Improving the energy efficiency of two-speed motors through the use of new pole-switched windings

Abstract

This article addresses the design and manufacturing of two-speed asynchronous motors with pole-changing windings. The need for developing two-speed motors with a single pole-changing winding is justified from the standpoint of energy and resource efficiency, as well as improved starting performance of high-power electric drives. An analysis of existing pole-changing winding designs is presented, highlighting their practical limitations in industrial applications. A new pole-changing winding with a 4/2 pole ratio and 48 stator slots was developed using the discrete spatial functions method based on star–delta–double star configurations. The electromagnetic characteristics of the proposed winding were analyzed. Based on this design, a new 4A200L8/4U3 two-speed motor was manufactured and tested under production conditions at the energy motors plant. Experimental results show that at p₁ = 4 pole pairs the motor delivers P₂ = 20 kW with efficiency η = 87%, cos φ = 0.82, I₁ = 43 A at slip s = 2.35%, while at p₂ = 2 pole pairs it develops P₂ = 36 kW with efficiency η = 91.5%, cos φ = 0.906, I₁ = 66 A at slip s = 1.5%. The results confirm more efficient utilization of the active magnetic core at lower polarity and demonstrate the feasibility of implementing such motors for energy-saving applications in heavy-duty drives requiring two equivalent operating speeds.