Leakage protector circuit schematic introduction
In the figure, L is an electromagnet coil, which can drive the knife switch K1 to be disconnected during leakage, and each bridge arm can increase the withstand voltage by connecting two 1N4007 series. R3 and R4 have large resistance values. Therefore, when K1 is closed, the current flowing through L is small enough to cause K1 to be disconnected. R3 and R4 are voltage equalizing resistors of the thyristors T1 and T2, which can reduce the withstand voltage requirement of the thyristor. K2 is a test button that functions as a simulated leakage. Pressing the test button K2, K2 is turned on, which is equivalent to leakage of the external line to the ground, so that the vector sum of the currents of the three-phase power line and the neutral line passing through the magnetic ring is not zero, and the detection coil on the magnetic ring a, There is an induced voltage output at both ends of b, and this voltage immediately triggers T2 conduction. Since C2 has a certain voltage in advance, after T2 is turned on, C2 is discharged through R6, R5, and T2, so that a voltage is generated on R5 to trigger T1 to conduct. After T1 and T2 are turned on, the current flowing through L increases, the electromagnet operates, and the drive switch K1 is turned off. The function of the test button is to check whether the function of the device is intact at any time. The principle of the electromagnet leakage caused by the leakage of the electric equipment is the same. R1 is a varistor that acts as an overvoltage protection.
Diagram of working principle of leakage protector
Figure 1 shows the working principle of the leakage protector. In normal operation, no leakage current flows through the leakage protector except the working current. At this time, the current flowing through the zero-sequence transformer (detecting the transformer) is equal, the direction is opposite, and the sum is zero. The induced magnetic flux in the transformer core is also equal to zero, the secondary winding has no output, the automatic switch remains in the on state, and the leakage protector is in normal operation. When the protected electrical equipment and the line are leaking or someone is getting electric shock, there is a ground fault current, so that the current flowing through the detecting transformer is not zero, the magnetic flux is induced in the transformer core, and the secondary winding has induction. The current is generated and output after being amplified, so that the operation of the leakage release device pushes the automatic switch to trip to achieve the purpose of leakage protection.