US3240996A

US3240996A - Switch of the circuit breaker type

Info

Publication number: US3240996A
Application number: US259055A
Authority: US
Inventors: Sohus Julius
Original assignee: Siemens Corp
Current assignee: Siemens and Halske AG; Siemens Corp
Priority date: 1962-02-23
Filing date: 1963-02-18
Publication date: 1966-03-15
Anticipated expiration: 1983-03-15

Description

March 15, 1966 J. SOHNS 3,240,996

SWITCH OF THE cmcum BREAKER TYPE Filed Feb. 18, 1965 United States Patent 3,240,996 SWITCH OF THE CIRCUIT BREAKER TYPE Julius Sohns, Erlangen, Germany, assignor to Siemens &

Halske Aktiengesellschaft, Berlin and Munich, Germany, a corporation of Germany Filed Feb. 18, 1963, Ser. No. 259,055

Claims priority, application Germany, Feb. 23, 1962,

3 Claims. (Cl. 317-11) The invention disclosed herein is concerned with a Switch in combination with a thermistor, the resistance of which increases with increasing temperature, to decrease the load on contacts controlled by the switch.

There are switches of the circuit breaker type known, for protecting, for example, lines or motors, which effect in the case of short circuits or overload a generally magnetically controlled cutout operation. At the contacts of such switches appears, upon cutout in the presence of a short circuit, a pronounced contact-frying action which reduces the useful life of the contacts materially.

The invention is concerned with a switch of the above noted type wherein a considerable reduction of the contact frying action is achieved by connecting the switch in series with a thermistor, the resistance value of which increases with increasing temperature, practically suddenly, for example, by more than one power of ten, such resistance increase occurring within a definite temperature range, which depends upon the composition of the thermistor material.

A properly dimensioned thermistor remains cold and has low resistance in the presence of the rated current on the switch. Upon appearance of a short circuit or considerable overload, the thermistor will be heated by the current flowing therethrough, and its resistance will increase. The shunt or overload current is thereby greatly reduced thus materially reducing the load on the contacts.

According to another feature of the invention, the thermistor is structurally combined with the switch, being disposed, for example, in the same housing therewith.

The invention will now be explained more in detail with reference to the accompanying drawing showing in schematic manner an embodiment thereof.

Referring now to the drawing, numerals 1 and 2 indicate terminals of a switch, for example, a switch of the circuit breaker or cutout type, and

numerals

3 and 4 indicate contacts which are disposed in series with a magnet coil ICC 5 and a thermistor 6. These elements are traversed by the line current, the coil 5 governing the operation of a magnet which in turn controls the

contacts

3 and 4 to open the circuit when the rated current is exceeded. The thermistor 6 is dimensioned so that it is only negligibly heated and presents low resistance to rated current flowing in the circuit. Upon considerable increase of the current, for example, in the case of a short circuit on the line, the thermistor will be heated and its resistance will suddenly increase in leaping fashion, thus reducing the current flowing through the coil 6 and the

contacts

3 and 4, without, however, impeding the operative actuation of the magnetic controlled by the coil 5. The frying of the contact-s upon opening thereof is in this manner reduced and the useful life of the contacts is increased.

Changes may be made within the scope and spirit of the appended claims which define What is believed to be new and desired to have protected by Letters Patent.

I claim:

1. A switch of the circuit breaker type having terminals to which is connected a circuit which is to be supervised, comprising a control device connected with said terminals, said control device comprising magnetically governed break contacts, means for operatively supporting said contacts, a thermistor, and circuit means for serially conmeeting said break contacts with said thermistor, said contacts opening responsive to current flowing in said circuit which exceeds the rated current flowing therein, to interrupt said circuit, the resistance of said thermistor increasing suddenly in leap-like manner within a given temperature range, thereby decreasing the current traversing said contacts upon breaking action thereof.

2. A switch according to claim 1, wherein said sudden increase of resistance of said thermistor amounts to more than one power of tens.

3. A switch according to claim 1, wherein said device forms a structural unit with the switch.

References Cited by the Examiner UNITED STATES PATENTS 1,694,223 12/ 1928 Lemmon 317-1 1 1,784,226 12/1930 Edsall 317-11 2,594,890 4/1952 Ellwood 31711 FOREIGN PATENTS 415,083 10/ 1962 Germany.

SAMUEL BERNSTEIN, Primary Examiner.

Claims

1. A SWITCH OF THE CIRCUIT BREAKER TYPE HAVING TERMINALS TO WHICH IS CONNECTED A CIRCUIT WHICH IS TO BE SUPERVISED, COMPRISING A CONTROL DEVICE CONNECTED WITH SAID TERMINALS, SAID CONTROL DEVICE COMPRISING MAGNETICALLY GOVERNED BREAK CONTACTS, MEANS FOR OPERATIVELY SUPPORTING SAID CONTACTS, A THERMISTOR, AND CIRCUIT MEANS FOR SERIALLY CONNECTING SAID BREAK CONTACTS WITH SAID THERMISTOR, SAID CONTACTS OPENING RESPONSIVE TO CURRENT FLOWING IN SAID CIRCUIT WHICH EXCEEDS THE RATED CURRENT FLOWING THEREIN, TO INTERRUPT SAID CIRCUIT, THE RESISTANCE OF SAID THERMISTOR INCREASING SUDDENLY IN LEAP-LIKE MANNER WITHIN A GIVEN TEMPERATURE RANGE, THEREBY DECREASING THE CURRENT TRAVERSING SAID CONTACTS UPON BREAKING ACTION THEREOF.