The beginnings and ends of phase windings
The beginnings and ends of phase windings
(OP)
Distance between the beginnings of three-phase windings is , generally, two thirds of the full pitch.
But this may not always be so, it depends on which shortened pitch is used.
For example: where are the beginnings for three phase winding, 33 slots, 8 poles, double-layer:
- the beginnings of the first, third and fifth pole-phase group or
- beginnings as shown in the attachment?
Which option is correct? Which is better?
Is somewhere I can find a detailed analysis of this topic?
Zlatkodo





RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
Zlatkodo
RE: The beginnings and ends of phase windings
But this may not always be so, it depends on which shortened pitch is used."
This is only for general estimation.
In fact, this distance depends on some factors:
1) Angle in electrical-degree in which you decide to pull out the leads (normally it is 120 degrees, but in some cases it may be 240, 360 degrees and so on).
2) The number of slot per one phase on one pole (referred to as q) and phase arrangement of windings.
3) In wound rotor of induction machines, the leads normally are arranged at 120 degrees in space (evenly distributed) for easy balancing.
4) Some other specific winding constructions.
In this example diagram, the parameter q is not a natural number.
Formula q=Z/(2.m.p) here you have q=33/(2.3.4)=11/8=1+3/8; this means each phase you have 8 poles with 3 having 2 coils and the remaining having 1 coil each.
And the electrical degree between the U-V and V-W leads here is 480 degrees.
RE: The beginnings and ends of phase windings
Thanks for the reply.
Does your answer means that both versions are right?
Is there still some opinions from other experienced rewinders?
The main question is:
How to determine the beginnings of the three-phase windings with fractional q?
Please see the attached internal connection diagrams for both the aforementioned versions.
Zlatkodo
RE: The beginnings and ends of phase windings
I think both diagrams in latest post give identical performance. If you trace the path from V1 to V2 and call current flowing "to the right" as V and to the left as V', then both connections give the same sequence:
U W' V U' W V' U W' V U' W V'....
And position of groups and number of coils per group is identical.
As far as whether some other arrangement of coil groupings (which have 1 and which have 2) might be better, the only way I know to check would be compute the distribution factor for all 3 phases using spreadsheet approach previously posted, and check which one gives highest and more balanaced distribution factor.
Those are good diagrams by the way.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
If you look at the designation for each group (U, U', W, W',V, V') and the number of coils in each group, I think there should be no question they are identical magnetically. (I am assuming that the external phases are defined by the letters, not by the colors.... which swapped... was that to trick us?)
I don't want to interfere with your thread. But after your question is answered and the discussion dies down, I would be interested to know for my own info how you came up with that particular sequence of 1-coil and 2-coil groups.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
In your given winding diagrams (dated Sep 10), the upper diagram might not applicable. There are two reasons:
1) The electrical angle between the U1-V1 and V1-W1 have to be n*120 degrees (n is a natural number).
The slot-to-slot electrical angle alfa=p*360/Z=4*360/33=43.64 deg.
In the upper diagram, from U1 to V1 you have 3 slots, so the electrical angle here is 43.64*3=130.92 deg., very much difference to 120 deg. The same with V1 to W1.
2) To ensure the best balance between the 3 phases, the sequence of coil number inside each phase have to be the same.
-In the upper diagram, you have the sequence (count from the lead-in):
U phase: 2 1 1 1 1 1 2 2
V phase: 2 2 1 1 1 1 1 2
W phase: 1 1 2 2 2 1 1 1
-In the lower diagram, the sequence of the 3 phases is the same 2 1 1 1 1 1 2 2
*Conclude: the lower diagram is correct.
To electripete: I am so sorry!
RE: The beginnings and ends of phase windings
I would certainly disagree emphatically with your statement that the bottom diagram is correct while the top is somehow not applicable, because I have already shown that these two diagrams perform identically.
These are single circuit windings. We have 11 series coils connected between V1 and V2 (and 11 between U1 and U2... and 11 between W1 and W2). The only thing that we changed between the top and bottom diagram is the order of connection of the coils (which one comes 1st after V1, which one 2nd, which one 3rd etc), without changing the polarity (or phase) of current in any coil. Now think about the implications of that:
1 – there is no difference magnetically. Each coil carries the same current with same polarity and this results in the same mmf distriction for top and bottom connection.
2 – there is no difference electrically. We have the same coils connected between U1 and U2 just in a different order, so when we add up all those series voltages the sum is the same.
Do you disagree with 1 or 2? Or have some other reason for thinking these two arrangements will act differently?
I think the bottom diagram conforms more to traditional expectations of what a winding "should" look like, but that doesn't mean it performs any differently than the top one.....they perform the same imo.
By the way, it looks like this is your first thread in the eng-tips motor forum. Welcome! Hope you'll stick around.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
But I'm not quite sure how bad is the first version (upper diagram )?
I think this topic is very important for rewinders, because (in such cases) most of them uses the rule: the beginnings of phases are the beginnings of the first , the third and fifth pole phase group.
Zlatkodo
RE: The beginnings and ends of phase windings
Let's draw the V phase electrical circuit. The number will represent the group number. We'll use unprime/prime notation to indicate the polarity of a given group.
