JPH1169605A - Earth leakage breaker with overvolatge protection function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent malfunction for surge or noise impressed through superimposing to a power supply voltage, by dividing the power supply voltage into leakage detecting circuit, connecting a divided voltage to a secondary coil of a zero-phase current transformer via a zener diode, and than grounding the other second coil via a capacitor. SOLUTION: When an overvoltage is impressed across the power supply terminals 101, the same overvoltage is also impressed cross A-C so that the potential B rises proportionally. When the potential B exceeds the preset zener level, the zener diode 303 becomes conductive and a current flows into one end D of a secondary coil of a zero-phase current transformer 203. When a current flows to D, a leakage detecting section 2 performs the same operation as that of the case when leakage current higher than the constant level is detected and causes a thyristor 201 to operate, thereby protecting a load device from an overvoltage by releasing the contacts of a relay 102. Here, when an irregular overvoltage is impressed, a current limiting resistor 304 limits the current flowing to D to a level lower than the constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage breaker with an overvoltage protection function for preventing a load device from being burned when 200V is accidentally applied to a load device for 100V, for example. .

[0002]

2. Description of the Related Art There are the following two methods as conventional techniques for a leakage detection circuit having an overvoltage protection function.

The first method is, as shown in FIG. 1, in which a Zener diode and a protection resistor are connected in series between the anode and the gate of the thyristor 201 used for the earth leakage cutoff operation, and the voltage is divided between the gate and the cathode. This is a circuit in which a resistor and a capacitor are provided in parallel. In this case, when the voltage of the power supply circuit is equal to or higher than the specified value, the Zener diode becomes conductive, a trigger current flows through the gate of the thyristor, and the thyristor is turned on, so that the relay 102 is turned off.

In a second method, a third winding is provided on a zero-phase current transformer as shown in FIG. 2, one end of which is connected to one end of a surge absorbing element, and the third winding and the surge absorbing device are connected. This is a circuit in which the other ends of the elements are connected to different poles of the power supply circuit. The basic principle of this circuit is to make a zero-phase current transformer detect a leak current flowing when an overvoltage that can be absorbed by the surge absorbing element is applied, and perform a pseudo-leakage cutoff operation.

[0005]

However, the conventional method has the following disadvantages and difficulties.

In the first method, since a voltage obtained by dividing the power supply voltage is directly applied to the gate of the thyristor via a Zener diode, when the power supply voltage contains a surge or noise, the instantaneous voltage is reduced. There is a disadvantage that a malfunction is easily detected by detecting even a fluctuation.

In the second method, it is necessary to increase the number of turns of the tertiary winding wound around the zero-phase current transformer in order to lower the set value of the overvoltage operation. However, the number of turns depends on the size of the zero-phase current transformer. Has a limitation and is expensive because the tertiary winding is manually wound and requires time and labor for assembly.

[0008]

SUMMARY OF THE INVENTION Therefore, according to the present invention, when a leakage occurs on the load side of a power supply circuit, the zero-phase current transformer detects the leakage current and outputs it to its secondary winding, and inputs the output to a leakage detection circuit. However, the circuit configuration of the earth leakage breaker is such that the thyristor is triggered when the input to the earth leakage detector circuit is equal to or more than a certain value, and the interruption operation is performed by the attraction operation of the electromagnetic trip coil by the trigger operation of the thyristor. Accordingly, an object of the present invention is to provide an earth leakage circuit breaker that is less likely to malfunction due to surge or noise applied by being superimposed on a power supply voltage and has an inexpensive overvoltage operation function.

[0009]

A power supply side terminal unit, a contact switching mechanism, a leakage detection control unit including a zero-phase current transformer, and a load side terminal unit are incorporated in a body consisting of a base and a cover. When a leakage occurs on the load side of the power supply circuit, the zero-phase current transformer detects the leakage current and outputs it to its secondary winding, and inputs the output to a leakage detection circuit to which a surge malfunction prevention circuit is added. When the input to the earth leakage detector circuit becomes a certain value or more, the thyristor is triggered, and the earth leakage breaker is configured to be cut off by the attraction operation of the electromagnetic trip coil by the trigger operation of the thyristor. By dividing the power supply voltage into a circuit and connecting it to one of the secondary windings of the zero-phase current transformer via a Zener diode and grounding the other of the secondary windings via a capacitor, a power supply is provided. When a voltage is applied, a voltage applied to the Zener diode exceeds a Zener level, the Zener diode becomes conductive, and a voltage higher than an operating value is applied to a secondary winding of the zero-phase current transformer to perform a cutoff operation. It is.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the overvoltage operation circuit of the present invention is applied to an earth leakage relay will be described below in detail with reference to FIG.

