Designing an Energy-Saving Induction Motor Operating in a Wide Frequency Range

Induction motors are an important consumer of electricity. Among induction motors, speed-regulated induction motors have the greatest energy-saving potential. However, motors operating in a very wide speed range require a completely different approach than motors operating on a single supply frequency. An example of such motors are the drives of industrial washing machines. The article aimed to present how using field-circuit methods, but above all, analytical methods increase the efficiency of such a motor by changing its design. Thanks to the change of the design and the core material, it was possible to obtain the efficiency of the motor for the frequency of 10 and 20 Hz, meeting the requirements of the IE1 efficiency class specified for the frequency of 50 Hz, while for the frequency of 10 Hz it is 17.9% higher than in the currently produced motor, and for 20 Hz—by 11.1%, while for the frequency of 350 Hz the level of efficiency was corresponding to class IE4. The presented considerations may be the basis for such a procedure for other drives with similar properties. Additionally, an important element of the article is the refinement of the analytical method of determining core losses.