Editor’s Note: This “encore” technical article first appeared in the September 2003 issue of Currents. It was written by former Technical Support Specialist Cyndi Nyberg Esau.

To make more efficient use of time and materials, winders may want to increase the number of parallel circuits when winding an AC stator (or wound rotor). However, there are limits to the number of parallel circuits that can be used in an AC stator (or wound rotor) design. In this article, some of the potential problems associated with increasing the number of parallel circuits will be analyzed.

If the original design of a mo-tor has few turns with large wires, or many wires in hand, it may be easier to rewind if the number of parallel circuits can be increased. Doubling the circuits, for example, doubles the turns per coil and cuts in half the wire size or the number of wires in hand. Of course, doubling the circuits also doubles the volts per coil.

It seems like more and more, motor manufacturers are winding relatively large motors with concentric coils. Unfortunately, not many service centers have winding heads that are big enough to make these concentric coils for a rewind. Consequently, by rewinding these to half-slot lap windings from full slot concentric windings, the turns per coils must be cut in half to keep the same connection. Very often these designs also have a low number of turns, with unequal turns being common as well. Therefore, it is often desirable to increase the number of parallel circuits to make winding the coils less difficult.

Discussion includes:

• Maximum circuits
• Unequal grouping
• Volts per coil
• Connection time
• Splitting groups
• 2-speed, 2-winding designs