Same load has different power factor when fed from different sources

[acolella]

I have some ECM fan motors that are running different power factors when fed from different sources. The motors are 230V single phase motors. The first source that they were fed from is a 600V/240V single phase step down transformer. When fed from this transformer I got the following measurements:

233.7 VAC
4.0 amps
653 watts
0.702 power factor
934 VA
-660 VAR
D 45.2° phase angle
6.06% THD voltage
94.3% THD current

The second source that they were fed from is a 480V delta primary 230V wye secondary three phase transformer. That isn't a typo either. This transformer has a 230V wye secondary. The exact same motors were tested and the exact same power analyzer was used to obtain the measurements. When fed from this transformer I got the following measurements:

236 VAC
5.5 amps
663 watts
0.51 power factor
1.296 kVA
-1.117 kVAR
D 59.2° phase angle
1.63% THD voltage
165% THD current

Has anybody ever seen this before? Why would the motors run a lower power factor/draw higher current at essentially the same voltage and power when connected to the three phase transformer?

 

[Joethemechanic]

Have you looked at the sine wave with an oscilloscope? Are there any harmonics on the 230 WYE trans that aren't on the other? What else is on each transformer? Do you have a lot of drives with 6 pulse front ends or some other rectification going on?

 

[Joethemechanic]

D 45.2° phase angle
6.06% THD voltage
94.3% THD current

D 59.2° phase angle
1.63% THD voltage
165% THD current

I think you are going to find your problem somewhere around here