Leakage current refers to the current formed by the surrounding medium or insulating surface as the leakage current between the metal parts insulated with each other, or between the live parts and the grounded parts in the case of no fault applied voltage. According to the U.S. UL standard, leakage currents include capacitive coupling currents and can conduct currents that can be accessed from home appliances. The leakage current consists of two parts, one is the conduction current I1 through the insulation resistance; the other is the displacement current I2 through the distributed capacitance, and the latter is XC=1/2pfc, which is inversely proportional to the power supply frequency, and the distributed capacitance current increases with frequency. However, the leakage current increases as the frequency of the power supply increases. For example: With thyristor power, its harmonic components increase the leakage current.
The leakage current tester is mainly composed of impedance conversion, range conversion, AC-DC conversion, amplification, and indication devices. Some also have over-current protection, sound and light alarm circuit and test voltage adjustment device, and its indicating device is divided into two kinds of analog and digital.
Operation method
1, plug in the power, connect the power switch, power indicator light;
2, select the power range, press the desired current button;
3, select the leakage current alarm value;
4, select the test time;
5. Connect the DUT to the measurement terminal, start the instrument, increase the test voltage to 1.06 times the rated working voltage of the DUT, switch the phase changeover switch, read the two readings, and select the reading leakage current value with a large value. When the transfer switch K is connected to the neutral line, the tester samples the leakage current between the neutral line and the case. When K and the phase line are connected, the leakage current between the phase line and the case is tested. It must be noted that: K is connected to the zero line or K is connected to the phase line, and the leakage current is not necessarily the same. This is because the location of the weak points in the insulation of household appliances is random. Therefore, the leakage current test should be converted by K polarity, whichever is greater as the leakage current value of the electric appliance under test.
Test considerations
1. When measuring the leakage current at the operating temperature, if the measured electrical equipment is not powered by an isolation transformer, the measured electrical equipment shall be insulated from the ground by a material insulating mat with reliable color insulation performance. Otherwise, some of the leakage current will flow directly through the ground without passing through the instrument, affecting the accuracy of the test data.
2. Leakage current measurement is carried out with electricity, and the shell of the device under test is charged. Therefore, the test personnel must pay attention to safety, all kinds of laboratories should formulate safe operating procedures, and must not touch the device under test before cutting off the current.
3. The influence of the environment on the test data should be minimized. The temperature, humidity, and the pollution of the insulation surface should be tested. The leakage current has a great influence. The temperature is high, the humidity is high, the insulation surface is heavily polluted, and the measured leakage current value is higher. Big.
The leakage current tester is mainly composed of impedance conversion, range conversion, AC-DC conversion, amplification, and indication devices. Some also have over-current protection, sound and light alarm circuit and test voltage adjustment device, and its indicating device is divided into two kinds of analog and digital.
Operation method
1, plug in the power, connect the power switch, power indicator light;
2, select the power range, press the desired current button;
3, select the leakage current alarm value;
4, select the test time;
5. Connect the DUT to the measurement terminal, start the instrument, increase the test voltage to 1.06 times the rated working voltage of the DUT, switch the phase changeover switch, read the two readings, and select the reading leakage current value with a large value. When the transfer switch K is connected to the neutral line, the tester samples the leakage current between the neutral line and the case. When K and the phase line are connected, the leakage current between the phase line and the case is tested. It must be noted that: K is connected to the zero line or K is connected to the phase line, and the leakage current is not necessarily the same. This is because the location of the weak points in the insulation of household appliances is random. Therefore, the leakage current test should be converted by K polarity, whichever is greater as the leakage current value of the electric appliance under test.
Test considerations
1. When measuring the leakage current at the operating temperature, if the measured electrical equipment is not powered by an isolation transformer, the measured electrical equipment shall be insulated from the ground by a material insulating mat with reliable color insulation performance. Otherwise, some of the leakage current will flow directly through the ground without passing through the instrument, affecting the accuracy of the test data.
2. Leakage current measurement is carried out with electricity, and the shell of the device under test is charged. Therefore, the test personnel must pay attention to safety, all kinds of laboratories should formulate safe operating procedures, and must not touch the device under test before cutting off the current.
3. The influence of the environment on the test data should be minimized. The temperature, humidity, and the pollution of the insulation surface should be tested. The leakage current has a great influence. The temperature is high, the humidity is high, the insulation surface is heavily polluted, and the measured leakage current value is higher. Big.
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