Leakage current tester operation method and usage precautions - Solutions - Huaqiang

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Kaixin micro test

Test probe P100-M3

The leakage current refers to the current formed between the metal parts insulated from each other in the electrical insulation or between the live parts and the grounded parts in the absence of a fault applied voltage, and the current formed by the surrounding medium or the insulating surface is called the leakage current. According to the U.S. UL standard, the leakage current is a current including a capacitive coupling current that can be conducted from a part of the household appliance. 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, the latter's capacitive reactance is XC=1/2pfc is inversely proportional to the power supply frequency, and the distributed capacitance current increases with frequency. And increase, so the leakage current increases as the power supply frequency increases. For example, using a thyristor, its harmonic components increase the leakage current.

The leakage current tester is mainly composed of impedance transformation, range conversion, AC/DC conversion, amplification, indicating device and the like. Some also have overcurrent protection, sound and light alarm circuit and test voltage adjustment device, and the indication device is divided into analog and digital.

Method of operation

1. Plug in the power, turn on the power switch, and the power indicator light is on;

2. Select the power range and press the desired current button;

3. Select the leakage current alarm value;

4. Select the test time;

5. Connect the measured object to the measuring end, start the instrument, raise the test voltage to 1.06 times (or 1.1 times) of the rated working voltage of the measured object, switch the phase change switch, read the second reading separately, and select the large value. Reading leakage current value. When the changeover switch K is connected to the neutral line, the tester samples the leakage current between the neutral line and the outer casing; when K is connected to the phase line, the leakage current between the phase line and the outer casing is tested. It must be noted that K is connected to the neutral 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 insulation weakness of the household appliance is random. Therefore, the leakage current test should be converted to polarity by K, and the larger value is taken as the leakage current value of the electric appliance to be tested.

Test considerations

1. When measuring the leakage current at the working temperature, if the device under test is not powered by the isolation transformer, the device under test shall be insulated from the ground by a material insulation pad with reliable color insulation performance. Otherwise, some leakage current will flow directly through the ground without passing through the instrument, affecting the accuracy of the test data.

2. The leakage current measurement is measured by charging, and the outer casing of the tested electrical appliance is charged. Therefore, the tester must pay attention to safety. All kinds of laboratories should have safe operating procedures. Do not touch the tested electrical equipment before the current is cut off.

3. The impact of the environment on the test data should be minimized. The temperature, humidity and contamination of the insulation surface should be greatly affected by the leakage current. The temperature is high, the humidity is high, the insulation surface is seriously polluted, and the measured leakage current value is compared. Big.