Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

meters for VFD drive measurements

Status
Not open for further replies.

spikeeeee

New Member
hello everyone

Am using a kelly induction motor controller KIM7210. It generates a three phase AC from a 72Volts DC power supply.
I tried to measure the parameters like voltage ,current and frequency using my protek multimeter. But when i do the calculations
based on the input and output values there is a huge efficiency contradiction. So am planning to buy a new digital multimeter which would display the accurate value of the voltages ,current and frequency of the three phase waveform. The voltage i want to measure is a 40Volts 3 phase AC and Maximum current of about 50Amperes.

So please suggest me a good meter which will have the low pas filter capability which would be immune to supply noise and would
display the accurate values of the above said parameters. And also tell me whats your view on using fluke87V and Fluke 289 for vfd measurements.
 
The output of the vfd's we use aren't filtered beyond what is necessary to prevent interference. Therefore, with the exception of analog panel meters which lack resolution, we have to employ additional filtering to get accurate vfd measurements with every meter we've got (including Fluke 87, 89, 189, and 289's.) Our amperage measurements are good but our voltage measurements are always skewed high without it, sometimes by as much as 200% at lower rpm's/voltages.

After all, how is the meter to distinguish whether you want the rms voltage associated with the modulated 25-100Hz AC output or the 16KHz AC used for the modulation? We find ours try (and fail) to accurately display the 16KHz rms value.

I believe the box I hook up to our DAQ system uses 10K 1W flame proof resistors between each phase and the 5B module inputs with 0.01µF 250VAC Y1 or Y2 safety caps between the inputs and earth ground. They remove enough of the 16KHz switching frequency to get usable 25-100Hz data.

It also works for the digital multimeters but they can't be used to reveal how well the drive is compensating for load disturbances as well as the DAQ system can. ;)
 
Last edited:
I'd look at www.fluke.com and get something for that specific task. You have lots of issues going on. There is the voltage and current waveforms and power factor issues which will not be easy to measure.

I forget the company I used for a power meter. They were able to measure at low voltages. We used a 3 phase meter for single phase AC down to nearly 20 V or so without issues. They are of utility quality. Current is CT transformer based. But this was 60 Hz. I doubt it could do high frequency.

Remember that AC input current could be just as bad. There is a good chance that the unit has a power factor controller in it.
 
Last edited:
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top