How to Use a Leakage Clamp Meter
The principle of leakage clamp ammeter:
Leakage current clamp meter is mainly composed of impedance conversion, range conversion, AC-DC conversion, amplification, indicating device and so on. Some also have overcurrent protection, sound and light alarm circuit and test voltage adjustment device, and the indicating device is divided into two types: analog type and digital type. According to the UL standard of the United States, leakage current is the current that can be conducted from the accessible parts of household appliances, including capacitive coupling current. Leakage current includes two parts, one part is the conduction current I1 through the insulation resistance; the other part is the displacement current I2 through the distributed capacitance, the capacitance of the latter is XC=1/2pfc, which is inversely proportional to the power frequency, and the distributed capacitance current increases with frequency And increase, so the leakage current increases with the power frequency. For example: power supply with thyristor, its harmonic component will increase the leakage current.
If the insulation performance of a circuit or a system is assessed, the current shall include all currents flowing into the ground (or conductive parts outside the circuit) through the insulating material, as well as the capacitive devices in the circuit or system ( Distributed capacitance can be regarded as a capacitive device) and the current flowing into the earth. Longer wiring will form a larger distribution capacity and increase leakage current, which should be paid special attention to in ungrounded systems.
Precautions for Leakage Clamp Meter:
1. The principle of leakage current measurement is basically the same as that of insulation resistance. Measuring insulation resistance is actually a kind of leakage current, but it is expressed in the form of resistance. However, the normal measurement of the leakage current is to apply the AC voltage, therefore, the current of the capacitive component is included in the component of the leakage current.
2. During the withstand voltage test, in order to protect the test equipment and test according to the specified technical indicators, it is also necessary to determine a maximum electric field strength that is allowed to flow through the tested equipment (insulated material) without destroying the tested equipment (insulated material). ) Maximum current value, this current is usually also called leakage current, but this method is only used in the above specific occasions. Note the difference.
3. The leakage current is actually the current flowing through the insulating part of the electrical circuit or equipment under the action of no fault and applied voltage. Therefore, it is one of the important symbols to measure the insulation of electrical appliances, and it is also the main indicator of the safety performance of products.
4. The leakage current tester is used to measure the leakage current irrelevant to work generated by the working power supply (or other power supply) of electrical appliances through insulation or distributed parameter impedance, and its input impedance simulates the impedance of the human body.
