Jonathan Robinson
Technical Education Committee Member
Burford Electric Service, Inc.

When rewinding a typical three-phase motor, an experienced motor winder can usually identify the winding pattern quickly. Coil pitch, group spacing and internal connections often repeat in a predictable manner. Years of winding experience is valuable because it saves time. However, there are also motors where anticipating a repeating pattern can get a repair center in trouble.

Some motors have windings that are not as symmetrical as winding technicians normally expect. A few examples are interspersed PAM (pole amplitude modulation) motors or interspersed Dahlander winding motors. Both motors are two-speed, one-winding designs. On motors like these, an incorrect assumption about how the winding repeats can result in a rewind that looks physically correct, at first glance, but does not operate correctly.

This creates a simple but serious problem: the winding in front of you may be the only copy of the original design. Once it is stripped, information that was not recorded is gone. For that reason, our repair center uses a slot-to-slot documentation method for complex windings that is intentionally slow and repetitive on the front end. This extra time on the front end is minor compared to the time and cost involved in reconstructing a complicated winding after the original has been destroyed and removed.

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