WO2020108477A1

WO2020108477A1 - Metal casing electrical product leakage alarming device having self-detection function

Info

Publication number: WO2020108477A1
Application number: PCT/CN2019/120931
Authority: WO
Inventors: 杨卫珍
Original assignee: 杨卫珍
Priority date: 2018-11-26
Filing date: 2019-11-26
Publication date: 2020-06-04
Also published as: CN109342873A

Abstract

A metal casing electrical product Leakage alarming device having a self-detection function, comprising a metal casing (1), an isolation sampling unit (2), a control unit (3) and an alarming unit (4). Two input ends of the isolation sampling unit (2) are respectively connected to the metal casing (1) and a power supply wire (5), and the output of the isolation sampling unit (2) is connected to the control unit (3). The output of the control unit (3) is connected to the alarming unit (4). One isolation sampling unit (2) is provided between the metal casing (1) and each phase line (L) as well as a zero line (N), and all the phase lines (L) form a high impedance loop by connecting to the isolation sampling units (2) on the phase lines (L), the metal casing (1), the zero line (N) and the isolation sampling unit (2) on the zero line (N). The alarming unit (4) comprises a detection device normal alarming unit (41) and a leakage alarming unit (42). The device has a self-detection invalidation determining function, thus greatly improving the safety of using electricity. The device can identify whether the electrical device has a leakage, identify a device state and issues different prompt alarms for the described various states.

Description

Electric leakage alarm device for metal shell electrical products with self-checking function

Technical field

The invention relates to electricity protection technology, in particular to a leakage alarm device of a metal shell electrical product with self-checking function.

Background technique

At present, the electrical leakage protection of electrical products mainly depends on the leakage protection switch. When the insulation resistance of the power supply line and the casing decreases or is short-circuited, the power supply generates a leakage short-circuit current through the ground wire connected to the metal casing of the electrical appliance, triggering the leakage protection switch Action to cut off the power supply to avoid greater accidents.

However, if the shell of the electrical product is poorly grounded and the ground wire is disconnected or virtually connected, the shell will carry dangerous voltage, which can easily cause electric shock.

The invention patent with the patent number 201310178530.0 discloses a ground wire electrification detection device, including a photocoupler, the first input terminal of which is connected to the ground wire through a first resistor, and the second input terminal is connected to the neutral wire and the second wire through a second resistor An output terminal is connected to the first DC power supply through a third resistor, and the second output terminal is grounded through a fourth resistor; the controller, whose voltage signal acquisition port is connected to the second output terminal of the photocoupler, is connected to the When the voltage of the second output terminal is greater than the threshold voltage, the alarm signal output port of the controller outputs an alarm signal; the alarm device connected to the alarm signal output port of the controller responds to the alarm signal output prompt output by the controller. The grounding electrification detection device disclosed by the invention can prompt when the electrical equipment leaks but there is no current flowing through the grounding wire, which improves the safety of the electrical equipment and reduces the probability of electric shock accidents by users.

The invention also has the following deficiencies:

1. If there is a short circuit between the phase line and the casing, and the detection device also fails, it is more likely to cause electric shock to the user.

2. The applicable electrical enclosure must be grounded and the ground wire is detected. When the phase wire is shorted to the electrical appliance shell (ground wire), the device can detect it; when the corresponding zero wire is shorted to the electrical appliance shell, it cannot be detected;

3. If the ground wire is poorly grounded, it cannot be detected;

It can be seen that the above-mentioned current charging detection device is obviously still defective in use, and needs further improvement.

In order to ensure the safety of the use of electrical products, it is extremely necessary to provide a leakage alarm device for metal shell electrical products with self-test function that can perform real-time self-inspection and detection. Also suitable for electrical products that cannot be grounded or are inconvenient to ground.

Based on years of rich practical experience and professional knowledge in the design work of electrical appliances, the inventor has actively researched and innovated with the application of academic principles, and finally created the leakage alarm device of the metal shell electrical product with self-test function of the present invention.

