JPH0414730A - Circuit breaker - Google Patents

Abstract

PURPOSE:To protect a semiconductor switching device from large current by short-circuiting a bypass circuit to a main circuit by closing a flow-changing switch simultaneously with shutting operation. CONSTITUTION:When large current runs to a main circuit 35 due to short- circuiting accidents, etc., a tripping apparatus 19 starts working by the operation of an instant tripping coil 21 and shutting operation is started by parting a movable contactor 15 from a fixed contactor 14. Simultaneously with that, over current runs in the reverse direction between a fixed conductor 24 and a movable conductor 26 of a flow-changing switch 25 to generate electromagnetic repulsive force and the movable conductor 26 is rotated downward in spite of a spring 50 by the electromagnetic repulsive force to contact a movable side contact point 28 to a fixed side contact point 29 and thus a bypass circuit 32 is short-circuited to a main circuit 34. As a result, large current in the main circuit 35 is flow-changed and shunted to the bypass circuit 32 through both contact points 28, 29 of the flow-changing switch 25.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a circuit breaker having a function of protecting circuit elements connected to load-side terminals from large currents such as short-circuit currents. .

(Prior art) Generally, when a large current flows in the main circuit due to a short-circuit accident, an enclosed circuit breaker is configured to separate the movable contact from the fixed contact using a tripping device to interrupt the large current. ing. However, there is a slight time delay before the large current is completely cut off due to the activation of the tripping device due to the occurrence of arcing, etc., and during that time, the semiconductor switching element connected to the load side terminal may also be short-circuited. Overcurrent will flow over time. For this reason, when a semiconductor switching element with a small overcurrent withstand capacity is used, there is a risk that the semiconductor switching element will generate heat exceeding its heat resistance temperature and be destroyed by the overcurrent flowing during the interrupting operation.

In order to solve this kind of problem, conventionally, as shown in FIG.
A semiconductor switching element 3 such as a triac is connected through the
On/off of the semiconductor switching element 3 controls the energization and disconnection of the load 4, and when a large current such as a short circuit current flows, the semiconductor switching element 3
There is something designed to protect the

In addition, when the semiconductor switching element on the load side has a relatively small rating (for example, 50A or less), a high current limiting circuit breaker is used.
The current limiting effect of this high current limiting circuit breaker is also used to protect semiconductor switching elements.

(Problem to be solved by the invention) However, with the former (connecting the quick-acting fuses 2 in series), it is not possible to restore the circuit immediately after an accident occurs, and the rapid-acting fuses 2 must be replaced, which requires restoration work. This is time-consuming and requires space for installing the quick-acting fuse 2, which goes against the demand for space saving.

On the other hand, in the latter case (when using a high current limiting circuit breaker), when a semiconductor switching element with a large rated current is used, the current limiting effect of the high current limiting circuit breaker alone exceeds the overcurrent withstand energy of the semiconductor switching element. Currently, the semiconductor switching elements cannot be protected.

The present invention has been made in consideration of these circumstances, and its purpose is to simplify the recovery work after an accident occurs, satisfy the demand for space saving, and further improve the overcurrent withstand capacity of semiconductor switching elements. An object of the present invention is to provide a circuit breaker that can reliably protect semiconductor switching elements from overcurrent regardless of their size.

[Structure of the Invention] (Means for Solving the Problems) The circuit breaker of the present invention includes a fixed contact between a power supply side terminal and a load side terminal, and a movable contact that approaches and separates from the fixed contact. A tripping device is provided to separate the movable contact from the fixed contact and interrupt the large current when a large current such as a short circuit current flows through the main circuit. In the device, a semiconductor switching element is provided in series with the main circuit, a bypass circuit is provided in parallel with the semiconductor switching element, and the switching element is turned on when a large current such as a short circuit current flows through the main circuit. It comprises a commutation switch that short-circuits a bypass circuit to the main circuit, and overload current protection means that detects when an overload current flows to the semiconductor switching element and turns off the semiconductor switching element. It consists of

(Function) When a large current such as a short circuit current flows in the main circuit, the tripping device is activated to separate the movable contact from the fixed contact and interrupt the large current. Simultaneously with this cutoff operation, the commutation switch closes to short-circuit the bypass circuit to the main circuit, thereby commutating the large current to the bypass circuit side, thereby protecting the semiconductor switching element from the large current.

By the way, even if the short-circuit current is not large and the tripping device does not operate, it may become an overload current for the semiconductor switching element, and such an overload current should not be passed through the semiconductor switching element. If this continues, the semiconductor switching element will break down.

Therefore, in the above configuration, when an overload current flows through the semiconductor switching element, the overload current protection means detects it and turns off the semiconductor switching element. Thereby, the semiconductor switching element can be reliably protected from overload current.