Reference numeral 1 denotes a body, which is composed of a resin-molded base and a cover, and has a power supply terminal 101, a relay 102, a load side terminal 103, and a leakage detector 2 incorporated in the body. Reference numeral 2 denotes a leakage detector, which is a thyristor 201 and a surge absorbing element 2 that operate the relay when a leakage occurs.
It is composed of a printed circuit board (not shown) on which electronic components such as 02 are mounted, and a zero-phase current transformer penetrating a main power supply circuit. Reference numeral 3 denotes an overvoltage operation circuit unit incorporated as a part of the leakage detector unit.
2. It is composed of a zener diode 303 and a current limiting resistor 304.

[0012]

Next, in the above-mentioned embodiment, the operation (operation) at the time of electric leakage is well-known and will be omitted.
Only the operation (operation) when an overvoltage is applied will be described.

In a normal state, the rated voltage is applied between the terminals 101 on the power supply side, and the rated voltage is also applied between A and C in FIG. The potential of B in FIG.
2, the overvoltage operation circuit section 3 does not perform any operation in this state.
When an overvoltage is applied between the power supply terminals, the same overvoltage is applied between A and C, and the potential of B increases in proportion. When the potential of B exceeds a preset Zener level (eg, 130%), Zener diode 30
3 becomes conductive and a current flows into one end (D in FIG. 3) of the secondary winding of the zero-phase current transformer 203. When the current flows into D, the leakage detector 2 performs the same operation as when a leakage of a predetermined value or more is detected, activates the thyristor 201, and opens the contact of the relay 102 (the main power supply circuit is cut off). Load equipment can be protected from overvoltage. The current limiting resistor 30
Numeral 4 is for limiting the current flowing into D to a certain value or less when an abnormal overvoltage is applied.

Next, the reason why the earth leakage breaker with the overvoltage protection function by the circuit shown in FIG. 3 does not malfunction due to surge or noise from the power supply will be described.

The leakage detector IC shown at 204 in FIG.
It has a function of determining whether the output of the secondary winding of the zero-phase current transformer is due to leakage due to the frequency of the commercial power supply or due to surge or noise other than the frequency of the commercial power supply and operates. In the circuit shown in FIG. 1, since a voltage obtained by dividing the power supply voltage is directly connected to the gate of the thyristor, a surge or noise superimposed on the power supply is also applied to the gate of the thyristor. It is easy to malfunction. However, in the circuit of FIG. 3 according to the present invention, even if a voltage on which a surge or noise is superimposed is applied to the power supply, the voltage is input to the leakage detection IC through the secondary winding of the zero-phase current transformer, so that the leakage is prevented. Since the detector IC does not output an operation signal by judging a surge or noise, no malfunction occurs.

[0016]

[Effect] An overvoltage protection function that is inexpensive because a circuit is configured by simply adding a resistor (three) and a zener diode (one) to the conventional leakage detector, and is less likely to malfunction even against surges and noise. The present invention can provide an earth leakage circuit breaker.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram 1 of a main part of a conventional circuit not using the present invention.

FIG. 2 is an explanatory diagram 2 of a main part of a conventional circuit not using the present invention.

FIG. 3 is an explanatory diagram of a main part of a circuit in an example in which the present invention is applied to an earth leakage protection relay.

[Explanation of symbols]

 Each reference numeral is common to FIGS. 1, 2, and 3. DESCRIPTION OF SYMBOLS 1 Body 101 Power supply side terminal part 102 Relay 103 Load side terminal part 2 Leakage detector part 201 Thyristor 202 Surge absorption element 203 Zero phase current transformer 204 Leakage detector IC 3 Overvoltage operation circuit part 301 Voltage dividing resistor 302 Voltage dividing resistor 303 Zener diode 304 Current limiting resistor

Claims (1)

[Claims] A power supply side terminal unit, a contact switching mechanism, a leakage detection control unit including a zero-phase current transformer, and a load side terminal unit are incorporated in a body composed of a base and a cover. When a leakage occurs on the load side, the zero-phase current transformer detects the leakage current and outputs it to its secondary winding, and inputs the output to a leakage detection circuit to which a surge malfunction prevention circuit is added. When the input to the circuit becomes a certain value or more, the thyristor is triggered, and the earth leakage breaker is configured to cut off by the attraction operation of the electromagnetic trip coil by the trigger operation of the thyristor. An overvoltage was applied to the power supply by providing a circuit in which the voltage was divided and connected to one of the secondary windings of the zero-phase current transformer via a zener diode and the other of the secondary windings was grounded via a capacitor. When the voltage applied to the Zener diode exceeds the Zener level, the Zener diode becomes conductive and a voltage equal to or higher than the operating value is applied to the secondary winding of the zero-phase current transformer to perform a cutoff operation. Leakage breaker with overvoltage protection function.