JP6284827B2 - Switch - Google Patents

Description

  The present invention relates to a switch having a bidirectional current interruption function applied to a power system of a DC system.

  In recent years, with the widespread use of solar power generation systems and emergency power systems using storage batteries, research and development of DC switchgear applied to these systems is progressing.

  By the way, conventional switchgear devices for DC (mechanical switches such as electromagnetic contactors, circuit breakers for circuit breakers, and earth leakage circuit breakers) wear out contacts due to the influence of an arc generated between the main circuit contacts during the switching operation. In order to cause malfunctions, arc extinguishing countermeasures have become an important issue in order to extend the life and reliability of switchgear.

  That is, when the mechanical switch is applied to a circuit of a DC system, a DC arc generated between the contact points due to the opening operation of the switch is difficult to extinguish compared to an AC arc. An arc extinguishing method has been proposed. As an example, a mechanical switch is used as a main circuit contact, and a contactless semiconductor switch is connected in parallel to the main circuit contact, and the main circuit current is commutated to the semiconductor switch during the opening operation of the mechanical switch. A switch is known in which the arc generated between the main circuit contacts is extinguished instantaneously and the semiconductor switch is controlled to be turned off to completely cut off the main circuit current (for example, Patent Document 1). reference).

  According to this switch, the DC main circuit current can be commutated to the semiconductor switch and cut off without the need to provide an additional arc extinguishing chamber (arc extinguishing grid plate) for extinguishing the arc in the mechanical switch. it can.

  By the way, in the switch disclosed in Patent Document 1, an independent driving power source is required for the gate drive circuit for controlling the semiconductor switch to be turned on and off. Therefore, the inventors omitted the drive power supply unit of the gate drive circuit, and instead applied the arc voltage generated between the main circuit contacts during the opening operation of the mechanical switch to the gate of the semiconductor switch. Has previously been proposed (see Patent Document 2), and its circuit configuration is shown in FIG.

  In the circuit diagram of FIG. 5, 1 is a main circuit (DC circuit) wired between a DC power supply and a load (not shown), 2 is a mechanical switch such as an electromagnetic contactor connected to the main circuit 1, and 3 is a machine It is a non-contact type semiconductor switch connected in parallel to the type switch 2, and (+), (-) in the figure represents the polarity of the main circuit power supply. Here, the mechanical switch 2 is provided with a double contact type main circuit contact 21 composed of a pair of fixed contacts 2a and 2b and a bridge movable element 2c per one pole, and a switch operator described later (the electromagnetic switch shown in FIG. 6). The bridging movable element 2c of the main circuit contact 21 is driven to the open and closed positions by an electromagnet for operating the contactor).

  On the other hand, the semiconductor switch 3 includes a semiconductor switching element 4 such as an IGBT or a MOS-FET (in the illustrated example, an IGBT (Insulated Gate Bipolar Transistor) is used for semiconductor switching, hereinafter referred to as “IGBT”), a resistor 5, 6 comprises a gate drive circuit 9 of IGBT 4 configured by combining a voltage divider circuit 6, a Zener diode 7 for overvoltage protection, and a capacitor 8 as shown in the figure, and a signal input terminal (gate resistor 5) of the gate drive circuit 9 The mechanical switch 2 is connected to the bridge mover 2c.

  FIG. 6 is a block diagram of an electromagnetic contactor applied to the mechanical switch 2. The assembly of the semiconductor switch 3 is mounted on the top of the electromagnetic contactor and connected to the main circuit terminal of the electromagnetic contactor. Like to do. In FIG. 6, 24 is a frame of an electromagnetic contactor, 25 is an operating electromagnet, 26 is a movable element support having a contact pressure spring 26a, and 27 is a main circuit corresponding to the double contact main circuit contact 21 of the mechanical switch. Terminal.