Top Diagram:
V1 - 3 - 6' - 9 - 12' - 15 - 18' - 21 - 24' ----------- V2
Bottom Diagram:
V1 - ---------9 - 12' - 15 - 18' - 21 - 24' - 3 - 6' - V2
All we did was move two coils to a different part of the series circuit. We didn't change the current or polarity in any coil. Analysis of the W phase would show the same thing.
How can changing the electrical position of coil within the circuit without changing the polarity possibly affect the performance?
(imo it can't)
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
You have 2 coils: Coil1 and Coil2 . Each has two terminals labeled as + and -.
Wire them up inside a box as follows:
A-----[+Coil1-]------[+Coil2-]---B
where A and B are the two labeled terminals coming out of the box.
Close the lid on the box and perform a set of experiments:
Apply dc voltage between A and B and measure resistance.
Apply ac voltage and measure inductance.
Apply dc voltage and measure flux pattern external to the box
Apply ac voltage and measure flux pattern external to the box.
Apply external time varying flux at certain location on the box and measure voltage at terminals A and B.
Now open the box and without changing the physical position of the coils, reconnect the coils as follows:
A-----[+Coil2-]------[+Coil1-]---B
Now reperform you experiments. You will not see any difference in results. You cannot tell from outside the box that the internal wiring has been changed!
Why is it so?
The coils still occupy the same position in space.
The terminal voltage is still the sum of the two coil voltages (V1+V2 = V2+V1)
The impedance seen from A-B has not changed (Z1 + Z2 = Z1 + Z2)
The coils still carry the same current as each other (I1 = I2 = IA).
It is a characteristic of a series circuit..... changing the order of the elements in the circuit does not change anything that we are interested in.
If you disagree, please tell me how you can possibly tell from the outside of the box (based on current, voltage, flux, or voltage induced as a result of applying external flux) whether the internals are in the first or second configuration? I say it is impossible to tell the difference.
It is the same change we made between top and bottom drawing.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
1) The electrical angle between the U1-V1 and V1-W1 have to be n*120 degrees (n is a natural number).
The slot-to-slot electrical angle alfa=p*360/Z=4*360/33=43.64 deg.
In the upper diagram, from U1 to V1 you have 3 slots, so the electrical angle here is 43.64*3=130.92 deg., very much difference to 120 deg. The same with V1 to W1.
I think this is the only difference between the two versions.
The issue is how it affects motor performance?
Zlatkodo
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
I agree with your experiment analysis. Perfectly correct with a single phase circuit.
But in three-phase circuit, you need to have a balance between three phases (electrically symmetrical).
I am a rewinder myself. I remember once I (for experiment purpose) tried to change the arrangement of a winding with fractional q (just like the example given by zlatkodo, but different parameters). Result was a big imbalance between phase currents to an unacceptable level.
RE: The beginnings and ends of phase windings
No, I dont want to ignore your words. By the way, I highly appreciate your knowledge and contribution to this forum. But I tried to say ( in my bad english), that the best practice is to make a beginnings at a distance of 120 or 240 or ...degrees.
I know that even many manufacturers take the beginnings from the first, third and fifth P.PH.G.
Why? I do not know the answer.They would have no extra costs if they would produce motors at another, better way.
How many times have you heard the question: why my brand new motor, connected to an absolutely balanced voltage, has a significantly different currents in phases?
Many rewinders often ask: why my motor after rewinding have such differences among the currents, even in "no-load" conditions, although the voltage is balanced?
I wonder if it is (sometimes) the cause of all that, this issue about which we speak.
For Koizumi: I am glad you are now , included in this forum (as an experienced rewinder),and I think it would be good to hear from you often.
Zlatkodo
RE: The beginnings and ends of phase windings
- 30 slots, 8 poles,
- 36 slots 10 pole.
It would be good to hear the answer to the question: which slots should be taken for beginnings ?
I have my own solution, which I would like to compare with second opinion.
(We're talking about double-layer windings).
Thanks in advance.
Zlatkodo
RE: The beginnings and ends of phase windings
koizumi – The mental experiment that I described corresponds to one phase of a three phase machine. We swapped electrical order of coils in the box (without changing physical position or polarity) because we swapped electrical order of coils within a single phase (not among phases). Yes, there are adjacent phases which interact. We can simulate the interaction with adjacent phases by measuring flux produced at a given location outside the box...... or by imposing a flux outside the box and measuring the induced voltage at the terminals. There will be no difference in the 2 experiments. So, when we swap coil electrical locations in our single phase box, nothing changes, including the way it interacts with adjacent phases... it is an equivalent box. We can do the same for all three phases and nothing changes.
One factor is that under no-load, the current unbalance is approximately 12-15 times as high as the voltage unbalance (as shown in figure 5.6 of the reference below). So it only takes a tiny voltage unbalance to create a large current unbalance.
ht
My answer to the question: where should we attach the phase leads is as follows: If it is a single-circuit winding, then it doesn't matter where the groups are located electrically between V1 and V2, as long as every group is included between V1 and V2 and all are connected with the proper polarity. So it doesn't matter where you attach the phase leads as long as you meet those same conditions (include all groups in the proper polarity.