Summary of the invention

The main purpose of the present invention is to overcome the above-mentioned shortcomings of the existing leakage protection device technology and provide a method that not only provides short circuit to the metal shell of the electrical product and the power supply line and is charged to provide leakage protection, but also can work on itself during use Warnings are carried out normally to avoid electric shock accidents of persons or equipment caused by faulty leakage protection devices.

The purpose of the present invention and solving its technical problems are achieved by the following technical solutions.

An electric leakage alarm device for a metal shell electrical product with a self-checking function includes a metal shell, an isolated sampling unit, a control unit and a warning unit. The two input terminals of the isolated sampling unit are respectively connected to a metal shell and a power supply line. The output of the sampling unit is connected to the control unit, and the output of the control unit is connected to the warning unit, wherein an isolated sampling unit is provided between each phase line and neutral line and the metal shell, and all phase lines are connected through The isolated sampling unit on the phase line, the metal shell, the isolated sampling unit connected to the neutral line and the neutral line form a high-resistance loop. The warning unit includes a normal warning unit and a leakage warning unit of the detection device.

When the electrical product equipped with the present invention is connected to the power supply, a tiny current is generated on the input loops of all the isolated sampling units, and a low voltage is generated on the output end of the sampling unit. This voltage is recognized by the control unit and controlled by the control unit. The detection device normal warning unit works to inform the user that the equipment and the detection device are normal and fault-free;

Once the phase line short circuit fault occurs, the phase line directly forms a loop through the metal shell, the isolated sampling unit connected between the metal shell and the neutral line, and the loop impedance is greatly reduced compared with the aforementioned high-impedance loop; When the neutral line in the line is short-circuited with the metal shell, the neutral line forms a loop through the metal shell, the isolated sampling unit and the phase line connected between the metal shell and the phase line, and the loop impedance is also greatly reduced compared to the aforementioned high-impedance loop. The corresponding isolation sampling unit outputs a high voltage. After the voltage is recognized by the control unit, the control unit controls the leakage warning unit to inform the user that the equipment has a leakage short-circuit fault, which cannot be used and must be repaired.

If the normal warning unit and the leakage warning unit of the detection device do not work after the power is turned on, it indicates that the detection device is faulty and must be repaired.

In addition to the above-mentioned necessary technical features, the following technical features can be further supplemented in the specific implementation process.

In the foregoing leakage alarm device for metal shell electrical products with self-checking function, wherein the isolated sampling unit is a current-to-voltage converter, the current input terminal of the current-to-voltage converter is connected to the power supply line through a current limiting resistor. The voltage output terminal of the current-to-voltage converter is connected to the control unit.

In the foregoing leakage alarm device for a metal shell electrical product with a self-test function, wherein the control unit is a CPU, the first output terminal of the CPU is connected to the normal warning unit of the detection device, and the second output terminal of the CPU is connected to the According to the leakage warning unit, the CPU outputs control signals from the two output ports according to the magnitude of the input voltage value of the input terminal, respectively, and controls the normal warning unit or the leakage warning unit of the detection device.

The aforementioned leakage alarm device of a metal shell electrical product with self-checking function, wherein the normal warning unit and the leakage alarm unit of the detection device are LED warning devices of different colors, or voice alarm devices, or remote network alarm devices, or a combination thereof .

The foregoing leakage alarm device of a metal shell electrical product with self-checking function, wherein the power supply line is two for single-phase electrical products, that is, a phase line and a neutral line, and the isolated sampling unit is divided into two groups at this time Connect the phase line and the metal shell and the neutral line and the metal shell. The output terminals of the two sets of isolated sampling units are connected in parallel and then connected to the input terminal of the control unit. For three-phase four-wire power supply systems and three-phase unbalanced electrical products, all There are four groups of isolated sampling units. An input terminal of any one of the four groups of isolated sampling units is connected to three phase lines and a neutral line through current limiting resistors respectively. The other input terminal of the four groups of isolated sampling units Connected to the metal casing, the output ends of the four groups of isolated sampling units are connected in parallel and then connected to the input end of the control unit; for electrical products of a three-phase balanced power supply system, the isolated sampling units are three groups, and the three groups of isolated sampling units One of the input terminals of any group is connected to three phase wires through a current limiting resistor, the other input terminal of the three groups of isolated sampling units is connected to the metal shell, and the output terminals of the three groups of isolated sampling units are connected in parallel and then connected to the control The input of the unit.