  Next, the current interruption operation of the switch shown in FIG. 5 will be described with reference to FIGS. That is, in the energized state where the mechanical switch 2 (electromagnetic contactor) is closed, the main circuit current (direct current) flowing through the main circuit 1 from the (+) pole side as shown by the solid line arrow in FIG. It flows to the (−) pole side through the main circuit contact 21 of the type switch 2. In this state, the IGBT 4 is OFF. When the mechanical switch 2 is opened from the energized state of the main circuit current, a DC arc arc is generated between the fixed contacts 2a and 2b and the bridge movable element 2c as shown in FIG. Arc voltage is generated. Although this arc voltage is determined by the gap length between the contact material and the contact, the arc voltage immediately after the opening operation starts is about 30 V, and the arc voltage increases as the opening gap increases.

  Then, the arc voltage generated between the main circuit contacts in accordance with the opening operation causes a control current indicated by a dotted arrow in the figure to flow through the gate drive circuit 9 of the IGBT 4 (see FIG. 5), thereby connecting to the gate of the IGBT 4. The capacitor 8 is charged with the voltage divided by the resistors 5 and 6, and the gate potential rises. Here, when the charging voltage of the capacitor 8 exceeds a predetermined gate threshold value, the IGBT 4 is turned on and switched to a conductive state, and the main circuit current that has been flowing to the main circuit contact 21 of the mechanical switch 2 until now is shown in FIG. As shown by the solid line arrow of 7 (c), it commutates to IGBT4.

  As a result, the arc generated between the contacts of the mechanical switch 2 disappears instantaneously. Further, since the arc voltage generated between the contacts of the mechanical switch 2 with the disappearance of the arc disappears, the charged charge of the capacitor 8 is divided by the gate drive circuit 9 as shown by the dotted arrow in FIG. It is discharged through the resistor 6. As a result, the gate voltage between the gate and the emitter of the IGBT 4 is lowered, the IGBT 4 is turned off, and the main circuit current is completely cut off as shown in FIG.

  In this switch, since the arc voltage between the contacts generated during the opening operation of the mechanical switch 2 is applied to the gate of the IGBT 4 for ON / OFF control, it is independent as in the above-mentioned Patent Document 1. The gate drive power supply and its power supply control are unnecessary, and the control circuit of the semiconductor switch can be simplified.

Japanese Patent Laid-Open No. 8-106839 JP 2013-41882 A

  By the way, the switch disclosed in Patent Document 2 is a semiconductor switch 3 in which one IGBT 4 having a polarity matched to the energizing direction of the main circuit 1 is connected in parallel to the mechanical switch 2 so that the mechanical switch 2 is opened. The arc voltage between the contacts generated at the time of the pole operation is applied to the gate drive circuit so as to perform the ON / OFF control of the semiconductor switch 3.

  This eliminates the need for an independent gate drive power supply for the semiconductor switch 3 and simplifies the control circuit, but the main circuit current and the energization direction of the semiconductor switch 3 are limited to one direction.

  On the other hand, a DC circuit in which the circuit current switches in the opposite direction between charging and discharging of the storage battery, such as the charging / discharging circuit of the storage battery applied to the emergency power system mentioned above, or a distributed DC power supply system such as photovoltaic power generation A bidirectional switch is required for a switch applied to a DC system circuit that performs reverse power flow through linkage. However, the switch disclosed in Patent Document 2 cannot be applied to a DC circuit that requires a bidirectional current cutoff function.

  The present invention has been made in view of the above points, and an object of the present invention is to improve the circuit configuration of the switch described in FIGS. 5 and 6 (Patent Document 2) and connect it in parallel to the mechanical switch of the main circuit. A bidirectional energization / shut-off function is added to the switch so that it can be applied to a storage battery charging / discharging circuit or a power flow system between photovoltaic power generators. It is an object of the present invention to provide an improved switch that can reliably prevent, by simple means, a problem that a semiconductor switch is erroneously ignited by a power supply voltage of an applied main circuit and cannot cut off a main circuit current.

