JP5828783B2 - DC circuit breaker - Google Patents

Description

  The present invention relates to a DC circuit breaker that protects a DC circuit.

  In recent years, a DC power supply method has been studied as one of energy saving measures in data centers. According to the conventional AC power supply method, AC / DC / AC conversion at the time of server input is required in addition to AC / DC / AC conversion at UPS (uninterruptible power supply), and power is wasted along with power conversion three times in total. To do. On the other hand, according to the direct current power supply method, the power can be supplied to the server by one power conversion of AC / DC, so that there is an advantage that power consumption can be reduced.

  By the way, in the case of the direct current power supply method, it is necessary to take measures against a short circuit accident in the direct current distribution unit, but at present, measures using a fuse are taken. For example, Patent Document 1 proposes a technique that does not generate arc discharge using a circuit that instantaneously blows a fuse when a short-circuit current flows in a DC circuit. In addition, a method is also known in which terminals of an AC circuit breaker having three or four poles as shown in FIG. In addition, a method for reducing the short-circuit current by making the extra length of the load side wiring of the circuit breaker excessive is also known.

JP 2011-243288 A

  However, according to the prior art, there is a problem that it takes time and time to replace the fuse to restore the electric circuit, and a dedicated circuit for preventing arc discharge is required. Further, according to the routing type DC circuit breakers 50 and 60, it is necessary to connect a large number of contacts per phase in series.

  Therefore, an object of the present invention is to provide a DC circuit breaker that can protect a DC circuit from a short-circuit current without using a fuse or connecting a large number of contacts in series.

  In order to solve the above problems, a DC circuit breaker according to the present invention includes a contact that opens and closes a DC circuit, a current-limiting reactor that limits a short-circuit current flowing in the DC circuit, and an output current of the current-limiting reactor that has a specified value. And a tripping device for opening the contact when exceeding.

  Here, the current limiting reactor includes an iron core provided with a magnet and a coil that generates a magnetic flux in a direction opposite to the magnetic flux of the magnet in the iron core when a short-circuit current flows. The coil includes a first coil wound around an iron core opposite to the magnet and a second coil wound around the magnet core, and the first coil can adjust the turn ratio of the winding portion.

  According to the DC breaker of the present invention, when the short-circuit current flows in the DC circuit, the trip device opens the contact in a state where the current-limiting reactor limits the short-circuit current, so that the occurrence of arc discharge is suppressed. The electric circuit can be safely interrupted. Therefore, there is an effect that the DC circuit can be protected from a short-circuit current by a simple and convenient configuration that does not require the use of a fuse or a multi-contact serial connection.

It is an electric circuit diagram of a DC circuit breaker showing an embodiment of the present invention. It is a magnetic circuit diagram which shows the current limiting reactor of the DC circuit breaker of FIG. It is the schematic which shows the conventional DC circuit breaker.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. A DC circuit breaker 1 shown in FIG. 1 includes a casing 2 that is installed in a switchboard of a data center, for example. On the outer surface of the casing 2, terminals T1 and T2 connected to a DC power source (not shown) and terminals T3 and T4 connected to a load circuit 3 including a number of servers are provided. The positive terminals T1 and T3 are connected by the electric wire 4, the negative terminals T2 and T4 are connected by the electric wire 5, and a DC electric circuit is formed by both the electric wires 4 and 5.

  Inside the casing 2, a contact 6 that opens and closes a DC electric circuit and a current limiting unit 7 that drives the contact 6 are provided. The contact 6 can be provided on the plus wire 4, on the minus wire 5, or on the two wires 4, 5. The current limiting unit 7 includes a current limiting reactor 8 for limiting the short-circuit current flowing in the DC circuit, and an electromagnetic trip device 9 for opening the contact 6 when the output current Is of the current limiting reactor 8 exceeds a specified value. Are provided in series. The electromagnetic trip device 9 is connected to one or two contacts 6 via a link 10. The current limiting reactor 8 includes a first coil L1 and a second coil L2 on the iron core 11, and diodes D1 and D2 are connected between both ends of the second coil L2.

