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

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 doublecage 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.