This paper deals with deep bar effect in squirrel cage rotors. Induction machines using this type of rotor are widespread. Some cages enhance the deep bar effect to improve the starting performances. In cited references, the analytical calculation of the equivalent circuit parameters has only been investigated for single-cage and double-cage rotors. In this paper, an analytical model is developed for the general case of n-cage rotor. The expressions of the equivalent circuit parameters are given and then applied to a double-cage slot. The results are compared to a finite element analysis for several slot dimensions. The limits of the model are shown for specific slot dimensions and conductor shapes. This paper shows that under typical dimensions the model provides good accuracy with the simulations on a wide range of frequencies.
The surfacemounted permanent magnet (SMPM) synchronous motor has high torque density and good dynamic response. Consequently, these machines have found applications in electridhybrid vehicles, where size and volume are at a premium and dynamic response is important for vehicle performance. In these applications, high torque output from the motor is required for short time duration. The high stator current associated with this mode of operation can induce saturation in portions of the motor magnetic circuit and thus introduce saliency into a normally symmetric machine. This phenomenon can be exploited in order to maximize the torque output of the motor for the same stator current. The case of a 75kW SMPM machine for automotive application is presented. By taking advantage of the saturation induced reluctance torque, up to 4% extra torque output is produced for the same maximum stator current. The improved performance is predicted using FEM calculations and is verified through experimental results.
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