In order to achieve the above object, according to the present invention, a semiconductor switch is connected in parallel to a main circuit contact of a mechanical switch connected to a main circuit of a DC system, and a main circuit current is generated during opening operation of the mechanical switch. In a switch that commutates to the semiconductor switch and extinguishes the arc generated between the main circuit contacts of the mechanical switch, and then shuts off the main circuit current commutated to the semiconductor switch by OFF control of the semiconductor switch.
The semiconductor switch is connected in parallel to the main circuit contact of the mechanical switch as a bidirectional switch consisting of two semiconductor switching elements connected in reverse series and FWD (free-wheeling diode) connected in parallel to each semiconductor switching element. In addition, an arc voltage generated between the main circuit contacts during the opening operation of the mechanical switch is applied to the gate of the semiconductor switching element via the gate drive circuit to control the semiconductor switch ON / OFF. In addition, the gate drive circuit is connected with a diode that prevents the power supply voltage of the main circuit from being applied in the forward direction to the gate of the semiconductor switching element when the semiconductor switching element is turned off after the mechanical switch is opened. (Claim 1), wherein the gate drive circuit and the mechanical switch Specifically, the main circuit contact of the switch can be configured in the following manner.
(1) A gate drive circuit of a semiconductor switch includes a voltage dividing circuit in which a voltage dividing resistor is T-connected between the signal input terminal and both ends of the semiconductor switch, and a T-shaped connection point of the voltage dividing circuit. The semiconductor switch includes a pair of reverse blocking diodes connected in reverse series between both ends of the semiconductor switch.
(2) On the other hand, the mechanical switch is provided with a double contact type main circuit contact comprising two fixed contacts per pole and a bridge mover, and the gate drive is connected to the bridge mover of the main circuit contact. The signal input terminal of the circuit is connected (Claim 3).
(3) Further, as a form different from the previous item 2, the mechanical switch is provided with two sets of main circuit contacts connected in series by dividing into two poles, and the gate drive circuit is connected to a connection portion between the main circuit contacts. Are connected to the signal input terminal (claim 4).

According to the switch configured as described above, the following effects can be obtained.
(1) First, a bidirectional semiconductor composed of two switching elements (for example, IGBTs) connected in reverse series to semiconductor switches connected in parallel to the main circuit contacts of a mechanical switch and FWD connected in reverse parallel to each switching element. The direction of energization of the main circuit current (DC) that flows through the main circuit by controlling the semiconductor switch using the arc voltage generated at the main circuit contact during the opening operation of the mechanical switch as a gate input signal. The main circuit current is transferred from the main circuit contact of the mechanical switch to the semiconductor switch in synchronization with the opening operation of the mechanical switch, without the need to provide a drive power supply independent of the gate control of the semiconductor switching element. Then, the main circuit current can be completely cut off by gate control of the semiconductor switch.
(2) A forward bias voltage based on a power supply voltage of the main circuit is applied to the gate of the semiconductor switching element in a state where the semiconductor switching element is turned off after the mechanical switch is opened. By connecting a pair of reverse blocking diodes connected in reverse series so as to block the current, it is possible to prevent the gate of the semiconductor switching element from being erroneously ignited after the current is cut off and to improve the operational reliability of the switch.
(3) On the other hand, the main circuit contact of the mechanical switch is a double-contact type contact that connects the signal input terminal of the gate drive circuit to the bridge mover, or is divided into two poles and connected in series. The signal input terminal of the gate drive circuit can be connected to the connection part between the contacts, and the signal input wiring of the gate drive circuit is made possible by adopting the latter method in which two sets of main circuit contacts are connected in series. There is an advantage that wiring can be easily performed using a connection terminal of a switch pulled out from the main circuit contact of the mechanical switch without disturbing the movement of the opening and closing operation of the mechanical switch.

