SU877782A1 - Starting device for self-exciting self-sustained inverter - Google Patents

Description

. t- The invention relates to power converter technology and can be used in self-excited self-excitation current inverters loaded on an oscillating circuit, in particular in frequency converters with a DC link for electrothermal, high-frequency quenching and smelting of metals. A trigger for an ion frequency converter is known. This device contains an autonomous inverter with a switching capacitor connected in parallel to the output and a load oscillating circuit with a starting resistor, parallel to which another resistor is connected by a contactor and a parallel connection to them that completely shunts these two starting resistors. The use of such a device during the start-up of autonomous current inverters does not allow getting high speed, and also has low reliability due to the presence of mechanical contacts in the power circuit, the response time of which is long 1. The closest in technical essence to the present invention is a device that includes an autonomous current inverter with a switching capacitor connected in parallel to the output of the inverter and a load oscillating circuit with anti-parallel thyristors and a starting resistor. Introducing anti-parallel thyristors that shunt the starting resistor according to a certain predetermined law can significantly improve the reliability and speed during start-up 2. However, the control system for counter-parallel thyristors is a rather complicated device that must determine the duration of each cycle of the valve switch and according to this, form, according to a certain law, changing from tact to tact, two sequences of pulses applied to these thyristors. In this case, in the case of a change in the load over a wide range, the reliability of this method of start-up is reduced, since the required turn-off time of the thyristors of the gate-switch depends on the parameters of the load circuit and the duration of the short-circuited state of the counter-parallel thyristors in each cycle.

 The purpose of the invention is to simplify the control system of counter-parallel thyristors, which are used to start an autonomous current-driven inverter with self-excitation, and to increase the reliability of the start.

The goal is achieved by: in a starting device for an autonomous inverter with self-excitation, made on the basis of a converter bridge with a smoothing choke in the DC circuit and with a switching capacitor in the diagonal of alternating current containing counter-parallel connected thyristors connected between the AC terminals the bridge and output pins, and the control unit of these Tiris TopaiyiH, in the DC circuit of the bridge, a current sensor and a voltage sensor are connected, the outputs of which through the OR circuit SCB relay element are connected to the input of said control unit.

The drawing shows a functional diagram of the Converter with a starting device.

The converter contains an autonomous current inverter 1, made on the basis of a converter bridge 2 with a choke 3 and a capacitor 4. Load 5 is connected to bridge 2 through thyristors 6, controlled by signals of control unit 7, sensor 8 is switched on in the constant bridge circuit of bridge 2. current and voltage sensor 9 connected through the circuit OR 10 and the relay element 11 to the input of the control unit 7,

The starting device of an autonomous inverter. With self-excitation operates as follows.

When the autonomous current inverter is started up until the current or voltage in the input circuit has increased to the specified values, the control system 7 does not generate control pulses, the anti-parallel thyristors are locked, and the load oscillating circuit is disconnected. Therefore, there is a rapid increase in the current in the input circuit and the voltage on the switching capacitor 4. When the input current or input voltage reaches a predetermined level, the signal of the corresponding sensor 8 or 9 through the circuit OR

110 is supplied to a relay element 11 including the control system 7. Control pulses to the counter-parallel thyristors arrive at zero steering angle. Thyristors b 5 connect the load oscillating circuit 5 directly to the output of the inverter. During further operation of the inverter, the counter-parallel thyristors 6 remain completely open,

The use of a starter device makes it possible to simplify the control system of counter-parallel thyristors, since it performs in the proposed device a simple function of connecting the load oscillatory

5 circuits after the input current or voltage on the switching capacitor reaches a predetermined value. At the same time, the reliability of the start-up increases, since in the first cycles the autonomous

0 a self-excited current inverter operates on a pure capacitive load up to the set of required switching voltage on the capacitor 4,

Claims (1)

Invention Formula Starting device for autonomous current exciter with self-excitation, made on the basis of a converter bridge with a smoothing choke. in a constant circuit and with a switching capacitor in the diagonal of an alternating current, containing anti-parallel connected thyristors connected between the outputs of the alternating current of the bridge and the output outputs, and a thyristor control unit, characterized in that, in order to simplify and improve reliability, the bridge's direct current includes a current sensor and a voltage sensor, the outputs of which through the OR circuit and the relay element are connected to the input of said control unit, . Information sources, taken into account in the examination 1, USSR Author's Certificate No. 218291, class, H 02 M 7/515, 1968, 2, USSR Author's Certificate No. 288122, cl. H 02 M 7/515, 1969.