Winding arrangement with different number of turns in coils
Winding arrangement with different number of turns in coils
(OP)
When redesigning the windings of large three phase low voltage motors, often happens that the number of turns / coil must be a number that is not whole, even in cases where the winding should be done with the maximum number of parallel circuits. We can get, for example 2.5 turns / coil.
In this case, the two-layer winding should be done with different number of turns in coils, for example, with 2 and 3 turns, so that in every slot we have a total of 5 turns. Such an arrangement depends on whether the number of coils in the pole-phase group is odd or even, whether the pitch is odd or even number, etc.
I'm interested in, whether there are some practical rules for determining such arrangement?
Zlatkodo





RE: Winding arrangement with different number of turns in coils
Muthu
www.edison.co.in
RE: Winding arrangement with different number of turns in coils
zlatkodo:
Do you mean re-design or re-wind? A re-wind does require an identical number of turns for a given slot number and voltage. For a re-design you can easily adjust the slot number and/or the number of parallel circuits to arrive at a whole number of turns per coil.
Regards
Wolf
www.hydropower-consult.com
RE: Winding arrangement with different number of turns in coils
Motor of 250 kW, Y-660 V, 4 pole, 60 slots have the
following original data:
lap, double-layer, 4 par. circuits, pitch 1-14, 6 turns / coil (6 + 6 in slot).
The motor we need to rewind to 380 V , (Y connection).
The new number of turns / coil should be: 6 x 380/660 = 3.45 turns / coil.
This number should not be rounded to 3 or to 4, because motor will not be good in both cases. Also, number of parallel circuits can not be increased (except in special cases).
In practice occurring even more complicated cases.
Zlatkodo
RE: Winding arrangement with different number of turns in coils
Muthu
www.edison.co.in
RE: Winding arrangement with different number of turns in coils
More generally, Nailen discusses "fractional turn" windings here:
http://f
I have the hardcopy of this article here at my desk including figures if there are any questions about the figures which are omitted from the on-line version. (Electrical Apparatus magazine is free for motor profressionals - highly recommended imo)
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RE: Winding arrangement with different number of turns in coils
zlatkodo:
I wished you had specified in detail what you had in mind.
A star to Muthu and Pete for proper and competent response.
Regards
Wolf
www.hydropower-consult.com
RE: Winding arrangement with different number of turns in coils
My example is just to explain what I asked. What if:
- voltage ratio is not 1.73 or
- connection is delta in the original and the new winding (most often the case in practice) or
- the pitch is odd or
- the pole-phase groups are unequal, with the same or even with different pitches etc.
I wonder whether someone has dealt with such cases in detail.
Yes, Electricpete, I saw that article, but unfortunately with no pictures.
I think that in some cases is almost impossible to make even such a simple redesign (like change winding for new voltage) with no significant deterioration in motor characteristics. Do you agree with me?
Zlatkodo
RE: Winding arrangement with different number of turns in coils
Given that the standard voltages are not that many and given that a lot of manipulative factors like wye/delta, parallel circuits, single/double layer, pitch factor etc. are available, I have not had any problem so far in ac motor redesigns. (DC motors are much restrictive in that matter).
Of course, I do agree there might be still cases that are not fit for a redesign. If you have any such case, I would be interested in taking a crack at it.
Muthu
www.edison.co.in
RE: Winding arrangement with different number of turns in coils
By the way, Muthu, I think you certainly know that the double layer winding can not be replaced with a single-layer just like that : the number of turns multiplied by 2.
This can be done only in rare cases when the double-layer winding was made with the full pitch. In other cases, the number of turns should be corrected again for 2-15% (sometimes even more), which mostly depends on the pitch of the double-layer winding. After these corrections you get another number of turns that may significantly differ from whole number, again.
Zlatkodo
RE: Winding arrangement with different number of turns in coils
Muthu
www.edison.co.in
RE: Winding arrangement with different number of turns in coils
Attached are some of the figures from Nailen's article.
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RE: Winding arrangement with different number of turns in coils
For some reason, it is difficult to find specific, useful information and schematics for rewinding.
Perhaps, in the future, I could publish my own collection of schematics and winding details.
Zlatkodo