Powerflex 525 Output Frequency Drops Out

[TAS]

My Powerflex 525 VFD “Output Frequency” starts to drop out (20, 19, 18, 17, 16, 15, 14, 14, 0, 13, 0, 12, 11, 10, 0, 9, etc.) when the Command Frequency approaches and falls below approx. 14HZ. The “Command Frequency” however does hold steady and does not drop out (20, 19, 18, 17, 16, 15 14, 13, 12, 11, 10, 9, etc.). The Pulse In Scale is set to 64.

I'm using the Pulse Train Input, and as a test started the frequency of the Pulse Train Input at a frequency such that the Command Frequency started at 20HZ, and then slowly adjusted the frequency of the Pulse Train Input down such that the Command Frequency decreased down towards 0Hz.

I did notice that this apparent drop out point is exactly one tenth of the Max Hz value. So for example, with Max Hz set to 140, the dropout starts to occur at approx. 14 (140 x 0.1 = 14). This apparent one tenth drop out point held true for other Max Hz values we tried, including:

Max Hz set at 60 started dropping out at 6

Max Hz set at 100 started dropping out at 10

Max Hz set at 140 started dropping out at 14

Max Hz set at 180 started dropping out at 18

Max Hz set at 190 started dropping out at 19

Max Hz set at 200 started dropping out at 20

Max Hz set at 250 started dropping out at 25

Max Hz set at 400 started dropping out at 40

[pturmel]

Double-check parameter 43 Minimum Freq, and also check parameters 448-455, Skip Freq/Band 1-4.

[TAS]

Thank you the prompt reply. 43 = 0, 448-455 = 0. Please see attached parameter list.

Parameters525 20240305.pdf

[TAS]

Please also see attached video, especially when the Command Frequency approaches 14Hz, then the Output Frequency begins to drop out.

525 Max Hz 140 - Recording 2024-03-01 102647 (1).mp4

[pturmel]

Hmm. Ugly.  I don't know the cause.

[ElectronGuru]

I haven't watched your posted video yet, but....

Parameter 36, Motor NP RPM; is that value correct? 115 RPM seems awfully slow.

Have you tried changing Parameter 47, Speed Reference to Drive Pot? If it starts behaving then you know the drive is ok and the problem is with the external speed reference source.

As for the pulse train input, have you moved the jumper for DigIn on terminal block 7? This must be moved to Pulse In for that feature to work.

I doubt this has anything to do with it but... The PF525 carrier frequency is 4KHz at anything above about 15 simulated Hz output. When you drop below about 10 simulated Hz output, the carrier frequency changes itself to 2KHz, then back to 4KHz when above 15Hz. Those aren't exact numbers, though. I've played with this many times using a scope on the output terminals UVW while watching the "Hz" on the PF525 display, and that 10 to 15 Hz area is a sort-of deadband for the carrier freq change. But it doesn't always hit on the exact values; just very near them, and you've said your values are hitting exactly every time. For all I know you could be experiencing this on a test bench but if you have any ambient EMI is the 2 to 4KHz range (other drives running nearby without shielded cables, welders, two-way radios, etc) that *could* be causing your issue. I know it's a stretch but once in a very great while I see something freaky like this.

[VFD Guy]

As stated, the rpm in wrong. Also, the flux current appears very high. I would correct nameplate info and retune. Sounds like your drive is hitting a limit and folding back