It is a circuit diagram of the switch concerning Example 1 of the present invention. FIG. 2 is an explanatory diagram of a main circuit current cut-off operation according to FIG. 1, wherein (a), (b), (c), and (d) are energized states of the main circuit current when the mechanical switch is closed; It is a figure showing the energization path in each state after the energized state immediately after the opening operation of a switch starts, the commutation state to a semiconductor switch, and the main circuit current interruption. It is a circuit diagram of the switch corresponding to Example 2 of the present invention. It is a circuit diagram of the switch corresponding to Example 3 of the present invention. It is a circuit diagram of the switch currently indicated by patent documents 2. It is an assembly block diagram of the switch which applied the electromagnetic contactor to the mechanical switch of the switch shown in FIGS. FIG. 6 is an operation explanatory diagram of FIG. 5, where (a), (b), (c), and (d) are the main circuit current energization state where the mechanical switch is closed, and the opening operation of the mechanical switch. It is a figure showing the electricity supply path | route in each state after the energized state immediately after a start, the commutation state to a semiconductor switch, and the main circuit current interruption | blocking.

  Embodiments of the present invention will be described below with reference to FIGS. In the drawings of the illustrated embodiment, members corresponding to those in FIGS. 5 and 6 are denoted by the same reference numerals and description thereof is omitted.

  First, FIG. 1 shows a circuit configuration of a switch corresponding to the first embodiment of the present invention. In FIG. 1, for example, the electromagnetic contactor shown in FIG. 6 is applied to the mechanical switch 2 connected to the DC main circuit 1, and the double contact main circuit comprising the fixed contacts 2a and 2b and the bridge mover 2c is applied. The contact 21 is switched between a closed position and an open position by an electromagnetic contactor operating device.

  The semiconductor switch 3 connected in parallel between the main circuit terminals 11 and 12 (corresponding to the main circuit terminal 27 of the magnetic contactor in FIG. 6) across the main circuit contact 21 of the mechanical switch 2 is reversed. The bidirectional semiconductor switch 3 is composed of IGBTs 4-1 and 4-2 connected in series and FWDs (free-wheeling diodes) 10-1 and 10-2 connected in reverse parallel to the IGBTs 4-1 and 4-2, respectively. In the illustrated circuit, the collector of the IGBT 4-1 and the collector of the IGBT 4-2 are connected in series, and the emitters of the IGBT 4-1 and IGBT 4-2 are connected to the main circuit terminals 11 and 12, respectively.

  In the illustrated circuit, the collectors of the IGBTs 4-1 and 4-2 are connected to each other, and the emitters of the IGBTs are connected to the main circuit branched from both ends of the mechanical switch 2. After interconnecting each other, IGBTs 4-1 and 4-2 may be connected in parallel to both ends of the mechanical switch 2 to constitute a semiconductor switch circuit.

  Further, between the gates g1 and g2 of the IGBTs 4-1 and 4-2 and the bridging movable element 2c of the mechanical switch 2, a signal input end side connected to the bridging movable element 2c of the mechanical switch 2 is provided. A voltage dividing circuit comprising a voltage dividing resistor 5, a voltage dividing resistor 6-1, 6-2 connected to each emitter of the IGBTs 4-1 and 4-2, connected to the voltage dividing resistor 5 in a T-shape; Reverse blocking diodes 13-1 and 13-2 connected in series in reverse polarity between voltage dividing resistors 6-1 and 6-2 across a T-shaped connection point with resistor 5, and voltage dividing resistors 6-1 A gate drive circuit 9 composed of a Zener diode 7 of a constant voltage element connected in parallel to 6-2 is constructed, and the fixed contacts 2a and 2b and the bridge movable element 2c are connected during the opening operation of the mechanical switch 2 as described later. The arc voltage generated between the IGBTs 4-1 and 4 through the gate drive circuit 9 Is applied to the second gate g1, g2 so that controls ON / OFF of the IGBT4-1,4-2 of the semiconductor switch 3. In the illustrated gate drive circuit 9, the reverse blocking diodes 13-1 and 13-2 have anodes connected to each other and cathodes connected to voltage dividing resistors 6-1 and 6-2, respectively. Yes.

