The stator coil of our 60MW Steam Generator has got failed. But we have a spare 75MW stator. We have planned to run the unit with 75MW stator and 60MW Rotor. The air gap difference between both the stators is around 15mm. There is no problem in coupling and other erection point of view. How about excitation requirement? Will it require more to deliver the same MVA? or will remain the same? Will there be any reduction in overall efficiency of the Generator? What are the parameters that may be different from original generator.

If anybody can guide..please

 

This is an excellent question for the manufacturer of the generators (presuming they are made by the same manufacturer).

If I recall correctly, the air gap between the rotor and the stator is pretty critical, but that recollection is from a university course on rotating machinery more than 30 years past.

But, still, you should be asking this of the manufacturer.

 

Thanks CSA.

Both the stators are from same manufacturer. We are bit worried whether any energy loss would be there due to excess air gap. We could not get any reliable confirmation from the OEM.

- Kadhir

 

Kadkir... there are certain key factors used to quantify an alternator’s capacity. Since the OEM is out of the picture, and presuming both the 75MW and 60MW stators have similar characteristics, then as a start please answer the following:

1. What are the original nameplate parameters of the 75MW and 60MW machines? Specifically: kV; kA, pf; speed or # poles; and short-circuit ratio, if available?

2. Does the 75/60 configuration result in an air-gap length which is increased by 15mm? In other words is the 75MW stator bore-diameter 30mm longer than that of the 60MW stator?

2. Is the ratio of stator-to-rotor slots for the 75/60 configuration equal to that of the original 60/60 machine? If not, please provide the correct number!

3. Are the effective lengths of the stator and rotor magnetic-structures equal? If not, then, what is the difference?

4. Are the magnetic-iron properties of the 75MW stator equal to that of the 60MW stator?

Regards, Phil Corso

 

Kadhir... I forgot to ask:

6. What is the measured core-bore diameter of both the 75MW and 60MW stators?

Phil