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Winding Generator
3

Winding Generator

Winding Generator

(OP)
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     
 

RE: Winding Generator

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

Muthu
www.edison.co.in

RE: Winding Generator

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
www.edison.co.in

RE: Winding Generator

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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RE: Winding Generator

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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RE: Winding Generator

(OP)
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    

RE: Winding Generator

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
www.edison.co.in

RE: Winding Generator

Quote:

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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RE: Winding Generator

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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RE: Winding Generator

Correction in bold

Quote (electricpete):

Knowing we have 144 slots, 12 poles:

Quote:

Attached you will find all coil specs...
Sure enough, 1-10.  Doesn't make any sense to me.

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RE: Winding Generator

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

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RE: Winding Generator

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
www.edison.co.in

RE: Winding Generator

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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RE: Winding Generator

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
www.edison.co.in

RE: Winding Generator

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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RE: Winding Generator

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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RE: Winding Generator

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
 

RE: Winding Generator


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
www.hydropower-consult.com       

RE: Winding Generator

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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RE: Winding Generator

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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RE: Winding Generator

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

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RE: Winding Generator

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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RE: Winding Generator

Correction in bold:

Quote (electricpete):

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

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RE: Winding Generator

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

Muthu
www.edison.co.in

RE: Winding Generator


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
www.hydropower-consult.com   

RE: Winding Generator

(OP)
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  

RE: Winding Generator

Muthu – interesting stuff, thanks.

Quote (wolf):

You may have noticed that various posts have been received which propably went beyond your original request for information.
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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RE: Winding Generator

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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RE: Winding Generator

Correction in bold

Quote:

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

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RE: Winding Generator


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
www.hydropower-consult.com  

RE: Winding Generator

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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RE: Winding Generator

Clarification in bold"

Quote:

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

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RE: Winding Generator

One picture tells more than thousand words.
  Zlatkodo

RE: Winding Generator

Muthu,
Note that  in my previous post it is about 144 slots and 12 poles.
Of course, you can create a single winding for 48 slots and 4 poles with step 1-13 or 1-11.
 See  my earlier diagram again, for a 24 slot and 2 poles .
After all, how you  make single winding for 48 slots and 4 poles?  You need to try to draw (no xls, please) how to do it with step 1-12 ?
Zlatkodo

RE: Winding Generator

You can start the winding (yours show only the start of the winding) but after certain coils, you cannot proceed further. You can try that neat PPT of yours with more coils if you feel like. I am not that good with PPT. :)

Muthu
www.edison.co.in

RE: Winding Generator

Interesting stuff.

In zltakodo's 1st powerpoint, we can see for configuration A (1-13 = full pitch) and B (1-11 with 4 coil sides per zone split into groups of 2 with associated coils spanning opposite direction) there is 8 slots available between pole-phase zones to fit the 8 coils sides associated with the other 2 pole phase zones, as required.   But for arrangement C (1-10), there are only 7 slots available.... doesn't seem to work. Can you clarify how are you going to get the 8 coil sides from the two other pole phase zones into those 7 slots?

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RE: Winding Generator

pete - My excel file shows the coil placement sequence. For example, in the 1-13 full pitch columns, you start with the one side of coil in slot 1 and the other side of the coil lies in slot 13. The you place the next coil in slot 2 and slot 14. You can proceed this way up to slot no. 12. The problem starts at slot no. 13 since it is already occupied by the other side of the coil in slot no. 1 and hence my red highlight.

In the 1-11 pitch, I used only alternate slots to place the winding. And here you hit the snag at slot no. 11 (which is already occupied by the other side of the coil in slot no. 1).

In both the odd pitches (1-10 and 1-12), you can see there are no such problems. And here too, you have to place coils in every alternate slots only. Sequential placing will not work in single layer.

It's just arithmetic progression actually. :)

Note this is only a problem in single layer winding. Double layer is not a problem unless you use multi-pitch coils.

Muthu
www.edison.co.in

RE: Winding Generator

Thanks zlatkodo.  I vote you a LPS for that.

Considering the only the coil pitch (and not endwinding interference *), I think there is no problem fitting coil sides into slots to produced a balanced winding of the proper pole pitch using the configurations shown by zlatkodo:
7 May 10 2:01  Configuration A for 1-13 (full pitch)
7 May 10 2:01  Configuration B for 1-11
7 May 10 23:47  Configuration C for 1-10 (same as original post)

The three configurations are laid out in attached spreadsheet.  I am using Muthu's approach to study only a 4-pole 48 slot machine which tells us everything we need to know (if we repeat it three times we have 12 pole 144 slot machine.)

The first is full pitch coil 1-13.  Results in winding factor 0.958 (same as distribution factor... pitch factor = 1).    If we try to alternate top/bottom, it doesn't work.  We would have tops in odd and bottoms in even, which means we would have  a top in both 1 and 13... can't do that.   So I just laid it out in simpler fashion where each pole phase zone is all tops or all bottoms.

The 2nd is 1-11.  It results in identical  identical coil positioning to the 1-13 (just different connections).  Therefore as expected the winding factor is the same = 0.958

The 3rd configuration would be applicable to the original post. It results in a lower winding factor 0.892, due to the fact that the coils within a given zone are spread out further.

Note these are all fundamental winding factors (not harmonic winding factors).

* Again this does not consider whether there will be interference in the endwindings.    It is a little beyond my ability to know definitevely which arrangements will/won't cause interference.

Muthu – I do not completely understand your objection, but I presume it has to do with endwinding interference. i.e. you reject 1-13 because it cannot be inserted as alternating top/bottom coil sides in sequential slots.  I can see alternating is better, but given that the coils resemble 2-layer coils and we can position them near top or bottom of the slot, then I'm not sure it is absolutely required.  Is it impossible to fit with all coils within a pole phase zone having same side (top or bottom) in the slot as I have shown in attached?   

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RE: Winding Generator

Clarification in bold:

Quote (electricpete):

The 2nd is 1-11.  It results in identical current distribution in the slot section same as the 1-13 (just different coil arrangement).  

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RE: Winding Generator

Thanks pete and zlatkodo. Yesterday, I went back and redid my excel. And arrived at the same configuration as you guys. One lives and learns. :)

LPS for both of you for making me think.

Muthu
www.edison.co.in

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