Why You Need Contact Resistance Test?
The contacts in the circuit breaker needs to checked periodically to ensure that the breaker is healthy and functional. Poorly maintained or damaged contacts can cause arcing, loosing phase, and even fire.
This test is especially important for contacts that carry large amounts of current (e.g. switchgear busbars) because higher contact resistance can lead to lower current carrying capacity and higher losses. Ductor testing is usually performed using a micro/milli-ohmmeter or low ohmmeter.
Measurement of the contact resistance helps in identification of fretting corrosion of contacts, and allows contact corrosion to be diagnosed and prevented. Increase in contact resistance can cause a high-voltage drop in the system, and that needs to be controlled.
Contact resistance tester working principle
It is very important in the contact resistance test to maintain consistent measurement conditions, to be able to compare with previous and future results for trending analysis. Therefore, when taking periodic measurements, the contact resistance test must be performed in the same position, with the same test leads (always with the calibrated cables supplied by the manufacturer), and in the same conditions, to be able to know when a joint, connection, weld or device will become unsafe.
Loop resistance tester using pulse-width modulated high-frequency switching power supply to provide more than 100A test current, press the measurement button, the high-frequency switching power supply output of more than 100A test current, at the same time sampling circuit to start sampling, the signal obtained by Amplifier amplifier, the A / D converter converts the analog signal into a digital signal, and then by the microprocessor data filtering, computing, processing, and finally send the display shows the measured current and resistance. After 10 seconds, the system will reset automatically. When the measured loop resistance is less than 400μΩ, the minimum resolution of the measurement is 0.1μΩ. When the measured loop resistance is greater than 400μΩ, the minimum resolution of the measurement is 1μΩ.
Post time: Feb-24-2022