Development of double-layer rotors for asynchronous drives of mining and transport machines

Abstract

Due to the simplicity of the design and high energy indicators, asynchronous electric motors (AM) are the main consumers in the power supply systems of mining enterprises. Large starting currents of motors lead to heating and damage to the insulation of the stator windings. An urgent problem to improve the reliability of mining and transport machines is the development of AM, providing smooth transients with increased starting torque and reduced starting current. In an AM with a closed-loop rotor, a magnetic conductor is performed by a charged cylinder on the rotor shaft, which is made of electrotechnical steel with high magnetic permeability. The electrical conductor is often a squirrel cage-type short-circuited rotor made of a material with high specific conductivity. A technology has been developed for producing ferro-copper alloys for the active outer cylinder of a double-layer rotor, replacing a "squirrel cage". These alloys combine the properties of an electric current conductor and a magnetic flux. This allows us to obtain the effect of displacement and reduction of current in the rotor, which is accompanied by an increase in the effective resistance of the rotor and the electromagnetic torque during the start-up process. Full-scale experiments have been carried out with asynchronous motors with various rotors having a displacement effect. Motors having double-cage or deep-groove rotors develop an increased starting torque at a relatively lower starting current. The starting quality of these motors is, on average, 1,5 times higher than that of a motor without current displacement. Replacing a double-cage rotor with a double-layer rotor leads to a decrease in the starting current by 25% and an increase in the starting torque by an average of 2,5 times. The quality factor of starting an asynchronous motor with a double-layer rotor is 3-4 times higher than the quality factor of starting similar motors with a conventional rotor cage without current displacement, 2-2,5 times compared with a double cage or a deep groove and 1,3-1,5 times compared with a rotor with a high electrical resistivity. The use of double-layer rotors limits voltage fluctuations in the network, ensures a reliable, smooth start, eliminates vibration and extends the service life of all equipment.