JPH01264277A - Power switch - Google Patents

Abstract

PURPOSE:To obtain a circuit breaker which is more simple in construction, by using a superconductor which is movable to a switching place of a circuit. CONSTITUTION:When an abnormality takes place and an overcurrent yields in an electric circuit or a load apparatus, the heating value of heating resistance 10 which is provided in the electric circuit by approaching a superconductor 1 increases and then, the temperature of the superconductor 1 rises. When its temperature exceeds a critical temperature, the superconductor 1 makes a transition from a superconducting state to a normal conducting one. Further, even when a large current exceeding a critical current density flows in the superconductor 1 because of a short circuit trouble and the like, its conductor is transited to the normal conducting state in the same way. If transited to the normal conducting state, the repulsive force between the superconductor 1 and a permanent magnet 2 disappears and only the restoring force of a spring 4 acts upon the superconductor 1. As a result, the superconductor 1 moves in the left direction and is tripped from contact points 3. Then, the current is cut off and a breaking indication 6 comes out at once.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a switching mechanism for electric circuits, and in particular, when an accident such as a short circuit occurs on the load side, the overcurrent is cut off and the electric circuit is switched off. This invention relates to a circuit breaker suitable for protecting equipment.

[Conventional technology]

Regarding conventional circuit breakers, see “Modern Power Distribution Technology JP11
2 to P119 (Denki Shoin, published in 1972). Conventional circuit breaker automatic trip devices that trip the contacts when an overcurrent occurs are broadly divided into thermal electromagnetic types that combine bimetals and electromagnets, and fully electromagnetic types that combine oil dashpots and electromagnets. . The principle of operation will be explained below using a thermal electromagnetic type circuit breaker as an example.

A circuit breaker will not operate if a current several times the rated current flows for a short period of time, such as the starting current of a motor, and will cut off (time-delayed tripping) in the case of a long-term overcurrent and disconnect the circuit or load. Equipment needs to be protected. Furthermore, when a large current (generally ten times the rated current or more) such as a short circuit current flows, it is necessary to instantly cut off the current (instantaneous tripping). For thermal electromagnetic circuit breakers, use bimetal for time-delayed tripping.

An electromagnet is used for instantaneous tripping. That is, when a large current exceeding ten times the rated current flows, the magnetic force between the electromagnet and the movable iron core moves the iron core, tripping the contacts and cutting off the current. If the overcurrent is smaller than this, the contact is opened using the bending effect of the bimetal due to the heat generated by the heating resistor installed near the bimetal.

Switching devices using superconductors include persistent current switches for superconducting coils. To pass a persistent current through a superconducting coil, the entire coil must be made of superconductor to form a closed circuit. Therefore, in order to extract a persistent current from a superconducting coil or to introduce a current into a superconducting coil, it is necessary to transition a part of the superconducting coil to a normal conducting state.

A persistent current switch is a mechanism in which a heater is provided close to a part of a superconducting coil to cause the superconducting coil to transition to a normal conductive state, allowing persistent current to be put in and taken out. This type of mechanism was developed in Japanese Patent Application Publication No. 5
8-30173, JP-A-58-32479, and JP-A-60-100487.

[Problem to be solved by the invention]

Automatic tripping devices for circuit breakers installed in low-voltage indoor electrical circuits require two types of operation: delayed tripping, which works in response to long-term overcurrents, and instantaneous tripping, which works in response to large currents such as short-circuit currents. becomes.

The conventional thermal electromagnetic type uses a bimetal for delayed tripping and an electromagnet for instantaneous tripping.

The fully electromagnetic type uses an oil dashpot for delayed tripping and an electromagnet for instantaneous tripping, which has the problem of a complicated structure.

An object of the present invention is to provide a breaker with a simpler structure.

[Means to solve the problem]

The contacts that open and close the electric circuit are electrically connected by a movable superconductor, and when the superconductor is in a superconducting state, the superconductor is pressed against the contact by the repulsive force with the magnet, making it conductive. When the superconductor transitions to normal conductivity, the repulsive force with the magnet disappears, and the restoring force of the spring pulls the superconductor away from the contact, cutting off the overcurrent. That is, the above object is achieved by opening and closing the circuit by utilizing the generation and disappearance of repulsive force with the magnet caused by the superconductor transitioning between the superconducting state and the normal conducting state.

