Publication: Induction motor modeling using finite element method
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Date
2010-04-01
Authors
Leong, Kong Nan
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Abstract
The objectives of this thesis are to model induction motor by finite element method (Opera-2D), to obtain motor equivalent circuit parameters from finite element method and compared with measurements and to model the effect of broken rotor bars on motor performance. The prototype of the motor to be modeled is a 24 slots and 30 rotor bars squirrel cage induction motor. This motor is a 3-phase 4-pole machine with power ratings of 0.5 Hp. Characteristics of an induction motor are studied through the torque-speed curve, its machine parameters and the equivalent circuit of the motor. The torque-speed curve was obtained through torque measurement of the prototype. Meanwhile, no-load and locked rotor test were performed on the prototype to obtain the machine parameters. With the dimension of the prototype, a model was created using Opera-2D software. The model was subjected to two types of analysis which includes steady state AC analysis (AC analysis) and rotating machine analysis (RM analysis). The results from simulation were compared with the results obtained from experimental and measurements on the prototype. The torque-speed curve from both the analysis is almost similar. However the rated torque from the simulation is not exactly the same with rated torque obtained from the measurement on the prototype. Other than that, the machine parameters obtained from simulation and experimental differ in the range of 4% to 23%. The differences are due to ideal case assumption of the software and other assumption made for the simulation. The broken rotor bar effect on the motor performance was studied using the rotating machine analysis (RM analysis). It is found out that the effects of broken bars were visible in the stator current waveform, resultant magnetic pull and the airgap flux density waveform. Besides, the location of the broken bars greatly affects the results in the stator current waveform, resultant magnetic pull and the airgap flux density waveform. Opera-2D software can be used to model this 24 slots and 30 rotor bars squirrel-cage induction motor successfully and the effect of broken rotor bars can be easily studied through RM analysis by Opera-2D software.