Performance estimation of three-phase induction motors from no-load startup test without speed acquisition

This paper presents a simple method to estimate the steady-state performance of three-phase induction motors using only measurements of stator voltages and currents, acquired during a no-load startup test and without speed acquisition. The procedure consists of two steps: (a) firstly, the parameters of the single-cage model are estimated while considering the rotor resistance and the leakage inductances variable with the slip; and (b) secondly, the steady-state performance is estimated from the equivalent circuit using the estimated parameters. The proposed method is experimentally validated through tests involving 229 medium-power motors with power ranging from 22 to 90 kW; the estimated performance is then compared with measurements obtained through standardized laboratory tests. In addition, we also estimated the performance using a known double-cage model with constant parameters and compare the results with those obtained with the proposed model. We demonstrate that the proposed method provides accurate estimates for the main performance characteristics, such as efficiency and rated torque, which usually cannot be correctly assessed without direct measurements. The method makes it possible to estimate the performance of medium-power induction motors within acceptable accuracy through quick and low-cost tests requiring few sensors, making it a potential substitute for expensive and labor-intensive laboratory tests.