Impedance calculation for die-cast rotors

Abstract:
To easily obtain the operation characteristics of induction motors, the application of the well-known equivalent circuit diagram is practical and convenient. In order to gain more precise characteristics the circuit diagram could even be extended to model additional losses or higher spatial harmonics. When using induction machines with die-cast rotors the value of the rotor impedance is frequency dependent, and especially when using rotor with closed rotor slots it depends also strongly on the operating current. Particularly in the case of closed rotor slots the classical literature is of no help when it comes to the calculation of the rotor impedance from geometry. With the help of the FEM-method the rotor parameters could be pre-calculated precisely and stored in tables for any geometry, accountinglbr non-linear material conditions and skin-effect. The FEM calculations were done using a widely-used, commercial software, which according to the authors experience with other FEM-software represents a good state in respect of functionality and performance of comercially available software.