Now it is important to note that when you decided which groups had 1 and which had 2, you took a phase pattern (such as 2 2 2 2 1 1 1 1 1) and shifted it by 1/3 of the slots in the motor to find the location where the pattern would begin between each phase. That is an essential step to help ensure balance (having 3 identical phases shifted exactly 120 degrees). So there is special significance to the location where where the leads begin in the bottom diagram that must be considered when laying out the coil groups..... but once they are laid out you can attach your phase leads anywhere you want (as long as you include all the coils of the phase and don't change their polarity).
The fact that the 3rd group is a number of slots from the 1st which does not correspond to exactly 120 degrees is an inevitable characteristic of fractional slot windings. In an integral slot winding, we can say that the number of slots corresponding to 60 electrical degrees is q = Q/(m*p) and we observe that every adjacnet group starts q slots or 60 degrees apart... the winding is perfectly positioned with respect to the field. In a fractional slot winding you don't have that luxury, because if you did then all the groups would have to have the same number of coils (q), and we know they don't in a fractional slot winding. So the groups do not line up perfectly with the ideal sinusoidal field and the distribution factor suffers. It is a fact that exists for fractional slot windings regardless of where you connect up the leads.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
To see a copy, google the following words: joliet coil grouping chart
It should be the first item on the list. For some reason it is tough to grab the link since it opens directly into word.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
Here is my attempt to analyse the case of Q = 30, Poles = 8.
q = 30/(8*3) = 30/24 = 5 / 4 = 1 and 1/4
So in each phase we have 10 coils: including two 2-coil groups and 6 1-coil groups. It can be split into repeating patterns 2 1 1 1.
In phase A we have groupings starting in slot 1:
2 1 1 1 2 1 1 1
In phase B we have groupingss starting in slot 11
2 1 1 1 2 1 1 1
In phase C we have groupingss starting in slot 21
2 1 1 1 2 1 1 1
If we overlay all 3 phases, it would look as follows starting in slot 1:
2 1 1 / 1 2 1 / 1 1 2 / 1 1 1 / 2 1 1/ 1 2 1 / 1 1 2 / 1 1 1
You could put the T-leads at the beginning and end of the phases, or any other location that includes all the coils with proper polarity for this single-circuit winding.
Note since there are two repeating groups per phase, we could also put them in parallels of 2 1 1 1 per circuit (2 circuits).
May analysis above matches what shows up in the EASA Tech Manual. But it doesn't match what shows up in the Joliet link which shows a patter: 2 2 1 / 1 2 1 / 1 1 2 / 1 1 1.... it looks to me like the ratio of 2's to 1's is too high.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
q = 36/(3*10) = 36 / 30 = 6 / 5 = 1 and 1/5
Each phase has 12 slots
Pattern = 2 1 1 1 1
Can be repeated.
The number of coils/group in phase A groups starting in slot 1:
2 1 1 1 1 2 1 1 1 1
The number of coils/group in phase B groups starting in slot 13:
2 1 1 1 1 2 1 1 1 1
The number of coils/group in phase C groups starting in slot 25:
2 1 1 1 1 2 1 1 1 1
Combine them all:
2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1 / 2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1
Again in this case it can be either single circuit or 2-parallel circuit. For single circuit winding electrical position of coils within the string (which one happens to be next to V1, which one happens to be next to V2 etc) is irrelevant as long as polarity is not changed. For 2 circuit winding, electrical position is mostly irrelevant except that in addition to observing proper polarity, we also have to partition the coils among parallels correctly, for example first 2 1 1 1 1 sequence from phase A goes into one parallel and second 2 1 1 1 1 sequence from phase A goes in the other parallel.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
You're given a lot of material for analysis.
1/. Q = 30, Poles = 8.
„IF WE OVERLAY ALL 3 PHASES, IT WOULD LOOK AS FOLLOWS STARTING IN SLOT 1:
2 1 1 / 1 2 1 / 1 1 2 / 1 1 1 / 2 1 1/ 1 2 1 / 1 1 2 / 1 1 1
THE B PHASE PATTERN STARTS IN SLOT 21 AND THE C PHASE STARTS IN 11."
I agree. My choice is : U-1, V-11 and W-6
both variants satisfy the criteria n * 120 degrees
„May analysis above matches what shows up in the EASA Tech Manual."
Unfortunately I have not seen EASA Tech Manual. What is the distance between the beginings for this case (Q = 30, Poles = 8) in this publication?
„But it doesn't match what shows up in the Joliet link which shows a patter: 2 2 1 / 1 2 1 / 1 1 2 / 1 1 1.... it looks to me like the ratio of 2's to 1's is too high."
Apparently, there is an error. I have seen more in the Joliet link .
2/. Q = 36 slots, Poles = 10.
2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1 / 2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1
My choice is: U-1, V-25, W-13
Zlatkodo
RE: The beginnings and ends of phase windings
But it doesn't match what shows up in the Joliet link which shows a patter: 2 2 1 / 1 2 1 / 1 1 2 / 1 1 1.... it looks to me like the ratio of 2's to 1's is too high.
Apparently, there is an error. I have seen more in the Joliet link . There must be:
2 1 1 / 1 2 1 / 1 1 2 / 1 1 1....
