Assuming that the failed motor can be rewound, the baseline or lowest initial cost approach is to rewind the motor to its original specifications.
As some older U-Frame motors were built with oversized slots, it is sometimes possible to perform a “high-efficiency” rewind and slightly increase the efficiency of the motor by adding more copper to reduce I2R losses.
If the original unit was wound with aluminum wire, it should be replaced with copper. A motor should be rewound with the same (or larger) winding wire size and configuration. If a repair shop does not have the correct wire size in stock and uses a smaller diameter wire, stator I2R losses will increase.
While a decrease in the number of turns in a stator winding reduces the winding resistance, it also shifts the point at which the motor’s peak efficiency occurs toward higher loads and increases the motor’s magnetic field, starting current, locked rotor, and maximum torque.
A change from 10 to 9 turns will increase the starting current by 23 percent, which can cause problems in the electrical distribution and motor protection systems. In a typical rewind, the stator is heated to a temperature high enough to bum out its winding insulation. The windings are then removed and replaced. Read More
