The operating principle of the leakage protection switch is: there are two groups on one iron core: one input current winding and one output current winding. When there is no leakage, the input current and the output current are equal, and the vector sum of the two magnetic fluxes on the iron core If it is zero, no potential will be induced on the third winding. Otherwise, the induced voltage will be formed on the third winding. After amplification, the actuator will be pushed to trip the switch. Fume Vape Shenzhen Uscool Technology Co., Ltd , https://www.uscoolvape.com
In addition to the leakage protection switch in front of the above UPS, although the UPS has no leakage phenomenon, due to the magnetic flux vector formed in each core of the harmonics and due to the hysteresis of the iron core, it cannot be zero, so there is a similar leakage. The illusion causes the leakage protector to trip frequently.
Leakage will pass the live line/zero line through an O-shaped magnetic ring as the primary, the secondary use NåŒ output to push an electromagnetic mechanism, and the electromagnetic mechanism will trip. The principle is that the current flows on the live and neutral lines under normal conditions. Equal to the outflow, so the induced secondary voltage is also zero. When there is a grounding resistance or short circuit between the live line or the neutral line, the voltage difference between the current on the live line and the zero line is induced by the secondary. A certain difference pushes the electromagnetic mechanism off the main circuit.
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.
Leakage protector is divided into electronic and electromagnetic type according to different tripping methods: 1 Electromagnetic trip type leakage protector, with electromagnetic tripper as the intermediate mechanism, when the leakage current occurs, the mechanism trips to disconnect the power supply. The disadvantages of this protector are: high cost and complicated manufacturing process requirements. The advantages are: the electromagnetic component has strong anti-interference ability and impact resistance (overcurrent and overvoltage impact); it does not need auxiliary power supply; the leakage characteristics after zero voltage and phase failure are unchanged. 2 electronic leakage protector, with transistor amplifier as the intermediate mechanism, when the leakage occurs, the amplifier is amplified and transmitted to the relay, and the relay controls the switch to disconnect the power. The advantages of this protector are: high sensitivity (up to 5 mA); small setting error, simple manufacturing process and low cost. The disadvantages are: the transistor has weak impact resistance and poor environmental resistance; it needs auxiliary working power (electronic amplifier generally needs more than ten volts DC power supply), so that the leakage characteristics are affected by the fluctuation of working voltage; when the main circuit is out of phase, the protector Will lose protection.
Although the working principle of the leakage protector is relatively simple, there will be such errors in the actual use, causing unnecessary misoperation or refusal. The following are some common examples encountered in the after-sales service.
Figure 2 is the wrong wiring of the installer, the neutral N terminal of the socket is mistakenly connected to the protective ground (PE) terminal, as shown in b of Figure 2, when the socket is used, the current passes through the zero line. The protective ground wire returns to the power supply, causing the leakage protector to operate. The correction method is shown in a in Figure 2.
Figure 3 misuses the three-phase three-wire leakage protector. Since the neutral line does not pass through the leakage protector, the leakage protector detects not the leakage current but the three-phase unbalanced current, so only one phase is connected in the three-phase line. At any load, the current trips far beyond the leakage current. The correction method is to replace the leakage protector with a three-phase four-wire leakage switch.
Figure 4: Two leakage protector lines are mixed. Figure 4a shows the differential current in 1LDB when the lamp is turned on, and three-phase unbalanced current appears in 2LDB, causing 1LDB and 2LDB to trip. In Figure 4b, two leakage protectors share a neutral line. , will not trip when 3LDB or 4LDB is closed separately. However, when used at the same time, the two leakage protectors will trip at the same time, resulting in two lines not being able to supply power at the same time, because the two loads will not be the same size.
Figure 5 can not be grounded repeatedly when installing the leakage protector, otherwise the current through the zero-sequence transformer is reduced, resulting in leakage protection that can not trip when the trip occurs.
Figure 6 is connected to the zero protection line. By detecting the transformer, when the device leaks, the phase line leakage current is returned to the detection transformer through the zero-protection line, so that the transformer does not detect leakage current, causing the leakage protector to not operate.
Finally, the installation position of the leakage protector should not be too high. The “test button†should be in the easy-to-operate position. The purpose of the test button is to simulate artificial leakage, forcibly tripping the leakage protection, verifying that it can work normally, at least once a month. . If it fails or does not work, it should be removed immediately for repair or replacement.