Zlatkodo
RE: The beginnings and ends of phase windings
It is hard to believe that such mistakes are accidentally created.
I suggest do not use the information from the table and also do not go to this link, or there is a possibility you can get something unwanted in your PC.
Zlatkodo
RE: The beginnings and ends of phase windings
Glad you came up with the same 30-slot 8-pole configuration.
You still mention about importance of choosing the correct terminal location. It is still not the case. For example the top and bottom windings you posted perform identically. Again, I am 100% positive of this conclusion.
What does a coil do magnetically? 2 things:
1 - it has voltage induced as a result of changing flux passing through it (v = N*dPhi/dt)
2 - it creates mmf to drive flux (obeying H = Integral I dot dL).
But neither one of these functions "cares" about the electrical position of the coil within a series circuit (as long as polarity is maintained):
1 - The induced voltage affects only the sum of voltage around the entire loop through all coils and voltage source. That sum does not depend on the relative electrical location of any coil within the series circuit. (V1 + V2 = V2 + V1)
2 - The mmf created by a coil depends only on the current. Current does not care what electrical position position of the coil within the circuit is... it cares only about the current... which is the same for all series coils within the circuit. (I1 = I2 = I).
For a set coils in specified physical positions, which have already been assigned phases, groups, and polarities that will not change, the electrical position of the coil within the series circuit does not matter.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
I think both diagrams are OK now.
But I still have one correction:
-In 30slot-8p diagram, indeed B phase starts in slot 11, and C phase in slot 21. Otherwise you could have other options, like A-1, C-6 and B-11 (zlatkodo's) or B-26, A-1 and C-6, etc.
-In 36slot-10p diagram, C phase starts in slot 13, and B-25.
Please remember that, in order to have full 6 poles per 360 electrical degrees, you have to count 6 poles in sequence A-Z-B-X-C-Y (zlatkodo please convert to UVW for me).
RE: The beginnings and ends of phase windings
Z=90; 14 poles;
Which slot should you pull out the T-leads?
I just put forward for you to think before telling you what happened.
RE: The beginnings and ends of phase windings
I'm glad you agree. I was worried this thread would end without anyone else agreeing on that point, that seems relatively straightforward.
I am not sure about your corrections:
For the 30-slot, 8-pole motor, I have laid out the group sequence A B' C / A' B C'... starting in slot 1 as follows (11 Sep 10 13:30):
2 1 1 / 1 2 1 / 1 1 2 / 1 1 1 / 2 1 1/ 1 2 1 / 1 1 2 / 1 1 1
The 11th slot occurs at the bolded number and it belongs to phase C as I corrected 11 Sep 10 13:56
The 21st slot occurs at the blue number and it belongs to phase B as I corrected 11 Sep 10 13:56
For the 36-slot, 10-pole motor, I have laid out the group sequence A B' C / A' B C'... starting in slot 1 as follows (11 Sep 10 14:17):
2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1 / 2 1 1 / 1 1 2 / 1 1 1 / 1 2 1 / 1 1 1
The 13th slot occurs at the bolded number and belongs to the B phase as I stated.
The 25th slot occurs at the blue number and belongs to phase C as I stated.
Well I am certainly aware there are 6 groups per 360 electrical degrees although I gave them a different name (A B' C A' B C'). Is there something I wrote that you think is incorrect?
q = 90 / (3*14) = 90 / 42 = 2 and 1/7.
It suggests that the 42 coils in a given phase should be arranged:
3 2 2 2 2 2 2 3 2 2 2 2 2 2
If we start A in slot 1, C in slot 31, and B in slot 61, and look at the sequence including all the phases, then we have the following AB'C / A' B C'/....:
3 2 2 / 2 2 2 / 2 3 2 / 2 2 2 / 2 2 3 / 2 2 2 / 2 2 2 /
3 2 2 / 2 2 2 / 2 3 2 / 2 2 2 / 2 2 3 / 2 2 2 / 2 2 2 /
Which can be done as 1 or 2 circuit winding.
The location of T-leads can be anywhere you choose as long as all coils are included in the proper phase with proper polarity (for one-circuit winding), and for 2-circuit winding allocate properly between the two circuits (first 3 2 2 2 2 2 2 from a given phase in one circuit and last 3 2 2 2 2 2 2 from that phase in the other circuit). Now you've got me wondering why you are asking about the T-leads...
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
We've just got an incident with a new winding.
Z=90; 14 poles;
Which slot should you pull out the T-leads?
I would propose the same winding arrangement as Electricpete, but with the leads as follows:
U-1, V-31 and W-61.
By the way, I'm just curious, which was a pitch of this winding (1-6 or another)?
Zlatkodo
RE: The beginnings and ends of phase windings
I see your sequence in phase counting is different with mine.
Yours is A-Y-C-X-B-Z so your lead assignment is different.
But the conventional way is A-Z-B-X-C-Y.
Anyway the diagram is still OK, no problem.
Back to the Z=90; 14 poles diagram.
One of our engineer, had put the winding arrangement as below
3 2 3 / 2 3 2 / 2 2 2 / 2 2 2 / 2 2 2 / 2 2 2 / 2 2 2 /
3 2 3 / 2 3 2 / 2 2 2 / 2 2 2 / 2 2 2 / 2 2 2 / 2 2 2 /
Lead position: A - 1; B - 6; C - 11;
And the motor is now running with a 15% imbalance in phase current.
