JP2013214406A - Circuit cut-off switch for dc circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit cut-off switch for a DC circuit that is adapted to a DC circuit in which a current flows bidirectionally and has a bidirectional current cut-off function capable of safely and surely cutting off a current.SOLUTION: In a circuit cut-off switch opening and closing a DC circuit that includes a mechanical switch 7; a semiconductor switch 10 (an IGBT 10a is adopted) connected in parallel to the mechanical switch 7; and a control circuit controlling the semiconductor switch 10, a diode bridge circuit 9 is connected in parallel to the mechanical switch 7, and the semiconductor switch 10 is connected between cathodes of two diodes and between anodes of the other two diodes of the diode bridge circuit 9 so that a current in the semiconductor switch 10 flows in a constant direction. For this reason, a bidirectional current flowing through the DC circuit can be cut off by a current direction flowing through the IGBT 10a being constant even if a current-carrying direction (current-carrying directions 1 and 2) of a DC current flowing through the circuit is changed.

Description

  The present invention relates to a circuit cutoff switch applied to a DC circuit such as a DC uninterruptible power supply system.

  In recent years, a DC power supply system that supplies DC power from a DC power source to a demand load has been developed, but a circuit breaker switch applied to this DC power supply system has a contact between contacts according to its switching operation. Measures to extinguish arcs that have occurred are an issue.

  In other words, when a mechanical switch with a normal contact is applied to a DC circuit, it is difficult to extinguish a DC arc generated between the contacts when the switch is opened and closed. One of them is a semiconductor switch connected in parallel between the contacts of the mechanical switch, and the arc generated between the mechanical contacts is quickly extinguished by commutating the current to the semiconductor switch when the mechanical switch is opened and closed. In addition, there is known a “mechanical switch inter-contact arc erasing device” (refer to Patent Document 1) in which the semiconductor switch is turned off to cut off the current. The configuration is shown in FIG.

  As shown in the figure, this circuit breaker switch is connected in parallel to a mechanical switch (mechanical contact) connected between the DC power source and the load, and to eliminate an arc generated between the contacts of the mechanical switch. A semiconductor switch (semiconductor switching element such as IGBT), a control circuit for turning on and off the semiconductor switch, a power supply circuit, and the like are included.

  In the energized state in which the mechanical switch is turned on and power is supplied from the DC power supply to the load, the semiconductor switch is in the OFF state. Thereby, the circuit current flows to the load through the contact of the mechanical switch. On the other hand, when the circuit current is interrupted, the semiconductor switch is first controlled to ON, and then the contact of the mechanical switch is opened. As a result, the current that has been flowing to the contact point of the mechanical switch is commutated to the semiconductor switch side simultaneously with the start of the contact opening operation, and the arc generated between the contact points of the mechanical switch immediately disappears. Thereafter, by turning off the semiconductor switch, the current flowing in the semiconductor switch is also cut off and the circuit current is completely cut off.

  According to the circuit breaker switch described above, it is not necessary to provide an additional arc extinguishing device for extinguishing the arc in the mechanical switch. In addition, the semiconductor switch is always energized OFF, and the current is energized for only a very short time when the current is interrupted, so there is no problem of transient temperature rise, and this can safely and reliably interrupt the DC circuit current. It becomes possible.

Japanese Patent Laid-Open No. 8-106839

  By the way, in the above-described circuit cutoff switch of Patent Document 1, since the direction of current flow interrupted by the semiconductor switch is determined in one direction, it is impossible to interrupt bidirectional current.

  On the other hand, as shown in FIG. 2, a power storage device 4 such as a secondary battery is branched and connected to a feeder line 3 between the DC power source 1 and the load 2 via a wiring path 5. In the DC uninterruptible power supply system in which the power storage device 4 is float-charged while supplying power to the load 2 and power supply from the DC power supply 1 is stopped, power supply from the power storage device 4 to the load 2 is continuously performed. The current (solid arrow) flowing through the wiring path 5 during floating charging of the power storage device 4 and the current during discharge (dotted arrow) are reversed. For this reason, the circuit cut-off switch 6 that is used by being connected to a circuit communicating with the power storage device 4 needs a bidirectional current cut-off function. In addition, a bidirectional current cut-off function similar to that described above is also required for a circuit cut-off switch applied to a grid-connected DC circuit that performs reverse power flow between distributed DC power supplies and the like.

