It is necessary to regularly inspect the contacts in the circuit breaker to ensure its normal operation. Poor maintenance or damaged contacts can cause arcing, phase loss, and even fire.
This test is particularly important for contacts that carry a large amount of current (such as switchgear busbars), as higher contact resistance can lead to lower current carrying capacity and higher losses. Catheter testing is typically performed using a micro/milliohmmeter or low ohmmeter.
The measurement of contact resistance helps to identify micro corrosion of contacts and allows for diagnosis and prevention of contact corrosion. An increase in contact resistance can lead to a high voltage drop in the system, which needs to be controlled.
Working principle of contact resistance tester
Maintaining consistent measurement conditions in contact resistance testing is crucial for comparison with previous and future results for trend analysis. Therefore, when conducting regular measurements, it is necessary to conduct contact resistance tests at the same location, using the same test leads (always using calibration cables provided by the manufacturer), and under the same conditions, in order to know when connections, connections, welding, or equipment will become unsafe.
The circuit resistance tester uses a pulse width modulation high-frequency switching power supply to provide a test current of over 100A. When the measurement button is pressed, the high-frequency switching power supply outputs a test current of over 100A. At the same time, the sampling circuit starts sampling, and the obtained signal is amplified by the Amplifier. The A/D converter converts the analog signal into a digital signal, which is then filtered, calculated, and processed by the microprocessor. Finally, it is sent to the display to display the measured current and resistance. After 10 seconds, the system will automatically reset. When the resistance of the tested circuit is less than 400 μ When Ω, the minimum resolution measured is 0.1 μ Ω. When the resistance of the tested circuit is greater than 400 μ When Ω, the minimum resolution measured is 1 μ Ω.
