Electric motors are the most fundamental source of motion generation mechanisms in both industrial and household products. Noise and vibration problems in such products can be remedied in general at each of the three stages; source-transmission path-receiver. Some problems, however, caused inherently by the motors can not be successfully resolved by working on the transmission path or the receiver alone. In this regard, importance of the noise and vibration problems in the motor itself has been increasing so far. In this paper, a method is presented, which can calculate electromagnetic forces in quantitative as well as qualitative aspects, based on equivalent transformer circuit. Here the rotor slot skew, permeance fluctuations and rotor dynamics are also taken into consideration. Even though this method does not yield information so detailed as the FEM, the computational burden is very low. By using this method, distributions of the electromagnetic forces in both spatial and temporal frequency domain are investigated and effects of the rotor eccentricity and rotor-slot-opening are also investigated. The reason why the exciting force increases and consequently the noise level goes up in reality with loading is explained. Finally, results of the simulation are compared with the experiments.
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