  However, since the circuit cut-off switch of Patent Document 1 described above cannot cut off bidirectional currents, the circuit current flow direction is reversed as in the DC uninterruptible power supply system shown in FIG. There is a problem that it cannot be applied to a direct current circuit.

  The present invention has been made in view of the above points, and its object is to provide a bidirectional current cutoff function by adding a simple means to the above-described circuit cutoff switch in which a semiconductor switch is combined with a mechanical switch. Another object of the present invention is to provide a circuit cutoff switch for a direct current circuit.

  In order to achieve the above object, according to the present invention, a circuit for opening and closing a DC circuit comprising a mechanical switch, a semiconductor switch connected in parallel with the mechanical switch, and a control circuit for controlling the semiconductor switch. In the cutoff switch, a diode bridge circuit is connected in parallel with the mechanical switch, and a current flowing through the semiconductor switch is constant between the cathodes of the two diodes of the diode bridge circuit and the anodes of the remaining two diodes. The semiconductor switches are connected so as to be in a direction (claim 1).

  Here, a semiconductor switching element composed of an IGBT, a MOS-FET, and a GTO thyristor is adopted as the semiconductor switch.

  According to the circuit cut-off switch configured as described above, the bidirectional current commutated from the mechanical switch to the semiconductor switch during the opening / closing operation of the mechanical switch is not limited by the flow direction of the circuit current flowing through the mechanical switch. Can be cut off.

  Therefore, a DC uninterruptible power supply system that supplies power to a load by branching a power storage device such as a secondary battery between the DC power supply and a load, or a DC circuit that performs reverse power flow between distributed DC power supplies In such cases, the direct current arc generated between the contacts during the opening / closing operation of the mechanical switch can be quickly erased, and the bidirectional current can be safely and reliably interrupted.

It is a block diagram of the circuit interruption switch by the Example of this invention. 1 is a system diagram of DC uninterruptible power supply as an example of a DC circuit to which a circuit cutoff switch of the present invention is applied. It is a block diagram of the circuit interruption switch currently disclosed by patent document 1 as a prior art.

  Hereinafter, an embodiment of the present invention will be described based on the example shown in FIG. The circuit cutoff switch of the illustrated embodiment is applied as a circuit cutoff switch 6 connected to the wiring path 5 of the power storage device 4 in the DC uninterruptible power supply system of FIG.

  In FIG. 1, a circuit cut-off switch 6 includes a mechanical switch 7 connected to a wiring path 5 of a DC circuit, a diode bridge circuit 9 connected in parallel to the mechanical switch 7 via an auxiliary contact 8, and the diode bridge circuit. 9 and a semiconductor switch 10 connected to 9.

  Here, the illustrated mechanical switch 7 is a double-cut switch (two contacts), but a single-cut switch (single contact) may be used. The mechanical switch 7 may be of a type that opens and closes in response to an electrical command such as a relay, or that manually or detects a fault current in a circuit.

  The semiconductor switch 10 is a semiconductor switching element 10a such as an IGBT, a MOS-FET, or a GTO thyristor (the illustrated embodiment employs an IGBT, and hereinafter, the "semiconductor switching element" is referred to as "IGBT") and the IGBT 10a. Diode D1 / D3, D2 in a diode bridge circuit 9 comprising a freewheeling diode (freewheeling diode) 10b connected in reverse parallel to each other and each collector and emitter terminal of the IGBT 10a comprising four diodes D1 to D4. / D4 is connected. Although not shown, the semiconductor switch 10 is attached with a control circuit for turning on and off the IGBT 10a and a power supply circuit for the same as in FIG.

  Next, the operation of the circuit cutoff switch 6 having the above configuration will be described. First, the open / close contact 7a of the mechanical switch 7 is closed when the circuit cutoff switch 6 is in the ON (energized) state. In this case, the IGBT 10a may be in either the ON state or the OFF state, and even if the auxiliary contact 8 is ON, the current flows through the IGBT 10a and the diodes D1 to D4 due to the ON voltage (about 2V × 3 = 6V). Absent.

