TWI445987B - Creepage alarm device and socket - Google Patents

Description

Leakage warning device and strip

The invention relates to electrical safety technology, in particular to an electrical leakage early warning device and a socket having the leakage early warning device.

Generally, the metal casing of the electrical equipment is connected to the earth to avoid short circuit between the internal circuit of the electrical equipment and the metal casing, and the leakage of the metal casing relative to the earth is higher than the safe voltage. However, the grounding connection of some electrical equipment may be misconnected, loose or disconnected during assembly or use, and the user cannot judge whether the electrical equipment is leaking or not, and there is a potential safety hazard.

In view of this, it is necessary to provide an electric leakage warning device.

An electric leakage warning device includes a constant current source, a measuring unit, an alarm unit, a controller and a power supply unit. The constant current source is connected to a metal casing of a consumer to be inspected for discharging a constant current to the metal casing. The measuring unit is configured to measure a voltage of a ground end of the local power source and a voltage difference between the metal casing and the ground. The controller is configured to drive the alarm unit to issue an early warning when the voltage at the ground is zero or the voltage difference between the metal casing and the ground is greater than a predetermined value. The power unit is configured to provide an operating voltage to the constant current source, the measuring unit, the alarm unit, and the controller.

Generally, even if there is contact resistance and wire resistance, etc., even the metal case and the The grounding end is electrically connected, and a resistance having a very small resistance (<10) exists between the metal casing and the grounding end and the grounding end and the ground. Therefore, when detecting by the leakage early warning device of the present invention, the constant current will flow through the resistance between the metal casing and the ground terminal and the ground terminal and the ground, so that there is a small gap between the metal casing and the ground terminal. The voltage difference (less than the predetermined value) and the ground terminal has a non-zero voltage. Therefore, if the measuring unit measures that the voltage of the ground is zero, it indicates that the metal casing is disconnected from the ground, and the constant current cannot flow to the ground; and if the voltage between the metal casing and the ground is If the difference is greater than the predetermined value, it indicates that the connection between the metal casing and the ground terminal is loose or poorly contacted, resulting in an excessive voltage of the metal casing (beyond the predetermined value). In the foregoing two cases, the controller determines that the electrical equipment is leaking and drives the alarm unit to issue an alarm, thereby preventing a power safety accident from occurring.

100‧‧‧Electric leakage warning device

10‧‧‧ constant current source

20‧‧‧Measurement unit

30‧‧‧Alarm unit

40‧‧‧ Controller

50‧‧‧Power unit

60‧‧‧ display

70‧‧‧Switch unit

200‧‧‧Electrical equipment

202‧‧‧Metal casing

204‧‧‧Power resistor

300‧‧‧Local power supply

302‧‧‧ Grounding terminal

304‧‧‧Firewire end

306‧‧‧ Zero end

Rg, Rt‧‧‧ resistance

400‧‧‧Insert

402‧‧‧Ontology

404‧‧‧ Cable

406‧‧‧ slots

406G‧‧‧Grounding terminal

406L‧‧‧Firewire plug terminal

406N‧‧‧Neutral plug terminal

408‧‧‧Interface

1 is a block diagram showing the state of use of an electric leakage warning device according to a preferred embodiment of the present invention.

2 is a perspective view of a plug-in according to a preferred embodiment of the present invention.

Figure 3 is a block schematic view of the strip of Figure 2.

Referring to FIG. 1 , the leakage warning device 100 of the preferred embodiment of the present invention is configured to detect whether the metal casing 202 of a power device 200 is electrically connected to the ground terminal 302 of the local power source 300, and is in the metal casing 202 and the ground terminal 302. An alarm is issued when the connection is disconnected or is bad, thereby preventing a power safety accident.

The power device 200 can be a machine, a device, an instrument, a meter, or the like of various household appliances or factories, and its internal power consumption is partially equivalent and expressed as a power resistor 204.

Local power supply 300 also typically includes a live terminal 304 and a neutral terminal 306. The ground terminal 302 and the neutral terminal 306 are connected to the ground, and the AC voltage of the live terminal 304 relative to the earth is about 220V. Generally, due to the contact resistance and the wire resistance, there is a resistance Rg having a small resistance between the ground terminal 302 and the ground. The voltage of the live terminal 304 relative to the earth may be different in different countries or regions or due to different power supply systems, and is not limited to 220V.