After reviewing, I see that the A - B and B - C electrical angle is 140 degrees. That's not suitable.
I see the arrangement proposed by electricpete is OK and I'll try on our motor.
Thanks electricpete and zlatkodo!
RE: The beginnings and ends of phase windings
1 - I have a spreadsheet. It shows distribution factor 0.853593736 0.875067314 0.853593736 for that configuration. For my configuration it shows distribution factor 0.896806749 0.896806749 0.896806749
2 - The three phases are not carbon copies of each other shifted by 120 degrees. Each phase has only one 3-coil group so that group needs to be exactly 120 degrees apart or some multiple. For your configuration the spread is not. alpha = 360*7/90 = 28. The your configuration 3-coil groups start at a distance 5 slots apart where 5*28 = 140 degrees. In contrast for mine the coils are 30 slots apart. 30*28 = 840 = 7*120 degrees. Note this consideration exactly 120 vs approximately 120 degrees is very important for laying out coils..... but not at all important for selecting T-lead location.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
I'm not trying to be a know-it-all... just in a hurry.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
When he says "the sequence of the geometric addition of the single emfs is of no influence on the resultant phase emf.", that is the same thing I meant by Va + Vb = Vb + Va.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
Thanks for the attachment.
I have had the opportunity to see several similar opinions, but also the opposite (one is attached). Unfortunately, it is not in english but there is a conclusion: if the distance between beginnings is not equal to n * 120 degrees, the motor has increased noise, reduced starting torque, and if we are talking about a generator, then it gives unbalanced voltages.
One thing I know, that I certainly will not make a mistake if I make a beginnings in accordance with n * 120th .... In addition, if we know in which slots phase starts , then we can more easily determine the winding arrangement for the case when we have no pre-defined templates.
By the way, I'll make a small program to determine the phase beginnings. Another, more important program to calculate all the winding data, I've already made (see: http://megaswf.com/serve/25158/ this is not advertising - is not for sale.)
Zlatkodo
RE: The beginnings and ends of phase windings
I respect your opinion in general - you certainly know a lot more about winding principles than me and there's a lot I can learn from you.
But on this one specific point, I am 100% positive of the conclusion: The top and bottom diagrams will perform identically. It is a matter of physics, not opinion. The basic principles are illustrated in the mental thought experiment described above. I would be glad to discuss it if there is specific aspect that you disagree (do you doubt the conclusion for the box... or think the box does not adequately represent a motor?).
He is either talking about grouping of coils (rather than connection of T-leads) or he is wrong.
I agree. Determining coil grouping and determing location of T-lead attachments are two separate things. What applies to determining coil grouping (requires knowledge of slots that are exactly 120 degrees apart electrically) does not apply to determining locations of T-leads (T-leads need not be attached at location exactly 120 degrees apart... for single-circuit winding, any connection that includes all coils in proper polarity is equivalent).
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
Unfortunately I can not see a whole chapter from a book (Liwschitz) that you previously sent in the attachment, but there is one thing I'm interested in (see my attachment). This is ,the mentioned in the book, case q = 1 5 / 13, for example: 108 slots and 26 poles.
Does this mean that in this case we can not get unbalanced winding with the proposed order of beginnings?
If we define the beginnings from U -1, V - 37, W - 25 instead of from slots 1, 7, 13 (as suggested in the book), whether such a winding is to be balanced?
Note: I do not have this book and I am unable to read the entire article.
Zlatkodo
RE: The beginnings and ends of phase windings
If we define the beginnings from U -1, V - 37, W - 25 instead of from slots 1, 7, 13 (as suggested in the book), whether such a winding is to be balanced?
It should be:
U -1, V - 37, W - 73
Zlatkodo
RE: The beginnings and ends of phase windings
26 poles, 108 slots
q = 108 / (3 * 36) = 18 / 13 = 1 5 / 13
Using Liwshitz-Garik notation
a = 1, b = 5, beta = 13 = number of poles in repeating unit
N = 18 = slots per phase in repeating units
8 * 1 + 5*2 in 13 slots 18/13
26/13 = 2 recurrent groups
P is lowest integer to satisfy d = m * N * P + 1 / beta is integer
P = 6 makes d = 25
d = m * N * P + 1 / beta = (3 * 18 * P + 1) / 13 = 25
Layout the slots in phase A:
=1
=1+d=26
=1+2*d=51
=(1+3*d - 3*N)=22
=1+4*d-3*N=47
=1+5*d-6*N=18
=1+6*d-6*N=43
=1+7*d-9*N=14
=1+8*d-9*N=39
=1+9*d-12*N=10
=1+10*d-12*N=35
=1+11*d-15*N=6
=1+12*d-15*N=31
=1+13*d-18*N=2
=1+14*d-18*N=27
=1+15*d-18*N=52
=1+16*d-21*N=23
=1+17*d-21*N=48
Thus the following slots belong in phase A: 1 2 6 10 14 18 22 23 26 27 31 35 39 43 47 48 51 52
Repeating for other phases, we come up with the pattern:
2 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 2 / 1 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 1
2 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 2 / 1 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 1
The distribution factor is 0.955 in all three phases. You could wind it in one circuit or two circuits.
