Using the Leakage Clamp Ammeter
The principle of leakage clamp ammeter:
The leakage current clamp meter is mainly composed of impedance conversion, range conversion, AC and DC conversion, amplification, indicating device, etc. Some also have overcurrent protection, audible and visual alarm circuits and test voltage adjustment devices. The indicating devices are divided into analog and digital types. According to the American UL standard, leakage current is the current that can be conducted from the accessible parts of household appliances, including capacitive coupling current. The leakage current includes two parts, one is the conduction current I1 through the insulation resistance; the other is the displacement current I2 through the distributed capacitor. The capacitive reactance of the latter is XC=1/2pfc and is inversely proportional to the power supply frequency. The distributed capacitor current increases with frequency. And increases, so the leakage current increases as the power frequency increases. For example: if a thyristor is used for power supply, its harmonic components will increase the leakage current.
If the insulation performance of a circuit or a system is assessed, in addition to all currents flowing through the insulating material into the earth (or conductive parts outside the circuit), this current should also include 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 ammeter:
1. The principle of measuring leakage current 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 formal measurement of leakage current applies an AC voltage, so the leakage current component contains a capacitive component of current.
2. When conducting a withstand voltage test, in order to protect the test equipment and test according to the specified technical indicators, it is also necessary to determine the maximum electric field intensity that is allowed to flow through the equipment under test (insulating material) without destroying the equipment under test (insulating material). Maximum current value, this current is also usually called leakage current, but this method is only used in the above-mentioned specific occasions. Please note the difference.
3. Leakage current is actually the current flowing through the insulating part of the electrical circuit or equipment in the absence of faults and applied voltage. Therefore, it is one of the important indicators to measure the insulation quality of electrical appliances, and it is also the main indicator of product performance.
4. The leakage current tester is used to measure the work-independent leakage current generated by the working power supply (or other power supply) of electrical appliances through insulation or distributed parameter impedance. Its input impedance simulates the impedance of the human body.
