On-load modelling of three-phase induction motors. A new method for determination of the rated current and equivalent circuit parameters

One of the main problems when analysing and modelling three-phase induction motors by means of finite elements is the calculation of currents through rotor bars. A method for calculating the necessary currents for the on-load analysis of the motor as well as for determining the parameters X'/sub 2/ and R'/sub 2/ is presented in this paper. The rest of the equivalent circuit parameters are determined by simulating the no-load behaviour of the machine. The key to this method lies on the calculation of the magnetising current and on the correction of errors made when derivatives are substituted by incremental quotients to calculate the induced EMF in the rotor bars. The method suggested has been used to analyse and design three-phase induction motors by means of the finite element method, being the results obtained similar to those measured in the laboratory once the machine has been manufactured.