Moreover, since the semiconductor switching element, bypass circuit, and overload current protection means are built into the circuit breaker, the peripheral circuitry of the circuit breaker can be made more compact than if these were installed outside the circuit breaker. can.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

First, the mechanical configuration of the circuit breaker will be explained based on FIG. 2. A power supply side terminal 12 and a load side terminal 13 are provided on both left and right sides of a main body case 11 of this circuit breaker. A fixed contact 14 whose right side portion is bent into a 0-shape is connected to the power supply side terminal 12.
A fixed side contact 14a is fixed to the upper surface of the tip of 4.

Above the fixed contact 14, a movable contact 15 is mounted on the shaft 1.
The movable contact 1 is provided so as to be movable up and down via the
A movable contact 15a fixed to the lower surface of the tip of the fixed contact 14 comes into contact with and separates from the fixed contact 14a of the fixed contact 14. The movable contactor 15 is connected to the operating handle 17 via a link mechanism 18, and the operating handle 1
7 in the right direction from the state shown in FIG.
In contact with the fixed side contact 14a! ! 3 (closed circuit state)
It is now possible to return to.

On the other hand, a tripping device 19 is provided on the right side of the link mechanism 18. This tripping device 19 has an oil case 20 made of a non-magnetic material wrapped around an instantaneous disconnection coil 21, and one end of the instantaneous disconnection coil 21 is connected to the movable contact 15 via a flexible conductor 22. , the instantaneous removal coil 2
The other end of 1 is connected to a heater 23a for heating a bimetal 23 that detects overload current. A fixed conductor 24 extending to the left is connected to the lower end of the heater 2Bg of the bimetal 23, and a movable conductor 26 of a commutation switch 25 is connected to the left end of the fixed conductor 24 via a pin 27 for vertical and downward movement. The movable conductor 26 is movably supported, and a movable contact 28 is provided on the lower surface of the right end of the movable conductor 26 . A fixed conductor 30 having a fixed contact 29 is provided below the movable contact 28 so as to protrude to the right, and the right end of the fixed conductor 30 is connected to the load terminal 13 . This constitutes a bypass circuit 32 extending from the fixed contact 29 of the commutation switch 25 to the load terminal 13 via the fixed conductor 30.

On the other hand, the movable conductor 26 of the commutation switch 25 is connected to one terminal of a semiconductor switching element 34 such as a triac via a flexible conductor 33, and the other terminal of this semiconductor switching element 34 is connected to the load side terminal 13. has been done. Therefore, the main circuit 35 through which the load current flows is the power supply terminal 12 - fixed contact 14 - movable contact 15 - flexible conductor 22 - instantaneous disconnection coil 21 - heater 23a - fixed conductor 24 - movable conductor 26
- Flexible conductor 33 - Semiconductor switching element 34 - Load side terminal 13
This will be the route. The bypass circuit 32 is provided in parallel to the semiconductor switching element 34 in the main circuit 35.

On the other hand, the movable conductor 26 of the commutation switch 25 is urged upward by the spring 50, and as shown in FIG. 32 and the main circuit 35 are maintained in an open state.

In this state, the load current does not commutate (shunt) to the bypass circuit 32, but flows along the path of the movable conductor 26--flexible conductor 33--semiconductor switching element 34--load side terminal 13. In this case, the fixed conductor 24 and the movable conductor 26 of the main circuit 35 are provided in parallel to each other so that the load current flows in opposite directions, and when a large current such as a short circuit current flows, the fixed conductor 24 and the movable conductor 26 24 and the movable conductor 26 due to a reverse current, the movable conductor 26 is rotated downward against the spring 50, and the movable contact 28 is fixed as shown in FIG. By contacting the side contact 29, the bypass circuit 32 is short-circuited to the main circuit 35.

An overload current protection means 36 is provided within the main body case 11 to protect the semiconductor switching element 34 from overload current. This overload current protection means 36 includes a bimetal 23 with a heater 23a as a means for detecting overload current, and when an overload current flows, the bimetal 23 deforms [7] and the normally closed contact 37 (see Fig. 1). ). This normally closed contact 37 is connected in series with a light emitting diode 39 which is a light emitting element of the photocoupler 38, and both ends of this series circuit are connected to external control terminals 40 and 41 provided on the main body case 11. On the other hand, Photo Cabra 38
The photothyristor 42, which is a light receiving element, has its anode side connected to the gate of a semiconductor switching element 34 (TRIAC) via a DC power supply 43, and its cathode side connected to a resistor 44.
It is connected to the load side terminal 13 side via.

When using a circuit breaker incorporating the overload current protection means 36 configured as described above, as shown in FIG. A power source 46 and a load 45 are connected in series, and an external operation switch 47 and an external DC power source 48 are connected in series between external control terminals 40 and 41.