The foregoing leakage alarm device for a metal shell electrical product with self-test function, wherein the isolated sampling unit is composed of a rectifier and a Hall element, and the two AC input terminals of the rectifier element are respectively connected to the metal shell and pass a current limiting resistor The power supply line is connected, the two DC output ends of the rectifier are connected to the input end of the Hall element, and the output of the original Hall element is connected to the input end of the control unit.

In the foregoing leakage alarm device for a metal shell electrical product with a self-test function, wherein the isolated sampling unit is a photocoupler, the two input ends of the photocoupler are respectively connected to the metal shell and the power supply line through a current limiting resistor, The output of the photocoupler is connected to the input of the control unit.

The foregoing leakage alarm device for a metal shell electrical product with self-test function, wherein the LED warning device includes a LED and a control switch, the output of the control unit is connected to a control switch, and the control switch is connected in series with the LED Connect to power.

In the foregoing leakage alarm device of a metal shell electrical product with a self-checking function, the control unit is a CPU or a voltage controller of an analog circuit.

In the foregoing leakage alarm device of a metal shell electrical product with a self-checking function, the control switch is an electronic switch or a mechanical electromagnetic switch.

The present invention uses a metal shell electrical product leakage alarm device with self-test function, which has the following beneficial effects:

1. The leakage alarm device of the metal shell electrical product with self-checking function of the present invention has a failure discrimination function, thus greatly improving the safety of electricity, not only can identify the electrical appliance as non-leakage, leakage within the safety threshold, or true leakage (danger Leakage), and can identify the status of the device, and give different prompting alarms to the above various states.

If the detection device fails, the user can judge that the detection device is invalid from no sound and light prompts, and immediately repair it as the first safety protection.

If the detection device is normal, the warning unit gives sound and light prompts, but the leakage warning unit does not give a prompt, indicating that the electrical equipment is in a safe and normal state.

If the normal warning unit of the detection device does not give out sound and light prompts, and the leakage warning unit gives a prompt, it indicates that the electrical equipment is in a serious leakage state and must be repaired immediately.

The leakage alarm device of the metal shell electrical product with self-checking function of the present invention is applicable to electrical products whose metal shell is grounded or not.

If the leakage switch is normal, in the event of a leakage accident, the safe power failure is handled by the leakage switch. Danger and cut off power supply. The safety factor is doubled than the previous leakage switch alone, and it is especially suitable for IT systems without a ground wire.

4. The present invention provides a safe and dangerous state warning. When the ground wire of the existing system fails, the leakage switch is triggered only when the user receives power, and the safety is much higher. Moreover, it is unprecedented to determine whether the detection system has failed.

5. The invention solves the electric shock danger caused by the failure of the detection device, can discriminate the safety of electrical equipment by light and sound, and can implement remote monitoring.

BRIEF DESCRIPTION

1 is a circuit block diagram of a leakage alarm device of a metal shell electrical product with self-checking function of the present invention;

2 is a schematic diagram of a circuit device when the present invention is applied to a single-phase electrical product;

3 is a schematic diagram of a circuit device of another embodiment when the present invention is applied to a single-phase electrical product;

4 is a schematic diagram of a circuit device of another embodiment when the present invention is used in a single-phase electrical product;

5 is a schematic diagram of a circuit device when the present invention is applied to a three-phase four-wire power supply appliance.

detailed description

The specific implementation of the present invention will be further described in detail below with reference to the drawings. The metal casing 1 of the electrical appliance may not be grounded.

