Leakage switch, mainly used to prevent the occurrence of leakage accidents, the operation principle of the switch is: there are two windings on an iron core, the main winding and secondary winding.The main winding also has two windings: the input current winding and the output current winding.When there is no leakage, the input current and output current are equal, and the vector sum of the two magnetic flux on the iron core is zero, the potential will not be induced on the secondary winding, or the induced voltage will be formed on the secondary winding, push the actuator by the amplifier, make the switch trip.

One, leakage switch connection method

Connection of leakage switch.The phase-leakage switch is a three-phase, four-wire system that is commonly used today. For a hot line (red, green, and yellow) with a zero line (blue), the voltage between the three hot lines is 380 volts, and the voltage between each hot line and the zero line is 220 volts.Single-phase leakage switch general wiring, write left zero right fire, in accordance with the connection.No matter three - phase or single - phase leakage switch is: the top line in, the bottom line out.

Principle of leakage switch

The action principle of leakage protection switch is: on an iron core, there are two groups: one input and one output current winding winding current, when there is no leakage, input current and output current is equal, in the core flux vector and zero, would not be in the third winding induction electric potential, or on the third winding will be induced voltage to form, to drive actuator enlargement, switch trip.

The leakage protection switch is added in front of the UPS mentioned above. Although there is no leakage phenomenon in the UPS, the flux vector formed by each harmonic in the iron core and the hysteresis of the iron core cannot be zero, so the illusion of similar leakage occurs, making the leakage protector frequently tripping.

Leakage will fire the zero line and at the same time through a type O the circular as primary, secondary use N turn output to promote a electromagnetic mechanism, electromagnetic agency action is tripping. Principle is normally wire and zero line current flows into equal outflow, so the induction of secondary voltage is zero, when the wire or there's a single line to ground zero line grounding resistance or short circuit, wire and zero line current appear on the voltage difference, through the secondary induction, when the difference in value to a certain will promote electromagnetic institutions to take off the main circuit.

Circuit besides working current in normal working conditions by without leakage current leakage protector, this time through the zero sequence current transformer (test transformer) are equal in size, the current in the opposite direction, sum to zero, the transformer iron core of induced magnetic flux is zero, no output secondary winding, automatic switch in the on state, the normal operation of the leakage protector.When protected electrical leakage occurred with line or when someone get an electric shock, there is a ground fault current, make through the detection of transformer in traffic and is not zero, transformer core flux, induction in second primary winding induction current, after amplification output, make the leakage trip action to promote automatic switch trip to achieve the purpose of leakage protection.

Leakage protection device is divided into electronic and electromagnetic types according to the different trip mode: (1) electromagnetic trip type leakage protection device, electromagnetic trip as the intermediate mechanism, when leakage current occurs so that the mechanism trip disconnect the power supply.The disadvantages of this protector are: high cost, complex production process requirements.The advantages are as follows: electromagnetic components have strong anti-interference and shock resistance (shock of overcurrent and overvoltage) ability;No auxiliary power is needed;The leakage characteristics of zero voltage and phase break are unchanged.(2) electronic leakage protection, transistor amplifier as an intermediate mechanism, when the leakage occurs by amplifying the amplifier after the relay, the relay control switch to make it disconnect the power supply.The advantages of this protector are: high sensitivity (up to 5mA);Small setting error, simple manufacturing process, low cost.The disadvantages are as follows: weak shock resistance and poor environmental interference resistance;Need auxiliary power supply (electronic amplifier generally needs dc power supply of more than ten volts), so that leakage characteristics are affected by the fluctuation of working voltage;When the main circuit is out of phase, the protector will lose its protection function.

Leakage switch test

Generally press the test button is enough to detect whether the leakage of electricity, the principle of the leakage protector is to detect whether the alternating current from the hot line to the zero line of one in and one out of the current is consistent to determine whether the action trip.

There are safe ways to test, but only if you have a home with a ground cord:

Find a three-pin socket and connect a resistor, capacitor (in series) and the other end to the ground pin on the L (standard electrical walk L wire) symbol.Because the electricity flows through the earth wire to walk, the leakage protector detects that the fire wire enters the current is larger than the zero line to return the current, therefore the action, tripping!

Capacitor can be used on the fan capacitor, the resistance to choose a 10 ohm above 1 watt resistance, after finishing the resistance and capacitor knot with insulation tape.