A comparison of stack preparation methods for bar insulation in diecast rotors

In order to make brushless doubly-fed machines (BDFM) cost effective to manufacture, diecasting must be employed to produce the specialized rotor. Since BDFM rotors require insulation between the bars and stack (also a concern for high efficiency induction machines), an investigation was undertaken assessing different stack treatments to provide insulation. Ten rotors were cast, using several pre and post casting treatments. The performance of some rotors compared favorably to an existing noncast manufactured BDFM rotor with close to ideal insulation. These results indicate that diecasting of BDFM rotors is feasible.