Motor with rectangular slots
Motor with rectangular slots
(OP)
What is the most appropriate method for securing the winding in the slots with a rectangular shape?
Zlatkodo
Zlatkodo
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Motor with rectangular slots
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RE: Motor with rectangular slots
If it's random wound, it's usually semi-enclosed slots that help retain a top stick.
I don't see either wedge grooves or semi-enclosed slots.
I guess if the coil were packed tightly side-to-side and vpi'd, that might be enough without a wedge for form wound? ... but I've never seen one like that.
Is it random wound for form wound?
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RE: Motor with rectangular slots
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RE: Motor with rectangular slots
I am agree with pete, the rectangular slots are used in form wound windings due to the coils will be fit pretty good in the slots.
In this case the picture show an old design and a the winding was developed in round wire(I don´t think this small motor was designed with formed coils, this action will be expensive.
Regards
carlos
RE: Motor with rectangular slots
From a magnetic standpoint, rectangular (vs trapezoidal) slot doesn't make sense for random wound. To cut up the circular core, we need to make either the teeth or the slot trapezoidal (the other can be rectangular). In form wound, we need rectangular slot for coil insertion, so we are forced into trapezoidal tooth which is not efficient due to tooth width wider at base that tip (so designing to avoid flux density near the tooth width forces us to use extra unnecessary iron at the tooth base). In random wound motor, there is absolutely no reason to use rectangular slot since it forces trapezoidal teeth,which waste iron. Maybe it is just a case that small motors are not "optimized" the same way as large motors.... other factors like standardization may weigh heavier for small motors.
I'll be interested to hear what type it really is. Looks very weird to me.
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RE: Motor with rectangular slots
(so designing to avoid flux density near the tooth width forces us to use extra unnecessary iron at the tooth base).
should've been
(so designing to avoid saturation near the tooth tip forces us to use extra unnecessary iron at the tooth base).
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RE: Motor with rectangular slots
Zlatkodo can hopefully provide the provide the nameplate voltage to confirm or deny this. Theoretically, he could actually provide us with the specific rewind data since I assume that he, a rewinder, is working on this motor in his shop or place of employment.
I have seen small random wound motors with square slots. For small motors, the electrical characteristics are not as demanding and the square slot core lamination is easier and less expensive to cut than one with a radiused slot.
Also, for small motors, an open slot as shown is easier to insert the wire than a closed slot. However, easier is a relative term since it is difficult to wind a motor this small no matter what the slot opening is.
The slot does appear to have a very small wedge groove. If so, use a flat piece of thick nomex cut to fit tightly into the groove similar to the way that a hard phenolic wedge would be applied to a larger, form wound motor.
Also, use slot liners, top and bottom separators, and slot fillers as required to get a tight slot fill from top to bottom.
Finally, it is always a good practice to use mylar phase paper between the phases and to tie the random winding firmly with at least one tie per coil.
RE: Motor with rectangular slots
Zlatkodo
RE: Motor with rectangular slots
If for some reason, you can't do that, at least make sure the slot liner wraps all the way around and perhaps tie it, rather than wrapping the slot liner around just far enough to meet the top stick... a litle bit of insurance against the possibility of that topstick coming out. But vpi would be better imo.
Just my opinion. Does anyone think it doesn't need vpi? (just curious).
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RE: Motor with rectangular slots
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RE: Motor with rectangular slots
h
Somewhere in there he made a statement that random wound motors with open (vs semi-closed) slots typically use magnetic wedges for purposes of reducing harmonics. Of course that makes the method of securing the wedges all the more vital.
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RE: Motor with rectangular slots
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RE: Motor with rectangular slots
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RE: Motor with rectangular slots
If you don't have any wedge grooves, cut your top sticks wide enough to wedge them in from the top. Tapping them down with a tamping tool.
Listo
RE: Motor with rectangular slots
Motorwinder is giving you good advice. I'd like to add - that if you have room in the slot, cut your slot liners above the laminations so you can fold them over the top of the coil and then your "wedge" will hold it down.
Thanks