Improving the Starting Torque in External-Rotor Induction Motors Using an Outer Can

The paper presents a model for an external-rotor squirrel-cage induction motor, where the cage rings are short-circuited (shunted) by a conducting outer can joining the two rings. It is found that this improves the cooling and operating characteristics. This end-ring shunting effect is discussed and new equivalent circuits for the rotor established. The special features of this machine are determined by consideration of the magnetic field. Tests and results are presented to highlight the operation of this induction motor configuration.