Synch. motor nameplate info 1

[jraef]

I have inherited an old GE synchronous motor that I must control, and it has some information on the nameplate that I have not seen before. Maybe someone here has more experiance with this. (BTW, I have contacted GE already and have yet to get a response on the design spec., wiring diagram etc. They seem to move in geologic time.)

Here is the nameplate info:
Rated HP=1250 RPM=200 PF=.80
Volt.=4000 Hz.=60 Code=B
Amps=180.4 Frame=9464 Type=T8 (might be TB)
Excitation=250VDC Amps=72.1
Cont. HP=1437.5 Amps=191.0 Rise=90C Stator prot.=RTD

Specifically it is the last line on this plate that I have never seen before. What would be the difference between "Rated" HP and Amps vs "Continuous" HP and Amps? Which amp rating would I use to size the controller and protection system?

"Venditori de oleum-vipera non vigere excordis populi"

 

[jbartos]

Question: Is this all what is on that motor nameplate?

 

[aolalde]

Jraef:

The last line is a different way to show the service factor capability of the motor, notice that this motor will increase the temperature rise to 90 °C if the 1437.5 HP (1437.5/1250= 1.15) are demanded.

The Nominal HP (1250 HP) are the base for starting current, torque characteristics, efficiency and life expectancy.

By the way lots of people think that SF applies to current. SF is applied to Power output with whatever resultant current. ( current depends on EFF and PF at that load)

 

[jbartos]

Comment: Nominal HP as well as service factor HP should be at the rated frequency of 60HZ.
If the motor is really old, then the Service Factor did not exist. However, the higher rating resembling service factor was used.

 

[jraef]

Thanks aolalde.
It seems so obvious to me now that you pointed it out. The sad thing is that I was even LOOKING for the Service Factor and was going to ASSume it was 1.0 since I didn't see it. 1437.5/1250=1.15. Duh, I was looking right at it and not seeing it! Must be getting old. Being that it will be used on a rod mill I had better protect it for the SF.

jbartos, there was additional info such as drawing numbers, serial numbers etc. but I was only stuck on the two HP thing.

Makes me wonder though, why don't smaller motors show the temperature rise when running into the SF? Seems like a good idea.

"Venditori de oleum-vipera non vigere excordis populi"

 

[jbartos]

Comment on the previous posting: The service factor implies the motor design for the stated temperature rating, e.g. B, F, H, etc. The motor thermal curve is supposed to cover the motor continuous duty at HPxSF, not to have the motor insulation prematurely aged or damaged.

 

[electricpete]

It's obvious is hindsight. But I read your original post and thought about it for awhile I certainly couldn't figure it out either. I even looked up NEMA MG-1 rating basis for sync motors! aolalde is on top of it as usual.

Again in hindsight, one other clue besides the ratio 1.15 would have been the temperature rise. Class B is 80C. Class B at SF is 90C.


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[jbartos]

Comment: If a motor manufacturer chooses to design the motor for HPxSF at Class B 80degC, then the motor at the rated HP will actually be working at less than Class B 80degC. This will be the better motor than one with HP Class B 80degC and HPxSF Class B 90degC. Obviously, the motor will meet NEMA MG-1.