When the powered device 200 is in use, the power consumption resistor 204 is coupled between the live terminal 304 and the neutral terminal 306 to obtain power. In order to prevent leakage of the electrical device 200, the metal casing 202 is connected to the ground terminal 302. However, even if the metal case 202 is electrically connected to the ground terminal 302, there is a resistance Rt having a small resistance value due to the contact resistance and the wire resistance.

The leakage warning device 100 includes a current source 10, a measuring unit 20, an alarm unit 30, a controller 40, and a power supply unit 50.

The constant current source 10 is connected to the metal casing 202 for discharging a constant current to the metal casing 202. Generally, the safe current flowing through the human body is 10 mA. Therefore, the constant current in the present embodiment is about 10 mA.

The measuring unit 20 is used to measure the voltage of the ground terminal 302. If the measured voltage is zero, it means that the metal casing 202 is completely disconnected from the grounding terminal 302, and the safe current cannot flow to the grounding terminal 302. In addition, the measuring unit 20 is also used to measure the voltage difference between the metal casing 202 and the ground terminal 302. If the voltage difference between the metal casing 202 and the ground terminal 302 is greater than a predetermined value, it indicates that the connection between the metal casing 202 and the ground terminal 302 is loose or poorly contacted, resulting in an excessive voltage of the metal casing 202. Generally, the resistance between the metal casing 202 and the ground (ie, Rt+Rg) is less than 100, the resistance Rg between the grounding terminal 302 and the ground is removed, and the measurement error is considered. Therefore, the metal casing 202 and the grounding end 302 are generally required. The resistance Rt between them is less than 10. And because of the safety of electricity flowing through the resistor Rt The flow is about 10 mA, so it can be determined that the predetermined value is about 0.1 V or so. Of course, the setting of the predetermined value should be determined on a case-by-case basis and is not limited to 0.1V.

The alarm unit 30 can be a light emitting diode (LED) 32 or a buzzer 34 (see FIG. 3). Of course, LEDs and buzzers can also be used at the same time. In addition, the leakage warning device 100 can also employ a display 60, such as a liquid crystal display, for displaying the measured voltage difference or resistance Rt for the convenience of the user.

The controller 40 is configured to control the alarm unit 30 to issue an early warning when the voltage of the ground terminal 302 is zero or the voltage difference between the metal casing 202 and the ground terminal 302 is greater than a predetermined value, for example, driving the LED to continuously or intermittently illuminate, and driving the LED to be illuminated to Turning off or driving the buzzer continuously or intermittently, wherein the LED is turned on or off means that the LED is long when the power device 200 is not leaking, and once the power device 200 is leaking, the LED is turned off.

The power supply unit 50 is used to connect the local power source 300 and convert the local power source into the operating voltages of the constant current source 10, the measuring unit 20, the alarm unit 30, the controller 40, and the display 60.

Preferably, the leakage warning device 100 of the present embodiment further includes a switching unit 70 connected in series with the power resistor 204 between the live terminal 304 and the neutral terminal 306. The switch unit 70 is configured to disconnect the power resistor 204 from the live terminal 304 when the power resistor 204 is initially inserted between the live terminal 304 and the neutral terminal 306; the controller 40 determines that the voltage at the ground terminal 302 is greater than zero and When the voltage difference between the metal casing 202 and the ground terminal 302 is less than a predetermined value, the power device 204 and the live terminal 304 are turned off after the electric device 200 is leaked; and the controller 40 determines that the voltage at the ground terminal 302 is When the voltage difference between the metal casing 202 and the ground terminal 302 is greater than a predetermined value, it is determined that the power device 200 is leaked and then the power resistor 204 and the fire terminal 304 are turned off. In the present embodiment, the switch unit 70 is a relay.

