Performance of some magnetic slot wedges in an open-slot induction motor

The paper presents an experimental assessment of magnetic slot wedges for use in induction motors with open stator slots. Four sets of magnetic wedges were investigated, and the results show that a good wedge design can so improve the electrical performance of an open-slot machine that it approaches the performance of the equivalent machine with semiclosed stator slots. The main advantages gained are reductions in magnetising current and in high-frequency pulsation losses on no load, with consequent improvements in efficiency and power factor. Leakage reactances are increased slightly by the use of magnetic wedges. In this respect, the performance of a machine with magnetic slot wedges lies between the performance of the equivalent machines with open and semiclosed slots, respectively. The requirements for an ideal magnetic-slot-wedge design are indicated.