Circuit breaker with leakage current detecting functions

Abstract: A circuit breaker has leakage current detecting functions, that is leakage detection, leakage alarm and disconnection the circuit in the leakage state from the power source side; in order to conduct such functions, the circuit breaker comprises a magnetic release device for disconnecting a circuit in the leakage state, a zero-phase current transformer for detecting a leakage current, a sensitivity selector, an amplifier and a leakage relay for issuing a leakage alarm signal.

Description: FIELD OF THE INVENTION AND RELATED ART STATEMENT 1. FIELD OF THE INVENTION The present invention relates to a circuit breaker with leakage current detecting functions which is provided with the leakage alarm/trip functions in addition to the protection functions to overload and short-circuit which are fundamental functions of the circuit breaker. 2. DESCRIPTION OF THE RELATED ART Conventional circuit breaker with leakage alarm function has been disclosed, for instance, in EP-A-0 386 768 (prior art according to Article 54(3) EPC) based on the Japanese patent application No. Hei 1-58530 (Tokugan Hei 1-58530) which was filed by the same assignee, essential part thereof is shown in FIG.3 and FIG. 4. FIG.3 is a perspective view of the conventional circuit breaker 1. FIG .4 is a circuit diagram of the circuit breaker 1 shown in FIG. 3. The conventional circuit breaker 1 is provided with functions of protections against overload and short-circuit. As shown in FIG. 3, a casing 2 comprises a base part 2a and a cover part 2b. The casing 2 further comprises input side terminals 3 of power source side and output side terminals 4 of load side. The cover part 2b has a top face panel 1a having a square hole 1b for providing access to the handle 9. A leakage indication lamp 10 is provided in a hole 10a in the top face panel 1a positioned near the handle 9 in a manner to be observed through the hole 10a. A reset button 11 and a test button 12 protrude through holes in the top face panel 1a near the handle 9 and the leakage indication lamp 10. As shown in FIG. 4, the casing 2 of the conventional circuit breaker 1 contains a zero-phase current transformer 5, a sensitivity selector 6, an amplifier 7 and a leakage relay 8. When the leakage relay 8 is actuated by an amplified signal of the amplifier 7, the above-mentioned leakage indication lamp 10 is lit and the lit state is held to indicate the existence of leakage. Latched or held indication of leakage indication state of the leakage relay 8 and the leakage indication lamp 10 are reset by pushing the reset button 11. The test button 12 is used when the user makes a simulation test against the leakage state. The leakage relay 8 issues an alarm signal through leakage alarm output lines 13 to an alarm device, as shown schematically in FIG. 4. When a leakage in the circuit connected to the output side terminals 4 of load side occurs, the zero-phase current transformer 5 detects the leakage current and issues an output signal. The output signal of the zero-phase current transformer 5 is amplified by the amplifier 7 to provide an amplified signal. The amplified signal drives the leakage relay 8 to issue an alarm signal for the alarm device. At the same time the leakage indication lamp 10 is lit to indicate the existence of leakage. The leakage relay 8 and the leakage indication lamp 10 are held in a leakage detection state by means of a known latching circuitry. The latch leakage indication state in the conventional circuit breaker 1 is reset by pushing the reset button 11 or by breaking the power supply to the input side terminals 3. In the above-mentioned conventional circuit breaker 1 having only a leakage alarm function, when a leakage in the circuit connected to the circuit breaker 1 occurs, the circuit breaker 1 issues the alarm signal to operate the alarm device connected to the leakage alarm output lines 13. And, an operator, who has listened to the alarm, operates the handle 9 of the circuit breaker 1 for disconnecting the circuit in the leakage state from the power source. Therefore, it necessarily takes a good deal of time to disconnect the leakaging circuit from the power source by the conventional circuit breaker 1. Thus, the conventional circuit breaker 1 has a possibility of inducing such a problem that a circuit breaking by the circuit breaker 1 is unduly deferred, thereby damaging the circuit and its component. OBJECT AND SUMMARY OF THE INVENTION An object of the present invention is to offer an improved circuit breaker which can automatically conduct a breaking operation for leakage, and which has a changeover means for switching between (i) a first state comprising leakage alarm function and (ii) a second state comprising a leakage alarm function and a breaking function. In order to achieve the above-mentioned object, the circuit breaker with leakage current detecting functions of the present invention comprises: a casing; a zero-phase current transformer contained in the casing for detecting a leakage current; a leakage relay contained in the casing for issuing a leakage alarm signal in response to the output signal of the zero-phase current transformer; a magnetic release device which is contained in the casing, and is to be operated by the output signal of the zero-phase current transformer and is further used to disconnect a circuit in a leakage state from the power source; and alarm/trip changeover terminals for switching between a leakage alarm operation and a leakage alarm with breaking operation. While the novel features of the invention are set forth particularly in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a perspective view of an embodiment of a circuit breaker with leakage current detecting functions of the present invention. FIG.2 is a circuit diagram of the embodiment of the circuit breaker with leakage current detecting functions of FIG.1. FIG.3 is the perspective view of the conventional circuit breaker. FIG.4 is the circuit diagram of the conventional circuit breaker of FIG.3. It will be recognized that some or all of the Figures are schematic representations for purposes of illustration and do not necessarily depict the actual relative sizes or locations of the elements shown. