Auxiliary and Signal Contact test bench
A. Testing "Auxiliary Contact" Mode
Setting: Set the side selector knob/lever to Auxiliary (usually the upper position or the position marked AX/OF).
Operation: Manually operate the circuit breaker handle to **"close" and "open"** the circuit.
Detection Standard:
Circuit breaker closed (ON) -> The multimeter should show continuity at the normally open contact (11-14) and open circuit at the normally closed contact (11-12).
Circuit breaker open (OFF) -> The multimeter should show open circuit at the normally open contact (11-14) and continuity at the normally closed contact (11-12).
Conclusion: In this mode, it must change state every time the handle is moved.
B. Testing "Alarm/Signal" Mode
Setting: Set the side selector knob to Alarm (usually the lower position or the position marked AL/SD).
Operation 1 (Manual Opening): Manually pull down the circuit breaker handle (open the circuit).
Detection Standard: The contact status should not change (should remain in the closed state). This is to distinguish between "manual opening" and "fault tripping".
Operation 2 (Simulating Fault Tripping):
If it's an RCBO: Press the "T" (Test) button on the circuit breaker cover.
If it's an MCB: Usually, a small screwdriver is needed to poke the tripping mechanism inside the circuit breaker (or a special test bench is used to simulate a short circuit).
Detection Standard: At the moment the circuit breaker trips, the auxiliary contact must immediately change state (normally open becomes closed, normally closed becomes open), sending an alarm signal.
3. Electrical Performance Testing
Contact Resistance: With the contacts closed, measure the resistance between the pins using a micro-ohmmeter. Generally, a very low resistance is required (e.g., < 50mΩ). High resistance indicates contact oxidation or poor contact, which can lead to signal transmission failure.
Dielectric Strength Test: Apply high voltage between the input and output terminals (usually 1500V or 2000V for 1 minute) to ensure that the insulation is intact and there is no leakage current that could cause harm.