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Working principle of contact resistance tester

time:2021/6/17   source:华天电力  reading:432 time

The switch circuit contact resistance tester is a product independently developed and produced by our company. The quality of the product is guaranteed, and the working principle of the switch contact resistance tester is interpreted.


1. Basic knowledge of switch circuit contact resistance tester


1. What is contact resistance?


Contact resistance is the additional resistance that occurs when the static contact and the moving contact are in contact with each other.


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2. What are the components of the contact resistance of the circuit breaker?


It is composed of the shrinkage resistance and the surface resistance of the contact part of the moving and static contacts.


3. The reason why the contact resistance of the circuit breaker is unqualified?


(1) The contact is burnt out when breaking a large short-circuit current.


(2) The stroke is changed due to poor adjustment of the mechanism, and the contact pressure or contact area changes when the overstroke is seriously unqualified.


(3) After the circuit breaker of the switch loop resistance tester is debugged and installed, it has not been put into operation for a long time, causing the surface of the moving and static contacts to oxidize, and the contact surface resistance increases.


2. Working principle


The switch contact resistance tester adopts the current-voltage method test principle, also known as the four-wire method test technology.


The current source outputs a constant current flowing through the standard resistance R0 and the resistance to be measured Rx. Sampling the voltage signal U0 on the standard resistance R0, after filtering and amplifying, send it to AD to convert into a digital quantity, and then calculate the current value I, see formula (1). Similarly, the voltage signal Ux on the resistance Rx to be tested is sampled, filtered and multi-staged amplifying, and then sent to AD to be converted into a digital quantity.

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