JPS62160615A - Current breaker against trouble - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

BACKGROUND OF THE INVENTION Pending U.S. patent application Ser. It is described that it is possible to separate the contacts without generating an arc. In this US patent application, a transistor element in combination with a voltage dependent resistor is used to switch current from a departing contact to a transistor and then from the transistor to a voltage dependent resistor. Some means of switching the transistor between conducting and non-conducting states is required to make the transistor conductive when the contacts first open and to make it non-conductive shortly after the contacts are separated. This US patent application uses saturable iron core current transformers as an advantageous method for switching power transistors on and off within a predetermined period of time. Since then, the same function that transistors perform has been made with positive temperature coefficient materials (PTCs), which have a relatively small resistance at low temperatures and a substantially greater resistance at higher intended temperatures. I realized what I could achieve through resistance.

U.S. Pat. No. 4,329,726 and U.S. Pat. No. 4,413.
No. 301 states that 5 to 100 amperes are used in series with separable contacts to protect the circuit by increasing the series resistance in the circuit when the PTC material conducts a current greater than the intended value. PTC materials have been described that can operate within the range of .

The use of negative temperature coefficient materials in circuit breaker devices is described in US Pat. No. 4,019,097.

This patent describes the use of materials such as vanadium dioxide or lanthanum cobalt oxide in series with the flux switching trip mechanism. The thermal response properties of the materials just described are utilized to sense that an overcurrent condition exists and allow the current through the trip mechanism to be increased to an operating condition value. See the US patents cited above for details. U.S. Patent Nos. 4 and 3
The materials described in No. 29,726 and No. 4,413.301 are capable of conducting current to such an extent that they can provide overcurrent protection in circuits such as those protected by molded case circuit breakers. I can't.

The object of the invention is to provide a fault current using a resistor with a positive temperature coefficient that is capable of interrupting the current in residential and industrial power buses without being damaged or destroyed. The purpose is to provide circuit breakers.

SUMMARY OF THE INVENTION By placing a positive temperature coefficient (PTC) resistor and a voltage dependent resistor (VDR) in parallel with a pair of mechanically switched contacts, A fault current interrupting circuit that can repeatedly interrupt the fault current is obtained. When the contact leaves, the current is
Initially, a PTC resistor with a small resistance value is initially switched.

The passage of current through the PTC material causes the material to heat up rapidly and its resistance to increase due to diffraction. Parallel P
The voltage across the TC resistor and VDR increases rapidly to the clamp voltage of VDH, turning on VDR and directing the current to VDR.
Switch to DH. Since the voltage across the VDR is substantially higher than the supply voltage, the current then rapidly drops to a small value, allowing the pair of auxiliary contacts to complete the breaking process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although it is known to use PTC resistors as series elements in circuit interrupting devices, it is also possible to use PTC resistors to switch the current from the departing contacts to a voltage dependent resistor in order to eliminate arcing between the contacts. It was not previously known to use such a material as a parallel circuit element.

A variety of materials can be used for PTC resistors, each with unique properties, but barium titanate (BaTi)
03) is the most well-known material,
Suitable for interrupting small currents. High-current composite metals that transition from low to high resistance as a function of temperature rise
Insulator materials are currently under research.

One fault current interrupter using PTC material is shown in FIG. The fault current circuit breaker 10 has fixed contacts 11.1
2 and a main contact assembly 1 consisting of a bridging contact 13.14
Connected between 5 and 5.

When an overload current flows through the power bus 16, these contacts separate. Current through the power bus is sensed by a current transformer. The primary winding of this current transformer comprises a power bus and the secondary winding is connected to an actuating mechanism to open the contact assembly 15 as soon as the current reaches a predetermined value. The use of such a single current transformer and actuation mechanism within a protection circuit is described, for example, in U.S. Pat.
No. 2, please refer to these US patents for details. Fault current interrupter 10 operates similar to the solid state current limiting circuit breaker described in previously referenced US Patent Application Serial No. 610,947. By switching the current from the contacts via a solid state switch, an "arc-free interruption" is then effected between the separable contacts.

Auxiliary contact assembly 1 with fixed contacts 19 and movable contacts 18
7 can also be used in combination with the fault current interrupter 10 if desired. A power bus 16 is connected to a power source via a line terminal 20 and to an operating load via a load terminal 21 . A resistor 22 with a positive temperature coefficient, hereinafter referred to as PTC resistor, is connected in parallel with the separable contact assembly 15 and a metal oxide varistor 23 (hereinafter MOV
It is connected to a voltage dependent resistor (hereinafter referred to as VDR) such as a voltage dependent resistor (hereinafter referred to as VDR) via a line 24. A typical Ria Ti 03 PTC resistance, as described in E. Anrich's article ``PTC Thermistors as Self-Forced Heating Elements'' published in Philips Technical Review, is shown at 26 in Figure 3. It has various characteristics. In this figure, the logarithm of the resistance value in ohms is, for example, 100°C to 1
A sudden and significant increase has been shown to occur at expected temperatures of around 60°C.

When actuating the fault current circuit breaker 10, when the contact assembly 15 is pulled apart, the current is immediately switched to the PTC resistor 22, which has a lower initial temperature and resistance value, as shown by the characteristics described with respect to Figure 3. .

