the (original) supplier of the equipment.