Q1: What is a insulation tester?
A1: Insulation tester, also known as megohmmeter or meggers, are widely used to measure cables for generators, motors, power transformers, wiring, appliances and other electrical installations such as control, signal, communication and power ) insulation resistance. They are often used in routine maintenance procedures to indicate changes in the insulation resistance of a motor over months or years. Large changes in insulation resistance may indicate potential failures. Therefore, regular calibration of the megohmmeter is required to ensure that the meter itself has not changed over time.
Q2: What is insulation resistance?
A2: Insulation resistance is the DC resistance of the insulation under the specified conditions, that is, the DC voltage is applied to the dielectric, after a certain period of polarization, the resistance corresponding to the leakage current flowing through the dielectric is called insulation resistance. It is the most basic insulation index of electrical equipment and electrical circuit.
Q3: How to measure insulation resistance?
A3: 1. Connect all the lines according to the method measured by the insulation resistance tester. The connection between the measuring lead and the pipe is more suitable for the use of magnetic joints or clips, and the connection point must be free of rust.
2. The measuring instrument should be a 500V/500MΩ (the error here cannot be greater than 10%) insulation tester. Turn the handle of the megohmmeter to reach the specified speed for 10 seconds. The resistance value indicated by the megohmmeter stably is the insulation resistance value of the insulating joint (flange), which is required to be greater than 10 megohms.
Tips: What should be paid attention to when using an earth ground resistance tester?
- Ground resistance tester working environment: relative humidity ≤75%RH, temperature 0～40℃.
- When connecting or disassembling the DUT, it must be carried out in the "reset" state.
- The connection between the special test line and the ground resistance tester must be in good contact, and both ends of the resistance under test must be clamped. When adjusting the loop current, pay attention to the digital change of the ammeter, and slowly adjust to the required current value.
- After the test is over, press the reset button first, and then return the current to zero. If there is an abnormal situation during the test, press the reset button first, and then quickly return the current to zero.
- Earth resistance testers that are found to be unqualified should stop testing and return them to the laboratory for measurement. Products or components tested within 2 hours should be re-tested with qualified earth resistance testers.
- The earth resistance tester should be measured regularly.