FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

1. TITLE OF THE INVENTION:
“Test Circuit for Earth Leakage Circuit Breakers”

2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.

(c) ADDRESS: Larsen & Toubro Limited
Electrical & Automation
North Wing, Gate 7, Level 0,
Powai Campus, Saki Vihar Road,
Mumbai 400 072, INDIA ________________________________________________________________________
3. PREAMBLE TO THE DESCRIPTION:

COMPLETE
The following specification
particularly describes the invention and the manner in which it is to be performed.

Test Circuit for Earth Leakage Circuit Breakers

Field of invention:

This invention relates to residual current circuit breaker/residual current operated circuit breaker with testing means for use in installation, such as residential and non-residential building.

Background of the Invention

Residual current circuit breaker is intended to protect persons against indirect contact, exposed conductive parts of the installation being connected to an appropriate earth electrode. They may be used to provide protection against fire hazards due to a persistent earth fault current.

Residual current breakers do not have any provision to protect the test circuit from damage, 1) If the cable termination is wrong like phase to phase at top & bottom, and pressing test knob for longer time in OFF position, in this case test circuit will burnt, 2) If the cable termination is wrong like phase to phase at top & bottom, and the testing contacts get interlocked/shorted in OFF position. Hence the test circuit will get burn due to continuous flow of current.

The present test circuits are more prone to getting burnt. There is always possibility of failure of test circuit facility in the device.

Therefore there is a need to provide a test contact system which overcomes all the drawbacks of the prior art.

Objects of the invention

Object of the present invention is to provide a test contact system, which protects a circuit breaker even if the two contacts get shorted in OFF position for long period.

Another object of the present invention is to provide a test contact system, which prevents direct shorting of contact even the circuit breaker get shorted by test mean.

Yet another object of the present invention is to provide a test contact system, which prevents burning of test circuit.

One more object of the present invention is to provide a test contact system, which provides test facility will be available forever with the device.

Summary of the invention

According to present invention there is provided a test contact system a test circuit of a circuit breaker, the system comprising:
a test knob disposed on the circuit breaker;
a test contact capable of being operated upon operating the test knob, wherein the test contact is charged by a neutral pole and internally short with line pole circuit;
a test pin contact adapted to connect with the test contact, wherein upon operating the test knob, the test contact gets connected or disconnected with test pin contact; characterized in that,
a test pin adapted to connect with the test pin contact to complete the circuit for testing ,when a rotor lock is in “ON” position and disconnect from test pin contact, when the rotor lock is in “OFF” position thereby preventing burning of a test circuit.

Typically, wherein the test pin contact is made of sheet metal made of copper beryllium.

Typically, wherein the rotor lock is made of raw polycarbonate plastic.

Brief description of the drawings

Figure 1 shows a front view of a circuit breaker in accordance with the present invention;

Figure 2 shows a perspective view of a circuit breaker in accordance with the present invention in ‘OFF’ position;

Figure 3 shows a perspective view of a test contact system in accordance with the present invention in ‘OFF’ position;

Figure 4 shows a perspective view of a test contact system of figure 3 in ‘ON’ position;

Figure 5 shows another perspective view of a test contact system of figure 3 in ‘ON’ position; and

Figure 6 shows a perspective view of a circuit breaker in accordance with the present invention in ‘ON’ position.

Detail Description of the Invention

Various embodiment of the present invention provide an actuation mechanism for coupling a plurality of electrical devices, the mechanism comprising a shaft for each electrical device, the shaft having a variable cross-section, the shaft adapted to reversibly engage with an internal operating system of the electrical devices; and a seat on a casing of each electrical device, the seat providing an access to the internal operating system of the electrical devices.

The present invention provides a test contact system for circuit breaker. The system protects a circuit breaker even if the two contacts get shorted in OFF position for long period. Further, the system prevents direct shorting of contact even the circuit breaker gets shorted by test mean. Furthermore, system prevents burning of test circuit and provides test facility will be available forever with the device.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring now to figure 2, a perspective view of a circuit breaker in accordance with the present invention is illustrated. The circuit breaker is shown to include test contact system. The test contact system is a circuit having a test knob (1), a test contact (2), a test pin contact (3) and test pin (4). Figure 1 shows a circuit breaker with a test knob (1) thereover.

Referring now to figures 3, 4, 5 and 6, various operating conduction of test contact system are illustrated. Figure 3 shows the test knob (1) in OFF position thereby the test contact system is also in off position. The test knob (1) is operable externally. Upon pushing the test knob (1) the test contact (2) is pushed towards the test pin contact (3) to complete the circuit and test the circuit breaker refer figure 4. The test contact (2) is charged (connected with a resistor in the circuit) by a neutral pole. The test contact (2) is internally shorted with line pole circuit.

Further, the test pin contact (3) is an internal part of the circuit breaker between test the pin (4) and the test contact (2). When the circuit breaker is in ON position, phase pole supply is given to this part through the test pin (4). The test pin (4) is the part of the test circuit, which connects and disconnects the test pin contact (3) when operated.

Referring now to figures 4 & 5, various views of test contact system in “ON” position in accordance with the present invention are illustrated. The test knob (1) is shifted to test position. The test contact (2) is in contact with the test pin contact (3). The test Pin Contact (3) is touching the test contact (2) because of which residual current flows through the circuit. This will lead to triping of the circuit breaker. The test pin (4) is touching the test pin contact (3) while test knob (1) is pressed and hence completing the test circuit.

In an embodyment, the test pin contact (3) is made of a sheet metal part made out of copper beryllium material. The rotor lock (5) is a plastic part made out of polycarbonate raw material refer figure 1. The test pin (4) is a wire form part made out of stainless steel material.

In general, if the test circuit is performed in OFF position and both test contact (2) and the test pin contact (3) get shorted for a longer time of unit and the 230V/415V is applied thereby causing burning of a resistor. By using of the test contact system of the present invention, even test is performed in OFF position, the test kit will not burn and will remain in intact condition. This will make the test facility available forever with the circuit breaker.

It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention or the scope of below mentioned claims. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.

We Claim:

1. A test contact system for a test circuit of a circuit breaker, the system comprising:
a test knob disposed on the circuit breaker;
a test contact capable of being operated upon operating the test knob, wherein the test contact is charged by a neutral pole and internally short with line pole circuit;
a test pin contact adapted to connect with the test contact, wherein upon operating the test knob, the test contact gets connected or disconnected with test pin contact; and
a test pin adapted to connect with the test pin contact to complete the circuit for testing when a rotor is in “ON” position and disconnect from test pin contact when the rotor is in “OFF” position thereby preventing burning of a test circuit.

2. A test contact system as claimed in claim 1, wherein the test pin contact is made of sheet metal made of copper beryllium.

3. A test contact system as claimed in claim 1, wherein the rotor lock is made of raw polycarbonate plastic.