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# Rewinding permanent start capacitor motor

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#### Vaughn

##### Junior Member level 2
I have a core/stamp from one of my cooler fan that is a permanent start capacitor single phase motor, I want to rewind it to get the maximum torque. I have winding wires with SWG #28 for main winding and #31 for aux winding, I am able choose any value of capacitor I don't find any formula to get the the number of turns for winding, I want to go with four pole cross winding pattern. The data of Stamp/core is
Outer Dia: 110mm
Inner Dia: 63mm
Stamp height: 32mm
No of Slots 24
Previously it was 220VAC 500W and 1440 RPM Motor.

*What is the formula to obtain th number of turns one can go with by assumed max wattage output that the motor could handle?
* I saw some chain kinda winding to, which one is more efficient chain type or cross type?

So this is an induction motor. Usually they have poor starting torque and bigger size for the same power (say a universal motor; one with brushes). You cannot increase the power beyond the rated one (perhaps you can go about 10-20% over the current limit with some luck) and the poor starting torque will not change by rewinding the stator.

When you change the wire diameter, you need to keep in mind the total magnetization should stay approximately the same. In other words, the NI (amp-turns) should stay very close. But external applied voltage must be reduced if you reduce the number of turns. That can be done with charts or manually using some iterative method. The calculations are similar to those for a transformer. But you also must ensure that the fatter wires can be accommodated in the existing slots.

Some increase in torque can be obtained using lower number of effective poles.

As c_mitra I'd expect that the motor is already designed for maximum power, specifically with fan load. When you say "maximum torque", you need to tell the corresponding speed. Or are you asking for maximum start torque at n=0? In this case, you probably want to increase the current through the second (capacitor-run) winding which also involves increasing the capacitor. How does the core look like, symmetrical two-phase or asymmetric shape? Share a photo?

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