Assuming one circuit, you could start the winding anywhere you want as long as polarity is not changed. Starting in U -1, V - 37, W - 73 would give the same results as starting in 1, 7, 13. The distribution factor for each phase can be calculated by adding up all the voltages induced in each coil within the phase... doesn't matter what order we add them – the sum is the same. Both sums are the same and they are both balanced.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
I also think this is a good winding arrangement but I would still use the U -1, V - 37 W – 73.
For others who are not familiar with this theme, some more informations.
There may be more proper arrangements for motor with fractional q.
If q = b + c / d, then we have a "c" proper arrangements.
In our case, q = 1 5 / 13, we have 5 of these arrangements, as follows:
211,211,212,112,1...repeat,
211,212,112,112,1...repeat,
211,212,112,121,1...repeat,
212,112,112,121,1...repet,
212,112,121,121,1...repet.
These arrangements can be defined in several ways. It may also be part of a computer program for three-phase motor design.
Zlatkodo
RE: The beginnings and ends of phase windings
I think it is all effectively the same winding. In fact we can generate 13 variations of the same winding.
The winding I described was 2 "recurring units": one on the first line and one on the 2nd line below:
2 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 2 / 1 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 1
2 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 2 / 1 1 2 / 1 1 2 / 1 2 1 / 1 2 1 / 2 1 1 / 2 1 1
We had N=18 and beta = 13. Each recurring unit is 3*N = 54 coils, located within 3*beta = 3*13= 39 groups. The two recurring units together give the required 108 coils in 78 groups (26 poles). As you observed, the sequence of numbers (coils per group) within a 39-group recurring unit is periodic at a frequency of 54/3 = 13. (i.e. the pattern of 39 numbers is really 3 repeating patterns of 13 numbers). Liwschitz-Garik doesn't mention this, but it makes sense that after we count off beta = 13 groups, we have traveled N=18 slots, and we have traveled an electrical angle of N * alpha = N*180/(3*q). Substituting q = N/Beta, we have travelled N*180*Beta/(3*N) = 60*beta or an exact integer multiple of 60 degrees. Since the Liwschitz-Garik's "slot star" represents all 3 phases in 180 degrees, the phases are considered 60 degrees apart (taking into account allowed polarity swap to keep the entire slot star in a 0-180 degree range). After we travel those N slots in Beta groups and exactly 60 electrical degrees, we must land on the "same position" (**) within the next phase. Since the phases are symmetrical (when beta is not multiple of 3), we must be starting the coil grouping pattern all over again at that point. Therefore the pattern must repeat itself when we land at the same position in the next symmetric phase after beta = 13 groups.
Since the pattern is periodic with interval beta = 13 groups, we can generate 13 variations just by starting at a different group within the 13-group periodic pattern each time.
Starting at the 1st group within my "recurring unit":
2 1 2, 1 1 2, 1 2 1, 1 2 1, 1, repeat....
Starting at the 2st group within my "recurring unit":
1 2 1, 1 2 1, 2 1 1, 2 1 1, 2, repeat....
Stargting at the 3rd group within my "recurring unit":
2 1 1, 2 1 2, 1 1 2, 1 1 2, 1, repeat....
And continuing starting at the 4th thru 13 group within my "recurring unit":
1 1 2, 1 2 1, 1 2 1, 1 2 1, 2, repeat....
1 2 1, 2 1 1, 2 1 1, 2 1 2, 1, repeat....
2 1 2, 1 1 2, 1 1 2, 1 2 1, 1, repeat....
1 2 1, 1 2 1, 1 2 1, 2 1 1, 2, repeat....
2 1 1, 2 1 1, 2 1 2, 1 1 2, 1, repeat....
1 1 2, 1 1 2, 1 2 1, 1 2 1, 2, repeat....
1 2 1, 1 2 1, 2 1 1, 2 1 2, 1, repeat....
2 1 1, 2 1 2, 1 1 2, 1 2 1, 1, repeat....
1 1 2, 1 2 1, 1 2 1, 2 1 1, 2, repeat....
1 2 1, 2 1 1, 2 1 2, 1 1 2, 1, repeat....
But, assuming that all coils are identical, and that there is nothing unique about the 3 phases other than a relative phase relationship, and recognizing that the location where we choose to attach the T-leads doesn't affect anything we care about electtrically or magnetically (as long as correct polarity is maintained), then these 13 variations are all effectively the same winding.
(** "same position" with respect to the pattern that allows flipping coil polarity to roll the slot star into 180 degree window instead of 360 degree window).
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
After a couple of days out of my office, back here seeing your discussions I myself am thinking of changing my concept of fractional q windings. My English is not very good, and I haven't got access to valuable sources of information, such as the book "Electrical Machinery", by Liwschitz-Garak and Clyde Whipple that you brought forward.
I agree that there are some arrangement variations in one given fractional q winding. In practical point of view, only one or two best option shall be chosen.
I'll try some practical experiment on a winding, at first about changing the position of T-leads, then file a record to you all. But it may take some time.
RE: The beginnings and ends of phase windings
You wrote:
I'll try some practical experiment on a winding, at first about changing the position of T-leads, then file a record to you all.
