SU760329A1 - Three-phase thyristorized switching device - Google Patents

Description

The invention relates to electrical engineering and can be applied to connect loads of a different nature to a three-phase AC network.

Known thyristor switches AC [1] with a direct connection of the power and control circuits.

The disadvantage of the known switch is the appearance of a voltage cut-off at a load of 30 el.grad.

The closest in technical essence to the present invention is a switch [2], containing counter-parallel-connected valves and a control unit for them, made in the form of a diode rectifier, the output of which is connected to the control electrodes of the valves through a control switch, resistors and isolation diodes.

The disadvantages of the device include the dependence of the parameters of the control pulse of the valves on the angle of activation of the control key and the appearance of a transistor effect due to the simultaneous supply of a control pulse to the valves under direct and reverse voltage. Everything

2

This leads to a deterioration in the reliability of the valves.

The aim of the invention is to improve the reliability of the thyristor.

5 The goal is achieved by the fact that in a three-phase thyristor switch, containing anti-parallel controlled and unmanaged valves in each phase and Yu control unit, made in the form of a three-phase diode rectifier, the output of which through a control switch, resistors and isolation diodes connected to control valve electrodes, control unit

provided with threshold elements included in the control electrode circuits of the valves and additional diodes that shunt the junction of the control 20 electrode-anode of the valves.

FIG. 1 is a circuit diagram of the switch.

FIG. Figure 2 shows the timing diagrams of the active load operation.

The switch contains anti-parallel controlled valves (thyristors) 1,2,3 and neg. 4,5,6 controlled valves (diodes)

30 and the control unit 7, made in

760329 4

·. · \ Iodine 24, power diode 6 to phase C, ipuy the control electrode of the thyristor 3 (Fig.1.2c, c).

After changing the sign of phase C (60 ζ.ΐ26 °), power diode 6 is locked and _ the control pulse is shifted to circuit ^{5 of the} control electrode of thyristor 3 along the circuit: phase A ₄ diode 9, control switch 12, resistor 15, diode 18, threshold the control element 21 is a thyristor electrode 3, a fae.a. Zapus'® repentant impulse at the same time produces a sufficient amplitude and steepness, ensuring the forced turning on of the thyristor 3 (Figure 2, c, c, a) 15'anvodnuyu circuit diode 24.,

As can be seen from the above, the diodes '22, 23,24 play a dual role. * In moments when the anode on the thyristors,

“the voltage is negative, the current controlling them 20 is diverted to the main circuit through a power diode biased in the forward direction by the load current, thereby preventing the appearance of a transistor effect in the thyristors;

25 after the opening of the thyristors through these diodes, the control current is diverted into ..

'The main circuit, bypassing the control electrode circuit. ’

FIG. 2c, and c shows the form of the current through these diodes, defined by 3® by the corresponding line voltages (the base width of the current pulses is 240 ^e ).

“The inclusion of thyristors 1 and 2 pro35 proceeds similarly to thyristor 3. The switching circuit of the power thyristors and diodes is given in the table.

3

the form of a three-phase rectifier 8 diodes 9,10,11, the output of which through the control switch 12, resistors 13,14,15, separation diodes 16, 17,18 and threshold elements 19,20,21 is connected to the control electrodes of the valves 1,2, 3 Transitions of the control electrode-anode of valves 1,2,3 are shunted by additional diodes 22,23,24. The load is connected to the output terminals 25,26,27. '

The switch works as follows.

When the key is open, the 12 thyristors are turned off and there is no current in the load circuit, since the diodes 4, 5, 6 are switched in opposite.

With a closed key 12, we consider the established process, starting from the moment ωί = 0 ° (figure 2);

In this case, the Current in the power circuits goes from phase C through diode 10, the load, thyristor 2 to phase B, as ωι grows. load current also flows from phase A through diode 4, load, thyristor 2 to phase B.

In control circuits (0 <ωΐ <60 °), current flows from phase C through diode 11, control switch 12, resistor 14, diode 23 thyristor 2 to phase B, bypassing the control electrode of thyristor 2; from phase A through diode 9, control switch 12, resistor 14, diode 23 - thyristor 2 to phase B; from phase C through diode 11, control switch 12, resistor 13, diode 22, diode 4 to phase A (up to the moment 30 °). After 30 '<ωΐί b0 ° and _o > and _s and the current begins to flow from phase A through diode 9, control switch 12, resistor 15,

Phase Items scheme 0-60 ° 60-120 ° 120-180 ° 180-240 ° 240-300 ° 300-360 ° 360-420 ° (0-60 °) four X X X - - X BUT one - - - X X X - five - - X X X - - AT 2 X X - - χ X

X ΐ X

X

Thus, due to the introduction of additional diodes 22,23,24, the prevalence of the _Zh trans transient effect in the thyristors, and the threshold elements 19,20,21 provide good parameters of control pulses ^! that increases the reliability of the thyristors.

Claims (1)

Claim Three-phase thyristor switch, containing counter-parallel controlled and unmanaged valves in each phase and a control unit made in the form of a three-phase diode rectifier, the output of which is connected to the control electrodes of the valves through a control switch, resistors and separation diodes, in order to increase reliability, the control unit is equipped with "in the circuit 65 of the control electrodes of the valves 760329 horn plugs and additional diodes that shunt the junction control electrode-anode valves.