Asynchronous phase rotor motor in reactive power compensator mode

Abstract

reactive power compensation remains an important factor for energy keeping. Usually, kondenser banks are used for compensation, the disadvantage of which is the difficulty of regulating the capacitance value with variable consumption of reactive power. For smooth regulation of reactive power, synchronous motors and semiconductor static compensators are used. But the search for using other alternative means of reactive power compensation remains relevant.

As an alternative compensator for reactive power, the article proposes the use of an induction motor with dual power supply. This problem is solved in two stages. At the first stage, a theoretical analysis of the process of generating reactive power by a dual-supply induction motor is considered. With dual power supply, a sinusoidal voltage is supplied to the stator, and a direct voltage is supplied to the rotor. In this case, the rotor winding turns into a DC electromagnet, which rotates synchronously with the rotational magnetic field created by the fixed stator windings

The magnetic field of the rotor winding moves relative to the stationary stator windings with the speed of the moving magnetic field of the stator. Their magnetic axes coincide because the engine is idling. To justify the reactive power generation mode, vector diagrams of the stator and rotor voltages and currents were compiled for three dual-supply asynchronous motor operation modes: 1) reactive power consumption mode, 2) non-consumption mode and 3) generation mode.

At the second stage, a power circuit and a control circuit for a dual-supply asynchronous motor are developed. The power circuit includes a phase meter in the stator electric circuit to measure the phase angle of the stator current from voltage, an ammeter of the electromagnetic system to measure the magnitude of the stator winding current. The rotor circuit includes additional active resistors for accelerating the motor to under synchronous speed, a direct cur-rent electromagnetic relay that measures the magnitude of the electromotive force of the rotor winding. A thyristor rectifier with feedback on the rotor winding current has been adopted as a direct current source.

A relay circuit has been developed for controlling a dual-supply induction motor. Experimental research have been carried out to determine the dependence of the stator current and its phase shift relative to the stator voltage on the value of the rotor winding current.

According to the results of the experiments, a graph of the dependence of the stator winding current on the value of the direct current of the rotor winding is constructed. From the graph it follows that with increasing rotor cur-rent, the stator current changes. First, the stator current decreases to a minimum value and then increases. This means that the type of stator current varies from inductive to active and to capacitive.

Thus, the use of an induction motor for generating re-active power has advantages over capacitor banks, as it allows its smooth controlment. But the power loss for generating reactive energy is greater than for capacitor banks.