200 horsepower, 2-pole rewind, span question
200 horsepower, 2-pole rewind, span question
(OP)
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





RE: 200 horsepower, 2-pole rewind, span question
Muthu
www.edison.co.in
RE: 200 horsepower, 2-pole rewind, span question
What are the wire sizes out of curiosity?
John
RE: 200 horsepower, 2-pole rewind, span question
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
RE: 200 horsepower, 2-pole rewind, span question
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).
RE: 200 horsepower, 2-pole rewind, span question
"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.
RE: 200 horsepower, 2-pole rewind, span question
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.