No load amps with Powerflex 700

[giselle]

I have a 60hp AC motor controlled by a ABB Powerflex 700 Vector control drive. I notice that the no load amperage is 21A. Is this normal? ie. Is the no load amperage with drive control usually higher than using a DOL starter? If yes, why?

 

[DickDV]

That depends entirely on how the drive parameters are set up. We really can't answer your question without knowing more about how the drive is configured.

Also, you either have an Allen-Bradley PowerFlex 700 or an ABB drive of some model. Note that these are two different brands.

 

[edison123]

What is the rated FLC ?

Muthu

http://www.edison.co.in

 

[mns15451]

21 A without load is ok. As a rough estimate the No-load current should be < 1/3rd of the FLC.

 

[ozmosis]

The no load current looks ok. A 60hp motor would be about 70~75FLA, so 21A seems about right, assuming 460Vac.
As DickDV points out, if the settings on your PF700 are not correct or the vector algorithm is not tuned correctly, then you could get over-excitation and hence more current at no load.

 

[giselle]

Correction: It is an Allen Bradley Powerflex 700 drive
The motor nameplate is as follows:
Reliance Electric Inverter Duty Motor
Frame: 364T
Hp: 60
RPM: 2475/2680
V: 460
Amps: 68.2/67.6
Hz: 83/93

The drive parameters:
Rated kW: 45
Rated V: 480
Rated Amos:77
Motor Type: Induction
Motor NP V: 460
Motor NP FLA: 68.2
Motor NP Hertz: 83
Motor NP RPM: 1750
Motor NP Power: 60
Motor NP Pwr Units: Horsepower
Motor Cntl Sel: FVC Vector

Any other info required?

 

[edison123]

For 68 Amps FLC, 21 amps is quite normal.

Thumbrule - No load current = 1/3rd rated current

Muthu

http://www.edison.co.in

 

[ozmosis]

it would appear to be a special motor winding at 83Hz but again, nothing too concerning about the no-load current. However, how did you establish that the DOL current was lower? (meaning, where did you get 83Hz as a base supply frequency other than from your VFD?)

 

[ozmosis]

Correction to my question just now: I didn't read your own question properly and had it in my head you had tried it DOL.

 

[electromike]

Could you describe what type of load you are driving? I would expect to see more than a 21amp no-load from a 4 pole motor at 1750 unless there is some type of stored mecahnical energy, such as a flywheel, "helping the load" in the system.

 

[ScottyUK]

electromike,

The vast majority of the no-load current is magnetising current, with a small in-phase current to meet the iron, copper and windage losses. Nothing you do to the shaft will modify the magnetising current because that is inherent in the design of the motor stator and rotor.


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If we learn from our mistakes I'm getting a great education!

 

[LionelHutz]

The important current is at full load. Then it should be rated current.