JPS61153905A - Arc extinguisher - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION Pending U.S. patent application Ser.
It is described to provide "arc-free" circuit interruption. This solid state switch contains a transistor,
This transistor has a saturable iron core of 8! It is turned on by the current transformer and turned off when the current transformer core reaches saturation. This U.S. patent application is cited by reference;
For more information on the relationship of the total current through the protected system to the system voltage as a function of time +1illIil by the solid state switch, see this US patent application.

British Patent Specification 1 No. 1.072.267 and No. 1,1
No. 52.903 is related to this invention in that it uses a voltage dependent resistor to switch a silicon controlled rectifier between a pair of separate contacts. These two British patent specifications are incorporated by reference.

No. 3,904,931 describes the use of silicon controlled rectifiers to shunt protected devices. In this case, when an overvoltage condition occurs in the circuit, a Zener diode is used to stabilize the voltage.

U.S. Pat. No. 3,887,849 discloses the use of a semiconductor switch in series between the circuit breaker and the load to delay application of source voltage to the load for a period of time greater than the circuit breaker trip time. Are listed. A Zener diode is used to turn on a semiconductor switch. This US patent is also cited by reference.

It is known to use solid state switches between contacts to break the circuit and to use various circuit devices to switch current from the contacts. Applicants have proposed using a position actuated switch, such as a single pole double throw switch device, in combination with a capacitor and a resistor to create an RC
It is understood that, by use as an arc extinguisher, a pair of auxiliary contacts simultaneously redirect current from the main contacts into an RC circuit to extinguish the arc that forms between the main contacts. However, Applicant uses a combination of voltage dependent elements constructed as described herein to deionize the initial arc plasma and cool the contact surface to a temperature below thermionic emission. switching the current to the first circuit element for a period of time sufficient to dissipate the energy stored in the inductance of the current path and reduce the current to a low enough value to interrupt the current. It is not known that switching to a second circuit element is taking place during this period.

1ri1ju1 This invention provides a solid-state arc extinguishing device using arc commutation. A solid state switch and a voltage dependent resistor are connected in parallel between a pair of separable contacts. A Zener diode is provided to turn on the solid state switch when the arc voltage between the separated contacts reaches a predetermined voltage. A capacitor connected across the voltage dependent resistor is charged to the clamp voltage of the voltage dependent resistor, which then conducts and switches current from the solid state switch. The clamping voltage is chosen to be higher than the grid voltage, so that the current approaches a lower value and breaks the circuit.

Figure 1 shows that the AC voltage source 9 has a resistance Rs and an inductance L.
A protected circuit 10 is shown supplying operating power via a switch 11 to a load represented by a combination of s. A switch 11 is connected to a pair of power bus conductors 14.15 via corresponding contacts 12.13. In order to extinguish the arc when the contacts 12, 13 separate, an arc extinguishing device 16 is arranged in parallel with the contacts. The arc extinguisher is constructed by connecting a thyristor or triac Q1, such as an SCR, in series with a capacitor C1 between the contacts. A varistor or bidirectional Zener diode z1 is connected between the gate of the triac and the power bus conductor 14 via a resistor Re. In some applications, the Zener diode is connected to the main terminal 20 opposite the gate, rather than the gate and power conductor of the triac.
It may be connected between. When contacts 12.13 are closed, no current flows through the gate of the triac, the triac is in the off state, and the capacitor C1 is completely discharged by the resistor Ro. When the contacts open, an arc is created between the contacts, and when the voltage reaches a first predetermined value, such as about 100 volts, current flows through the Zener diode, turning on the triac. Current is switched from the arc to the capacitor, allowing the contacts to cool and the capacitor charging to a second predetermined voltage, approximately 1000 volts. This voltage is the clamping voltage of the voltage dependent silicon carbide or metal oxide varistor MOV.

After this, MOV conducts and current is switched to MOV. Since the clamp voltage is higher than the system voltage Vo, the current quickly approaches zero, thus completing the disconnection process.

When an SCR is used in place of a thyristor in the circuit of FIG. A bridge rectifier is required. When using a DC voltage source instead of the AC voltage source 9, a thyristor can be used instead of a triac, and then a Zener
The Zener diode turns on the thyristor when the diode voltage reaches a first predetermined voltage.