Referring to FIG. 2, the strip 400 of the preferred embodiment of the present invention includes a body 402, a cable 404, and an electrical leakage warning device 100. Two slots 406 are defined in the body 402. Of course, the number of slots 406 is not limited to two, depending on the needs. Each slot 406 includes a grounding terminal 406G (ground), a live plug terminal 406L (live), and a neutral plug terminal 406N. The grounding plug terminal 406G, the live wire plugging terminal 406L and the neutral wire plugging terminal 406N are respectively connected to the grounding terminal 302, the live wire end 304 and the neutral wire end 306 via the cable 404, and are provided for the cable plug of the electric device 200 (not shown). Insert to get power. The constant current source 10, the measuring unit 20, the controller 40, the power supply unit 50, and the switch unit 70 are disposed in the body 402. The alarm unit 30 includes an LED 32 and a buzzer 34 disposed on the body 402. Display 60 is also disposed on body 402. The body 402 is further provided with a connecting interface 408, which is connected to the constant current source 10 and the measuring unit 20, and can be connected to the metal casing 202 through a matching connecting line (not shown). As such, the constant current source 10 can flow a constant current to the metal casing 202, and the measuring unit 20 can measure the voltage of the metal casing 202.

It can be understood that the switch unit 70 is inserted into the local power source 300 and is in the off state. Only the power device 200 is connected to the plug 400 and the controller 40 determines that the voltage of the ground terminal 302 is greater than zero and the metal casing 202 and ground. When the voltage difference between the terminals 302 is less than a predetermined value, the state is turned to the on state.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention, for example, the scattering portion may include a lattice pattern surrounded by a plurality of first strip-shaped grooves and distributed along the optical axis of the lens. A spiral pattern consisting of a plurality of second strip-shaped grooves in a spiral shape, etc., shall be covered in the following Please be within the scope of the patent.

100‧‧‧Electric leakage warning device

10‧‧‧ constant current source

20‧‧‧Measurement unit

30‧‧‧Alarm unit

40‧‧‧ Controller

50‧‧‧Power unit

60‧‧‧ display

70‧‧‧Switch unit

200‧‧‧Electrical equipment

202‧‧‧Metal casing

204‧‧‧Power resistor

300‧‧‧Local power supply

302‧‧‧ Grounding terminal

304‧‧‧Firewire end

306‧‧‧ Zero end

Rg, Rt‧‧‧ resistance

Claims (10)

An electric leakage early warning device, comprising: a constant current source connected to a metal casing of a power device to be inspected for discharging a constant current to the metal casing; and a measuring unit for measuring the grounding of the local power source a voltage at the terminal and a voltage difference between the metal casing and the ground; an alarm unit; and a controller for zeroing the voltage at the ground or a voltage difference between the metal casing and the ground being greater than a predetermined The value drives the alarm unit to issue an alarm. The electric leakage warning device according to claim 1, wherein the constant current is 10 mA. The electric leakage warning device according to claim 1, wherein the alarm unit is a light emitting diode or a buzzer. The leakage warning device according to claim 3, wherein the controller is configured to control the continuous or intermittent illumination of the LED when the voltage of the ground is zero or greater, and control the LED to be illuminated to Off or control the buzzer to sound continuously or intermittently. The electric leakage warning device according to claim 1, wherein the predetermined value is 0.1V. The leakage warning device of claim 1 further comprising a display for displaying a voltage difference between the metal housing and the ground. The electric leakage warning device according to claim 1, wherein the local power source further comprises a live terminal and a neutral terminal; the leakage warning device further includes a series connection with the electric device at the live end and the neutral end. And a switching unit that turns on the powered device and the live terminal only when the voltage of the ground is greater than zero and the voltage difference between the metal casing and the ground is less than the predetermined value. The electric leakage warning device according to claim 7, wherein the switching unit is a relay. A socket comprising a body and a cable; the body is provided with at least one slot; each slot comprises a grounding terminal, a livewire terminal and a neutral connector; the grounding terminal, The live wire plug terminal and the neutral wire plug terminal are respectively connected to the grounding end, the live wire end and the neutral wire end of the local power source through the cable, and are inserted into a power plug of the electric device to obtain power supply; wherein the plug wire is further The invention comprises a leakage early warning device, comprising: a constant current source connected to the metal casing of the electrical equipment of the electrical equipment for discharging a constant current to the metal casing; and a measuring unit for measuring the voltage of the grounding terminal And a voltage difference between the metal casing and the ground; an alarm unit; and a controller for driving when the voltage at the ground is zero or a voltage difference between the metal casing and the ground is a predetermined value The alarm unit issues an alarm. The strip according to claim 9, wherein the body is provided with a connecting interface connected to the constant current source and the measuring unit, and connected to the metal casing by a matching connecting wire.