Motor HP and FLA Differences

[wiigelec]

We have several Westinghouse type AZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 33 A. We also have a newer Siemens type CZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 54 A.

Why the huge discrepency?

Thanks

 

[ptonsparky]

What does the C vs A mean?

 

[Gregg Harris]

different power factor or efficiency

 

[Besoeker]

We have several Westinghouse type AZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 33 A. We also have a newer Siemens type CZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 54 A.

Why the huge discrepency?

Thanks

Simple calcs with typical assumptions suggests that 33A is believable.
But 54A is not.

 

[Sahib]

Check for air gaps between stator and rotor between the two makes.

 

[Besoeker]

Check for air gaps between stator and rotor between the two makes.

Do you really think the newer Siemens motor would have a significantly larger air gap?

It's a 12-pole motor so I would expect it to have a fairly low power factor.
But, to get to 54A, it would need to be lower than 0.5. Not really very likely, is it?

 

[wiigelec]

I double checked the nameplates, the FLA values are 33.8 and 48.4...

 

[winnie]

Have you had a chance to compare actual running amps?

Is it possible that what you are calling 'FLA' has a service factor component included, rather than the current at rated load?

Is it possible that the number is peak rather than RMS?

Have you contacted the manufacturer to get the datasheet for the motor?

-Jon

 

[Besoeker]

We have several Westinghouse type AZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 33 A. We also have a newer Siemens type CZ 200 hp 600 rpm 4000 V motors with nameplate FLA of 54 A.

Why the huge discrepency?

Thanks

4000V seems an odd voltage.

 

[wiigelec]

Sorry not the best photos but as good as I could get:

 

[wiigelec]

Running amps are approximately 26 and 43...

 

[Besoeker]

Sorry not the best photos but as good as I could get:

If you stand a little bit to one side, you might avoid the flash reflecting directly back at the camera.

 

[Jraef]

In the old Allis-Chalmers motors, type AZ meant Air Tube cooled (TEAAC), in other words you pumped air through the built-in motor air-to-air heat exchanger with an external blower. The Type CZ is TEFC, so the motor is driving it's own fan. That will degrease the efficiency between the two on the motor nameplate, but on the AZ, you must provide the air through the tubes and keep it cool, and that means energy too. If you are putting the motor in the air stream anyway, such as a boiler FD fan, then the air flow was "free", you just ducted a portion of it through the air tubes on the motor and on into the boiler, where the motor heat was in essence used anyway. If you are NOT using that AZ motor as an FD fan, then you must add the external blower power to your energy use.

AZ style motor:

 

[Jraef]

4000V seems an odd voltage.

4000V is our standard motor Utilization Voltage level for a 4160V supply.

 

[Jraef]

By the way if you are using these on VFDs, that CZ is also (I believe) an IEEE841 design, meaning it is made to be used on an inverter drive. That old A-C motor would not have been.

 

[Besoeker]

In the old Allis-Chalmers motors, type AZ meant Air Tube cooled (TEAAC), in other words you pumped air through the built-in motor air-to-air heat exchanger with an external blower. The Type CZ is TEFC, so the motor is driving it's own fan. That will degrease the efficiency between the two on the motor nameplate, but on the AZ, you must provide the air through the tubes and keep it cool, and that means energy too. If you are putting the motor in the air stream anyway, such as a boiler FD fan, then the air flow was "free", you just ducted a portion of it through the air tubes on the motor and on into the boiler, where the motor heat was in essence used anyway. If you are NOT using that AZ motor as an FD fan, then you must add the external blower power to your energy use.

I still can't see it accounting for the differences in FLC. I usually work on about 1% for windage and friction. Here we are looking huge differences in efficiency.
Something does not compute....

 

[wiigelec]

Both motors have integral cooling fans driven by the rotor shaft. No VFDs, across the line start...