  Next, the current interruption operation of the switch shown in FIG. 1 will be described with reference to FIGS. In the illustrated circuit, the main circuit terminal 11 is energized with the (+) pole (power supply side) and the main circuit terminal 12 with the (−) pole (load side).

  First, FIG. 2A shows the energized state of the main circuit 1 with the mechanical switch 2 closed. In this state, the main circuit current flowing through the main circuit 1 is directed from the (+) pole side to the (−) pole side. And flows through the main circuit contact 21 of the mechanical switch 2 as indicated by a solid line arrow. In this state, each of the IGBTs 4-1 and 4-2 of the semiconductor switch 3 is in an OFF state.

  When the mechanical switch 2 is opened from the energized state of FIG. 2A, the fixed / movable contact is opened, and the fixed contacts 2a and 2b of the main circuit contact 21 and the bridge are connected as shown in FIG. 2B. An arc arc is generated between the movable armature 2c and an arc voltage is generated between the contacts. Here, the arc drive between the fixed contact 2b / the bridge movable arm 2c is connected to the movable arm 2c. The forward bias is applied between the gate g2 / emitter of the IGBT 4-2 via the circuit 9. As a result, the gate potential of the IGBT 4-2 rises according to the time constant of the voltage dividing circuit via the voltage dividing resistors 5 and 6-2 and the input capacitance (capacitance between the gate and the emitter) of the IGBT 4-2. When the gate potential rises to a voltage value limited by the Zener diode 7 (the limit voltage of the Zener diode 7 is set to 15 to 18 V in accordance with the gate threshold voltage of the IGBT), the IGBT 4-2 is turned on and turned on. Switch.

  When the IGBT 4-2 is turned on, the main circuit current that has been flowing to the main circuit contact 21 of the mechanical switch 2 until now is commutated to the semiconductor switch 3 as shown in FIG. Thus, the main circuit current is commutated so as to return to the branch point B of the main circuit through the FWD 10-1 and IGBT 4-2 connected in reverse parallel to the IGBT 4-1 from the branch point A of the main circuit 1, The arc generated at the main circuit contact 21 of the switch 2 disappears instantaneously.

    Further, since the arc voltage generated between the contacts of the main circuit contact 21 as the arc disappears also disappears, the voltage applied to the gate g2 of the IGBT 4-2 is the voltage generated between C1 and C2 in the figure. The voltage is determined only from the voltage dividing ratio of the voltage dividing resistors 6-1 and 6-2. In this case, the voltage between C1 and C2 is the sum of the forward voltage of the FWD 10-1 connected in reverse parallel to the IGBT 4-1 and the ON voltage (saturation voltage) of the IGBT 4-2. The voltage is low. As a result, the charge stored in the input capacitance of the IGBT 4-2 is discharged to the voltage dividing resistor 6-2, and the gate potential of the IGBT 4-2 is lowered. As a result, the IGBT 4-2 is turned off and switched to the OFF state. As a result, the main circuit current commutated to the semiconductor switch 3 is cut off (see FIG. 2D).

    By the way, in this case, if there are no reverse blocking diodes 13-1 and 13-2 connected to the gate drive circuit 9 of the illustrated embodiment, the main circuit 1 is connected between the C1 and C3 by the OFF operation of the IGBT 4-2. A power supply voltage is applied. For this reason, a forward bias is applied to the gate g2 of the IGBT 4-2 and the gate potential is increased again. As a result, the main circuit current that is commutated to the semiconductor switch 3 is cut off due to the IGBT 4-2 being misfired (turned on). There is a risk of being lost.

