subject: Principle & Operation Associated With Leakage Ongoing Specialist [print this page] As per the American UL standard, leakage current tester is the current which is often conducted by the accessible parts of the household appliances, including capacitance coupling current. Leakage current is composed of two parts, conduction current I1 which passes the insulation resistance and displacement current I2 which passes the distributed capacitance. The capacitive reactance of the latter is Xc=1/2fc. It is inversely proportional to the mains frequency. The current of distributed capacitance is directly proportional to the mains frequency. Therefore, the leakage current is also directly proportional to the mains frequency.
If the insulation property of a circuit or system is to be examined, this current shouldn't only include the current which flows to the earth by insulating materials or the insulating parts outside the circuit, but also have the current which flows in to the earth by capacitive components (Distributed capacitance can be considered as capacitive components.) in the circuit or system. Long wiring may produce large distribution capacity and increase leakage current. Which you cannot use will need to be paid more attention, especially in a non-grounded system.
The principle of leakage current test is actually the exact same with all the test of insulation resistance. The test of insulation resistance is actually a type of leakage current, merely shown in the form of insulation resistance. In normal leakage current test, alternating voltage is offered. Therefore, there's capacity current as part of the leakage current.
When a hipot test is being operated, we might also identify a maximum current value which is allowed to pass the measured equipment with no damage to the uppermost level of field intensity of the measured equipment (insulating materials). This maximum current value is also named as leakage current in the special occasion above. Leakage current tester can be used for the measurement of the leakage current produced when the working power (or other power) passes the insulating materials or distribution impedance. The input impedance of leakage current tester stimulates the impedance of body of a human.
Operation of Leakage Current Tester
1. Plug in the power supply and place on the power. The ability indicator is on.
2. Select power range and press the corresponding button of current.
3. Choose alarm price of leakage current.
4. Pick testing time.
5. Connect the tested equipment on the metering port, start the leakage current tester, boost the testing voltage to 1.06 times (or 1.1 times) of the rated operational voltage of the tested equipment, press the phase change switch, get the 2nd reading separately and pick the maximum leakage current value. When the switch K is connected with zero line, the data adopted by the leakage current tester is the leakage current value between the neutral line and the case. When the switch K is connected with phase line, the data is the leakage current value between the phase line and the case. It has to be noted that the leakage current values are different when the switch K is connected with zero line and when the switch K is connected with phase line. That's because the location of insulation imperfection in household appliance is random. Therefore, hipot tester ought to switch polarity by K and get the maximum data as the leakage current value of the tested appliances.