[Effect]

The basic properties of superconductors are shown in Figure 2 (a) and (b).
This is explained by:

As shown in Figure 2 (a), the superconductor has a critical temperature Tc
Below we show a superconducting state, the temperature increases and the critical temperature T
When the temperature exceeds c, the state transitions to a normal conduction state. Also, Figure 2 (
a) As shown in middle ■, when the current density flowing through the superconductor is less than the critical current density Jc, it exhibits a superconducting state, and the critical current density J
When the temperature exceeds c, the state transitions to a normal conduction state. Similarly, the magnetic field also transitions from the superconducting state to the normal conducting state with the critical magnetic field Ha as the boundary, as shown in Figure 2 (2). In the superconducting state, superconductors exhibit perfect diamagnetic properties and repel anything that generates a magnetic field, such as a magnet. If a 1000 gauss magnet is used, the repulsive force will be 0.4 N per d, and a 40 g object can levitate against the motion. When a superconductor transitions from a superconducting state to a normal conducting state, the repulsive force due to perfect diamagnetism disappears.

Next, the operating principle of the present invention will be explained.

A superconductor, which electrically connects two contacts that open and close an electric circuit, exhibits a superconducting state when there is no abnormality in the electrical circuit, and the repulsive force from a magnet placed close to the superconductor causes a spring, etc. The superconductor is pressed against the contact by overcoming the pulling force of the superconductor. Current therefore flows from one terminal to the other through the superconductor. When an overcurrent such as an overtime current of an electric motor flows in an electric circuit for a long time, a heating resistor provided in the electric circuit close to a superconductor generates heat, and the temperature of the superconductor rises. When the temperature of the superconductor exceeds the critical temperature Tc, it transitions from a superconducting state to a normal conducting state, and the repulsive force with the magnet disappears. When an abnormality such as a short circuit occurs in the electrical circuit and a large current flows, the current density flowing through the superconductor becomes the critical current density Jc.
exceed. Therefore, the state transitions from the superconducting state to the normal conducting state, and the repulsive force with the magnet disappears. As the repulsion force disappears due to the rise in temperature and current density, a tripping force acts on the superconductor, and the superconductor that was electrically connecting the contacts separates from the contacts and cuts off the current. As a result, current interruption during overcurrent can be simplified from the conventional combination of a bimetal and an electromagnet to only a superconductor.

〔Example〕

An embodiment of the present invention will be described below as shown in FIGS. 1(a) and 1(b).
, (C). FIG. 1(a) shows a case where there is no abnormality in the electric circuit or load equipment and the superconductor 1 is in a superconducting state. The superconductor 1 is fixed to the new display 6 via a shaft 11, and receives a leftward force that causes the compressed spring 4 to return to its original state. Further, in the superconducting state, the superconductor 1 exhibits complete diamagnetic property and receives a rightward force due to repulsion from the permanent magnet 2 fixed to the case 9. Since the repulsive force with this permanent magnet 2 is larger than the restoring force of the spring 4,
The superconductor 1 is pressed against a pair of contacts 3 that are electrically insulated from each other. Therefore, the contacts are electrically connected by the superconductor 1, and the current flows through the superconductor 1 to the power supply side terminal 1.
2 and the load side terminal 13.

When an abnormality occurs in the electric circuit or load equipment and an overcurrent occurs, the amount of heat generated by the heating resistor 10 provided in the electric circuit in close proximity to the superconductor 1 increases, and the temperature of the superconductor 1 rises. When the temperature of the superconductor 1 exceeds the critical temperature, the superconductor 1 transitions from a superconducting state to a normal conducting state. Further, even if a large current exceeding the critical current density flows through the superconductor 1 due to a short circuit accident or the like, the superconductor 1 similarly transitions to the normal conducting state. When the superconductor 1 transitions to a normal conductive state, the repulsive force between the superconductor 1 and the permanent magnet 2 disappears, and only the restoring force of the spring 4 acts on the superconductor 1.

As a result, the superconductor 1 moves to the left and is separated from the contact 3, and as shown in FIG. 1(b), the current is cut off and a new display 6 pops out. The superconductor 1 transits from a normal conducting state to a superconducting state due to a temperature drop due to current interruption, and a repulsive force acts between it and the permanent magnet 2 again. It is necessary to prevent the superconductor 1 from coming into contact with the contact point 3 due to this force and from automatically returning the power supply. Therefore, a structure was adopted in which the superconductor 1 is fixed by a stopper 8 in which a spring 7 having one clockwise rotational force is provided on the rotating shaft and a notch provided in the shaft 11. To turn on the power again, rotate switch 5 counterclockwise to remove the stopper. When the stopper is released, the superconductor 1 moves to the right due to the repulsive force with the permanent magnet 2,
It is pressed against the contact 3 and returns to the energized state shown in FIG. 2(a).

Figure 3 shows the relationship between the current and the cutoff operation time in this example.The present invention utilizes the fact that the current flowing through a superconductor exceeds a critical current density and transitions to a normal conduction state. Time-deferred sushi is performed by utilizing the fact that the temperature of the superconductor exceeds a critical temperature and transitions to a normal conductive state. That is,
In the case of instantaneous tripping, the current flowing through the circuit is equal to the set value Ic
The circuit area of the superconductor was set so that the critical current density of the superconductor is reached when the current density reaches the critical current density (generally about 10 times the rated current).