    In this respect, the reverse circuit diodes 13-1 and 13-2 are connected in series with opposite polarities between the voltage dividing resistors 6-1 and 6-2 in the gate drive circuit 9 as shown in the circuit shown in FIG. The power supply voltage of 1 is blocked by the diode 13-1 and is not applied to the gate g2 of the IGBT 4-2. Therefore, the electric charge stored in the input capacitance of the IGBT 4-2 continues to be discharged and the potential of the gate g2 is lowered, the gate potential becomes 0 V, and the IGBT 4-2 is completely turned off. Thereby, the main circuit current commutated to the semiconductor switch 3 is completely cut off, and a series of shut-off operations of the switch is completed.

  2 (a) to 2 (d) have been described with respect to the case where the main circuit terminal 11 of the DC circuit 1 is energized as the (+) pole and the terminal 12 as the (−) pole. When the direction of the main circuit current is energized from the main circuit terminal 12 to 11 (the main circuit terminal 12 is the (+) pole and the main circuit terminal 11 is the (−) pole), the mechanical switch 2 is reversed. Among the arc voltages generated between the main circuit contacts during the opening operation process, the arc voltage generated between the fixed contact 2a / movable contact 2c is applied between the gate g1 / emitter of the IGBT 4-1 through the diode 13-1. As a result, the IGBT 4-1 is turned on, and the main circuit current is commutated to the semiconductor switch 3.

  As described above, when the mechanical switch 2 is opened, either one of the IGBTs 4-1 and 4-2 is ON / OFF controlled in accordance with the current direction of the main circuit so that the mechanical switch 2 can be connected. The bidirectional current can be interrupted without generating an arc without being influenced by the direction of the flowing main circuit current.

  Next, the setting of the gate drive circuit 9 will be supplementarily described. That is, when the IGBTs 4-1 and 4-2 are turned on during the opening operation of the mechanical switch 2 and the main circuit current is commutated to the semiconductor switch 3, the gates g1 and g2 of the IGBTs 4-1 and 4-2 are connected. The applied voltage (forward bias) is the arc voltage generated between the main circuit contacts 21 of the mechanical switch 2, the resistance values of the voltage dividing resistors 5, 6-1, 6-2 in the gate drive circuit 9, and the corresponding amount. It depends on the pressure ratio. Therefore, the resistance values of the voltage dividing resistors 5, 6-1 and 6-2, and the voltage dividing ratio thereof are determined by receiving the arc voltage generated between the contacts of the mechanical switch 2 and the gate potentials of the IGBTs 4-1 and 4-2. Is set to rise to a predetermined threshold voltage. Specifically, when the arc voltage generated between the main circuit contacts 21 of the mechanical switch 2 is 30 V, the resistance ratio between the resistor 5 and the resistors 6-1 and 6-2 is about 1: 1 or more. Set to.

  The turn-on time for the IGBTs 4-1 and 4-2 to transition from the OFF state to the ON state is determined by the time constants of the input capacitance of the IGBT and each voltage dividing resistor of the gate drive circuit 9 that functions as a charging resistor. Therefore, the gate resistance value is set so that the turn-on time is within a range of, for example, several tens of μsec to several hundred μsec, and the IGBT 4-2 is turned on within about several hundred μsec from the start of the opening operation of the mechanical switch 2. Set the turn-on to complete.

  Next, as application examples of the present invention, circuit configurations of Example 2 and Example 3 are shown in FIGS. In the first embodiment described above, the main circuit contact 21 of the mechanical switch 2 (see FIG. 1) is a double contact type contact composed of a pair of fixed contacts 2a, 2b and a bridge mover 2c, and the bridge mover. The signal input terminal leading to the gate drive circuit 9 of the semiconductor switch 3 is connected to 2c so that the arc voltage between the contacts generated during the opening operation of the mechanical switch 2 is taken out.

