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

 

[edison123]

Can't open the attachment. Probably hair-pin type coils. They are tough to do. Requires very skilled winders.

Muthu

http://www.edison.co.in

 

[pirulo]

Dear Muthu

Here a New Attachment

Pirulo

 

[edison123]

Pirulo

It's an open slot and looks like a double layer winding, not a single layer winding. The single layer winding machines normally have semi-closed slots. Do you have a winding diagram ? Did the client give these specs ?

Muthu

http://www.edison.co.in

 

[electricpete]

I have never worked in a repair shop and never seen a single layer winding.

fwiw, here’s my guess how the winding would be arranged (which is probably obvious for you guys)
4*Atop 4*Btop 4*Ctop 4*Abottom, 4*Bbottom, 4*Cbottom,
That is 12 coils in 24 slots – repeat a total of 6 times.

To get alternating polarity of pole-phase zones, all coils in a given phase would be wound with same polarity (the alternating polarity comes from alternating top and bottom). For the setup given above, A and C would be same polarity, B would be wound with opposite polarity (with respect to line side).

It seems like there is some wasted iron. Why would they design it that way?


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[electricpete]

Based on Muthu's comments, looking again it looks like it is a 2 layer winding with two different size coils?

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[pirulo]

Hello pete,

Can´t be double layer because the coils = slots/2, for 12 poles x 3 phases =36 groups and 72 coils/36 = 2 coils per group. The span is 1-10 so the winding could be done.

Usually in one double layer you will have two active coils in each slot but in a single layer we will have only one.

The slot is not 100% filled with the coil maybe some designer use the same iron core for other machines with more output and for this one they used to avoid cost. So the solution was to use a single layer winding.

I never see this kind of design and for it I am requesting all coleagues.

Regards

Pirulo

 

[edison123]

I very much doubt that this is a single layer winding and someone intentionally left 50% of the slot unused. Never seen it before.

I would go for a double layer winding even if the original was single layer with 100& slots used. My $0.02.

Muthu

http://www.edison.co.in

 

[electricpete]

Can´t be double layer because the coils = slots/2, for 12 poles x 3 phases =36 groups and 72 coils/36 = 2 coils per group. The span is 1-10 so the winding could be done.

I may be misunderstanding, so bear with me. A single layer winding can only be full pitch 1-13. So if the coils are short pitch, it has to be double layer, right?

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[electricpete]

Knowing we have 72 slots, 12 poles:
There are 36 pole-phase zones in either configuration (double-layer or single layer)
Could be single layer with in the format that I described above: 3 May 10 7:40 (72 coils)
Could be double layer with 4 coils per group. Q=4*3*12= 144 coils

The drawing does clearly show two spacers including one wrapped inside the coil which would make it impossible to put two of those coils in a slot... drawing does show single layer.

You said span 1-10 which suggests to me it is double layer.

The previous two facts (spacer and span 1-10) seem inconsisent.


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[pirulo]

Hello all

Attached you will find all coil specs, maybe the coil drawing will tell more , sorry all in french the costumer request 80 coils for this generator with 144 Slots.

Thanks
Pirulo

 

[electricpete]

Correction in bold

Knowing we have 144 slots, 12 poles:

Attached you will find all coil specs...

Sure enough, 1-10. Doesn't make any sense to me.

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[electricpete]

Would you guys agree that it is impossible to build a single-layer winding with short pitch?

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[edison123]

pete - Single layer coils are always full-pitched.

pirulo - That's not a single layer coil. A single layer coil fills the entire slot and its shape is completely different. It's a double layer coil used only in alternate slots. That's the reason for those fillers. And I've never seen anything like this winding.

Muthu

http://www.edison.co.in

 

[electricpete]

I would say it’s impossible to do anything useful with those coils as shown in the drawings.

You can’t make a single layer winding because the pitch is less than full pitch.

You can’t make a double layer winding because the spacer wrapped inside the coil prevents you from putting 2 in a slot.

Seems like the options are to change the design toward single layer full pitch or toward double layer without spacer.


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[edison123]

pete - with 1-10 pitch, a double layer winding with top coils & bottom coils in alternate slots is doable. The question is why would anyone do that ?

Muthu

http://www.edison.co.in

 

[electricpete]

Are you suggesting:
A - 2 coil sides per slot (in which case the coil as shown on drawing with spacer inside it's groundwall insulation won't fit)
or
B - One coil per slot.. and still called a double layer? (in which case I can't picture what that would look like).

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[zlatkodo]

A small correction:
There are lots of single-layer windings, which is not made with a full pitch. See simple example in attachment.
Zlatkodo

 

[electricpete]

Thanks Zlotakodo. Maybe that is what Muthu was talking about. Each zone has half top coil sides followed by half bottom coil sides. It seems like that could cause some challenges for avoiding interference of the endwindings. Maybe that would be the reason for providing a larger slot where coils can be positioned near top or near bottom to avoid interference of endwindings ?

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[zlatkodo]

Pirulo,
I guess your winding is one of the following two:

1. - Relatively simple single-layer winding with pitch 1-11. (You need to check the pitch, one more time ).

2. -If you are sure that pitch is 1-10 , yes, this single-layer winding can be done but diagram is more complicated.

I think your statement:
"The slot is not 100% filled with the coil maybe some designer use the same iron core for other machines with more output and for this one they used to avoid cost."
could be correct.
Zlatkodo