Power Quality Meter On Inverter Fed Motor

Hi All
I Have a power quality meter that I have previously used on A DOL motor as a data logger. I want to do the same on two inverter fed motors. I know the PQ meter will not be accurate because of the PWM content of the drive output but I actually want to compare the two motors.
In this case would the readings be repeatable (ie if they vary with the pwm is it a predictable variation). This would allow a valid comparison of the two motors running through a mix cycle.

Thanks
Ian smith

why not just measure the input to the drive rather than the output?

Hi Myles
I had not thought of measuring the input to the drive but I suppose input=output x efficency. I will have to try that tommorrow.
At at the moment the energy usage value monitered by the Mixer control system comes out of the Drive control via a RIO link to the PLC. How accurately would the input power to the rectifier track the output power figure from the inverter as provided by the drive control system?

Cheers
ian

i would think the power figure the drive has would be accurate. what ttype of drive is it? there are many specific drive experrts on the forum who could answer that better than I. but how accurate do you need? if it is a comparrison between two motors i would think measuring the input with your meter would give you a pretty good figure.

cheers

myles

Its an Allen Bradley PowerFlex 700. I am also investigating using an OPC server to collect the data into Excel. But the PQ Meter is a lot simpler for me.

ian