Analysis of the Magnetic Losses from the Induction Machines Supplied by Inverters

Abstract

In the paper are being analyzed the magnetic losses that occur in the induction machines of low and medium power while being supplied by inverters realized with IGBT transistors. The analysis method is based on the over-position effect principle. As a working hypothesis is being neglected the saturation effect. During analyzes is being deduced the computing relations which allow the quality and quantity determination of the magnetic losses in the situation of the deforming supplying system. The theoretical results obtained using the computing program CALCMOT are back-up-ed by the experimental checks realized on two tri-phased induction motors with the powers: 0.37 [kW] / 1500 [rpm], respectively 1.1 kW]/1500[rpm].

The Behavior in Stationary Regime of an Induction Motor Powered by Static Frequency Converters

“…U 1(1) U e1 (1) I 1(1) I' 2 (1) I 01 (1) R m (1) X m(1) For the equivalent scheme in Fig.1.a, corresponding to the fundamental, the electrical parameters are defined as: nnnn n cs a nn n (5) In the relations (5), f1 and f1n are random frequencies of the rotating magnetic field, and the nominal frequency of the rotating magnetic field respectively. For  order harmonics, the scheme from Fig.…”

“…Under these conditions of non-sinusoidal supply, the asynchronous motor may be associated to an equivalent scheme, corresponding to all harmonics. The scheme operates in the fundamental frequency f1 (1) and it is represented in Fig. 2.…”

“…2. According to this scheme, it can be formally considered that the motors, in the case of supplying through the power frequency converter (the corresponding parameters and the dimensions of this situation are marked with index "CSF") behave as if they were fed in sinusoidal regime at fundamental's frequency, f1 (1) with the following voltages system:                   A 1(CSF) 1 B 1(CSF) 1 C 1(CSF) 1 22 u2 Us i n t ; u2 Us i n t ; u2 Us i n t 33 , (15) where,…”

“…The procedure is similar for the reactance. The rotor phase reactance, corresponding to the fundamental, X'2 (1), and also the reactance corresponding to the higher harmonics, X'2(  ), are replaced by an equivalent reactance X'2(CSF). As in the case of the rotor resistance, we can write:…”