SU1298882A1 - Three-phase thyristor switch - Google Patents

Abstract

The invention relates to electrical engineering and can be used in three-phase AC circuit breakers for networks with insulated neutral. The purpose of the invention is to ensure reliable shutdown. To do this, auxiliary power thyristors 7, 8.9 are introduced into the device, connected to the switching capacitor 17 by means of diodes 10-15, which allows for nonselective forced switching, in which the control of the system. My switching does not depend on the polarity of the phase load currents. The device contains in each phase A, B, C a key formed by two anti-parallel connected main power thyristors 1-6. The common connection points of all the diodes are interconnected through a series-connected capacitor 17 charged in the pre-switching period and the switching thyristor 16. 1 il. to taeA. “What about

Description

The invention relates to low-voltage electrical devices, in particular, to three-phase AC thyristor circuit breakers for insulated-neutron networks, for example, ships.

The purpose of the invention is to increase reliability.

The drawing is a schematic diagram of the power section of the proposed switch (the control unit and the capacitor charge unit are not shown).

The three-phase thyristor AC switch for insulated neutral networks contains, in phases A,

8, With the main power thyristors 1 - 6, auxiliary power thyristors 7 9, through which the phase currents flow

Ki load in steady state.

and diodes 10 - 15 switch. Moreover, diodes 10-12 serve to connect among themselves the points of connection of the main and auxiliary power thyristors with the same polarity of connection in the semiconductor switches formed by the thyristors 1, 2, 7; 3, 4, 8; 5, 6, 9, and diodes 13-15 serve to connect the switch output terminals to each other. The common connection points of the diodes of the switch 10-12 and 13-15 are interconnected through a series-connected switching thyristor 16 and a capacitor 17 charged in the pre-switching period with the polarity of the charging voltage indicated on the drawing. The thyristor switch also contains output terminals 18-20.

The operation of the thyristor switch is characterized by two modes - on and off.

Turning on the thyristor switch is provided while simultaneously providing control signals to the power thyristors 1-9.

In the off mode, the circuit removes control signals simultaneously from all power thyristors 1 through 9, after which the pulse control signal is sent to the switching thyristor 16. The operation of the thyristor switch in three-phase networks with isolated neutral in the off mode is based on the fact that the sum of the phase currents is always zero:

 .

where 1,1,1, - load currents in phases A, B, C.

five

0

5 Q 35

40

45

50

55

In this case, in order to ensure the forced shutdown of the thyristors 1–9, it is sufficient to forcibly lock the auxiliary power thyristors 7–9, which conduct the load currents during the precommutation period. If, for example, in the pre-switching period, a positive polarity flows in phase A and negative currents flow in phases B and C (the directions of currents in the phases are indicated by arrows in the drawing), after removing control signals from the power thyristors

1–9, only power thyristors 1, 4, 8, 6, and 9 will be conductive, and power thyristors 2, 7, 3, and 5 will already be turned off. In this case, after the impulse control signal is applied to the switching thyristor 16, the capacitor 17 is connected to the auxiliary power thyristors 8 and 9 using diodes 11, 12, 14 and 15 and the thyristor 16 (emergency discharge of the capacitor 17 through diodes 10 and 13 and thyristors 1,

2 and 16 E circuit does not occur, because the thyristor 2 is in the off state). Since the polarity of the voltage of the charge of the capacitor 17 is blocking for power thyristors 7–9, the auxiliary power thyristors 8 and 9, which are electrically conductive during the pre-commutative period, are forcibly turned off. Turning off the main power thyristors 1, 4 and 6f i.e. the circuit breaker is completely disconnected, will occur after the completion of the recharging of the capacitor 17 by the load current through the diodes 13-15, 11, 12, the thyristor 16 and the main power thyristors 1, 4 and 6 under the action of the mains voltage. The circuit returns to its original state after recharging the capacitor 17 to the set voltage value using a charge unit.

Similarly, shutdowns are provided with other fields of pre-switching currents in phases.

Formula and 30 brethren

Three-phase thyristor AC switch for networks with insulated neutral, the power part of which contains in each phase a key containing two main-parallel main power thyristors 311288884

pa and common to all phases of the capacitor, the powerful power thyristors of three

characterized in that the keys are interconnected.

In order to improve the reliability of the power-off diodes, the key outputs are connected between

neither, entered into each key of the auxiliary is also through diodes common

telny power thyristor which 5 points of connection of all diodes

connected in series with the main connected to each other through

power thyristor having the same-consecutively connected convoy polarity, diodes, capacitor and commutating common points of junction of the main and auxiliary.

Claims (1)

Claim A three-phase thyristor AC circuit breaker for networks with isolated neutral, the power part of which contains in each phase a key containing two counter-parallel connected main power thyristors and a capacitor common to all phases, characterized in that, in order to increase the reliability of shutdown, they are introduced into each key is an auxiliary power thyristor, which 5 is connected in series with the main power thyristor having the same switching polarity, diodes, common connection points of the main and auxiliary forces x thyristors three keys are interconnected .Through dyody, keys outputs are interconnected also through the diodes, the common connection point of the diodes are interconnected via a series connection of a capacitor and a thyristor switching.