Measure current of each phase from VFD output.

Hi all.

Will something like this work on a VFD output ?
Carlo Gavazzi E83-2050
The VFD output frequency will be between 45-55 Hz. I know that its switching frequency will be in the 4-10 kHz range.

If the Carlo Gavazzi device wont work, do anyone know an alternative that does ?

Thanks in advance !

No answer as to whether or not it will work, but I'm assuming since you're asking about CTs that pulling it out of the drive over the network is not an option?

Because the output is non-sinusoidal most measuring devices don't work well on the output of a VFD, although I can't speak to your specific question. In my experience, the drive itself is the best measurement source for output current.

mylespetro said:

[..]I'm assuming since you're asking about CTs that pulling it out of the drive over the network is not an option?

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Tom Jenkins said:

In my experience, the drive itself is the best measurement source for output current.

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Unfortunately the drives I use (Siemens G120) only measure current in 1 phase.

Tom Jenkins said:

Because the output is non-sinusoidal most measuring devices don't work well on the output of a VFD, although I can't speak to your specific question.

Click to expand...

There are clamp-ammeters that are 'true RMS' rated, so I am thinking that maybe there are DIN rail transmitters that are as well.

I have to correct myself, the Siemens G120 actually do measure the 3 phase currents.
So it is probably the easiest solution to get the data out via Profinet.

JesperMP said:

Unfortunately the drives I use (Siemens G120) only measure current in 1 phase.
There are clamp-ammeters that are 'true RMS' rated, so I am thinking that maybe there are DIN rail transmitters that are as well.

Click to expand...

In addition, it needs to have a low-pass filter. You can (and do!) get wildly different VFD readings from a Fluke 323 and 376FC, for example. Measuring in series, an 87V will outperform a 117 for the same reason.

There is a company that makes devices that do a really good job of measuring motor current even when VFDs are involved. A former employer used them on older drives that did not have a reliable output power monitoring capability. They measure volts and amps on all three phases for their UPC series. I didn't look at all their products to see if they offer one that will output a signal for each phase current, but the precision with which that food company could calculate product temperature based on viscosity as measure by a Load Controls UPC was impressive. We could tell how cold the batch was within 0.5 degree F.

https://www.loadcontrols.com/products/