Amp draw on 50hp VFD

[M_A_A]

The drive IS capable of displaying output amps(which was roughly 22-23 on the display). This was checked on the output leads with the clamp-on and measured really close to the readout.

Myself and the senior electrician just found it hard to understand how the input draw was as low as it was(2 to 3 amps/phase for such a large motor).

As I mentioned I am a little foggy on the theory of VFDs and 3amps in and 23 out just caught me off guard. I know motor loading has a lot to do with it though.

Can anyone suggest a good online resource for reading up on VFDs?

Thanks again,
Mark

 

[Besoeker]

The drive IS capable of displaying output amps(which was roughly 22-23 on the display). This was checked on the output leads with the clamp-on and measured really close to the readout.

Myself and the senior electrician just found it hard to understand how the input draw was as low as it was(2 to 3 amps/phase for such a large motor).

As I mentioned I am a little foggy on the theory of VFDs and 3amps in and 23 out just caught me off guard. I know motor loading has a lot to do with it though.

Mark

As mentioned previously, power factor is a big difference. In the input side of the VSD it might be close to unity. For some motors I have dealt with, it is lower than 0.1 on no load.
Unless you routinely deal with such things it can be quite a surprise when you make the measurements.