Pump Amp Problems

[ChemEnginGuy]

I am having serious problems with a centrifugal pump, with VFD drive. The motor is spec. is 150 HP and 1800 RPM.

The VFD will only let the pump run at 51% capacity without tripping on high amps. I am wondering if there were any suggestions as to why high amps might be a problem. Flow is much lower than expected as well.

 

[1gibson]

Watch the spin-down (turn it off and watch the coupling until it stops.) Abrupt stop = something is rubbing. Slow/smooth decrease in speed until rotation stops means that something else is the problem.

Capacity refers to flow when dealing with centrifugal pumps; flow at what VFD setting? Or by capacity did you mean VFD setting (51% of 50 or 60 hz, 25.5 or 30.6 hz?)

If it is an axial flow pump (high flow low head) then horsepower requirement will rise near shutoff. Maybe there is no problem other than higher than anticipated system resistance forcing the flow back on the pump curve. This is unlikely, in most cases impossible, to cause a trip at half speed.

Confirm direction of rotation (do this while watching the spin-down.)

 

[DRWeig]

Is the motor perhaps a dual-voltage (12 leads), wired incorrectly?

Best to you,

Goober Dave

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[LittleInch]

How about giving us the full story - pump curve, inlet pressure, outlet pressure, flow rate, temperature, density, static head, motor voltage and current, system description etc. So far we have virtually nothing to help you assess what could be the issue.

Is this a new pump and motor or a retrofit vfd or a new motor or what?? If you can also say what is the 50% is as 1 Gibson says would help a lot.

So far all we have is you saying you've got a problem. There are many possible issues, but give us data and we might be able to help. No more info all we can do is guess...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[ScottyUK]

Did the pump work OK before the VSD was added, if there is a 'before' case?

There are numerous drive parameters which could cause this. Here's a few to start with:

- wrong volt/Hz setting, if this is a scalar drive
- bad or no auto-tune, if this is a vector drive
- wrong motor connections
- wrong motor rating in config settings
- wrong current limit in config settings
- wrong base voltage in config settings