Abstract
Due to the rapid increase in the number of variable speed AC drives, the analysis of their energy efficiency has become highly essential. However, such an analysis requires consideration of a wide variety of factors. This includes considering the energy loss in the frequency converter, depending on the motor type. In this article, a computational comparison of the energy properties of variable frequency pump drive employing two types of electric machines, i.e. an induction and a synchronous reluctance motor, is presented. The effect of the motor type on the losses in a low-voltage two-stage frequency converter using analytical and numerical models, with a further comparison, is investigated. Furthermore, an alternative approach to determine the current magnitude and power factor of the load of the converter is suggested. Eventually, this study provides a quantitative estimate of the increase in losses in the converter caused by using the two different motor types. Several experimental tests are conducted on induction and synchronous 1.1 kW reluctance motors.
Highlights
In the recent years, improving the energy efficiency of variable speed electric drives has received a great attention; this is because the electric motors consume about 70% of industrial electricity and about 40%–45% of produced electricity [1,2,3]
It can be seen that when using synchronous reluctance motors (SynRMs) the share of losses in complete drive module (CDM) from the total losses of the drive is significantly higher due to the reduction of losses in the motor
The obtained calculated losses of the analytical and the numerical methods correspond; the proposed analytical model would be preferred in the simulations because of the low computation time
Summary
In the recent years, improving the energy efficiency of variable speed electric drives has received a great attention; this is because the electric motors consume about 70% of industrial electricity and about 40%–45% of produced electricity [1,2,3]. In order to determine the IE class of FCs, IEC 61800-9-2 suggests a number of methods, among them an analytical loss model in FCs. Recently, some research work has been devoted to the comparative analysis of various types of electric motors in variable speed drive applications [7,8,9]. To improve the models of reference [5], the authors in this article suggest applying interpolation to the data on the motor efficiency, as described in reference [5,9,23], and to the data on its current and power factor values, to calculate losses in the FC This approach is more accurate and general than the indirect determination of these values, based on the relative values of the motor torque and the apparent power of the FC, as proposed in reference [5]. A quantitative estimation of the increase in losses in the frequency converter when using SynRM is investigated compared with that of IM
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