SU1543473A1 - Current-limiting device for automatic switches - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to increase the reliability of operation in the nominal mode. The device contains contact 4.7 and 5.8 and arc-suppressive 9 and 10 systems, contact holders 2 and 3 movable contacts installed on the axes of rotation, flexible conductors 19 and 20, current supply leads 17 and 18 with sections 21 and 22 connected between a metal elements 23, 25, 24, which are electrically insulated from sections 21 and 22 with heat-resistant adhesive composition 26 and 27. When the current-carrying elements of the automatic switch and the current-limiting device are heated by the current in the nominal mode, the excess heat from the current-carrying elements of the automatic switch off studio, which are connected to current supply terminal 17 present a flexible conductor 19 and of the contact 2 is withdrawn through the thermally conductive circuit 21,26,23,25,24,27 and 22 for connection to external conductors connected to the current supply terminal 18. The conductive yl 1.

Description

The invention relates to electrical engineering, in particular to current limit. circuit breakers.

The purpose of the invention is to increase the reliability of operation in the nominal mode.

The drawing shows a current-limiting device, a cut,

The current-limiting device for circuit breakers consists of an insulating body 1 having partitions, between which contact holders 2 and 3 are installed at each pole, on which movable contacts 4 and 5 are U-shaped,

contact holder 6, on the opposite ends of which fixed contacts 7 and 8 are fixed, which are installed between contact holders 2 and 3 of arc extinguishing systems 9 and 10. Contact holder 2 and 3 are mounted on fixedly fixed in insulating casing 1 axis x and 12 rotation, passage Through the elongated holes 13 and 14. Contact pressing is provided by springs 15 and 16 installed respectively between contact holders 2 and 3 and the walls of insulating body 1 "Current supply leads 17 and 18 connected to the console

I

CO Ј

"at

clock holders 2 and 3 and flexible conductors 19 and 20, have sections 21 and 22 which are covered by metal elements 23 and 24 interconnected by a metal element 25. The space between the metal elements 21 and 23, 22 and 24 is filled with an electrically insulating heat-resistant adhesive composition 26 and 27.

The current limiting device operates as follows: 1 In nominal mode, pins 4 and 173 and 5 and 8 are closed under the action of springs 15 and 16, which allows current to flow through the current circuit breaker system and current limiting device Circuit breaker elements that are connected to the current supply terminal 17 The flexible conductor J9 and the contact-holder 2 are heated by this current more than the contact-holder 3, the flexible-conductor 0 and the current-carrying terminal 18 connected to the external connection cable. conductor. This is due to the fact5 that pins 4 and 7 and 5 and 8 are additional sources of heat, pg from the contact surface of the circle r g rz-ccMj, which prevents the automatic iv elements from ri and the elements 17 9 iSs L -OKOO PSM IJ og device 4, and 5, 8 - external supply conductor, in contrast to the electrical point och 3, 20, 8 current-limber., the construction cable from which the effective warm head is carried out to the external sub- 1 connecting conductors having a larger cross section and, consequently, a smaller heat exchange at heat flow and the ka. As a result of this, a temperature difference appears between the current-carrying terminals 17 and 5 8 of the current-limiting device. The heat flux under the influence of this difference passes through the heat-conducting circuit, the shunt current-carrying device and consisting of metal elements 21, 23 and 225 24, separated by an adhesive composition 26 and 27 in order to provide electrical insulation 1 from each other of sections 23 and 22 of the current supply leads 17e 18 and 2 ts

Since the metaplastic elements of the shunt circuit are heated by a heat flow, the adhesive composition must be heat resistant,

4734

The low thermal conductivity of the adhesive composition in comparison with metal elements is compensated by an increase in the area of mutual contact of the metal elements 21 and 23 and 22 and 24, which leads to a decrease in the thermal resistance of the heat-conducting circuit and an improvement in the heat-conducting properties of the current-limiting device.

The magnitude of the mutual contact area required for intensive heat removal can be determined as follows. The thermal resistance of the heat-conducting (shunt) circuit Ktr is found by the expression

R

T u

kЈ

(one)

-

20

and the resistance of two pairs of contacts RT by expression

R

mk

but

(2)

-

25 where d is the thickness of the insulating layer

five

0

Di and Dy are the specific thermal conductivities of the insulating layer materials and contacts, respectively;

s is the area of mutual contact of metal elements separated by an adhesive composition; and - the radius of the contact spot. Substituting the value of a f / 2R (p - specific: Ie electrical resistance of the material of the contacts, R, - contact resistance) in (2) we obtain (p. 2RJ

RT) RcLk

Effective heat transfer over the “splinter” circuit will be provided

(3)

 { R

ccc

(four)

those.

0

five

.Ј..Ј;, 2 A usRK from where we get the desired condition

ЈЈЈCL &. .

s)

(five)

2 L u R k

When the condition (5) is fulfilled, intensive heat removal from the circuit breaker to external connecting conductors is provided, which prevents it from overheating above the permissible temperature and deviating the protective characteristics of the release from the set ones.

In addition, the improvement of heat removal from the circuit breaker through the current limiting device eliminates the economically impractical need to reduce the rated current of the circuit breaker. without reducing the size of the latter, or use oversized circuit breakers at the same rated current.

Thus, in comparison with the known devices, the proposed device ensures reliable operation of the automatic switch together with the current-limiting device in the nominal mode.

Claims (1)

Invention Formula Current limiter A device for circuit breakers containing an insulating body, a contact system, spring-loaded contact carriers of moving contacts mounted on axes, flexible conductors, current-supplying terminals, characterized in that in order to increase the reliability of operation in the nominal mode, it is equipped with heat-conducting metal elements connecting current-conducting leads with each other and consisting of sections separated from each other by electrical insulating heat-resistant adhesive constitution. № 2} 1 П .3 25 Compiled V.Konosov Editor LoVseselovska Tehred L.Serdyukova Proofreader T.Malets Order 404 Circulation 459 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5 hch Subscription