I've got a VFD for a Pentair Superflo VS pump that takes either 120 or 240 volts (single phase) to drive a three phase motor (at 120 or 240-ish volts)... but I don't have the motor and I'd like to measure the output voltage/frequency and also see if the drive works at all.
My questions are:
1. My Fluke 87-3 has no VFD/LPF function so I'm assuming an ac voltage reading would be off, but I'm pretty sure a frequency reading would also be off... is that true?
2. I'd like to hook up a load to test the drive... in this post (
https://www.eevblog.com/forum/beginners/can-anyone-make-sense-of-this-vfd-waveform/msg3247882/#msg3247882), seanb suggested using 3 incandescent bulbs in a star (wye) configuration as a load, but my inverter only has 3 output terminals (i'm assuming the ground is a mechanical connection to the casing)... doesn't a star require a neutral? Should I use a delta configuration instead?
Fyi the drive looks like this:
https://bestpoolshop.com/product/pentair-superflo-vs-pump-drive-only-kcca0192-0002/Thanks for any input!
and I'd like to measure the output voltage/frequency and also see if the drive works at all.
Why would the VFD not work?
but I'm pretty sure a frequency reading would also be off... is that true?
Very likely.
seanb suggested using 3 incandescent bulbs in a star (wye)
Star oder delta-connection doesn't matter, it depends on the nominal voltage of the bulb. With star-connection you are on the safe side.
but my inverter only has 3 output terminals
As every VFD.
i'm assuming the ground is a mechanical connection to the casing)
Correct.
doesn't a star require a neutral?
No. Neither with light bulbs, nor with actual motorwinding-star-connection (has to be always left isolated). This is also true for line-powered "star-loads", if they are symmetrical of course.
You can estimate the error for frequencies above 50Hz from the fluke manual. The 87b has an input impedance of 10M.
If an lpf is needed add a simple RC section. Make sure the capacitor is "class X".
If you keep R under 10k the error is very below the cut off frequency.
Thank you both for the replies
Why would the VFD not work?
I repair a lot of Pentair pool automation boards, and this inverter came in a box containing some damaged items so I'm just assuming there's an issue with it - there's a chance it's fine.
No. Neither with light bulbs, nor with actual motorwinding-star-connection (has to be always left isolated). This is also true for line-powered "star-loads", if they are symmetrical of course.
Thank you for clearing that up for me!
and Terry thanks for that diagram... I was interested in making my own filter but wasn't super confident (not sure why?). I should have just built one and checked it with a signal generator and a scope first (although my 1054z has a 1M input impedance vs the Fluke's 10M). +1 for class-x caps!
Just get a motor. VFDs are literally not supposed to be used for anything else but drive motors. There is not much you can test, and unnecessary tests are not only waste of time because they just mislead you, they also pose a risk you do something which damages the VFD or get hurt yourself.