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereafter, preferred embodiments of the present invention are elucidated with reference to the accompanying drawings of FIG.1 and FIG.2. FIG.1 shows a perspective view of the embodiment of the circuit breaker with leakage current detecting functions in accordance with the present invention. The circuit breaker 100 comprises a circuit breaker part of a known configuration including fixed contacts, movable contacts, arc suppressing devices, a contact driving mechanism and a trip mechanism for tripping the contact driving mechanism in response to an overload current state or a short circuit state to break the circuit having such trouble. As shown in FIG.1, a casing 20 of the circuit breaker 100 comprises a base part 20a and a cover part 20b; and a terminal base part 19 is fixed to a side face of the casing 20. The casing 20 further comprises input side terminals 23, 23, 23 at its power source side and output side terminals 24, 24, 24 at its load side. The cover part 20b has a top face panel 100a having a square hole 100b, which is for providing access to a handle 29 connected mechanically to the contact driving mechanism. The handle 29 is operated for manually driving the contact driving mechanism. A leakage indication lamp 30 is viewable through a hole 30a in the top face panel 100a positioned near the handle 29. The leakage indication lamp 30 is provided to indicate a leakage state. A reset button 31 and a test button 32 also protrude through holes in the top face panel 100a near the handle 29 and the leakage indication lamp 30. The reset button 31 is provided for resetting the leakage indication state. The test button 32 is used in case of confirming the leakage state as a simulation. The terminal base part 19 having eight (8) connection terminals is fixed to a longitudinal side face of the casing 20, as shown in FIG.1. FIG.2 shows a circuit diagram of the embodiment of the circuit breaker 100 with leakage current detecting functions of FIG.1 of the present invention. As shown in FIG.2, the circuit breaker 100 further comprises a zero-phase current transformer 25, a sensitivity selector 26, an amplifier 27, a leakage relay 28 and a magnetic release device 14. The zero-phase current transformer 25, which is inductively coupled to the lines 33 connected to the power source, produces an output signal when the vector sum of the currents passing through the lines 33 does not cancel. Each line 33 connects between one of the input side terminals 23, 23, 23 and one of the output side terminals 24, 24, 24 through a short-circuit detector 35 and an overcurrent detector 34. The sensitivity selector 26 is used for changing the sensitivity for detecting leakage current which occurs in the circuit connected to the output side terminals 24, 24, 24. When an output signal from the zero-phase current transformer 25 reaches above the predetermined leakage current value, such as 30mA, 100mA or 200mA, the sensitivity selector 26 issues an output signal. The amplifier 27 amplifies the output signal of the sensitivity selector 26, and issues an amplified output signal. The amplified signal drives the leakage relay 28, which issues an alarm signal through alarm output terminals 16a, 16b, 16c for the leakage current. As shown in FIG.2, terminals 16b and 16c of the alarm output terminals 16a, 16b, 16c are short-circuited normally. And, the terminals 16a and 16c of the alarm output terminals 16a, 16b, 16c are disconnected from each other. Alarm/trip changeover terminals 15₁, 15₂, which are provided on the terminal base part 19, are for connection to an alarm/trip control switch (not shown). The magnetic release device 14 and a leakage relay coil 281 of the leakage relay 28 are both connected to the amplifier 27 in the following manner: when the amplifier 27 actuates the leakage relay coil 281 of the leakage relay 28, the magnetic release device 14 is also actuated by the amplifier 27 if the terminals 15₁ and 15₂ of the alarm/trip changeover terminals 15₁, 15₂ are electrically connected to each other by the alarm/trip control switch (not shown). When the terminal 15₁ of the alarm/trip changeover terminals 15₁, 15₂ is not connected to the terminal 15₂ of the alarm/trip changeover terminals 15₁, 15₂ as a result of the alarm/trip control switch which is connected to the alarm/trip changeover terminals 15₁, 15₂ is in open state, the magnetic release device 14 is not actuated, whereas the leakage relay coil 281 is energized. As a result, in this circumstances, the leakage relay 28 of the circuit breaker 100 issues the alarm signal only, when the leakage is detected by the zero-phase current transformer 25. On the other hand, when the terminal 15₁ of the alarm/trip changeover terminals 15₁, 15₂ is electrically connected to the terminal 15₂ of the alarm/trip changeover terminals 15₁, 15₂ by the alarm/trip control switch in close state, the magnetic