Jc Here, S is the circuit area of the superconductor, Jc is the critical current density of the superconductor, and Ic is the set current for instantaneous tripping.

In addition, when the overcurrent is below the set value Ic, the temperature of the superconductor is raised to a critical temperature or higher using a heating resistor provided near the superconductor, thereby performing a time delay. The amount of heat generated per unit time Q by the heating resistor is given by the following equation.

Q=RI" Here, R is the resistance value of the heating resistor, and Δ is the current flowing through the heating resistor. Therefore, the larger the overcurrent, the faster the temperature rise of the superconductor, and it becomes possible to shut off the superconductor in a short time.

According to the present invention, the number of basic parts can be reduced to 15 compared to the 20 basic parts of a conventional thermal electromagnetic type that combines a bimetal and an electromagnet.

The structure can be simplified. Furthermore, the breaking capacity can be easily changed by changing the area of the superconductor circuit and the resistance value of the heating resistor.

In the present invention, a permanent magnet is used to induce a repulsive force with the superconductor, but an electromagnet can also be used instead of the permanent magnet.

In the present invention, a superconductor and a contact point when an overcurrent occurs.

The restoring force of the spring was used to remove the .

Other forces can also be used. An example is shown in FIG. Figures 4(C) and 4(d) utilize the attractive force between the permanent magnet and the ferromagnetic material 14, and the left side shows the superconducting state and the right side shows the normal conducting state. The superconductor 1 and the ferromagnetic material 14 have a bonded structure. In the superconducting state, the superconductor exhibits complete diamagnetic properties and no magnetic flux passes through it, so the attractive force between the permanent magnet 2 and the ferromagnetic material 14 is very small. Therefore, the superconductor 1 is pressed against the contact point 3 due to the repulsion from the permanent magnet 2.

When the superconductor 1 transitions to a normal conducting state due to an overcurrent, the repulsive force disappears and the magnet begins to pass through the superconductor 1.

Therefore, an absorbing force acts between the permanent magnet 2 and the ferromagnetic material 14, the superconductor 1 is separated from the contact 3, and the current is cut off.

Figures 4(e) and 4(f) use gravity for tripping, with (e) being a superconducting state and (f) being a normal conducting state. In the superconducting state, the repulsive force between the superconductor 1 and the permanent magnet 2 exceeds gravity, and the superconductor 1 is pressed against the contact point 3. When the superconductor transitions to a normal conducting state due to an overcurrent, etc., the repulsive force disappears and only gravity acts, causing the superconductor to fall and open the contacts.

FIG. 5 shows another embodiment of the invention. In addition to the isolation mechanism shown in FIG. 1, the present invention includes a zero-phase current transformer for detecting leakage current. The zero-phase current transformer consists of an iron core 15 and a secondary winding 16 wound around the iron core.

When a leakage occurs, magnetic flux due to the difference between the forward current and the return current is generated in the iron core 15, and a voltage is induced in the secondary winding 16. The secondary output of this zero-phase current transformer is used directly or amplified to transition the superconductor to a normal conducting state. FIG. 5(a) shows a coil 17 connected to the secondary side of a zero-phase current transformer and connected near the superconductor 1 of the switching mechanism shown in FIG. Due to the occurrence of electrical leakage, current flows through the coil 17 provided on the secondary side of the zero-phase current transformer, generating a magnetic field. This magnetic field causes the superconductor 1 to transition to a normal conducting state, the contact 3 is opened, and the lt current is cut off.

Fig. 5(b) shows a heating resistor of 1o instead of the coil in (a).
It has been established. When a current leakage occurs, current flows through the heating resistor 10 to raise the temperature of the superconductor above the critical temperature. Therefore, the superconductor 1 becomes a normal conductor, the repulsive force with the permanent magnet 2 disappears, and the contact 3 is opened. According to the present invention, the structure of the earth leakage breaker can be simplified.

