400VAC / 60Hz supply into a PF525.

I have a (*) PowerFlex 525 being supplied with 400VAC, 60 cycle, 3-phase. This is not a type-o, this is accurate.

Now, the drive clearly states that this is acceptable, since it has a wide range of input power. So, that’s good.
And, when I go online to the drive, sure enough, the DC Bus is ~545VDC, versus the traditional ~650VDC. Again, expected and good.

However (there’s always a however)….

This drive is connected to a motor with a nameplate that gives both 400V / 50 cycle and 460V/60 cycle nameplate values. (An SEW gearmotor).

The OEM decided to enter in the nameplate values for a 460V motor, and the drive does run.

Also in play here is the fact that that the OEM somehow thought to underspeed the gearboxes, meaning that in normal running, the drive is commanded to speeds in the 70HZ to 90HZ range. This is a mystery to me..because of the economy of scale, perhaps this is more closely engineered than it first appears. (I cannot verify this, unfortunately)

So, it seems to me, a few things:
#1: We need to de-rate the possible horsepower that the drive can actually deliver. Obviously, this is working, since the system is working and the loads are being driven with no apparent degradation in performance. See above, for all I know, the OEM took all this into account in the design phase.

My question is: Even though the motor has two ratings: 400VAC/50HZ/1450RPM and 460VAC/60HZ/1762RPM, which rating is the correct one for the NP values in the drive?
I ask because it seems better to hold the voltage at 400 when moving past base speed..but I might be wrong, as I am more and more these days.

Offhand, I don't think it matters which set of nameplate values you use as long as you enter the same set of voltage/current/HP/Hz. Have you checked the PF525 manual to see about derating it because of the input voltage? I know you have to dramatically derate it to run with a single phase input, but I would think that, as long as the voltage is within spec that it can handle its rated output. You'll definitely want to double check that, though.



In general, in its simplest form of speed control, the drive will vary the voltage to maintain a constant V/Hz ratio. Motor overheating can occur if the V/Hz ratio isn't maintained, especially in a motor that isn't inverter rated. You might want to verify the motor specifications with SEW to determine its speed range and max frequency and voltage.

In this part of world we often see motor with nameplates 380/400V and 50/60 Herz options.
I spoked with the guys from "Sever" motor factory, which made excellent motors under their own name and made motors for many famous producers (SEW among others) and they gave me following recommendation:

1. If motor has on name plate both 50/60 Herz option, use FLA and RPM that is written on name plate according to supply frequency and voltage.
2. If motor has on name plate only 50 Herz option, and you use it with 50Hz, use FLA that is written on name plate and base RPM that is correct according to frequency you use it and voltage.
3. If motor has only 60 Hz nameplate, but you power supply is 50Hz, use 10% greater FLA and base RPM that is correct according to frequency you use it.

Base voltage entered in VFD should always be real.

I stick to it, and never had problem.

My understanding is that it doesn't matter which one you enter since the V/Hz ratio is the about the same either way. The drive cannot output more than 400VAC with the 400VAC supply, so there would be no difference in voltage output throughout the entire frequency range anyways.


Entering the 460VAC numbers has a slight benefit to the OEM in that if it ever gets connected to a 460VAC supply, it will automatically utilize >400VAC on the output once the frequency goes above 50Hz.