As shown in FIG. 1, the leakage alarm device of a metal shell electrical product with self-checking function of the present invention includes a metal shell 1, an isolated sampling unit 2, a control unit 3 and a warning unit 4. The two input ends of the isolated sampling unit 2 are respectively Connected to the metal shell 1 and connected to the power supply line 5 via an isolation resistor 6, the output of the isolated sampling unit 2 is connected to the control unit 3, and the output of the control unit 3 is connected to the warning unit 4, wherein the power supply An isolated sampling unit 2 is provided between each phase line L and zero line N of the line 5 and the metal shell 1, and all the phase lines L are connected to the zero through the isolated sampling unit 2, the metal shell 1 connected to the phase line The isolation sampling unit 2, the isolation resistance 6 and the neutral line N on the line N form a high resistance loop. The warning unit 4 includes a normal warning unit 41 and a leakage warning unit 42 of the detection device.

When the electrical product equipped with the present invention is connected to the power supply, a minute current is generated on all the input circuits of the isolated sampling unit 2 and a low voltage is generated at the output end of the sampling unit. The normal warning unit 41 of the detection device works to inform the user that the equipment and the detection device are normal and without failure;

Once the phase line short circuit fault occurs, the phase line directly forms a loop through the metal shell, the isolated sampling unit connected between the metal shell and the neutral line, and the loop impedance is greatly reduced compared with the aforementioned high-impedance loop; When the neutral line in the line is short-circuited with the metal shell, the neutral line forms a loop through the metal shell, the isolated sampling unit and the phase line connected between the metal shell and the phase line, and the loop impedance is also greatly reduced compared to the aforementioned high-impedance loop. The corresponding isolation sampling unit outputs a high voltage. After the voltage is recognized by the control unit, the control unit controls the leakage warning unit 42 to notify the user that the equipment has a leakage short-circuit fault, which cannot be used and must be repaired.

If the normal warning unit and the leakage warning unit of the detection device do not work after the power is turned on, it means that the detection device is faulty and must be repaired.

The detection device normal warning unit 41 and the leakage warning unit 42 are light-emitting diode warning devices. The light-emitting diode warning device includes a light-emitting diode and a control switch. The output of the control unit is connected to a control switch. The control switch and the light-emitting device Connect the power supply after the diode is connected in series.

The control unit is a CPU or a voltage controller of an analog circuit.

The control switch is an electronic switch, such as a triode switch, or a mechanical electromagnetic switch.

Example one

FIG. 2 is a specific embodiment of a leakage alarm device for a metal shell electrical product with self-checking function of the present invention.

In this embodiment, the isolated sampling unit 2 is a current-to-voltage converter 21. The current input terminal 211 of the current-to-voltage converter 21 is connected to the power supply line 5 through a current limiting resistor 6, and the other current input terminal 212 is connected to the metal shell 1, and the two

voltage output terminals

213 and 214 of the current-voltage converter 21 are connected to the

input terminals

31 and 32 of the control unit 3.

In this embodiment, the control unit 3 is a CPU, the first output terminal 33 of the CPU is connected to the detection device normal warning unit 41, and the second output terminal 34 of the CPU is connected to the leakage warning unit 42, The CPU outputs control signals from the two output ports respectively according to the magnitude of the input voltage value at the input terminal, and respectively controls the normal warning unit 41 or the leakage warning unit 42 of the detection device. Among them, the detection device normal warning unit 41 is used to indicate the status of the leakage protection device of the present invention, and the leakage detection unit 42 is used to indicate whether the electrical equipment is leaking. Real-time monitoring of electrical appliances to eliminate potential shock hazards.

In this embodiment, the normal warning unit and the display unit of the detection device are light-emitting diode warning devices of different colors, including a first indicator light D1 and a second indicator light D2. The first indicator light D1 passes through the first transistor Q1 Connected to the CPU and the power supply VCC, the second indicator light D2 is connected to the CPU and the power supply VCC through the second transistor Q2. Specifically, the bases of the first transistor Q1 and the second transistor Q2 are connected to the CPU; the first transistor Q1 and the second transistor Q2 are NPN transistors, the collector is connected to the power supply VCC, and the emitter is connected to the indicator light. Connect the other end of the indicator to GND. The first indicator light D1 and the second indicator light D2 are light-emitting diodes of different light colors. The failure and normal state of the new type of leakage protection device can be identified according to the lightness and non-lightness of the first indicator light. According to whether the second indicator light is on or off, it can be judged whether a leakage occurs.

