Thyristor electric motor drive is the electric motor drive in which the operating mode of its actuating motor (AM) or another actuator is regulated by a rectifying installation on thyristors.
In the AC thyristor electric motor drive, asynchronous and synchronous three-phase motors are most often used as the AM, the operating mode of which can be controlled by changing the frequency and amplitude of the voltage applied to the stator. In the case of a synchronous motor, the operating mode can be controlled also by changing the current in the field magnetizing coil. In a thyristor electric drive of this type which is powered by an alternating current source, the control rectifying installation is usually a thyristor frequency converter made with either a DC or AC intermediate link or a direct-coupled circuit. When powering such thyristor electric motor drives from a DC source, a self-commutated inverter is used as a rectifying installation. The reversal of the actuator in a thyristor AC drive is performed by changing the order of the voltage phase sequence applied to the stator.
Direct current motors with series, parallel, compound or independent excitation are used in a DC thyristor electric motor drive. Their operating modes regulation can be performed along the armature or field circuit. In a thyristor electric motor drive of this type powered by an alternating current source, the rectifying installation is a thyristor current rectifier. If the power supply of such thyristor electric motor drives is provided by a direct current source, the rectifying installation is implemented in the form of a pulse-type DC regulator or an "inverter - rectifier" system with an intermediate link of an increased frequency alternating current. In a thyristor DC electric motor drive, the reversal of the actuating motor is effected by changing the current direction in the armature winding or the motor field (using the second same rectifying installation, inverse-parallel connected with the first versus the actuating motor circuit).
For the galvanic isolation of the feed and load circuits, and also if necessary, to reconcile the power source and the actuating motor voltage values in the thyristor electric motor drive a transformer is used, including it at the input of the rectifying installation (if the thyristor electric drive is powered by an alternating current source) or in its intermediate link (when the thyristor drive is powered by a direct current). The control of the energy flow is carried out through the rectifying installation by means of a manual or automatic operating and regulation system. It includes power supplies, frequency and voltage control, generates control pulses for the power circuit rectifying installation thyristors, as well as short-circuit, overload and overvoltage protection blocks. Modern operating and regulation systems are performed on typical logic blocks and integrated circuits, which have small dimensions, high speed and reliability. Natural or forced air or liquid cooling is used to remove heat from thyristors and actuating motors.
Thyristor electric drives are used in various industries and transport. The power of the thyristor electric motor drive is from a few kW to 10 MW and higher.
Design mission
The device is designed for installation on the cargo cranes as the control panels for various crane mechanisms electric motors. They can be installed in place of existing panels (contactor, requiring repair or replacement)
Configuration
The device includes thyristor contactors, intermediate relays and time lag relays, realizing the commercial engine control algorithm, power machine, current motors protection relays. The thyristor contactors used in the stator circuit of the electric motor consist of 2 thyristors, switched back-to-back for each switched phase. The contactors used in the rotor circuit consist of 3 thyristors included in the triangle. The thyristors are switched on by applying the anode voltage through the quenching resistor and the contact of the control relay to the control electrode. The first relay is used as the actuator.
Benefits
In essence, the device is a contactor control system in which thyristors serve as the power contactors. Hence, its main advantage is that contacts do not burn out, which means there are less time and money for repair and preventive measure;
● the fault time of the crane is reduced;
● service charge is reduced.
Structurally on one panel, there are control devices of one mechanism (up to 4 motors) or two mechanisms (1 motor). All panels are produced for each crane individually, taking into account:
● factory control algorithm, including various braking modes (sub-synchronous braking, countercurrent braking, dynamic braking with external excitation or self-excitation);
● the existing on the crane cabinets dimensions ;
● power and low-current wires location.
In this regard, the device installation on the crane does not cause difficulties and does not require the replacement of controllers, rotor resistors, cables.