FIG. 6 shows another embodiment of the invention. This embodiment is a circuit opening/closing device used in applications such as thermostats to maintain a constant ambient temperature. The superconductors 1, - and the permanent magnets 2 are provided in a constant temperature bath 24, and a conductor 22 that electrically connects the contacts 3 is fixed to the superconductor 1 by a shaft 11. When the superconductor 1 is in a superconducting state, the superconductor 1 levitates due to the repulsive force with the permanent magnet 2, the superconductor 1 and the fixed conductor 22 come into close contact with the contact 3, current flows to the heater 23, and the ambient temperature decreases. Rise. When the ambient temperature exceeds the critical temperature of the superconductor 1, the repulsive force with the permanent magnet 2 disappears, the superconductor falls due to the movement, the contact 3 is opened, and the ambient temperature decreases. By opening and closing the contacts 3, the ambient temperature is maintained at the critical temperature of the superconductor 1. The temperature control of the cooler is the opposite of that of the heater 23, in that the contacts are opened by the repulsive force acting below the critical temperature of the superconductor 1, and the contacts are closed when the critical temperature is exceeded and the repulsive force disappears. In the present invention, the set value of the ambient temperature can be changed using superconductors having different critical temperatures. Furthermore, even when using the same superconductor, the critical temperature can be changed by applying a magnetic field to the superconductor using a coil or the like, and the set value of the ambient temperature can be changed.

This embodiment makes it possible to adjust the temperature of a constant temperature bath or the like without a temperature sensor.

〔Effect of the invention〕

According to the present invention, the number of basic components of the conventional thermal electromagnetic type can be reduced, and the shear and breaking capacity of the breaker can be easily changed by changing the circuit area of the superconductor and the resistance value of the heating resistor. .

[Brief explanation of the drawing]

FIGS. 1(a), (b), and (c) are cross-sectional views of a breaker according to an embodiment of the present invention, with FIG. 1(a) showing the superconducting state, and FIG. 1(b) indicates the normal conduction state,
Figure 1 (C) is a diagram showing an equivalent circuit, Figure 2 (a) is a graph diagram showing the relationship between current density and temperature of a superconductor, Figure 2 (b) is a graph diagram showing the relationship between magnetic flux density and temperature, and Figure 3 is a diagram showing the relationship between magnetic flux density and temperature. An operational characteristic diagram of a breaker according to an embodiment of the present invention, Figures 4 (8) to (f) are explanatory diagrams of the operation of a superconductor during normal conduction transition, and Figure 5 (a) is an embodiment of the present invention. A circuit diagram of an earth leakage breaker according to an example, FIG. 5(b) is a circuit diagram of an earth leakage breaker according to another embodiment of the present invention, and FIG. 6 is a circuit diagram of a temperature control power switch according to an embodiment of the present invention. It is a diagram. 1... Superconductor, 2... Permanent magnet, 3... Contact,
4...Spring, 5...Switch, 6...New display, 7...Rotation spring, 8...Stopper, 9
...Case, 10...Heating resistance, 11...Shaft, 1
2... Power supply side terminal, 13... Load side terminal, 14...
・Magnetic material, 15... Iron core, 16... Secondary winding, 17
...Coil, 18...Load, 19...Transformer, 2
0...Earth leakage breaker, 21...Earth, 22...
Conductor, 23... Heating resistance, 24... Constant temperature oven. Figure 1 1゜(C) j Figure 2 (Ku) C 1/J-n door world Figure 3 I Ic Denka Figure 4 (α) (6] t4 /4 Figure 5 (t2.n1 ″l

Claims (1)

[Scope of Claims] 1. An electric circuit having contacts for opening and closing the circuit, characterized in that a superconductor that can move to the opening and closing points of the circuit is used. 2. A power switch having contacts for opening and closing a circuit, characterized in that a superconductor that can move to the opening/closing point of the circuit is used. 3. A power switch according to claim 2, characterized in that a magnet is provided in close proximity to the superconductor, and the circuit is opened and closed by utilizing the presence or absence of a repulsive force between the magnet and the superconductor. 4. A power switch according to claim 3, characterized in that a resistor is provided in a circuit close to the superconductor. 5. In claim 3, a zero-phase current transformer and a coil and/or a resistor are provided on the secondary side of the zero-phase current transformer, and the coil and/or the resistor are connected to the superconductor. A power switch characterized by being placed close to each other. 6. A power switch according to claim 4 or 5, characterized in that the restoring force of a spring is used to electrically isolate the contact and the superconductor. 7. Claim 4 or 5, wherein a ferromagnetic material is connected to the superconductor, and the contact and the superconductor are electrically isolated by an absorbing force between the ferromagnetic material and the magnet. A power switch characterized by: 8. In claim 4 or 5, the contact, the superconductor, and the magnet are arranged in this order from above in the direction of gravity, and the contact and the superconductor are electrically isolated by gravity. A power switch characterized by: 9. Claim 6, 7 or 8, characterized in that when the contact and the superconductor are electrically isolated, means for fixing the superconductor and means for releasing the fixation are provided. power switch. 10. A temperature regulator, characterized in that a superconductor is provided in a space that maintains a constant temperature, and the generation and removal of heat in the space is controlled by detecting the presence or absence of a repulsive force between the superconductor and a magnet. .