converting double layer windings
converting double layer windings
(OP)
How do you convert from double layer lap 1-9 to single layer full pitch concentric and double layer concentric? What coil span would you recommend when converting to double layer concentric?
The stator has 36slots, 12 turns per coil, 2 parallel star. The coils are random wound pull through.
The stator has 36slots, 12 turns per coil, 2 parallel star. The coils are random wound pull through.





RE: converting double layer windings
RE: converting double layer windings
I wouldn't think the small savings in copper would outweigh the increased labor to design and wind the concentric winding.
=====================================
(2B)+(2B)' ?
RE: converting double layer windings
RE: converting double layer windings
For the OP, there is no benefit to using the double layer concentric but it would be a span of 7,9,11 with 12 turns, two wye connection with the same size wire.
RE: converting double layer windings
The copper savings I envison for concentric would be in the endwinding (not the slot) since the coil pitch is smaller, especially for the inner coils within a group.
=====================================
(2B)+(2B)' ?
RE: converting double layer windings
Keep in mind that the copper that is saved due to the smaller span of inner coils of a concentric windings is, more or less, offset by the additional copper that is required for the increased span of the outer coils.
With respect to which type of winding is easier to manufacture, for small diameter stators most winders will say that concentric is easier. This is because the difficulty of setting up to wind coils with different spans, and sometimes different turns, is offset by the reduced difficulty in laying concentric coils versus lap coils in a small stator.
For larger stators like you have, say >12" inside diameter, most winders will say that lap coils are easier since only one span and number of turns are required when manufacturing the coils and laying the coils under the lap is not as difficult.
RE: converting double layer windings
RE: converting double layer windings
RE: converting double layer windings
Replacement winding must be equivalent to the original.
The main condition for this is the equality of factor windings.
In this case there is no at all an absolutely equivalent single-layer replacement (lap or concentric) for double-layer lap winding with span 1-9.
Winding redesign can not be done just like that. Previous analysis has to be made.
If you change the winding factor you need to change the "turns / coil" and cross sectional area of wire.
Of course, this way you will also change the power and torque of motor.
Also, the ratio of "volts / coil" worsens (becomes 2 times higher) if the two-layer winding is replaced with a single-layer.
What is the impact of higher harmonics in the new winding, should be considered? Etc......
More on motor winding redesign is here.
In this particular case it's possible to replace the original winding with an equivalent double-layer concentric winding with step 1-11, 2-10, 3-9. But why would you do that? Electricpete is right, there is no any benefit .
My recommendation is: the change of original design should be avoided. However, if you want to do it, a previous analysis should be done.
RE: converting double layer windings
Motorwinder pointed out savings in copper, although this wasn't the main reason from rewinding the stator in single layer concentric, it may be a good reason for motor designers to consider single layer windings with 2 groups of coil per phase to save copper.
What is the effect of having 2 times volts/coil?
RE: converting double layer windings
RE: converting double layer windings
RE: converting double layer windings
RE: converting double layer windings
Good design is limited to 50-60 V / coil.
If your winding is form wound that criterion is not important.
One example of poor design you can see here (see title "4 pole, 440 V; Is that connection OK?")
RE: converting double layer windings
I have never seen a concentric winding using form coils as required by a 4kv connection. I imagine that such a thing is possible but, in my experience, it is not done.
RE: converting double layer windings
RE: converting double layer windings
Do you have some pictures of this winding?
RE: converting double layer windings
RE: converting double layer windings
It is 4000V.
RE: converting double layer windings
Can you explain more about it?
=====================================
(2B)+(2B)' ?
RE: converting double layer windings
Pete, it would appear the it is not just the end turns, it is the entire winding that is made of 'cables'.
All I can say is that I would hate to have to wind that, especially considering that the slot opening is smaller than the cable and this is truly a 'pull through' winding.
My other comment is; why would you design something like that? I could almost imagine this as being a re-design from low voltage to medium voltage but, it is hard to imagine that the stator slot would be big enough to accomodate that amount of increased (cable) insulation while still allowing for enough circular mils of copper to carry the current.
I m interested to hear lyen12's explanation of the reason behind this design.
RE: converting double layer windings
RE: converting double layer windings
RE: converting double layer windings
The copper cross section is about the same, as the wire insulation required to keep the water out also traps heat effectivley, as well as has a lower allowable operating temperature.
Another thing, not winding related, is why the heck would you have holes in the stator that allow the water to leak in and out. From what I can see of that design, there seems to be much better ways to do it, but I can not see the whole system it is used in and may be missing something that makes it practicle.
RE: converting double layer windings
I have never thought of the phase separators. If all of the winding wires are insulated against 4kV, for example, shouldn't the windings are protected against the line-to-line voltage? You have raised a good point. Is there any equations that I could use to determine the voltage gradient of the insulation?
RE: converting double layer windings
=====================================
(2B)+(2B)' ?
RE: converting double layer windings
=====================================
(2B)+(2B)' ?
RE: converting double layer windings
The theory says yes, but there are too many variables. In practice, we have seen most failures on this type of winding (other manufacturers, as we prefer the lap winding for ease of use and installation) with a small recorded voltage spike on more than one phase cause failure of the insulation between phases with no phase seperators. The cost of the phase seperators is so small, why not use the cheap insurance. As a personal choice I would also say use slot liners, more as a mechanical protection than electrical. Most of my caution comes from the fact that our motors may be in a hole 2000+ft down, and we do not want to see it again until the pump it is attached to is the failure from old age.