Operation Method of a Leakage Clamp Ammeter:
The leakage current clamp meter mainly consists of impedance conversion, range conversion, AC/DC conversion, amplification, and indicator devices. Some also have overcurrent protection, sound and light alarm circuits, and test voltage regulation devices, and their indicator devices are divided into analog and digital types. According to UL standards in the United States, leakage current refers to the current that can be conducted from the accessible parts of household appliances, including capacitive coupling current. The leakage current consists of two parts, one is the conduction current I1 through the insulation resistance, and the other is the displacement current I2 through the distributed capacitor. The capacitance impedance of the latter is XC=1/2pfc, which is inversely proportional to the power frequency. The distributed capacitor current increases with the increase of frequency, so the leakage current increases with the increase of power frequency. For example, when using a thyristor power supply, its harmonic components increase the leakage current.
1. Plug in the power, turn on the power switch, and the power indicator light will turn on;
2. Select the power range and press the desired current button;
3. Select the leakage current alarm value;
4. Choose a testing time;
5. Connect the measured object to the measuring end, start the instrument, increase the test voltage to 1.06 times (or 1.1 times) the rated working voltage of the measured object, switch the phase conversion switch, read the secondary readings separately, and select the leakage current value with the larger value. When the switch K is connected to the neutral line, the tester samples the leakage current between the neutral line and the casing; When K is connected to the phase line, the leakage current between the phase line and the casing is tested.
6. It must be noted that when K is connected to the neutral line or K is connected to the phase line, the leakage current may not be the same. This is because the location of insulation weaknesses in household appliances is random. Therefore, the leakage current test should be conducted by converting the polarity of K and taking the larger value as the leakage current value of the tested electric heating appliance.