Thank you for sharing your practical experiences with others. That is why I voted a star for your post.
I think that this post was useful for all, (there are lots of free, useful informations for rewinders, even for those who do not wish to share their experiences with others).
Zlatkodo
RE: The beginnings and ends of phase windings
I was a little disappointed that no-one else weighed in on the question asked 10 Sep 10 12:45 and answered by me 10 Sep 10 15:43.
It seems to me that in a forum full of electrical engineers, it should not be so hard to agree that from in an electric motor, there is absolutely no difference (*) if we change the order of coils in a series circuit without changing their polarity or physical location. This comes from basic analysis of the electric circuit and the magnetic circuits.
(* of course it is limited to phenomenon of interest to electric motor and does not include high frequency wave behavior.)
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
Also, I'd like to hear other rewinders.
You should clarify something. Does this mean that the phase-beginnings can also be the beginnings of the first, second and third group?
BTW, I just finish my program, which refers to the determination of the symmetrical winding arrangement for all the double-layer, lap windings (for q> = 1), for all slot-pole combinations in the range 12-300 slots, 2-60 poles.
For a few seconds, the program provides :
- choice of one of the proposed symmetrical arrangements,
- determination of symmetrically distributed phase-beginning and phase-ends,
- the possibility of parallel circuits,
- recommended step, etc. See an example for 75 slots, 14 poles here:
ht
h
If any of rewinders must verify the arrangement in a particular case, let's feel free to contact me.
Zlatkodo
RE: The beginnings and ends of phase windings
One illustration is the top and bottom windings you posted 10 Sep 10 12:45... they will perform identically. If you have specific configuration to illustrate your question, maybe it would help me understand your question.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
RE: The beginnings and ends of phase windings
RE: The beginnings and ends of phase windings
The 1-10 jumper connection marked (A) is from the EASA connection book. The 1-10 jumper (B) is a modification of this winding. The 1-10 jumper (C) connection is my version designed to place all of the leads on the outside and in repeating order for ease of winding. The 1-7 Jumper marked (book) is another from the EASA connection book and the 1-7 jumper connection marked (mod) is my version of this connection, again designed to place the leads on the outside, in repeating order, and grouped together for ease of winding.
RE: The beginnings and ends of phase windings
Which is slot-number for the last example ?
Zlatkodo
RE: The beginnings and ends of phase windings
The connections are not dependent on slot numbers. The pole groups that are represented could be one coil (18 slots) or 100 coils (1800 slots - an unlikely number but not impossible).
RE: The beginnings and ends of phase windings
Please read my first post.
Here we talk about:
- what is the distance between the phase-beginnings (expressed in number of slots) and
- whether that distance is equal to two thirds of the full pitch ((expressed in number of slots).
What is the number of slots in your case ?
What is the distance between the phase-beginnings in your case?
By the way, the distance between the phase-beginnings is the same for both cases that you mentioned (see attachment).
Zlatkodo
RE: The beginnings and ends of phase windings
Thanks for weighing in. When I saw you showed back up on the forum in the 4kv/13kv thread, I had a feeling you might be interested comment on this, so I bumped it to the top. I vote you LPS joining the discussion. By the way, another discussion that I have some questions (for which I don't have answers) is the discussion that emerged about wiring opposite poles in series or parallel here thread237-281260: 1-long jumper 360-deg or 300deg... 2-“skip group”?
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
For the sake of discussion, assume that the stator has 54 slots. Since I do not understand your point, please perform the slot number analysis and let us know what the results are.
You are right that the 1-7 jumper diagrams have beginnings in the same place. Only the ends are different. Since you are focused on the beginnings, I made another connection for you to consider. It is symmetrically asymmetrical.
Pete: I don't know what LPS is but if it is a good thing then thank you. If it is a bad thing then I do not want to know.
RE: The beginnings and ends of phase windings
RE: The beginnings and ends of phase windings
First about your earlier example.
For 54 slots and 6 poles , el. angle between two slots is 20 el. degrees.
The full pitch is 9.Distance between beginnings is 6 slots or angle 6*20=120 degrees ( this is 1*120).This is exactly two-thirds of full pitch.
Please see Koizumi post from 10.Sep. and this picture1:
http://im
Now about your last example.
There is a similar case. The distance between the phase-beginnings is 12, 18 and 24 slots and that is:
- 12 * 20 = 240 = 2 * 120 el. degrees
- 18 * 20 = 360 = 3 * 120,
- 24 * 20 = 480 = 4 * 120.
It is a multiple of two-thirds of the full pitch. See:
http://im
I mean, there's no reason for such connections in the application with integral-slot windings, when we have a better solution.
BTW, what is the benefit of this arrangement?
Personally, I avoid such a winding arrangement with k = 3, (360/120).
Something more: for me is a bit strange this practice of drawing a diagram specifically for "star" and "delta". In this way, each scheme-collection is unnecessary twice larger and the scheme for themselves seems more confusing.
Zlatkodo
RE: The beginnings and ends of phase windings
Here's what I think he's saying:
1 - The power system has 120 degrees difference between phase leads.
2 - The point where we connect the leads needs to be 120 degrees apart to avoid mismatch in the phase of the voltages applied by the system and phase voltages induced by the motor.
