CN209896685U

CN209896685U - Open central line leakage protection circuit

Info

Publication number: CN209896685U
Application number: CN201921079069.2U
Authority: CN
Inventors: 蔡峰毅; 陈金环; 许海恩
Original assignee: XIAMEN ZTC TECHNOLOGY Co Ltd
Current assignee: XIAMEN ZTC TECHNOLOGY Co Ltd
Priority date: 2019-07-11
Filing date: 2019-07-11
Publication date: 2020-01-03
Anticipated expiration: 2029-07-11

Abstract

The utility model relates to an open neutral line leakage protection circuit, which comprises a zero sequence current transformer ZCT, a leakage protection chip IC, a thermistor Rt, a silicon controlled rectifier SCR and a release TK, wherein the zero sequence current transformer ZCT is sleeved on a live wire L and a zero line N before a Load, one end of the secondary coil is connected with Vref end of the leakage protection chip IC, the other end is connected with VFB end of the leakage protection chip IC through a capacitor C4, SCR Trigger end of the leakage protection chip IC is connected with control electrode of SCR, the positive pole of the silicon controlled rectifier SCR is connected with one control input end of a release TK, the negative pole of the silicon controlled rectifier SCR is connected with diodes D2 and D3 in series and then is connected with a ground wire E, the other control input end of the release TK is connected with a live wire L, two contact switches of the release TK are connected with the live wire L and a zero wire N in series respectively, a thermistor Rt is located between a zero sequence current transformer ZCT and a Load, one end of the thermistor Rt is connected with the zero wire N, and the other end.

Description

Open central line leakage protection circuit

Technical Field

The utility model belongs to the electronic circuit field specifically relates to an open central line earth leakage protection circuit.

Background

Along with the development of technology and the improvement of living standard, electrical appliances with various functions are more and more, people can hardly leave various electrical appliances in life, along with the increasing popularization of the electrical appliances, the chances of people to be in electric contact with the electrical appliances are more and more, in order to enable users to be better protected, a power supply circuit of a plurality of electrical appliances is provided with an electric leakage protection circuit, when electric equipment leaks electricity, or a person gets an electric shock or the equipment is damaged in an insulation mode, the electric leakage protection circuit can automatically cut off a power supply within dozens of milliseconds, so that the users are prevented from being harmed by the electric shock, and the life safety and property safety of the users are protected.

However, the existing leakage protection circuits have many disadvantages: 1. the circuit structure is complex, the cost is high, the stability is poor, and the reliability is low; 2. the electromagnetic compatibility is poor, and the common mode conducted disturbance test in the frequency range lower than 150KHz in the national standard GB18499 cannot be passed. 3. When the zero line is disconnected (open neutral line), leakage protection cannot be achieved. For this reason, chinese utility model patent CN206894221U discloses an earth leakage protection circuit, which can pass the common mode conducted disturbance test in the frequency range lower than 150KHz, which is required in the national standard, by providing capacitors C5 and C6. However, the circuit cannot cut off the power supply under the condition of preventing the live wire and the zero wire from being reversely connected, and can damage the load.

Disclosure of Invention

The utility model aims at providing an open central line earth leakage protection circuit to solve above-mentioned problem. Therefore, the utility model discloses a specific technical scheme as follows:

an open neutral line leakage protection circuit can comprise a zero sequence current transformer ZCT, a leakage protection chip IC, a thermistor Rt, a silicon controlled rectifier SCR and a release TK, wherein the zero sequence current transformer ZCT is sleeved on a live wire L and a zero line N before a Load, one end of a secondary coil of the zero sequence current transformer ZCT is connected with a Vref end of the leakage protection chip IC, the other end of the secondary coil is connected with a VFB end of the leakage protection chip IC through a capacitor C4, two ends of the secondary coil of the zero sequence current transformer ZCT are connected with a resistor R6 and a capacitor C5 in parallel, an Rset end of the leakage protection chip IC is connected with a Ground end of the leakage protection chip IC through a resistor R4 and a capacitor C6 which are connected in parallel, an SCR Trigger of the leakage protection chip IC is connected with a control electrode of the silicon controlled rectifier SCR, an anode of the silicon controlled rectifier SCR is connected with one control input end of the release TK, a cathode of the silicon controlled rectifier SCR is connected with a diode D2 and a D3, two contact switches of the release TK are respectively connected in series with a live wire L and a zero line N, the thermistor Rt is located between the zero sequence current transformer ZCT and a Load, one end of the thermistor Rt is connected with the zero line N, and the other end of the thermistor Rt is connected with a ground wire E.

