Loop resistance tester, also known as transformer loop resistance tester, is mainly used to test the contact resistance of dynamic and static contacts of high-voltage circuit breakers. The circuit resistance of the circuit breaker mainly depends on the contact resistance of the dynamic and static contacts. The presence of contact resistance will increase. The loss of the conductor during energization will increase the temperature of the contact point. Its value directly affects the current-carrying capacity during normal operation, and to a certain extent the short-circuit current cut-off capacity. It is also an important data reflecting the quality of installation and maintenance work. At present, the loop resistance tester mainly has three test methods, the specific operations are as follows:
1. Bridge method: When using a double-arm bridge to measure the resistance of the circuit breaker's conductive circuit, it is difficult to eliminate the oxide film with large resistance due to the weak current flowing through the measuring circuit, and it is difficult to measure too much value. The current is small, and it is difficult to form shrinkage at the contact point of contact, that is, the shrinkage resistance cannot be measured.
2. Voltage drop method: When a direct current is applied to the circuit under test, a voltage drop will be generated on the contact resistance of the circuit. The current value and voltage value through the circuit are measured, and the measured contact resistance will be calculated. The test process is cumbersome, and the measurement results are manually calculated, and there are certain errors.
3. Micro-ohmmeter method (loop resistance tester): The principle is the voltage drop principle, but the measurement and calculation are processed by the single-chip microcomputer, which greatly reduces the workload.