Rotor eddy current analysis and optimisation design of intermediate ring in novel double squirrel‐cage induction motor

Abstract

The intermediate ring (IR) in the novel squirrel-cage rotor is vulnerable to electrical faults for its relatively small dimension. With the investigation of IR current features, this study mainly proposes an optimisation design strategy of IR to avoid excessive thermal stress at a start-up instant. The amplitude and phase relations of various rotor currents are reflected in the proposed current phasor diagram. In terms of the internal distribution of one concrete current, the circuit analysis theory is applied by dividing the whole conductor into multiple subconductors. The leakage flux around the conductors is simplified, respectively, according to the spatial symmetry. With reference to the existing bar design, the IR design scheme is mainly guided by two essential principles regarding the current-related parameters. Finally, the validity of the designing process of IR is verified by the coupled simulations and temperature-rise experiments. The surface temperature of the designed IR is not the highest, and the partial temperature difference is limited and reasonable.