Furthermore, a capacitor C3 is connected between the group end and the Vref end of the leakage protection chip IC, and a capacitor C2 is connected between the group end and the C Delay end of the leakage protection chip IC.

Furthermore, Neutral of the leakage protection chip IC is connected to a cathode of the SCR, and a capacitor C1 is connected between a control electrode of the SCR and the cathode.

Further, the cathode of the silicon controlled rectifier SCR is connected with the zero line N through a resistor R2 and a diode D1 which are connected in parallel.

Further, a voltage dependent resistor MOV1 is connected between the live wire L and the neutral wire N, and a voltage dependent resistor MOV2 is connected between the neutral wire N and the ground wire E.

Furthermore, one end of a primary coil of the zero sequence current transformer ZCT is connected with the live wire L, and the other end of the primary coil is sequentially connected with a key TEST and a resistor R1 in series to be connected with the zero line N.

Furthermore, the open neutral line leakage protection circuit further comprises a fuse F, and the fuse F is connected in series with the live line L.

The utility model adopts the above technical scheme, the beneficial effect who has is: the utility model discloses the circuit is simple, the stable performance, and the action is reliable, can the earth leakage protection when power zero line disconnection, and connects when reverse at power live wire, zero line, can cut off power protection load immediately, ensures safe in utilization.

Drawings

To further illustrate the embodiments, the present invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. With these references, one of ordinary skill in the art will appreciate other possible embodiments and advantages of the present invention. Elements in the figures are not drawn to scale and like reference numerals are generally used to indicate like elements.

Fig. 1 is a schematic circuit diagram of the present invention.

Detailed Description

The present invention will now be further described with reference to the accompanying drawings and detailed description.

As shown in fig. 1, an open neutral leakage protection circuit may include a zero sequence current transformer ZCT, a leakage protection chip IC, a thermistor Rt, a thyristor SCR, a trip TK, and the like. The model of the leakage protection chip IC is 2140, and in this embodiment, the model of the leakage protection chip IC is FM2140 (Low Power Two-wire ground Fault arc extinguishing chip). Of course, in other embodiments, the leakage protection chip IC may be another type or specially made leakage protection chip IC having the same or equivalent function and structure as the FM2140, which can be easily implemented by those skilled in the art and will not be described in detail.

And the zero sequence current transformer ZCT is sleeved on the live wire L and the zero wire N before the Load. Specifically, one end of a primary coil of the zero sequence current transformer ZCT is connected with the live wire L, and the other end of the primary coil is sequentially connected with a key TEST and a resistor R1 in series to be connected with the zero line N. One end of a secondary coil of the zero sequence current transformer ZCT is connected with a Vref end of the leakage protection chip IC, the other end of the secondary coil is connected with a VFB end of the leakage protection chip IC through a capacitor C4, and a resistor R6 and a capacitor C5 are connected in parallel with two ends of the secondary coil of the zero sequence current transformer ZCT. The Rset end of the leakage protection chip IC is connected with the Ground end of the leakage protection chip IC through a resistor R4 and a capacitor C6 which are connected in parallel, an SCR Trigger end of the leakage protection chip IC is connected with a control electrode of the SCR, the anode of the SCR is connected with one control input end of the release TK, the cathode of the SCR is connected with a diode D2 and a diode D3 in series and then is connected with a Ground wire E, the other control input end of the release TK is connected with a live wire L, and two contact switches of the release TK are connected with the live wire L and a zero wire N in series respectively. And the thermistor Rt is positioned between the zero sequence current transformer ZCT and the Load, one end of the thermistor Rt is connected with a zero line N, and the other end of the thermistor Rt is connected with a ground line E.

It should be noted that the effect of the capacitors C5 and C6 in the circuit is to enable the circuit to pass the "common mode conducted disturbance test in the frequency range below 150 KHz" as required in the national standard GB18499, which does not affect the leakage protection performance of the circuit. Therefore, the capacitance values of the capacitors C5 and C6 can be selected according to practical situations, which can be easily realized by those skilled in the art and will not be described in detail.

