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resistance of the contact part of the moving and static contacts.
3. What is the reason for the failure of the circuit breaker contact
resistance?
- The contact burns out when a large short-circuit current is broken.
- Due to poorly adjusted mechanism, the stroke is not fixed,
resulting in a change in stroke. When the overtravel is severely
unqualified, the contact pressure or contact area changes.
- After the circuit breaker is commissioned and installed, it has not
been put into operation for a long time, so that the surface of the
moving and static contacts is oxidized and the contact surface
resistance is increased.
- Long-term operation deforms the spring and reduces the contact
pressure.
- Mechanical wear caused by long-term operation of the
mechanical part.
- For oil-less circuit breakers, it may also be acidic due to the acid
value of the insulating oil, eroding the contact surface. Or floating
impurities in the oil, after the short-circuit current between the
moving and static contacts. Residual particulate carbonaceous,
metal powder, increases contact resistance.
4. Factors affecting contact resistance?
- Material properties: electrical resistivity, hardness, chemical
properties, mechanical strength and electrical resistivity of metal
compounds.