For such DC applications, both Zener diodes and thyristors can be replaced by four-layer diodes, such as two-terminal Schockley diodes. The voltage across the diode itself is chosen to turn the diode on. For AC applications, bidirectional voltage dependent four-layer diodes replace Zener diodes and thyristors since no gate is required to turn on the diode. An example of such a bidirectional voltage dependent diode is
“Psyduck” is a trademark of Unitroad Kanbanyi.
S 1daC) J. The subsequent time sequence of switch voltages Vs is shown at 17 in FIG. The contact point is to
leaving for the first time. An arc voltage is generated at this time, which reaches the Zener voltage 2 at time tl, at which time the bidirectional Zener diode conducts, switching the current from the arc through the triac to the capacitor C1. At time t2, capacitor voltage v3 exceeds the clamp voltage of MOV, and the current is switched to MOV. At time t3, the current through the circuit is completely interrupted and the switch voltage is reduced to the applied voltage Vo
is equal to

FIG. 3 shows the system current 18 corresponding to the time period shown in FIG. 2 of the switch voltage 17. Contact opens for the first time
1. It can be seen that during the period from 2 to 2 when the MOV conducts for the first time, the current decreases only slightly. After that, the current rapidly attenuates through the MOV and stops flowing at time t3.

Capacitor C1 is disclosed in pending U.S. Patent Application Serial No. 6
It may also be replaced with a resistor having a positive temperature coefficient as described in No. 65,841. A resistor with a positive temperature coefficient is
It is said to have a relatively small resistance value at low operating temperatures and a very large resistance value at higher operating temperatures.

In order for the circuit described in this invention to operate efficiently, the ratio of high temperature resistance to low temperature resistance should be approximately 1000:1.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of the arc extinguishing device of this invention, and Fig. 2 is a circuit diagram of the arc extinguishing device of the present invention.
FIG. 3 is a graph showing the voltage across the contacts in the arc extinguisher shown as a function of time; FIG. 3 is a graph showing the current through the circuit shown in FIG. 1 as a function of time; Explanation of main symbols 12.13: Contact QI Two-semiconductor switch CI: Capacitor zI: Zener diode

Claims (1)

Claims: 1) a pair of separable contacts for interrupting current flowing through the circuit and a switchable semiconductor in series with voltage storage means, the switchable semiconductor and the voltage storage means; are connected between the separable contacts for switching current from the contacts, and further for turning on the switchable semiconductor at a first predetermined voltage between the contacts. An arc extinguishing device having a first voltage dependent element in circuit relationship with a switchable semiconductor. 2) In the arc extinguishing device according to claim 1), a second predetermined voltage is connected between the contacts for switching current from the voltage storage means at a second predetermined voltage between the contacts. arc extinguishing device with a voltage-dependent element. 3) An arc extinguishing device according to claim 1, comprising a resistor with a positive temperature coefficient used in place of the voltage storage means to switch the current from the contacts. 4) The arc extinguishing device according to claim 1), wherein the switchable semiconductor is a thyristor or a transistor. 5) The arc extinguishing device according to claim 2), wherein the second voltage dependent element is composed of a metal oxide or a silicon carbide varistor. 6) The arc extinguishing device according to claim 4, wherein the thyristor is constituted by a silicon controlled rectifier or a triac. 7) The arc extinguishing device according to claim 1, wherein the first voltage dependent element is a diode or a varistor. 8) The arc extinguishing device according to claim 1), wherein the voltage storage means is constituted by a capacitor. 9) In the arc extinguishing device according to claim 1), the switchable semiconductor is constituted by a triac, and the first voltage-dependent element is connected to the gate of the triac and one of the contacts. Arc extinguishing device connected between one side. 10) In the arc extinguishing device described in claim 1),
An arc extinguishing device having a current limiting resistor in series with the first voltage dependent element. 11) In the arc extinguishing device described in claim 1),
An arc extinguishing device having a resistor in parallel with the voltage storage means. 12) a pair of separable contacts for interrupting the current flowing through the circuit and a voltage dependent semiconductor in series with voltage storage means, both of which voltage dependent semiconductor and said voltage storage means are connected to said voltage storage means; connected between the separable contacts for switching current from the contacts at a first predetermined voltage between the contacts; and the voltage storage when a second predetermined voltage is developed across the contacts. An arc extinguishing device having a voltage dependent element in circuit relationship with said voltage dependent semiconductor for switching current from said means. 13) The arc extinguishing device according to claim 12), wherein the voltage dependent semiconductor is composed of a four-layer diode. 14) The arc extinguishing device according to claim 12, wherein the voltage dependent element is composed of a metal oxide or a silicon carbide varistor.