3 – The phase difference between phase leads can be computed simply by looking at their separation in slots times slot angle.
That's the basic logic, right?
It sounds right on the surface, but it's not (the problem is #3). Here's why it is incorrect: Your are just using a number to represent phase of a voltage, but voltages and their associated phases only have significance when we define the associated loop. So we need to draw a mental picture of the machine and the power supply and do a more methodical comparison.
Let's say the machine is connected in wye: U1/V2/W1 are phase leads and U2/V2/W2 are the neutral point.
Let's say the power supply is balanced and also connected in wye, or at least hast theoretical neutral voltage which we can visualize. For the power supply, the voltage from U to neutral is 120 degrees apart from the voltage from V to neutral, which is 120 degrees different than the voltage from W to neutral.
Does the motor represented by the top diagram of zlatkodo posted 10 Sep 10 12:45 satisfy the same 120 degree phase relationship among the line to neutral voltages? In particular, is the voltage from U1 to neutral 20 degrees apart from the voltage from V1 to neutral?. We certainly can NOT figure that out by looking at how many slots apart are U1 and V1 as koizumi did 10 Sep 10 22:1 because U1 and V1 are just connection points.... we cannot possibly know the voltage to neutral from looking at a connection point without considering it's relationship to the neutral! To find a voltage to neutral of phase U we would have to look at the full path between U1 and neutral. To find the voltage to neutral of phase V we would have to look at the full path between V1 and neutral. The voltage from any line to neutral is the vector sum of voltages of the associated coils connected from line to neutral. Each coil has a phase difference of 43.64 degrees as koizumi noted. For each coils in U phase, there is a corresponding coil in V phase located exactly 11 slots away. 11 slots * 43.64 = 480 degrees = 360+120 degrees = 120 degrees. So for each coil in U phase there is a corresponding coil in V phase exactly 120 degrees away. When we add up the vector sum of all the coils in U phase and the vector sum of all the coils in V phase, the results of course remain 120 degrees apart. So there is no difference in the phase relationship of voltages imposed by the power supply and voltages induced in the motor.
It was a long way around to get to this conclusion this way (I thought it was much mcuh simpler just looking at the known characteristics of series circuit!). But the key was to be very methodical about visualing the whole circuit and clearly specifying what voltages you are looking at (every voltage involves two points). Maybe you can piece it together a different way that makes more sense to you (the same logic can be done with delta connection but it is trickier).. If you still don't agree, you can either 1- ask questions about my analysis above or 2 - try to define more precisely what are the relevant voltages that are being compared similar to what I did above and post them here for discussion.
For those that don't agree, I appreciate your patience. I am optimistic that eventually we will come to an agreement. Again, I am 100% certain of the conclusion.
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
U1/V2/W1 are phase leads
should have obvsiouly been
U1/V1/W1 are phase leads
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
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(2B)+(2B)' ?
RE: The beginnings and ends of phase windings
You should go back and look at the other connections that I provided. Your analysis only works if the connection has beginning lead connections that are all on the outside of the winding or all on the inside of the winding.
This is because each pole in the motor is 120 degrees out of phase from all of the poles of the other phases. If you place the all of the beginning leads on the outside of the winding, the slot # will add to 120 degrees or a multiple. If you place all of the beginning leads on the inside of the winding, the slot # will add up to 120 degrees or a multiple. If you place some beginnings on the inside and some on the outside, your analysis does not work.
Try your analysis on the other connections that I provided. They are attached again for your convenience.
RE: The beginnings and ends of phase windings
There are many ways to connect a winding. I have seen many variations of the same winding and asked the same questions that you asked me. What is the difference? Is one better than the other? The answer is that in most cases there is little or no difference.
The different variations can be explained by saying that they were created by different people with different ideas of what might be best.
As an example, if you look back at my post on 19 Oct 10 13:39, I stated that two of the connections that I posted were "my version designed to place all of the leads on the outside and in repeating order for ease of winding."
My preference is for a connection that is easy to construct with a minimum chance for error. This means placing beginning leads at the first slot in the group, grouping the leads together for ease in paralleling, and ordering the leads in a some repeating pattern that is easy to follow.
This preference results in connections that match your rule of 120 degree lead separation. However, for me this is simply a preference. It is not a requirement for the connection to work.
That being said, the connection I posted on 22 Oct 10 8:06 was drawn specifically for you. Did you see your name in the 'customer name' place? Although this meets the 120 degree rule, this is not a design I would use. I simply drew it to see what you reaction would be to the different lead locations. Your response was very useful to understand the point you are trying to make.
Finally, to answer your question about the practice of drawing a diagram specifically for "star" and "delta." The number of leads that are used (3,6,9, or 12) is based on the type of controller and the variety of voltages that the motor can be used with. For motors that use a full voltage starter, a soft start, or a VFD drive there is no need to use more than three line leads in the connection. The remaining connections are all made internally. If you did not do this the delta or wye connection would have to be made externally and would require a much larger junction box, would be prone to error from people making the wrong connection, and would be prone to fault from failure of the extenal connection in the junction box.
Again, the simpest solution is the best so internal star or wye connections are often used where ony three line leads are required.