Improved estimation of induction machine parameters

Induction machine parameters are often estimated from no-load and blocked-rotor tests. At different machine operating points, the parameter values may vary because of the nonlinearities caused mainly by the skin effect and saturation. Some investigators have already published techniques to estimate the parameters more accurately. Their techniques are either complicated or involve many simplified assumptions and are valid only at specific points. This paper proposes a less complicated yet accurate technique by making use of on-load machine performance measurements as input data. The proposed technique is formulated in an iterative algorithm while making few assumptions. The results obtained clearly show the influence of the skin effect and saturation on the rotor resistance, magnetizing and leakage reactances. Handy expressions that can predict the machine parameters as functions of the slip are derived. Machine performance is calculated by using the estimated parameters. This performance is compared with the true measurements. Excellent agreement is encountered. The performance is also compared with that obtained from a recent published technique and the superiority of the proposed technique is noted.