Next, the operation of the above configuration will be explained. To start energizing the load 45, the operating handle 17 is rotated to bring the movable contact 15 into contact with the fixed contact 14 to close the main circuit 35, and the external operating switch 47 is turned on. As a result, the light emitting diode 39 of the photocoupler 38 is connected to the external DC power supply 48 through the normally closed contact 37.
The photothyristor 42 is turned on by the light emission of the light emitting diode 39, and the semiconductor switching element 3 is turned on.
A gate current is applied to 4 to turn on this semiconductor switching element 34. In this state, the AC power supply 46 is connected to the power supply side terminal 12 - fixed contact 14 - movable contact 15 - flexible conductor 22 - momentary disconnection coil 21 - heater 23a - fixed conductor 24 - movable conductor 26 - flexible conductor 33 - Semiconductor switching element 3
A load current flows through the path 4-load side terminal 13-load 45. Thereafter, when a large current flows through the main circuit 35 due to a short-circuit accident or the like, the tripping device 19 is operated by the instantaneous disconnection coil 21, and the movable contact 15 is separated from the fixed contact 14 to start a breaking operation. At the same time, an overcurrent flows in the opposite direction between the fixed conductor 24 and the movable conductor 26 of the commutation switch 25, generating electromagnetic repulsion, which causes the movable conductor 26 to resist the spring 50. It is rotated downward to bring the movable contact 28 into contact with the fixed contact 29 as shown in FIG. 2, thereby short-circuiting the bypass circuit 32 to the main circuit 34. Thereby, the large current of the main circuit 35 is commutated and shunted to the bypass circuit 32 through both contacts 28 and 29 of the commutation switch 25. The current division ratio at this time is the resistance rl of the flexible conductor 33, the resistance r2 of the semiconductor switching element 34, the resistance "1" of the bypass circuit 32, and the contact resistance r4 of both contacts 28 and 29, and the current IR of the semiconductor switching element 34. The ratio between the current I of the bypass circuit 32 and the current I of the bypass circuit 32 is as follows.

IR: Is −(r3+r4): (r+ +r2)
In this case, the resistance r of the bypass circuit 32 is mainly the resistance of the fixed conductor 30 (copper conductor) and is extremely small, and it is clear that the contact resistance r4 of both contacts 28 and 29 is also extremely small. The magnitude relationship between the current IR and the current I5 of the bypass circuit 32 is IR((15).

By the way, during the breaking operation, as shown in FIG. 3(a), with respect to the estimated short circuit current In, the breaking current 1c is reduced due to the current limiting due to the arc resistance between the contacts 14a and 15B of the movable contact 15 and the fixed contact 14. is current limited, and the current peak value is Pl
to P2.

This breaking current 1e is generated by the semiconductor switching element 34 by closing both contacts 28 and 29 of the commutation switch 25 and short-circuiting the bypass circuit 32 to the main circuit 35 at t after the start of the breaking operation. The current IR flowing in the third
While the bypass circuit 3 decreases rapidly as shown in Figure (b),
2, the current Is begins to commutate and shunt from tl as shown in FIG. 3(c). As a result, the current IR flowing through the semiconductor switching element 34 becomes significantly smaller than that in the past, and the semiconductor switching element 34 can be reliably protected from melting and burning due to Joule heat. Moreover, the commutation of the current to the bypass circuit 32 by opening the commutation switch 25 described above is performed smoothly regardless of the magnitude of the overcurrent withstand capacity of the semiconductor switching element 34Ω. Semiconductor switching element 3
4 can be reliably protected from overcurrent in the event of a short-circuit accident, regardless of the magnitude of its overcurrent resistance.

By the way, even if the current value of the short circuit current is not large and the tripping device 19 does not operate, it may become an overload current for the semiconductor switching element 34. 34, the semiconductor switching element 34 will break down.

To deal with this, in the above embodiment, when an overload current flows to the semiconductor switching element 34, the bimetal 23 of the overload current protection means 36 is deformed by the heat generated by the heater 23a, and the normally closed contact 37 is opened. do. As a result, the light emitting diode 39 of the photocoupler 38 is cut off, the photothyristor 42 is turned off, the gate current of the semiconductor device element 34 is cut off, and the semiconductor switching element 34 is turned off. This turn-off opens the main circuit 35, cuts off the overload current, and reliably protects the semiconductor switching element 34 from the overload current.

When recovering after a short-circuit accident occurs, when the operation handle 17 is rotated clockwise, the movable contact 15 is pushed down by the link mechanism 18 linked thereto, and the contact 15a of the movable contact 15 is The contact point 14a of the fixed contactor 14 is contacted, and the main circuit 35 is closed. Therefore, there is no need for the troublesome work of replacing the quick-break fuse 2 as in the prior art, and the restoration work is extremely simple.

