Changing 3 phase induction motor characteristics

[TurbineGen]

I have a few general questions regarding 3 phase induction motors:

Question 1: We have an 1100 hp induction motor that was originally speced out for 4160 volts. Our supply power is 2300 Volts. The vendor changed the winding somehow to reduce the motor's voltage to 2300 volts. I was not able to ask how they did this. Is it likely they changed the motor termination from a WYE to a Delta, or they wired the windings in parallel, or some other method? I do not know how the motor was originally terminated, nor do I know how it is terminated now.

Question 2: Nearly every motor I have seen is "wave wound" in that each winding encompasses several stator teeth. It seems to me the only advantage of this is that it is easier to wind rather than winding each individual tooth but will result in a higher internal resistance due to the longer end turn length. Are there any other advantages? Can I rewind a wave wound motor winding each stator tooth individually? Will winding each tooth individually give me better performance/efficiency?

Thanks in advance,


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If it is broken, fix it. If it isn't broken, I'll soon fix that.

 

[ankervik]

If your original motor spec was 4160v Y the vendor has likely reconnected the winding in delta internally (which would give you 58% or 2412v). If they reconnected YY the voltage would be too low for your 2300v supply.
Don't know exactly what you mean about changing a "wave winding" to a winding around each tooth? These motors are generally lap wound in one form or another. Wave windings are usually confined to bar wound rotors & DC armatures.

 

[electricpete]

Nearly every motor I have seen is "wave wound" in that each winding encompasses several stator teeth

As stated above, you have misused the term wave wound. Lap winding is typical for induction motor stators.

Can I rewind a wave wound motor winding each stator tooth individually? Will winding each tooth individually give me better performance/efficiency?

No. One objective of winding design is to create an approximately sinusoidal mmf around the airgap (since only the fundamental component contributes to the average ouput, and harmonics can cause vibration and other problems). I would suggest to read up on how traditional windings accomplish this, and then try to accomplish the same thing using your concept. I believe you will not get very far in creating a sinusoidal (in space) mmf in a 3 phase motor using coils wrapped around individual teeth.


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