Electrical parameter estimation considering the saturation effects in induction machines

This paper presents two methods to estimate the electrical parameters of induction motors to be applied at the self-commissioning phase. The first method considers the operation at linear conditions. From the linear model all parameters of the machine are estimated close to the rated operating point. After this, the saturation effects are included in the model and the magnetizing curve of the machine is obtained. In both cases the estimation procedures are based on its continuous-time model and is performed using the recursive least-squares algorithm (RLS). The use of the continuous time models requires the calculation of the derivatives of current and voltage measured signals, which are determined using polynomial interpolation (spline-type) techniques. To obtain all the electrical parameters the equivalent machine concept is defined. In order to avoid any machine intervention, only no-torque signals are used in the standstill tests. The conditions to produce these no-torque voltages with the PWM inverter, avoiding ripple torque generation, are analyzed. The paper includes experimental results which confirm the good performance of the proposed procedures.