Contactor size

[pwrengrds]

I have a contactor for a synchronous motor that has no nameplate. The current motor field is rated at 75 amps and the contactor has a 100 amp shunt attached. I am being asked if it would support a 150 amp synchronous motor field. Could anyone provide feedback as to the size and rating of the contactor shown on the attached, no nameplate that I have seen.

Thank you, David

 

[pwrengrds]

Attached is another photo of the contactor

 

[waross]

Coment:
How old is that contactor?
I would try to ascertain the rating of the synchronous motor starter of which this field contactor is a part.
If the complete starter is adequately sized to run the new motor than this contactor may be adequate.
AND, if the motors are similar, eg: reasonably close rated speeds, similar construction.
Overall, your customer wants to increase the current to 150% on a contactor of unknown rating.
There would have to be some extraordinary site conditions before I would try it.
With 100 Amp and 150 Amp fields, I am guessing that these motors are over 1000 HP.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pwrengrds]

It's a 200% increase in field current, motors are about the same size.
Motor data, they are currently using the online motor.
1 – Online 3000 hp, 16 pole, .8pf, 724 amp motor with field windings that are 250V / 74A => 18.5kW
1 – Spare 2750 hp, 18 pole, .8pf, 676 amp motor with field windings that are 210V / 150A => 31.5kW

The intent was to replace a GE DC static exciter with a DECS250E, keeping the contactor for startup. Right now the cables to the motor look like 4AWG, (rated at 95 amps) which makes sense with the operating current of 75 amps.

I'm just wondering if I need to replace the contactor, if someone can look at it and tell me it's likely current rating. The cables would mostly have to be replaced. They want to see if using the spare motor is feasible.

 

[jraef]

Looks like an old GE DC locomotive contactor. Not that they were used exclusively on locomotives, but that’s what they were originally designed for. Current ratings for DC contactors like that are expensive to attain, so it’s highly unlikely that it is rated for 2x what it is being used for now, that would have been an expensive waste at the time the controller was designed.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[pwrengrds]

I think it was from 1980, has a power vac breaker for a 2300 volt starter. See attached drawing. It's from Burlington, IA so the GE DC locomotive contactor is spot on.