Solving Induction Motor Equivalent Circuit using Numerical Methods for an In-Service and Nonintrusive Motor Efficiency Estimation Method

Motor efficiency evaluation enables the energy savings in industry. However, because of the uninterrupted characteristic of industrial processes, traditional methods defined in IEEE Std-112 cannot be used for these in-service motors. A novel nonintrusive method for in-service motor efficiency estimation based on a modified induction motor equivalent circuit has been developed by the authors. A highly nonlinear and 4-dimensional system of equations needs to be solved to obtain the parameters of the motor equivalent circuit and finally the motor efficiency. This paper continues this topic and presents an in-depth discussion on solving these motor parameters using three numerical methods under various conditions. Newton´s method exhibits the best suitability in this application because of its simplicity and fast convergence. In the rare cases where Newton´s method does not converge, the particle swam optimization and simulated annealing methods are used. Finally, the proposed motor efficiency estimation method is verified by the experimental results from a 4-pole 7.5 hp TEFC induction motor. The performances of these three numerical methods are evaluated and compared