  When the circuit breaker switch 6 is turned on, the mechanical switch 7 is turned on first, or the semiconductor switch 10 is turned on first to close the switching contact 7a of the mechanical switch 7 later. Also good. However, when the semiconductor switch 10 is turned ON first, the time from the ON of the IGBT 10a to the ON operation of the mechanical switch 7 can be controlled as short as possible in consideration of the temperature rise of the element due to the energization of the IGBT 10a. desirable. On the other hand, when the mechanical switch 7 is turned on first, no current flows through the IGBT 10a due to the on-state voltage of the IGBT and the diode. Therefore, from the turning on of the mechanical switch 7 until the IGBT 10a is turned on. There is no problem even if the time control is relatively long.

  On the other hand, when the circuit interrupting switch 6 is turned off (shut off) and the circuit current flowing through the wiring path 5 is interrupted, the IGBT 10a of the semiconductor switch 10 is turned on prior to opening the contact of the mechanical switch 7. It is preferable to control. That is, when the opening / closing contact 7a of the mechanical switch 7 is opened first and the IGBT 10a is controlled to be turned on later, the mechanical switch 7 is opened until the IGBT 10a is turned on after the opening / closing contact 7a of the mechanical switch 7 is opened. The arc arc continues to occur between the seven contacts (between the fixed contact and the movable contact), so that the contact wears out quickly.

  When the mechanical switch 7 is opened when the current is interrupted, an arc arc is generated between the contact points to generate an arc voltage. In this case, the arc voltage between the contacts is determined by the contact material and the electrode gap, and an arc voltage of about 15 V per contact is generated at the beginning of the opening operation. In the case of the double cut contact (two contacts) in the illustrated embodiment, Generates an arc voltage of about 15V × 2 = 30V. Thereafter, the arc voltage rises as the opening distance of the switching contact 7a increases, and when this arc voltage exceeds the on-voltage of the IGBT 10a and the diodes D1 to D4, the circuit current is commutated from the mechanical switch 7 to the IGBT 10a. The arc arc generated between the contact points of the switch 7 is extinguished. Then, after the current commutates to the IGBT 10a, the circuit current is completely cut off by turning off the IGBT 10a. As shown in the illustrated embodiment, if the auxiliary contact 8 is provided on the side of the commutation circuit passing through the semiconductor switch 10 and the auxiliary contact 8 is opened after the IGBT 10a is turned off, the diode bridge circuit 9 and the IGBT 10a of the semiconductor switch 10 are provided. It is possible to cut off the leakage current flowing through the commutation circuit via the.

  On the other hand, in the circuit cutoff switch 6 of the illustrated embodiment, the IGBT 10 a is connected in parallel to the mechanical switch 7 via the diode bridge circuit 9. As a result, even when the circuit current flows in the energizing direction 1 indicated by the solid arrow or the energizing direction 2 indicated by the dotted arrow through the wiring path 5 to which the circuit cutoff switch 6 is connected as shown in the drawing, the diode bridge circuit 9 is used. Thus, the direction of current flow through the IGBT 10a of the semiconductor switch 10 is the same direction, so that the circuit current flowing in both directions can be interrupted.

  Thereby, by applying the above-described circuit cutoff switch 6 to the direct current uninterruptible power supply system shown in FIG. 2, the circuit current flowing in both directions can be safely and reliably cut off.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 Load 4 Power storage device 6 Circuit interruption switch 7 Mechanical switch 7a Open / close contact 8 Auxiliary contact 9 Diode bridge circuit D1-D4 Diode 10 Semiconductor switch 10a Semiconductor switching element (IGBT)

Claims (2)

In a circuit cut-off switch for opening and closing a DC circuit comprising a mechanical switch, a semiconductor switch connected in parallel with the mechanical switch, and a control circuit for controlling the semiconductor switch,
A diode bridge circuit is connected in parallel with the mechanical switch, and the current flowing through the semiconductor switch is in a constant direction between the cathodes of the two diodes of the diode bridge circuit and the anodes of the remaining two diodes. A circuit cut-off switch for a DC circuit, wherein the semiconductor switch is connected to a DC circuit.   2. The circuit cutoff switch according to claim 1, wherein the semiconductor switch is a semiconductor switching element made of IGBT, MOS-FET, or GTO thyristor.

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