Pump motor FLA

[p6g2p6]

Hi, I have a question regarding the Full Load Amps that is provided on a centrifugal pump's nameplate. Is the FLA equal to the maximum current that the motor will draw?

I noticed for most centrifugal pumps, the power input peaks around the middle of the curve, then drops off a bit as the pump starts to run out. Does this mean that the FLA is at the "peak", and the current will drop when the pump operates closer to the end of the curve?

Thanks in advance.

 

[LittleInch]

FLA is what the motor will draw at its max power rating which is usually more than the max power requirement for the pump.

Most pumps I see thebpower rises continuously with flow.

Are you confusing that with the efficiency curve which usually peaks in the middle?

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[electricpete]

> I noticed for most centrifugal pumps, the power input peaks around the middle of the curve, then drops off a bit as the pump starts to run out.

As LittleInch said it's probably not common. But I do I think it is sometimes associated with mixed flow pumps. To my simple thinking radial flow pumps tend to have increasing BHP with flow, axial flow pumps tend to have decreasing bhp with flow, and mixed flow pumps don't necessarily fit either pattern and they sometimes have a peak in the bhp vs flow curve somewhere within the operating range.

> Does this mean that the FLA is at the "peak"

Not at all. A peak in the BHP vs flow curve if it exists would be a characteristic of the pump. FLA is a characteristic of the motor.....

> Is the FLA equal to the maximum current that the motor will draw?

No., FLA tells you the current at maximum steady state loading and rated conditions. The motor will carry loads higher than that for short times, but if that loading is sustained it can cause motor thermal damage (or trip).

> and the current will drop when the pump operates closer to the end of the curve?

Yes, if you enter a region of the pump curve where the pump bhp starts dropping with increasing flow, then the motor current would drop as well

 

[p6g2p6]

LittleInch, pretty sure its the power I'm looking at. See attached.

electricpete, thank you for your responses. This was helpful!

 

[LittleInch]

That is NOT a "normal" centrifugal pump.

Centrifugal pumps "normally" drop about 20% max head from no flow to end of curve, not 90%.

That's close to an axial or mixed flow.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Would be interesting to know the pump brand and model, certainly at first look an unusual curve.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[p6g2p6]

Artisi, it is a Grindex Matador N pump.

 

[LittleInch]

That's a submersible Drainage pump.

P6g2p6 - take it from me that that is not "most centrifugal pumps", more like "this strange sort of pump"....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

Certainly any unusual curve for Grindex, what is its origin?
It aapears to be an installation performance curve or an anticipation performance curve for the pump submerged in a sump - note the NPSHr curve, to achieve the NPSHr showing on the curve assumes the pump is submerged a few feet below water level.

I doubt very much this is a standard performance curve - having been involved with Grindex sales, application and service many years back, I've never come across anything that looks like this curve.

Having said that, and without putting too much thought into it, the power could /would certainly drop way out on the curve to suit the flow and head for the duty - thus is a contractors type pump and designed to run under any condition - low flow high head, high flow low head or anywhere in between.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)