  In contrast, in the embodiment shown in FIGS. 3 and 4, in the second and third embodiments, the main circuit contact of the mechanical switch 2 is divided into two poles, and two sets of contacts 21-1 are connected in series. 21-2, and the signal input terminal (voltage dividing resistor 5) of the gate drive circuit 9 is connected to the connection part (point D in the figure) between the contacts. In the second embodiment (see FIG. 3), the two sets of contacts 21-1, 21-2 are one-sided contacts, and in the second embodiment (see FIG. 4), the two sets of contacts 21-1, 21-2 are double contacts. It is a shape contact.

  That is, in Example 1 (see FIG. 1), since the signal input side terminal of the gate drive circuit 9 is connected to the bridging movable element 2c (movable member) of the main circuit contact 21, a small size such as an electromagnetic contactor is used. When a mechanical switch is used, it is difficult to connect and wire the signal input terminal of the gate drive circuit 9 to the bridge movable element of the main circuit contact 21 due to restrictions on the contact assembly structure, and the connection lead wire May interfere with the movement of the main circuit contact opening and closing operations.

  On the other hand, the main circuit contact of the mechanical switch is divided into two sets of contacts 21-1 and 21-2 as in the second and third embodiments (see FIGS. 3 and 4). For example, if a general-purpose magnetic contactor (2 to 3 pole type) or a circuit breaker for wiring (single phase) shown in FIG. 6 is used for the type switch, the main circuit terminals ( In addition to the serial connection between the contacts and the wiring of the signal line leading to the gate drive circuit using the screw terminal), the lead to the gate drive circuit 9 as in the first embodiment (see FIG. 1). There is no possibility that the lead wire interferes with the opening / closing operation of the contact and hinders its movement.

DESCRIPTION OF SYMBOLS 1 Main circuit 11,12 Main circuit terminal 2 Mechanical switch 21,21-1, 21-2 Main circuit contact 3 Semiconductor switch 4-1, 4-2 IGBT (semiconductor switching element)
5,6-1,6-2 Voltage-dividing resistor 7 Zener diode 9 Gate drive circuit 13-1, 13-2 Diode 10-1, 10-2 FWD
g1, g2 IGBT gate

Claims (4)

A semiconductor switch is connected in parallel to the main circuit contact of the mechanical switch connected to the main circuit of the DC system, and the main circuit current is commutated to the semiconductor switch during the opening operation of the mechanical switch. In the switch that cut off the main circuit current commutated to the semiconductor switch by turning off the semiconductor switch after extinguishing the arc generated in
The semiconductor switch is connected in parallel to the main circuit contact of the mechanical switch as a bidirectional switch consisting of two semiconductor switching elements connected in reverse series and FWD (free-wheeling diode) connected in parallel to each semiconductor switching element. In addition, an arc voltage generated between the main circuit contacts during the opening operation of the mechanical switch is applied to the gate of the semiconductor switching element via the gate drive circuit to control the semiconductor switch ON / OFF. In addition, the gate drive circuit is connected with a diode that prevents the power supply voltage of the main circuit from being applied in the forward direction to the gate of the semiconductor switching element when the semiconductor switching element is turned off after the mechanical switch is opened. A switch characterized by that.   2. The switch according to claim 1, wherein the gate drive circuit of the semiconductor switch includes a voltage dividing circuit formed by connecting a voltage dividing resistor between the signal input terminal and both ends of the semiconductor switch, and the voltage dividing circuit. A switch comprising: a pair of reverse blocking diodes connected in reverse series between both ends of a semiconductor switch across a T-shaped connection point of a circuit.   2. The switch according to claim 1, wherein the mechanical switch is provided with a double contact type main circuit contact comprising two fixed contacts per pole and a bridge mover, and the bridge mover of the main circuit contact. And a signal input terminal of the gate drive circuit.   2. The switch according to claim 1, wherein the mechanical switch includes two sets of main circuit contacts divided into two poles and connected in series therebetween, and the gate drive circuit is connected to a connection portion between the main circuit contacts. A switch with a signal input terminal connected.