3PH Power Logger, Drive Output

W@ttson

W@ttson

Senior Member
Location
NJ-USA
Occupation
PE
Hello,

I have two 3 phase power loggers. They are from two different manufacturers. I attached each to the output of a drive to measure 3 phase voltage, current, power to a motor.

Each power logger agrees with the other until the frequency is reduced to change the motor speed to 20% of rated speed. At that time, one power loggers current measurements jump to a really high value while the other manufacturers current measurements stay constant.

Anyone have any idea why?

Anyone have a particular meter that they would recommend on the output of a drive to simultaneously datalog 3 ph voltage, 3 ph current, 3ph power to the motor?

Thank you
 
One of the loggers is probably integrating the current measurement and the other grabbing peaks.

To answer the second question, I won't try. You should be able to get power info out of the VDF itself, or you could put loggers on the line side and correct for the slight inefficiency of the drive itself.
 
Measuring power on the output of a drive is a complex endeavor, not to be taken lightly. The output of a drive is not a pure sine wave, it is a series of high speed DC pulses and the gaps between them to affect how an induction motor reacts to them AS IF it was getting AC power. Data loggers are not typically designed to properly interpret these pseudo-sine waves. I always suggest using the drive data, because the complexities of doing this accurately are part and parcel to making the drive function correctly, so they are already doing it. If your VFD is not giving you the info you need, spend the money on a better VFD rather than a super expensive data logger.
 
I just don't understand why I can put a hand held meter with Lo (low pass filter) on the output of a drive and get correct current data. I can do similarly with a handheld for voltage but the expensive powerlogger that I use somehow falls short.
 
ptonsparky said:
I'm not sure why the data from the drive would be questioned. (Ignoring the issue with VFDs and the Iranian nuclear program of a few years ago)
Even my low-end drives can display the data you are looking for.
But if you have the spare $8,000.
Click to expand...
Low end drives can display but likely won't make a log of much more than maybe fault history.

If the drive is capable of network connections there may be software that can connect to it and log such data though.

I think the last A-D drive I set up had an USB and RJ45 ports on it. Not sure what functions can be used through them though. Would think one could monitor current drive status though and the ability to log things would be dependent on software capabilities.

That drive was likely not one of their lowest end drives.
 
Exactly, looking to log all those values and have an external verification at the same time. This way in the future the data at time of commissioning can be referenced as a baseline.
 
I am doing it now with a GS20 drive, an EA9 HMI and a CLICK plc. Not the exact data the OP wants but I could. It saves the days data to an SD card. I can have it Email me or whoever the heck wants one, a daily CSV file.
DateTEMP DIFFVFD ON AMPON HZWATER PRESSURE
1/21/2025 0:00​
0.900001526​
3.064999938​
41.35499954​
47.88999748​
1/21/2025 0:00​
0.300003052​
3.094999909​
41.66500092​
47.88999748​
1/21/2025 0:00​
0.200004578​
3.039999962​
41.42499924​
47.88999748​

ETA: It took some time but less than $2000. I needed the VFD anyway so don't even count that.
 
ptonsparky said:
I am doing it now with a GS20 drive, an EA9 HMI and a CLICK plc. Not the exact data the OP wants but I could. It saves the days data to an SD card. I can have it Email me or whoever the heck wants one, a daily CSV file.
DateTEMP DIFFVFD ON AMPON HZWATER PRESSURE
1/21/2025 0:00​
0.900001526​
3.064999938​
41.35499954​
47.88999748​
1/21/2025 0:00​
0.300003052​
3.094999909​
41.66500092​
47.88999748​
1/21/2025 0:00​
0.200004578​
3.039999962​
41.42499924​
47.88999748​

ETA: It took some time but less than $2000. I needed the VFD anyway so don't even count that.
Click to expand...
If this is for your well like I think it probably is, I'm impressed with the water pressure column being so precisely the same in each row. Though not sure what the same time stamp is about for each row.
 
so that future me and other people that are looking for this solution have more to go by, I got talking with Fluke and their best recommendation was to use a ScopeMeter. Similar to this one: Fluke MDA 550

It doesn't do exactly what I had hoped which is take in 3 ph currents and 3 phase voltages at the same time and datalog them but this will get down to DC frequency all the way up to some ridiculous MHz range and at least do 3 voltages and a current at one time. It should also be able to give a watts output. I haven't tried it yet but a friend of mine has a similar scope meter and was able to get watts on his.
 
W@ttson said:
This is to confirm acceptance of the drives data. Need an external source to confirm the data we receive is correct. I was thinking something like this would do it (not what we used): https://www.fluke.com/en-us/product...Qpl5J46oAfLyaq0syCTJdY7KiQ60emZtma5cOUcGpgpzK
Click to expand...
Haven't used the one you showed but I suggest fluke 1736. I've hooked it up to the load side of the motor VFD last year to do diagnostics, it read everything perfectly. But it depends what you want to test
 
Last edited:
Tainted said:
Haven't used the one you showed but I suggest fluke 1736. I've hooked it up to the load side of the motor VFD last year to do diagnostics, it read everything perfectly. But it depends what you want to test
Click to expand...
Did you datalog at frequencies lower than 20Hz?
 
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