Winding Generator 3

[pirulo]

Hello All

We was requested in order to make a new winding for one generator the name plate is : 3.5 MVA 5.5 KV 367.4 Amps Cos Phi 0.9 12 Poles 50 Hz 500 RPM. The slot numbers are 144 and the winding have 72 coils. So only one coil side in each slot single layer windind. The attached drawing shows the following : One coil will be inserted in the top of the slot and the bottom`s space is filled. Then other coil is inserted at bottom of other slot and top is filled.Take a look of the attachment.

Any one with experience with this windings, all explanations and inputs will be wellcommen.

Thanks and regards

Pirulo

 

[wolf39]

By definition this is a single layer-winding as this particular winding consists of only one layer per slot.

The coils are of the multi-turn coil type (or double-diamond coil type). I assume that this winding is a replacement winding for quite an old generator. The generator utilization factor is pretty low and we have a total of 144 slots x 4 turns per coil = 576 turns. The original winding most likely was a conventional multi-turn coil winding with two layers and either 4 turns per coil with two parallel circuits (giving us 576 turns total) or with 2 turns per coil and one circuit only (giving us also 576 turns total). The latter design would require 10 or 12 parallel strands per turn which would make each turn quite bulky. For easier manufacture I tend to think that the first design was selected originally.

The reason for this unusual replacement winding is quite simple: This French solution cuts the number of coils in half thus saving quite a bit of money. The low generator utilization and the selected current density of about 3 Amps per square mm doesn't require a conventional coil winding with fully filled slots. Especially if the specified loss evaluation is low.

Regards

Wolf

http://www.hydropower-consult.com

 

[electricpete]

I agree the core appears designed for two ratings since there is enough room to fit two coils in if you add the spacers.

zlatkodo - on your single layer fractional-pitch-coil wiring diagram... if I draw an end view and try to draw the coil extensions, they have to cross over each other. Has this winding been physically realized? Can you shed any light on how the interference is overcome?

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[electricpete]

Attached illustrates the problem with interference of the endwindings that I am thinking of. It is an endview of the winding.

The challenge is draw lines to connect the like colors:
A phase
1/2 to 11/12
13/14 to 23/24

B phase
5/6 to 15/16
17/18 to 3/4

C phase
9/10 to 19/20
21/22 to 7/8

At first glance, I don't think it can be done. There are three possible interpretations:
1 - it can be done, I just didn't figure out why.
2 - it can't be done, but somehow there is a difference between my drawing and the physical configuration... I haven't set up the problem right.
3 - it can't be done, and I have set up the problem right... that would mean you can't wind a motor like this. (probably this is the least likely outcome)

What do you think?

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[electricpete]

note that slide 2 of the previous attachment shows the endview that I was discussing.

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[electricpete]

Following up on my previous post which focused on the physcial layout of winding posted by zlatkodo....

Attached are two rough depictions of what the winding might look like viewed from the end if we stretched it out into a line.

Slide 1 looks like a Herringbone. It requires a lot of moving connection points up and down within the slot.

Slide 2 is a basketweave. It requires two types of curves. I don't think it is realistic since we also have the actual curve of stator circumference which destroys the symmetry of those two types curves.

I guess Herringbone is the best I can come up with. It looks like a challenge to me, but I'm just thinking out loud here.

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[electricpete]

Correction in bold:

Slide 1 looks like a Herringbone. It requires a lot of moving the coils up and down within the slot

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[edison123]

Here's how a coil of a single layer, open slot winding looks like.

http://www.fight-4-truth.com/winding jig.jpg

For a semi-closed slot, the coils have a completely different shape and the end windings are in 2 or 3 tiers.

Muthu

http://www.edison.co.in

 

[edison123]

Single layer winding with hairpin coils in 2 tier end winding.

Muthu

http://www.edison.co.in

 

[edison123]

Oops, the linky

http://www.karma.se/showproducts.php?lang=2&category=58

Muthu

http://www.edison.co.in

 

[wolf39]

pirulo:

You may have noticed that various posts have been received which propably went beyond your original request for information. Your thread originally asked for general information only. In case you still have specific questions, please tell us.

For our information please let us know what the original winding looked like and generator manufacturing date.

Regards

Wolf

http://www.hydropower-consult.com

 

[pirulo]

Hello Wolf

Thanks for the interest, we are a motor repair shop and we was receive the two attached drawings for quote 80 Coils.No more Information.The Alternator is in France But I hope speaking with the costumer we can get the information.