release device 14 is actuated by the amplified signal of the amplifier 27. As a result, the magnetic release device 14 drives to trip the contact driving mechanism of the circuit breaker part, and the circuit in the leakage state is disconnected from the power source side. The terminal base part 19 which has the alarm output terminals 16a, 16b, 16c and the alarm/trip changeover terminals 15₁, 15₂ further comprises control terminals 17 COM , 17 RST , 17 TST which are a reset terminal 17 RST , a test terminal 17 TST and a common terminal 17 COM for a remote control. The reset terminal 17 RST serves for resetting the leakage indication state by a remote control to short-circuit the terminals 17 COM and 17 RST . And the test terminal 17 TST of the control terminals 17 COM , 17 RST , 17 TST is used for confirming the operation in a leakage state by making a simulation by a remote control to short-circuit the terminals 17 COM and 17 TST . Next, operation of the above-mentioned circuit breaker 100 with leakage current detecting functions is described. When a leakage in the circuit connected to the output side terminals 24 occurs, the zero-phase current transformer 25 detects the leakage current and issues an output signal. And the sensitivity selector 26 issues an output signal to the amplifier 27 when the output signal of the zero-phase current transformer 25 goes above the predetermined leakage current. The output signal of the sensitivity selector 26 is amplified by the amplifier 27 and the amplifier 27 produces an amplified signal. The amplified signal drives the leakage relay 28, which issues an alarm signal through the alarm output terminals 16, to the alarm device as schematically shown in FIG.2. At the same time, the magnetic release device 14 is actuated to disconnect the circuit of leakage state from the power source if the alarm/trip changeover terminals 15₁, 15₂ are electrically connected by the alarm/trip changeover switch. And further the leakage indication lamp 30 is lit to indicate the existence of leakage in the circuit. The magnetic release device 14, the leakage relay 28 and the leakage indication lamp 30 are held in the leakage detection state by means of a known latching circuitry in the amplifier 27. The leakage detection state of them are reset by either of pushing the reset button 31, by receiving a reset signal through the reset terminal 17 RST of the control terminals 17 COM , 17 RST , 17 TST , or by breaking the power supply to the input side terminals 23. In order to check the leakage alarm functions of the circuit breaker 100 of this embodiment, the test button 32 may be pushed, or a test signal may be applied to the test terminal 17 TST of the control terminals 17 COM , 17 RST , 17 TST . In other words, the leakage detection state can be simulated by the circuit breaker 100 so as to check the function of the circuit breaker 100 and the related circuitry connected to the circuit breaker 100. Apart from the above-mentioned embodiment wherein the terminal base part 19 having plural connection terminals 15₁, 15₂, 16a, 16b, 16c, 17 COM , 17 RST , 17 TST is fixed to the side face of the casing 20, a modified embodiment may be such that plural lead wires, which are colored to be distinguished by various functions thereof, are led outward from the side face of the casing. And further, apart from the above-mentioned embodiment wherein the leakage indication lamp 30 is lit to indicate the existence of leakage, a modified embodiment may be such that a projectable leakage indication button is provided so as to be projected over the surface of the top face cover of the casing. Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been changed in the details of construction and the combination and arrangement of parts may be restored to without departing from the scope of the claims.

Claims: A circuit breaker with leakage current detecting functions comprising: a casing; a zero-phase current transformer contained in said casing for detecting a leakage current; a leakage relay contained in said casing for issuing a leakage alarm signal in response to said output signal of said zero-phase current transformer; a magnetic release device which is contained in said casing, and is to be operated by said output signal of said zero-phase current transformer and is further used to disconnect a circuit in a leakage state from said power source; and alarm/trip changeover terminals for switching between a leakage alarm operation and a leakage alarm with breaking operation. A circuit breaker with leakage current detecting functions in accordance with claim 1, which further comprises: a leakage current indicator for indicating detection of said leakage current by energization of said leakage relay; a reset button for resetting said leakage relay, said magnetic release device and said leakage current indicator; and a test button for simulating a leakage state thereby to check the functions of the leakage detection operation of said circuit breaker. A circuit breaker with leakage current detection functions in accordance with claim 2, which further comprises remote-control terminals which have a reset terminal for resetting said leakage relay, said magnetic release device and said leakage current indicator and a test terminal for simulating a leakage state thereby to check the functions of leakage detection operation of said circuit breaker.

Inventors: AKIYAMA TOSHIHIRO, MATSUMOTO SHIGERU, AKIYAMA, TOSHIHIRO, MATSUMOTO, SHIGERU
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1991
Main classification: H01H83
IPC codes: H01H83, H01H71, H01H73