CURRENT IN STATOR WINDINGS OF INDUCTION MOTORS

For the validation of the developed mathematical model of an induction motor an expression for calculating effective values of the consumed induction motor current from the network has been derive . Due to its small value the idle current of the motor is not taken into account, and the effective value of the reduced rotor winding current is taken as a stator winding current. Taken as basic is the expression for electric losses in the rotor winding of the induction motor, connecting the electromagnetic torque with the reduced current of the rotor winding. The obtained expression for the nominal values of the stator winding current shows that this current is exactly proportional to the electromagnetic moment of the induction motor. The proportionality factor primarily includes the optimum values of the stator bore relative diameter and the magnetic induction in the air gap, as well as the maximum value of a function of time, characterizing the degree of utilization of the engine’s active materials. The denominator of the proportionality factor for current contains phase voltage of the motor, thus the current is inversely proportional to that phase voltage. This is explained by the fact that at a fixed load on the shaft, the consumption of network capacity is also constant and therefore the phase current of the motor is inversely proportional to the phase voltage. Given the expression of current consumed from the power network and being optimal in terms of the motor’s active materials utilization, it is possible to assess the quality of existing series of induction motors designed and manufactured during the last decades. The result of the comparison showed that induction motors series 4A, RA and 7АИ are close enough to the optimum.

Authors: М. А. Vaganov, А. V. Shelemba

Direction: Electrical Engineering

Keywords: The current of the stator winding, the rotor winding current, electromagnetic torque, active resistance of the rotor winding, the optimum longitudinal transverse geometry, the effective value of the stator current, the proportionality factor for the current of the stator winding

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