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Knowledge points of loop resistance tester

time:2020/11/4   source:华天电力  reading:228 time

1. Question: What is contact resistance?

Answer: The contact resistance is the additional point that appears when the static contact and the moving contact are in contact with each other

2. Question: What are the parts of the circuit breaker contact resistance?

Answer: It is composed of the shrinkage resistance and the surface resistance of the contact part of the dynamic and static contacts.

3. Question: What are the reasons for the unqualified contact resistance of the circuit breaker?

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Answer: a. Contact beaker when breaking large short-circuit current.

b. The stroke is changed due to poor adjustment of the mechanism. When the overtravel is seriously unqualified, the contact pressure or contact area will change.

c. After the circuit breaker is commissioned and installed, it has not been put into operation for a long time, and the surface of the moving and static contacts is oxidized, and the contact surface resistance increases.

d. Long-term operation will deform the spring and reduce the contact pressure.

e. Mechanical wear caused by long-term operation of mechanical parts.

f. For the low-oil circuit breaker, it may cause acidic reaction due to the unqualified acid value of the eye oil, which will corrode the contact surface. Or floating impurities in the oil, after the short-circuit current is broken between the moving and static contacts, the residual carbonaceous particles and metal powders increase the contact resistance.

4. Question: What factors affect the contact resistance?

Answer: a. Material properties: resistivity, hardening, chemical properties, mechanical strength and resistivity of metal compounds.

b. Contact form: point contact, line contact, surface contact.

c. Contact surface condition: When an oxide film is formed on the contact surface (except for silver), the resistance of the oxide film is much larger than that of the metal itself.

d, contact pressure

e. The roughness of the contact surface.

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