SU1277224A1 - Control device for hoisting electromagnet - Google Patents

Abstract

The invention relates to a lifting and transport equipment and can be applied to control a lifting electromagnet. The aim of the invention is to reduce the heating of the lifting electromagnet with a constant performance. The electromagnet 4 is connected to the output of the reverse rectifier, the magnetization group of which is made in the form of a three-phase thyristor bridge rectifier 2, and the demagnetization group is in the form of a single-phase half-wave rectifier 3. The switching mode is performed by a three-position key 5. The switch-on mode is forced. When the current relay 7 trips, its contact 8 opens. This increases the resistance in the control circuit of the thyristors of the bridge rectifier 2, and consequently, the angle of opening of the thyristor. When the magnetization group is turned off, the energy accumulated in the winding (L of electromagnet 4, is recovered through the three-phase transformer into the network. 1 Il.

Description

 The invention relates to lifting and handling equipment and can be applied to control lifting electromagnets.

The purpose of the invention is to reduce the heating of a lifting electromagnet with constant performance.

The drawing shows a diagram of a device for controlling a lifting electromagnet.

The device includes a three-phase transformer: torus 1, a reversible controlled rectifier, which includes a magnetization group 2, made in the form of a three-phase thyristor bridge emulator, a demagnetization group 3, made in the form of a single-phase one-wavelength rectifier consisting of two thyristors, and a master, a master, 3, control unit 5, made in the form of a three-position switch, protective diodes 6, current relay 7 with opening contact 3, resistor 9, three-phase diode rectifier 10.

The magnetization of the electromagnet mode (three-position control switch in position B), the power current flows, excluding periods of commutation of the thyristors through one phase power transformer secondary winding - a thyristor anode group transducer winding electromagnet coil current relays, one thyristor cathode group transducer, a second phase power transformer winding .

At the initial moment of time, the contact of the current relay is closed, the control current of the thyristors is maximum, the output voltage of the converter is high. When the current in the electromagnet circuit reaches the current of the relay, it triggers and opens its contact, an additional resistance is introduced into the control circuit, the output voltage of the converter decreases, thus the process of forcing the power current occurs.

When switching the control key 5 to the position A, the supply of voltage to the control electrodes of the thyristors stops. However, due to the large inductance of the electromagnet winding, significant electromagnetic energy accumulates in it, therefore the power current continues to flow through the circuit discussed above through two previously opened thyristors, and

energy is the electromagnet winding. The current is continuous, it coincides with the direction of the EMF of the winding and the electromagnet. At the same time, the voltage on the secondary windings of the transformer is variable. Therefore, during periods when the secondary voltage of the transformer is directed oppositely to the EMF of the electromagnet winding (inverter mode), there is an intense decrease in the power current. In the next period (the rectifier mode) there is a slight increase in current. Inverter and rectifier modes alternate, 8 invertor mode, the current decreases by a larger amount than increases in the rectifier mode. After the current becomes less than the holding current

They are closed and the electromagnet winding is disconnected from the network. The decay time of the current to a value less than the holding current of the thyristor is determined by the time constant of the electromagnet winding, and for lifting electromagnets of the type is approximately 1-1.5 s. After this, the control key is turned to position C, the voltage of the opposite sign is briefly applied to the winding of the electromagnet, which allows removing the residual magnetization of the lifting electromagnet. Then

key 5 is again in position A,

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The use of an inverter mode of operation of the magnetization group of the rectifier will make it possible to exclude the discharge resistance and the diode from the circuit, since the magnetization circuit is used as the discharge circuit.

In the demagnetization mode, energy stored in the electromagnet winding is recovered.

Claims (1)

The invention relates to lifting equipment and can be used to control lifting electromagnets. The purpose of the invention is to reduce the heating of a lifting electromagnet with constant performance. The drawing shows a diagram of a device for controlling a lifting electromagnet. The device includes a three-phase transformer: torus 1, a reversible controlled rectifier, which includes a magnetization group 2, made in the form of a three-phase thyristor bridge emulator, a demagnetization group 3, made in the form of a single-phase one-wavelength rectifier consisting of two thyristors, and a master, a master, 3, control unit 5, made in the form of a three-position switch, protective diodes 6, current relay 7 with disconnecting contact 3, resistor 9, three-phase diode rectifier 10. In the magnetizing mode of an electromagnet (three-position control switch in position B) the power current flows, excluding the switching periods of the thyristors through one phase secondary winding of the transformer - one thyristor of the anode group of the converter, the winding of the electromagnet, the winding of the current relay, one thyristor of the cathode group of the converter, the second phase winding of the transformer. At the initial moment of time, the contact current relay is closed, the control current of the thyristors is maximum, the output voltage of the converter is increased. When the current in the electromagnet circuit reaches the value of the relay actuation, it triggers and opens its contact, an additional resistance is introduced into the control circuit, the output voltage of the converter decreases so the power current is formed. When switching the control key 5 to the position A, the supply of voltage to the control electrodes of the thyristors stops. However, due to the high inductance of the electromagnet winding, significant electromagnetic energy is accumulated in it, so the power current continues to flow through the circuit discussed above through two previously opened thyristors, and the source of energy is the electromagnet winding. The current is continuous, it coincides with the direction of the EMF winding of the electromagnet. At the same time, the voltage on the secondary windings of the transformer is variable. Therefore, during periods when the secondary voltage of the transformer is directed oppositely to the EMF of the electromagnet winding (inverter mode), there is an intense decrease in the power current. In the next period (rectifying mode), there is a slight increase in current. The inverter and rectifier modes alternate; in the inverter mode, the current decreases by a larger amount than it increases in the rectifier mode. After the current becomes less than the thyristor holding current, they close and the electromagnet winding is disconnected from the network. The decay time of the current to a value less than the holding current of the thyristor is determined by the time constant of the electromagnet winding, and for lifting electromagnets of the type is approximately 1-1.5 s. After this, the control key is turned to position C, the voltage of the opposite sign is briefly applied to the winding of the electromagnet, which allows removing the residual magnetization of the lifting electromagnet. After that, key 5 is again set to position A. Using the inverter mode of operation of the magnetization group of the rectifier will eliminate the discharge resistance and the diode from the circuit, since the magnetization circuit is used as the discharge circuit. In the demagnetization mode, energy stored in the electromagnet winding is recovered. Claims An apparatus for controlling a lifting electromagnet comprising a reversible controlled rectifier comprising a magnetization group and a demagnetization group, terminals for connecting an electromagnet winding, a control unit, a resistor, protective diodes and terminals for connecting to a three-phase mains supply, and terminals for connecting The windings of the electromagnet are connected to the outputs of a reversible controlled rectifier, characterized in that, in order to reduce heating, the electromagnet with a constant a three-phase diode rectifier, a three-phase transformer, a current relay with a break contact, a magnetization group of the reversing rectifier is made in the form of a three-phase thyristor bridge rectifier, and a demagnetization group in the form of a single-phase single-wave rectifier, and a unformed rectifier; control is made in the form of a three-position key, and the cathode of one of the protective diodes, the anodes of the The shield diodes in the magnetization group are interconnected and connected to the first fixed contact of the three-position key, the anodes of the protective diodes of the demagnetization group interconnected and connected to the second fixed contact of the three-position key current relay, another output of the specified resistor through a three-phase diode rectifier connected to the secondary three-phase transformer a, the primary winding of which is connected with leads for the connection of a three-phase mains, the winding of the current relay is connected to the coil of the electromagnet.