In this embodiment, a capacitor C3 is connected between the Ground terminal and the Vref terminal of the leakage protection chip IC, and a capacitor C2 is connected between the Ground terminal and the C Delay terminal of the leakage protection chip IC.

In this embodiment, Neutral of the leakage protection chip IC is connected to a cathode of the SCR, and a capacitor C1 is connected between a control electrode of the SCR and the cathode.

In this embodiment, the cathode of the SCR is connected to the neutral line N through a resistor R2 and a diode D1 connected in parallel.

In this embodiment, a voltage dependent resistor MOV1 is further connected between the live line L and the neutral line N, and a voltage dependent resistor MOV2 is connected between the neutral line N and the ground line E.

In this embodiment, the open neutral line leakage protection circuit further includes a fuse F, and the fuse F is connected in series to the live line L. When the circuit or the load is short-circuited, the fuse F is opened to ensure the safety of the circuit.

The utility model discloses an operating principle of open central line earth leakage protection circuit is, when power zero line N breaks off, form the return circuit between silicon controlled rectifier SCR's negative pole and the ground wire E, so when the load takes place the electric leakage, or when the person electrocutes, produce induced voltage through zero sequence current transformer ZCT's secondary coil, compare and handle through earth leakage protection chip IC, the electric leakage current reaches setting action current value, silicon controlled rectifier SCR switches on, release TK moves, the power cut-off, play electric leakage and electric shock protection effect; when a live wire L and a zero line N of a power supply are reversely connected, a secondary coil of the zero-sequence current transformer ZCT generates induction voltage through the thermistor Rt, the induction voltage is compared and processed through the leakage protection chip IC, the silicon controlled rectifier SCR is conducted, the release TK acts to cut off the power supply, the electrical hidden danger is avoided, and the personal safety and the property safety are guaranteed.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. An open neutral line leakage protection circuit is characterized by comprising a zero sequence current transformer ZCT, a leakage protection chip IC, a thermistor Rt, a silicon controlled SCR and a release TK, wherein the zero sequence current transformer ZCT is sleeved on a live line L and a zero line N before a Load, one end of a secondary coil of the zero sequence current transformer ZCT is connected with a Vref end of the leakage protection chip IC, the other end of the secondary coil of the zero sequence current transformer ZCT is connected with a VFB end of the leakage protection chip IC through a capacitor C4, two ends of the secondary coil of the zero sequence current transformer ZCT are connected with a resistor R6 and a capacitor C5 in parallel, an Rset end of the leakage protection chip IC is connected with a Ground end of the leakage protection chip IC through a resistor R4 and a capacitor C6 which are connected in parallel, an SCR Trigger end of the leakage protection chip IC is connected with a control electrode of the silicon controlled SCR, an anode of the silicon controlled SCR is connected with one control input end of the release TK, a cathode is connected with a diode D2 and a D3 in series, two contact switches of the release TK are respectively connected in series with a live wire L and a zero line N, the thermistor Rt is located between the zero sequence current transformer ZCT and a Load, one end of the thermistor Rt is connected with the zero line N, and the other end of the thermistor Rt is connected with a ground wire E.

2. The open neutral leakage protection circuit of claim 1, wherein a capacitor C3 is connected between the group terminal and Vref terminal of the leakage protection chip IC, and a capacitor C2 is connected between the group terminal and the C Delay terminal of the leakage protection chip IC.

3. The open Neutral leakage protection circuit of claim 1, wherein Neutral of the leakage protection chip IC is connected to a cathode of the SCR, and a capacitor C1 is connected between a control electrode of the SCR and the cathode.

4. The open neutral leakage protection circuit of claim 3 wherein the cathode of said SCR is connected to said neutral conductor N through a resistor R2 and a diode D1 connected in parallel.

5. The open neutral leakage protection circuit of claim 4 wherein a varistor MOV1 is further connected between said live line L and said neutral line N, and a varistor MOV2 is connected between said neutral line N and said ground line E.

6. The open neutral leakage protection circuit of claim 1, wherein one end of the primary coil of the zero sequence current transformer ZCT is connected to the live line L, and the other end is connected to the neutral line N in series with a key TEST and a resistor R1.

7. The open neutral leakage protection circuit of claim 1 further comprising a fuse F connected in series with said line L.