200 horsepower, 2-pole rewind, span question

[luxx989]

I was using EASA's "AC Motor Verification and Redesign" program to figure windings for a motor. It is a Worldwide model:WWE200-36-445/7TS, 200 Horsepower, 2-Pole, 48 slot motor. Factory windings were concentric and had spans of 1-18,1-20,1-22,1-24,1-18,1-20,1-22,1-24 with a 1-Delta connection and 22 wires in hand. I wanted to cut my wires in hand down so I ran it for a 2-Delta and it gave me a span of 1-16 for lap windings. My question is about the span, 1-16 seems to low for a 2-pole 48 slot motor. I expected it to be closer to 22 or so. Even a 1-Delta says 1-16. It has given me options for similar lower spans on 2-pole motors before but I always went with high spans just under half the slots or close. Can a 2-pole be wound successfully with a span closer to 1/3 the number of slots? And does it being 200 horsepower make it different from a smaller motor concerning the span? Thanks

 

[edison123]

2 pole machines usually have 2/3rd pitch to reduce harmonics and end winding length. In this case, the span should be 1-17. Voltages or type of connection (wye or delta) has got nothing to do with the winding pitches. Of course, you need to calculate the original net winding pitch and see if it matches 2/3rd pitch factor (0.866). If not, you need to adjust your turns accordingly.

Muthu

http://www.edison.co.in

 

[dArsonval]

Original coils with 22 wires in hand? WOW

What are the wire sizes out of curiosity?

John

 

[zlatkodo]

Hi, Luxx,

I wanted to cut my wires in hand down so I ran it for a 2-Delta and it gave me a span of 1-16 for lap windings.

That would be a big mistake and waste of time and copper.
The span can not be changed just like that.
- If you'll do a span of 1-16 with same turns / coil, you'll get saturation, high Amps and heat. Very quickly the motor will burn out.
- If you'll make a spam 1-16 and adjust your turns / coil accordingly, you have to be aware that you will reduce HP by one-third approximately . It is very bad if the software you're using will not warn you what the final outcome will be if changing the span in that manner.

Winding Design & Repair

 

[zlatkodo]

In addition:
Regarding the 2-circuits connection, note that "conventional" 2-circuits connection is not best option for 2 pole motors of this size.
Some kind of "skip interleaved connection" should be implemented instead.
Here is diagram for similar case ie. 36 slots, 2 Pole Winding with 2 Circuits, unusual but commonly used in high rated motors (internal connections are the same for 36 and 48 slots with 12 groups).

 

[luxx989]

This is the answer I received to solve my problem. The error was my own by not fully understanding basically.

"The Verification and Redesign program selected 1-16 pitch because that resulted in the closest match to the original magnetic flux densities based on an integer (whole number) turn winding. The current program also allows selection of half-turn windings. In this case, although not stated in the discussion, the turns were 2-3-2-3-2-3-2-3. Selecting half-turns would have resulted in a 1-21 pitch being the closest flux match. Regarding the pitch selections for 2-pole windings the usual range is about 0.7-0.9. Wider pitches are usually better because they require fewer turns. However, coil insertion becomes more difficult as the pitch increases."

dArsonval: it was 22 #14 gauge wires, but only 2 and 3 turns

zlatkodo: I have 6 groups not 12. I was always going to adjust the turns. The software is fine, it has always worked flawlessly. Any issues I have are always user error or mistakes on my part. And $29 for a single connection diagram is a little bit ridiculous. I have hundreds of diagrams, I just needed to enter my data correctly.

I ended up going with 5 turns at a span of 1-22 and a 2-Delta connection. This lets me still reduce my wires by half, double the turns, and keep the flux densities I needed to match the factory windings as close as possible. Which was my original intention.

If someone is a paid member of EASA they have free tech support available, and a huge database of diagrams available. I think we did originally have to pay for a cd, but there are hundreds and hundreds of diagrams on it. EASA answered my question. But at first I didn't understand completely, that's why I posted here. I do not trust anything that is not backed by EASA, nor would I recommend anyone else do so. Thanks for the responses everyone.

 

[WindingForeman]

luxx989,

1/ Changing from 1-circuit connection to 2-circuit connection causes a 100% increase in voltage stress between turns.

2/ The coil grouping for a 48-slot, 2-pole, double-layer winding is 6 groups of 8. To cut down the coil overhang of a conventional concentric winding, the motor manufacturer employs 2 series-connected concentric groups of 4. These 2 groups are separated by (4 x 7.5) or 30 electrical degrees. If you attempt to use a conventional lap winding with a coil throw of 1 to 21 or 1 to 22, your motor will draw high amps. If you don't hear anything from your customer, the motor is probably sitting on the shelf. I ran into it before so my advice is to put back the original winding and experience no stress & headache.