SU847481A1 - Method of control of phase-wound induction electric motor - Google Patents

Description

I

The invention relates to electrical engineering and can be applied to electric drives of powerful mechanisms that require deep control of the rotational speed in a wide range.

There is a known method of controlling an asynchronous motor with a phase-rotor, based on a combination of two types of dual power circuits. The transition from one circuit to another is accomplished by switching the stator winding. The latter is connected either to the AC mains or to the rotor windings fed from an auxiliary voltage source, having previously disconnected it from the AC mains Dj

The disadvantages of this method of controlling an asynchronous electric motor are the presence within the range of speed control - rotation of the rotor of the dead zones in which normal operation of the electric motor is impossible, as well as low energy indices.

The closest to the invention to the technical essence and the achieved result is a method of controlling an induction motor with a phase-rotor, in which the stator windings of the induction motor from an alternating voltage source are disconnected, adjust the amplitude and frequency of the energized voltage from an alternating voltage source through a controlled power converter with the subsequent switching of the stator windings and changing the order of the phase alternation at the output of the Uprash: capacitor of the power converter fZj.

The disadvantage of this method of controlling the speed of rotation of the rotor is the limited range of adjustment of the speed of rotation of the electric motor.

The purpose of the invention is to expand the range of adjustment of the rotational speed of the rotor and the expansion: & nergycKHx indicators.

The goal is achieved by the fact that after disconnecting the stator windings from the alternating voltage source, they are connected to the rotor windings with the phase alternation, the frequency at the converter output changes from zero to the limit, providing the rotor rotation speed equal to twice the rotation speed in the gap, after which the stator windings are disconnected from the rotor windings and connected to a source of alternating voltage, change the order of alternation of phap at the output of the power converter and change its output frequency from the value of Equalizing to zero, providing a rotor speed equal to the synchronous field velocity in the gap at the frequency of the alternating voltage source, then set the initial phase rotation order at the output of the power converter and change the era output frequency from zero to the maximum, ensuring the rotor speed of the rotor corresponding to the sum of the limiting frequencies of the alternating voltage source and the power converter.

The drawing shows a diagram of the device that implements the proposed method.

The device consists of an asynchronous electric motor 1, the stator winding of which can be connected to: a source of alternating voltage 2 via contacts 3 of the contactor or rotor windings 4 via contacts 5 of the contactor. The windings of the rotor 4 are connected to the output of a controlled power converter 6, the power input of which is connected to a source of alternating voltage 2. Sensors for monitoring variable modes and an electric drive control unit (not shown in the diagram) are contained in block 6,

The device implements the proposed method works as follows.

The stator winding of the electric motor 1 is disconnected from the alternating voltage source 2 by the contacts 3 of the contactor, and is electrically connected to the rotor winding 4 with alternating phases using the contacts 5 of the contactor. The output of the power Converter 6 adjusts

frequency and amplitude of voltage from zero to maximum, determined by its circuit design. For example, the direct converter according to the zero scheme is up to J6 Hz. on bridge circuit - up to 16 Hz, on bridge circuit - up to 25 Hz, up to 25 Hz, p. forced switching - up to 50 Hz and above ,. as a result, the rotor speed takes a value from zero to double the rotational speed of the field in the gap. After that, the stator windings are disconnected from the rotor windings 4 by the contacts 5 of the contactor and connected to the alternating voltage source 2 by the contacts 3 of the contactor. At the output of the power converter 6, the phase rotation order is changed and its output is adjusted to the frequency from the slip value to zero.

Claims (2)

At the same time, the rotational speed of the rotor increases to a synchronous speed of zero S gap, determined by the limiting frequency of the source 2 of alternating voltage. For example, for a network of 50 Hz - 3000 rpm for an engine with one pair of poles. In the case of an inverter, this value increases accordingly. Then, the initial order of phase alternation at the output of the power converter 6 is set and its output frequency is changed from zero to the limit. In this case, the rotational speed of the rotor of the electric motor passes into the zone above the synchronous rotational speed of the rotor and reaches a JV value corresponding to the sum of the limiting frequencies of the alternating voltage source and the power converter. The reverse sequence of operations is possible, i.e. when the rotational speed of the rotor is adjusted from zero to the synchronous rotational speed of the field in the gap, changing the frequency at the output of the power converter from a value corresponding to the frequency of the synchronous rotor level. In this case, the stator winding of the electric motor 1 is connected to the alternating voltage source 2, and the rotor windings 4 are connected to the output of the power converter 6, t, e. contactor contacts 3 are closed, and contacts 5 are open. After the rotor has reached a synchronous or lower rotational speed, the stator windings are switched, the Contactor contacts 3 open, and the contacts 5 close. At the output of the power converter 6, the phase rotation order is changed and the output frequency is adjusted from the value corresponding to the slip to the limit determined by its circuit design. The invention The method of controlling an asynchronous motor with a phase-rotor, in which the windings of the asynchronous motor are disconnected from the alternating voltage source, the amplitude and frequency of the applied voltage from the alternating voltage source are controlled through a controlled power converter with subsequent switching of stator windings and changing phase alternation at the output (controlled power converter, characterized in that, in order to extend the range of regulation and increase energy indicators, after disconnecting the stator windings from the alternating voltage source, connect them to the rotor windings with alternating phases, change the frequency at the output 8 1 of the converter from zero to the limit, providing the rotor rotation speed equal to double the rotation speed of the field in the gap, then the stator windings are disconnected from the rotor windings and connected to the alternating voltage source, change the order of phase alternation at the output of the power converter and change its output frequency from the value of To zero, providing the rotor rotation speed equal to the synchronous field velocity in the gap at the frequency of the alternating voltage source, then set the initial phase rotation order at the output of the power converter and change its output frequency from zero to the maximum rotor rotation speed corresponding to the sum limiting frequencies of an alternating voltage source and a power converter. Sources of information taken into account in the examination 1. The author's certificate of the USSR No. 63399, cl. H 02 R 7/08, 1942. 2. USSR author's certificate number 229879, cl. H 03 R 1/24, 1965.