Further, in addition to the above-mentioned light warning, the warning unit in the leakage detection device of the metal shell electrical product with self-checking function of the present invention may also be provided with a voice warning device 8, or a remote network warning device 9, or a combination thereof, the second The indicator light D2 is connected in parallel with the voice alarm device and the remote network alarm device.

The remote network alarm is a wireless transmitter, and the wireless transmitter is connected to the CPU. The CPU is connected to the user terminal through a wireless transmitter. The user terminal can be a mobile device or a remote computer. Determine whether it is working properly.

The CPU is also connected with a power-off relay, which is used to cut off the power supply of the device and prevent secondary electric shock accidents. The coil of the power-off relay is connected to the CPU, and the normally open contact of the power-off relay is connected to the coil of the AC contactor.

For small-sized electrical appliances, it is impossible to install a power-off relay in the location; in the absence of a ground wire or a poor ground wire, if there is a leakage accident, an alarm signal can be sent to the crowd around the power equipment and the remote monitoring station to prevent the accident Wire-to-earth electric shock hazard, wire-to-wire electric shock hazard caused by secondary accidents, especially when using IT power supply systems.

When both the first indicator light D1 and the second indicator light D2 do not turn on, it means: the leakage current (IR) is very small, and the leakage protection device is damaged; when the first indicator D1 turns on, and the second indicator D2 does not turn on , Indicating that the leakage current (IR) is within the safe range, and the electrical system is normal; when the second indicator D2 is on, there are also: the alarm is triggered and/or the user terminal has alarm information, indicating; electrical system leakage, Need to protect and power off, notify relevant personnel and departments to deal with relevant accidents through sound and light alarm or wireless transmission system, to prevent the occurrence of electric shock accidents.

By selecting the impedance of the current-voltage conversion unit U1 and the current-limiting resistor R1, when IR is less than 1mA, the leakage protection device is disabled, and the first indicator D1 and the second indicator D2 are not turned on; IR is greater than 1mA, and When it is less than 29mA, the leakage voltage of the appliance is within the safe and controllable threshold range, the first indicator D1 is on, and the second indicator D2 is not on; when IR is greater than 30mA, the second indicator D2 is on, indicating that the electrical system is leaking. Sound and light alarm, electrical appliances disconnect the power supply.

Example 2

FIG. 3 shows another embodiment of the present invention. In this embodiment, the isolated sampling unit 2 is composed of a current-voltage converter 21 and a rectifier 22. The current input terminal of the current-voltage converter 21 211 is connected to the power supply line 5 through a current limiting resistor 6, another current input terminal 212 is connected to the metal shell 1, and two

voltage output terminals

213 and 214 of the current-voltage converter 21 are connected to the input of the rectifier 22

Terminals

221 and 222, and the

output terminals

223 and 224 of the rectifier are connected to the

input terminals

31 and 32 of the control unit 3. The purpose is to convert the AC output of the current-to-voltage converter to DC through a rectifier.

Example Three

4 shows another embodiment of the present invention. In this embodiment, the isolated sampling unit 2 includes a rectifier 23 and a Hall sensor 24; the input terminal 231 of the rectifier 23 is connected through a current limiting resistor 6 The power supply line 5, the other input terminal 232 is connected to the metal shell 1, the two output terminals 233, 234 of the rectifier 23 are connected to the

input terminals

241, 242 of the Hall sensor 24, the The

output terminals

243 and 244 are connected to the

input terminals

31 and 32 of the control unit 3. The purpose is to convert the alternating current through the rectifier to direct current and then isolate it by the Hall sensor and convert it into a direct voltage to send to the control unit.