Furthermore, a semiconductor switching element 34 is installed inside the main body case 11 of the circuit breaker. Since the bypass circuit 32 and overload current protection means 36 are incorporated, there is no need for space for the conventional fast-acting fuse 2, semiconductor switching element 34, etc. outside the main body case 11, resulting in space saving and compact design. It also satisfies the demands of

In the above embodiment, the bimetal 23 with the heater 23a is used as a means for detecting the overload current flowing through the semiconductor switching element 34, but instead of this, the overload current can be detected by a current detecting means such as a current transformer. The detection signal is processed by an electronic circuit including an amplifier circuit, etc., and the semiconductor switching element 34
The structure may be such that the gate current is cut off.

Alternatively, an intelligent power IC may be used as the semiconductor switching element 34 instead of a triac or thermistor,
The semiconductor switching element itself may detect an overload current and self-shut off. In this case, the semiconductor switching element itself is provided with overload current protection means.

Furthermore, when a short circuit accident occurs, the main circuit 35 is connected to the bypass circuit 3.
In order to promote the commutation to 2, a current limiting contact (a contact that opens due to electromagnetic repulsion generated by a short-circuit current) may be provided in series with the semiconductor switching element 34.

In addition, the present invention can be modified in various ways, for example, the configurations of the link mechanism 18 and the tripping device 19 may be changed as appropriate.

[Effects of the Invention] As is clear from the above description, the present invention provides a semiconductor switching element in series with the main circuit, and a bypass circuit in parallel with the semiconductor switching element to prevent large short-circuit currents from occurring in the main circuit. When current flows, the commutation switch is turned on to short-circuit the bypass circuit to the main circuit, while when an overload current flows to the semiconductor switching element,
Since the overload current protection means detects this and turns off the semiconductor switching element, the large current in the event of a short-circuit accident is immediately diverted to the bypass circuit, and the large current does not flow to the semiconductor switching element. can be done as well as
What is the short-circuit current? Even if the current value is not large, when a current that causes an overload to the semiconductor switching element flows, the overload current can be cut off by turning off the semiconductor switching element using the overload current protection means, and the semiconductor switching element can be shut off. It has the advantage that switching elements can be reliably protected from overload current, and unlike conventional high current limiting circuit breakers, protection can be achieved regardless of the overcurrent withstand capacity of semiconductor switching elements. Furthermore, even when recovering after an accident occurs, there is no need for the troublesome work of replacing quick-acting fuses as in the past, making the recovery work extremely simple. Furthermore, since the circuit breaker incorporates semiconductor switching elements, bypass circuits, and overload current protection means, there is no need for space outside the circuit breaker for installing quick-acting fuses, semiconductor switching elements, etc. It also satisfies the demands for space saving and compactness.

[Brief explanation of the drawing]

1 to 3 show an embodiment of the present invention,
Figure 1 is an electrical circuit diagram, Figure 2 is a longitudinal front view of the entire structure, and Figure 3 is an electrical circuit diagram.
Figures (a) to (c) are diagrams showing changes over time in the current of each part during the interrupting operation. FIG. 4 is an electric circuit diagram showing a conventional example. In the drawing, 11 is a main body case, 12 is a power supply side terminal, 13 is a load side terminal, 14 is a fixed contact, 15 is a movable contact, 1
7 is an operation handle, 18 is a link mechanism, 19 is a tripping device, 21 is an instantaneous disconnection coil, 23 is a bimetal, 23
a is a heater, 24 is a fixed conductor, 25 is a commutation switch,
26 is a movable conductor, 30 is a fixed conductor, 32 is a bypass circuit, 34 is a semiconductor switching element, 35 is a main circuit, 36 is an overload current protection means, 37 is a normally closed contact, 38 is a photocoupler,
39 is a light emitting diode, 40 and 41 are external control terminals,
42 is a photosilisk, 45 is a load, and 47 is an external operation switch. Applicant: Toshiba Corporation

Claims (1)

[Claims] 1. A fixed contact between the power supply side terminal and the load side terminal,
A main circuit is constructed by providing a movable contact that connects and separates from the fixed contact, and the movable contact is separated from the fixed contact when a large current such as a short circuit current flows through the main circuit. In a circuit breaker equipped with a tripping device for interrupting large currents, a semiconductor switching element is provided in series with the main circuit, a bypass circuit is provided in parallel with the semiconductor switching element, and the bypass circuit and the main circuit are connected to the main circuit. a commutation switch which is provided to open and close between the circuit and the semiconductor switching element and which is turned on when a large current such as a short circuit current flows through the main circuit to short-circuit the bypass circuit to the main circuit; a circuit breaker comprising overload current protection means that detects when an overload current flows and turns off the semiconductor switching element.