Eaton SVX9000 stuck on minimum speed

[Jake Janzen]

I'm seeing the darndest thing. When the drive is off, the "frequency reference" monitor shows that the VFD is receiving the analog signal from the Siemens panel. But as soon as the drive is commanded on, it is stuck on minimum speed, and shows the minimum as the frequency reference, regardless of the signal sent to it. The motor current is well below the limit, the acceleration time is normal. I tried replacing the OPTA9 I/O board, but the new one acts the same way. I'm thinking of replacing the VFD; but it is a strange way for it to fail, and I worry there is some parameter I am missing. Has anyone ever seen this before?

[bolt950rider]

Pretty normal for VFDs to have minimum speeds programmed into them and or the controls to have minimums set too.
I usually find the lowest speed we can reliably get out current switch to close and program it into the VFD so we know when it is running or not and isn’t too low of a speed to close the contact.
Also testing and balancing may adjust them so that minimum air/water flows are achieved..and other reasons.
It’s likely done so on purpose. But may be worth while to see if it’s the controls telling it to do it or the vfd, maybe something is overridden in the controls.


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[Jake Janzen]

This VFD drives a pump, and without ramping up to speed it does not make the differential pressure set-point. There is also an equivalent VFD/pump set-up that doesn't behave the same way. And I can verify with a meter that the controller is sending the speed signal, and it is received at the I/O board.

[Cagey57]

Jake,
Look at he programming of the DI's. It sounds like you have one setup as "Preset Speed" rather that something like "Forward Enable"

[Jake Janzen]

Cagey57,

That was it!! She's humming now. Thanks so much for the tip.