Example 4

The above three embodiments are all single-phase power supply electrical products, and there are two power supply lines, namely a phase line L and a neutral line N. FIG. 5 shows an electrical product with three-phase four-wire unbalanced power supply. In this embodiment, the isolated sampling unit 2 is four groups, and the input terminal 21 of any group of the four groups of isolated sampling units 2 passes the limit. The current resistance 6 is respectively connected to three phase lines L1, L2, L3 and a neutral line N, and the other input terminal 22 of the four groups of isolated sampling units is connected to the metal casing 1, and the output terminals 23 of the four groups of isolated sampling units are Connect the input terminal of the control unit 3 in parallel after 24.

Under normal fault-free conditions, the three phase lines are connected to the metal shell through the isolated sampling unit to form a Y-shaped connection. The voltage between each phase line and the metal shell is the phase voltage, and the impedance of each phase branch is sufficiently large Under the condition of, the current of each phase through the input terminal of the isolated sampling unit can be small enough, and its current value is the line voltage divided by the sum of the impedance of the two isolated sampling units and the two current limiting resistors; connected between the neutral line and the metal shell The current at the input of the isolated sampling unit is the phase voltage divided by the sum of the impedance of the two isolated sampling units and the two current limiting resistors, and its current value should be less than the line voltage divided by the impedance of the two isolated sampling units and the two current limiting resistors Sum; at this time the control unit controls the normal warning unit 41 of the detection device to work. Once a short circuit between a phase line and the metal shell occurs, the voltage between the other two phases and the metal shell is the line voltage. At this time, the current through the input terminal of the isolation sampling unit is 1.73 times that under normal conditions; The current at the input of the isolated sampling unit is twice the normal value. At this time, the control unit 3 controls the leakage warning unit 42; if the zero line is short-circuited with the metal shell, the current flowing through the input terminal of the isolated sampling unit connected to the phase line is the phase voltage divided by the impedance and a limit of an isolated sampling unit The sum of the current resistance is twice that under normal circumstances.

For three-phase three-wire balanced power supply appliances (such as three-phase motors), the isolated sampling unit 2 is in three groups. The input terminals 21 of any group of the three groups of isolated sampling units 2 are connected to three phases through current limiting resistors 6 respectively. Line L1, L2, L3, the other input terminal 22 of the three groups of isolated sampling units is connected to the metal shell 1 to form a Y-shaped connection, the

output terminals

23, 24 of the three groups of isolated sampling units are connected in parallel and then connected to the control unit 3 Input.

Under normal fault-free conditions, the three phase lines are connected to the metal shell through the isolated sampling unit to form a Y-shaped connection. The voltage between each phase line and the metal shell is the phase voltage, and the impedance of each phase branch is sufficiently large Under the condition of, the current of each phase through the input terminal of the isolated sampling unit can be sufficiently small, and its current value is the phase voltage divided by the sum of the impedance of an isolated sampling unit and a current limiting resistor. At this time, the control unit 3 controls the detection device to warn normally Unit 41 works, indicating that the detection device is normal and can be used with confidence; once a phase line shorts to the metal shell, the voltage between the other two phases and the metal shell is the line voltage, and the current through the input terminal of the isolation sampling unit is normal 1.73 times under. At this time, the control unit 3 controls the leakage warning unit 42 to work, to warn of serious leakage, stop use, and must be repaired.

In other embodiments of the present invention, the isolated sampling unit may be a photocoupler, and two input ends of the photocoupler are respectively connected to the metal casing and the power supply line through current limiting resistors. The output is connected to the input of the control unit.