  As shown in FIG. 2, a magnet 12 is provided on a part of the iron core 11, the second coil L <b> 2 is wound around the iron core 11 on the magnet 12 side, and the first coil L <b> 1 is wound around the iron core 11 opposite to the magnet 12. It has been. The first coil L1 includes a movable terminal T5 connected to the electromagnetic trip device 9, and is configured such that the turns ratio of the winding portions L1a and L1b can be adjusted according to the position of the movable terminal T5. The first coil L1 is wound so as to generate a magnetic flux in the opposite direction to the magnetic flux Ma of the magnet 12, and the second coil L2 is wound so as to generate a magnetic flux in the same direction as the magnetic flux Ma of the magnet 12. When a short-circuit current flows through the first coil L1, the first coil L1 generates a magnetic flux Mb in the opposite direction to the magnetic flux Ma of the magnet 12 in the iron core 11.

  In the DC circuit breaker 1 having the above configuration, when a normal bus current I flows through the electric wire 4, the turns ratio of the coils L <b> 1 and L <b> 2 is set so that a magnetic flux Ma in the same direction as the magnet 12 is generated in the iron core 11. Therefore, when the magnetic flux Ma of the magnet 12 is enhanced and a direct current flows, the coils L1 and L2 are in a low inductance state, and the bus current I is output to the trip device 9 without being limited, and the trip device 9 Holds the contact 6 closed. When an overcurrent flows through the electric wire 4, the tripping device 9 flows through the electromagnetic coil while holding the current as in the conventional case, and the contact 6 is detached at a specified timing.

  On the other hand, when a short-circuit current flows, the magnetic flux Mb of the first coil L1 overcomes the magnetic flux Ma of the magnet 12, the direction of the magnetic flux is reversed, and a large magnetic flux passes through the magnetic gap at the center of the current limiting reactor 8. Bring change. That is, a large magnetic flux change occurs by shifting from the third quadrant of the BH curve to the first quadrant. This magnetic flux change is accompanied by a partial pressure of the winding portions L1a and L1b of the first coil L1, that is, current amplification by mutual induction of the transformer, a large current flows through the coil of the tripping device 9, the contact 6 is tripped, and the DC circuit Is cut off.

  Since the short-circuit current flowing through the contact 6 is limited by the current-limiting reactor 8 when the electric circuit is interrupted, the occurrence of arc discharge can be suppressed and the contact 6 can be safely detached. Further, since the output current Is of the current limiting reactor 8 can be amplified to a value corresponding to the short-circuit current by adjusting the turn ratio of the winding portions L1a and L1b in the first coil L1, the operation of the electromagnetic trip device 9 It is possible to cut off the current limit of the DC circuit without changing the characteristics.

For example, when the turns ratio of the first coil L1 is L1a: L1b = N: 1 (= I: N × I), the output current Is of the current limiting reactor 8 is (N + 1) × I
It becomes. However, the relationship between the current values is bus current I <output current Is.

  The DC circuit breaker of the present invention is not limited to the use in the data center, and can be applied to various facilities that use DC power. In addition, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately changing the configuration of each part without departing from the spirit of the invention.

DESCRIPTION OF SYMBOLS 1 DC circuit breaker 3 Load circuit 6 Contact 7 Current limiting unit 8 Current limiting reactor 9 Electromagnetic trip device 11 Iron core 12 Magnet L1 1st coil L2 2nd coil

Claims (3)

  A contact that opens and closes the DC circuit, a current-limiting reactor that limits the short-circuit current that flows in the DC circuit, and a trip device that opens the contact when the output current of the current-limiting reactor exceeds a specified value DC breaker that is characterized.   2. The DC circuit breaker according to claim 1, wherein the current limiting reactor includes an iron core including a magnet and a coil that generates a magnetic flux in a direction opposite to the magnetic flux of the magnet in the iron core when a short-circuit current flows.   The coil includes a first coil wound around an iron core on the opposite side of the magnet and a second coil wound around the iron core on the magnet side, and the first coil is capable of adjusting a turns ratio of the winding portion. Item 5. The DC circuit breaker according to Item 2.

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