A Method for Determining Nonlinear Inductances of Electrical Equivalent Circuit for Three-Phase Induction Motor

Accurate values of the equivalent circuit parameters of three-phase induction motor are critical for its precise performance evaluation. Motor parameters, mainly the inductances obtained from conventional no-load and blocked rotor tests are constant parameters for all load conditions. However, due to inherent nature of the core material property, i.e., nonlinear B-H curve, the inductances do not remain constant in practical. This work proposes a method comprising simple tests using which all the motor nonlinear inductances can be determined. The motor mathematical model under the test conditions is also developed. The results obtained from equivalent circuit using the nonlinear inductances are validated with experimental results for two different motors and good agreement has been achieved. It is observed that the motor performances calculated using nonlinear inductances matches more closely to experimental results as compared to that using constant inductances.