Estimation of back-EMF of PM BLDC motors using derivative of FE solutions

Based on finite element analysis, an effective method is developed to estimate the back-emf produced in electric machines during operation. For a given rotor position, the method utilizes only one finite element solution in its computation, and no numerical derivative is required. The accuracy of the back-emf estimated can thus be improved, and the computing time can be reduced. Computational results obtained from the proposed method to calculate the back-emf of permanent magnet brushless DC motor is introduced in the paper.