Regards

Pirulo

 

[electricpete]

Muthu – interesting stuff, thanks.

You may have noticed that various posts have been received which propably went beyond your original request for information.[/quote wolf]
Wolf:
Can you give an example description of the physical arrangement for any fractional-pitch lap-wound single-layer winding?

Let’s try the one discussed in the original post...
I’ll get you started...
144 slots, 12 poles, 3 phases, single layer, 72 coils, coil span 1-10
144slots/(12poles*3phases) = 4 slots per pole-phase zone.
The logical thing to try might be putting coils sides in slots in the following order:
A, A, A, A, B, B, B, B, C
But what comes next? It would have to be A because the span is 1-10. (a complication that doesn’t arise in double-layer windings). So where do we put the remaining C coils?
Or is there some alternate creative approach (zlatkodo’s) ?

I will look forward to your response, Wolf. Thanks.

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[electricpete]

Wolf, also if the approach you propose is zlatkodo’s, please address:
1 – my questions regarding endwinding layout
2 – how to adapt the approach to coil span 1-11 instead of 1-10.
Thanks again.

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[electricpete]

Correction in bold

how to adapt the approach to coil span 1-10 instead of 1-11.

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[wolf39]

Pete:

As I see it:

Every slot is filled with one coil layer, so we could say we have a single layer winding in front of us. But this statement may be misleading. The double layer diamond coils selected are typical double layer windings. The end winding layout therefore is a conventional one, i.e. no extra tiers/levels/planes are required.

According to the scetch posted 3 May 10 9:58 the diamond coils have 4 turns per coil and a coil span of 1 - 10. Because we have 144 slots and 72 coils, every slot is filled with half a coil. 72 slots are filled with the bottom part of a coil and the other 72 slots are filled with the top part of a coil.

Slot #1 is assumed to accommodate the bottom coil section of coil #1. Therefore, with a coil span of 1 - 10, slot #10 accommodates the top part of coil #1. The next slot to accommodate the bottom part of coil #2 is slot #3 (not slot #2). So, all bottom coil sections are placed in odd slot numbers and the top coil sections are placed in even slot numbers.

Before I go further, let me know what you think.

Regards

Wolf

http://www.hydropower-consult.com

 

[electricpete]

Wolf – thanks for your reply. I appreciate it.

I can certainly see that alternating top and bottom coils helps alleviate congestion for a full-pitch single layer winding. However I still don’t see how it helps accommodate the fractional coil pitch single layer winding.

Here is my first attempt to lay out what you described:
Slot1 A1bottom
Slot2 A2top (A2bottom was in slot 137)
Slot3 A3bottom
Slot4 A4top (A4bottom was in slot 139)
...
Slot 10 A1top
Slot 11 A5bottom (A5 top will be in 20)
Slot 12 A3top
Slot 13 A6bottom (A6 top will be in 22)

We have at this point two interrelated problems:
1 – The center of the first pole-phase zone is slot 2.5 and the center of 2nd pole-phase zone is 11.5. They do not difffer by a full pole pitch. That doesn’t meet the winding objective.
2 – We only have 4 slots in between slot 4 and 10 to fit the pole phase zones for B and C... but we need six. Where are you going to put those last two C phase coils?

Again zlatkodo’s approach gets us close. I don’t think that’s what your describing with alternating upper/lower coil sides in sucessive slots, but I could be wrong.

I would be interested to hear more, especially enough layout to see how the coil pitch is accommodated.

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[electricpete]

Clarification in bold"

I can certainly see that alternating top and bottom coil sides in successive slots

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[zlatkodo]

One picture tells more than thousand words.
Zlatkodo

 

[zlatkodo]

Pirulo, Electricpete,
In attachment you can find more details for three possible types of winding for 12 poles and 144 slots.
In application, each of these three schemes has its advantages and disadvantages and the choice must be made by additional criteria.
Zlatkodo

 

[edison123]

zlatkodo

I don't see how you can have even numbered pitch like (1-13 or 1-11) in a single layer winding. You can have only odd numbered pitch like (1-10 or 1-12) in a single layer winding.

I have attached a coil placement excel sheet for a 48 slot, 4 pole machine.

The red numbers indicate the slot clashes.

Muthu
www.edison.co.in