RU225396U1 - Rotary starting device - Google Patents

Abstract

The utility model relates to the field of electrical engineering, namely to the field of automated electric drives and converter technology. The technical objective of the claimed utility model is to create a simplified scheme for smoothly adjusting the speed and torque of an asynchronous motor, minimizing power controls for the acceleration or speed control process. The technical result is achieved by the fact that the device contains a fully controllable electronic switch (for example, a transistor), operating in the mode of a pulse-width regulator and providing a smooth change in the equivalent rotor resistance.

Description

The utility model relates to the field of electrical engineering, namely to the field of automated electric drives and converter technology.

There is a known method for controlling an asynchronous motor with a wound rotor, in which an inverter, unregulated and adjustable rectifiers are connected in series in the rotor circuit. The measured current at the inverter input is compared with the specified value and, based on the comparison results, the voltage at the output of the adjustable rectifier is adjusted to reduce the discrepancy between the measured and specified current values at the inverter input. The speed is adjusted by changing the voltage frequency at the inverter input (RU 2099850, 04/18/1996, N02R 7/63 (1995.01), N02R 7/46 (1995.01)).

There is a known method for regulating the speed of an asynchronous motor of a centrifugal hydraulic pump and a three-phase voltage converter for its implementation, in which a rectified and filtered voltage is formed and, using an inverter, converted into three-phase for pumping the engine. The frequency and sequence of switching of the inverter keys are set using the start pulses of the control unit, and the inverter is also periodically shunted using a shunt key. Pulse-width modulation of the engine pumping is carried out using a pumping switch connected to the inverter power circuit and switching the inverter power supply circuit according to the control unit signals synchronously with the inverter keys, and the latter is bypassed in pauses between turning on the pumping key (RU 2116517, 09.20.1996, F04D 15/00 (1995.01), N02R 7/46 (1995.01)).

A device and method for controlling an asynchronous electric motor is known, containing an inverter that converts DC voltage into alternating current with adjustable frequency and adjustable voltage in pulse-width modulation mode, and a circuit for regulating the output voltage of the inverter by changing the modulation depth by commands to change the output voltage, carried out by commands to change the components of the magnetizing and torque-forming current of the stator of an asynchronous motor, to which voltage is supplied from the inverter. The control device contains a circuit for measuring the torque-generating component of the stator current of an asynchronous motor, a circuit that adjusts the command to change the magnetizing component of the stator current in accordance with the difference between the values of the measured component of the magnetizing component of the stator current and the command, a circuit that adjusts the output frequency of the inverter in accordance with the adjusted a command to change the magnetizing component of the stator current and a circuit that limits the depth of modulation from below by the required value or other conditions (RU 2193814, 03/19/1997, N02R 21/00 (2000.01)).

A common disadvantage of these devices is the use of complex control circuits to solve simple problems of engine acceleration and limited speed control, which are redundant for a number of tasks of controlling technological processes using an electric drive.

The technical objective of the claimed utility model is to create a simplified scheme for smoothly adjusting the speed and torque of an asynchronous motor, minimizing power controls for the acceleration or speed control process.

The technical result is achieved by the fact that the device contains a fully controllable electronic switch (for example, a transistor), operating in the mode of a pulse-width regulator and providing a smooth change in the equivalent rotor resistance.

In fig. Figure 1 shows a diagram of the proposed device, where the following designations are adopted:

M - asynchronous motor with a wound rotor;

QF1 - high voltage switch;

VD1÷VD6 - three-phase bridge;

R1 - load resistor of rotor M;

R2 - rotor discharge resistor M;

VT1 - transistor switch;

KM1 - contactor;

CS controller - control system controller;

FOCL - bidirectional fiber-optic communication line;

Rx - control signal;

Tx - status signal.

The rotary starting device works as follows.

The equivalent rotor resistance of an asynchronous motor is a rectifier bridge, at the output of which a power device is installed, implemented in a resistive voltage divider and a switch based on a fully controlled bipolar transistor with an insulated gate. The transistor, through galvanically isolated devices, is controlled by a controller, implementing a given or adaptive pulse-width regulation algorithm. By changing the WID fill factor, a soft start and, if necessary, moderate control of engine speed are realized.

The electric drive is turned on by closing the high-voltage switch QF1. The contacts of the high-voltage switch QF1 give a command to the SU Controller to start switching the transistor switch VT1. The rotor voltage, with a frequency and amplitude proportional to the rotational speed M, is rectified by a three-phase diode bridge VD1÷VD6. The rectified voltage is applied to a powerful resistive divider R1, R2. The value of R1 determines the sliding of the motor M under load with the transistor switch VT1 fully open and, at the same time, sets the possible maximum peak current of this transistor switch VT1 at the beginning of the acceleration of the motor M (when the voltage at the output of the three-phase bridge VD1÷VD6 and on R2 is maximum). The sum of the resistor values (R1+R2) determines the starting torque on the motor shaft M when the high-voltage switch QF1 is turned on in the stator circuit, and is a calculated value for each specific motor and its starting conditions.

When the power transistor switch VT1 operates in the pulse-width controller (PWID) mode with a given rate (determined by changing the duty cycle as a function of time), the rms current in the rotor circuit determines the acceleration rate. The average equivalent value of the resistance, which is the load of the rotor winding M, is proportional to the fill factor WIR. With this method of regulation, M operates on an artificial mechanical characteristic determined by the supply frequency of the stator circuit and the value of the equivalent resistance of the rotor circuit.

As acceleration occurs, the WID duty cycle approaches unity, and the rms current through the transistor becomes maximum. If there is no need to regulate the speed M, after the complete and constant opening of the transistor switch VT1, the contactor KM1 closes, shunting the rotor circuit. M reaches a natural mechanical characteristic.

An additional security measure is the bidirectional optical communication of the fiber-optic line, which provides both control of the transistor switch VT1 by WID, and the CS Controller receives feedback on the state of the driver and transistor switch VT1.

The control system controller generates a predetermined acceleration rate or a customizable speed control law as a function of time. The SU controller checks the serviceability of the circuit by receiving the supply voltage, checking the Rx, Tx signals, data on the presence of ventilation, etc. The start of the WID is determined by the SU controller based on the presence of an acceleration task M, the voltage at the output of the three-phase bridge VD1÷VD6 and the flow of current in the circuit R1, R2.

The SU controller also provides, if necessary, protection of the circuit of the transistor switch VT1 and R1, R2 by current and voltage, generating a collective alarm signal for external devices. The error code displayed on the controller screen will help identify the cause of the failure.

Claims (1)

A control device for an asynchronous motor with a wound rotor, containing a rectifier bridge, the input of which is connected to the phase terminals of the rotor of the asynchronous motor, characterized in that a resistive voltage divider consisting of a discharge resistor and a load resistor connected in series is connected to the output of the rectifier bridge, and an electronic switch is connected in parallel to the discharge resistor, controlled by a controller that implements a pulse-width modulation algorithm.

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