As the current passes through the PTC resistor and its temperature and resistance increase rapidly, the voltage across the parallel combination of PTC resistor 22 and MOV 23 increases correspondingly to the clamping voltage of the MOV, and the current immediately increases. Make it possible to switch to MOV. Although this voltage is now substantially higher than the supply voltage, it quickly reduces the current through the MOV to a very small value.

MOv is U.S. Pat. No. 4,374. It may have a composition as described in No.-049. At this time, the clamp voltage can be adjusted by changing the manufacturing method and the composition of the MOV material.

PTC resistor 22 in FIG. 1 is heated by internal power 12R. Here, R is the resistance value of the PTC resistor. When current is first switched to the PTC resistor, R is small, so the power loss is small and the temperature rises slowly. As the temperature increases, R increases, resulting in higher power losses and faster heating. However, since power is a function of the current squared, the heating rate is highly influenced by the magnitude of the current.

The fault current circuit breaker 10 shown in FIG. 2 is similar to the circuit breaker of FIG. A PTC resistor 22 is connected in parallel to the contact assembly and also to MOV 23 via line 24.25. PTC low anti-22 is
A thin layer of MOV material 27 is fused to one end, which has a very low clamping voltage on the order of about 5 volts. When the current is switched from contact assembly 15 to PTC resistor 22, M
Heating power is generated by the product of the voltage across the OV material 27 and the current through the MOV material.

Alternatively, the constant voltage drop generated by the MOV layer 27 can be distributed to the grain boundaries in the material making up the PTC resistor 22, or if more rapid heating is desired, the MOV It can be used in combination with layers. Since the initial heating power or current is a linear function, in this example, the initial temperature rise rate is higher and the first
The illustrated embodiment is not sensitive to current magnitude.

When using a high current single-metal-insulator PTC material such that the conductive metal is encapsulated within a matrix of MOV44 material to form a PTC-MOV resistor, a separate MOV44 material is used.
OV23 is no longer needed. Metal or PTC-MOV
The resistor is given an initial low temperature and low resistance conductivity, and current is initially switched from contact assembly 15. P
As the current through the TC-MOV resistor and its temperature increases, the volume of the MOV material expands, interrupting the conductivity of the metal, thus reducing the voltage across the PTC-MOV resistor to M
Allow the voltage to increase to the clamp voltage of the OV material. M.O.V.
The current when switching to the material then decreases rapidly.

This is because the MOV's clamp voltage is substantially higher than the power supply voltage.

Although the fault current interrupter of the present invention has been described in the context of protecting equipment and wiring contained within a power busbar, this is by way of example only. This fault current circuit breaker is used in cases where "arc-free" switching is required, such as in explosive atmospheres in mines, or "noise-free" switching, such as sensitive electronic components in computers. It can be used in any situation, such as when

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a circuit breaker according to the present invention, FIG. 2 is a circuit diagram of another embodiment of the circuit breaker shown in FIG. 1, and FIG.
The figure shows the relationship between the resistance value and temperature of the resistor with a positive temperature coefficient used in FIGS. 1 and 2. Explanation of main symbols 11.12, 13, 14: Contact 22: PTC resistance

Claims (1)

Claims: 1) a pair of separable electrical contacts arranged to interrupt current flow through an electrical circuit, with electrical connections in parallel between the electrical contacts; a resistor with a positive temperature coefficient that switches the current to the resistor with a positive temperature coefficient when the current is removed. 2) a pair of separable electrical contacts arranged to interrupt the flow of electrical current through an electrical circuit, with a parallel electrical connection between the electrical contacts, and when the electrical contacts are separated for the first time, interrupting the electrical current; A resistor with a positive temperature coefficient is electrically connected in parallel with the resistor with a positive temperature coefficient, and a voltage across the resistor with a positive temperature coefficient is expected. a voltage-dependent resistor that switches the current to the voltage-dependent resistor when the voltage reaches the voltage-dependent resistor. 3) The fault current breaker according to claim 2), wherein the voltage dependent resistor is made of silicon carbide or metal oxide. 4) In the fault current circuit breaker according to claim 1), the resistor having a positive temperature coefficient has a layer of a material having voltage dependence, and the material having a positive temperature coefficient has a layer of a material having a voltage dependence. A fault current circuit breaker designed to speed up the rate at which the scheduled temperature is reached. 5) In the fault current circuit breaker according to claim 1), the resistor having a positive temperature coefficient is made of a material having crystal grain boundaries, and the crystal grain boundaries have voltage dependence. Fault current circuit breakers containing materials with 6) In the fault current circuit breaker according to claim 2), the resistor having a positive temperature coefficient and the voltage-dependent resistor are made of a composite material, and for this reason, the electrical contact is Upon release, the current is switched to one component of the composite material at a first temperature and then switched to another component of the composite material at a second temperature higher than the first temperature. Fault current interrupter. 7) a pair of contacts and a resistor connected between the contacts, the resistor being constructed of a composite material having a positive temperature coefficient of resistance, such that the resistor is at a first temperature; the material has a first resistance value at a higher temperature and an even higher resistance value at a second higher temperature, and the material also has a voltage dependence, such that the resistor has a first voltage drop across it. a fault current interrupter having a third resistance value at and a lower fourth resistance value at a higher second voltage drop across the resistor. 8) In the fault current circuit breaker according to claim 7), the composite material includes a first material having a positive temperature coefficient of the resistance value and a second material having the voltage dependence. Fault current circuit breaker consisting of.