PM line-start short motors with double tooth-coil winding

Inhalt:
In fan and pump drives, 2- and 4-pole AC line-start motors are preferred in the lower power range. Premium efficiency classes are achievable in this power range with PM line-start motors. The latter ones are designed with a three-phase stator that is manufactured with a distributed integer-slot winding. Particularly unfavorable is a core length which is a lot shorter than the stator diameter. In such short motors, 70 - 90 % of the winding copper is inactive in the end-winding region, which has a large negative effect on the motor performance. This kind of 2- and 4-pole short motors would require winding systems with considerably shorter end windings. Distributed tooth-coil windings are one possible solution. In this paper, the principle of a distributed tooth-coil winding will be described using the example of a double tooth-coil winding. Based on a simulation study, we will outline the effect of different three-phase windings on the steady-state performance as well as on the starting and pull-in behavior.