The above are only the preferred embodiments of the present invention and do not limit the present invention in any form. Although the present invention has been disclosed in the preferred embodiments as above, it is not intended to limit the present invention. Anyone familiar with the profession Technical personnel, without departing from the scope of the technical solutions of the present invention, when the technical contents disclosed above can be used to make some changes or modifications to equivalent embodiments of equivalent changes, but any content that does not depart from the technical solutions of the present invention, according to the present invention Any simple modifications, equivalent changes, and modifications made to the above embodiments by the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

An electric leakage alarm device for a metal shell electrical product with a self-checking function includes a metal shell, an isolated sampling unit, a control unit and a warning unit. The two input terminals of the isolated sampling unit are respectively connected to a metal shell and a power supply line. The output of the sampling unit is connected to the control unit, and the output of the control unit is connected to the warning unit, characterized in that each phase line and neutral line are provided with an isolated sampling unit between the metal shell and all phase lines are connected through The isolated sampling unit on the phase line, the metal shell, the isolated sampling unit connected to the neutral line and the neutral line form a high-resistance loop. The warning unit includes a normal warning unit and a leakage warning unit of the detection device.
The leakage alarm device of a metal shell electrical product with self-checking function according to claim 1, characterized in that the isolated sampling unit is a current-voltage converter, and the current input terminal of the current-voltage converter is connected through a current limiting resistor In the power supply line, the voltage output terminal of the current-to-voltage converter is connected to the control unit.
The leakage alarm device for a metal shell electrical product with self-checking function according to claim 1, characterized in that the control unit is a CPU, and the first output end of the CPU is connected to the normal warning unit of the detection device, the CPU The second output terminal is connected to the leakage warning unit, and the CPU outputs control signals from the two output ports according to the magnitude of the input voltage value at the input terminal, respectively controlling the normal warning unit or the leakage warning unit of the detection device.
The leakage alarm device of a metal shell electrical product with self-checking function according to claim 1, characterized in that the normal alarm unit and the leakage alarm unit of the detection device are light-emitting diode alarm devices of different colors, or voice alarm devices, or remote Network alarm device, or a combination thereof.
The leakage alarm device of a metal shell electrical product with self-checking function according to claim 1, characterized in that the power supply line is two for single-phase electrical products, namely phase line and neutral line. The isolated sampling unit is composed of two groups connected to the phase line and the metal casing and the neutral line and the metal casing. The output terminals of the two groups of isolated sampling units are connected in parallel and then connected to the input terminal of the control unit. For unbalanced electrical products, there are four groups of isolated sampling units. An input terminal of any one of the four groups of isolated sampling units is connected to three phase lines and a neutral line through current limiting resistors respectively. The other input terminal of the sampling unit is connected to the metal casing, and the output terminals of the four isolated sampling units are connected in parallel and then connected to the input terminal of the control unit; for electrical products of a three-phase balanced power supply system, the isolated sampling units are three groups, An input terminal of any one of the three groups of isolated sampling units is connected to three phase wires through a current limiting resistor, and the other input terminal of the three groups of isolated sampling units is connected to the metal casing, and three groups of isolated sampling units The output end of is connected in parallel to the input end of the control unit.
The leakage alarm device for a metal shell electrical product with self-test function according to claim 1, characterized in that the isolated sampling unit is composed of a rectifier and a Hall element, and the two AC input terminals of the rectifier are respectively connected to the metal The housing is connected to the power supply line through a current limiting resistor, the two DC output ends of the rectifier are connected to the input end of the Hall element, and the output of the Hall original is connected to the input end of the control unit.
The leakage alarm device of a metal shell electrical product with self-check function according to claim 1, characterized in that the isolated sampling unit is a photocoupler, and the two input ends of the photocoupler are respectively connected to the The metal casing and the power supply line, the output of the photocoupler is connected to the input end of the control unit.
The leakage alarm device for a metal shell electrical product with self-checking function according to claim 4, characterized in that the LED warning device includes a LED and a control switch, the output of the control unit is connected to a control switch, and the control switch The power supply is connected in series with the light emitting diode.
The leakage alarm device for a metal shell electrical product with self-check function according to claim 2, wherein the control unit is a CPU or a voltage controller of an analog circuit.
The leakage alarm device for a metal shell electrical product with self-checking function according to claim 8, wherein the control switch is an electronic switch or a mechanical electromagnetic switch.