The biggest difference between small circuit breakers and control appliances is that in addition to the reliability of their operating characteristics, people are more concerned about their protective effect on the failure of electrical equipment, that is, they are required to successfully protect the electrical equipment during actual use. The rate is high. The frequency of refractory failures of small circuit breakers depends not only on the reliability of the circuit breaker itself, but also on the frequency of failures of lighting lines or electrical equipment. The frequency of faulty failures is related to the frequency of interference signals. It also depends on the drift of components and circuit parameters of the circuit breaker and its anti-interference performance. It is difficult to carry out reliable simulation tests. The frequency of operation failures mainly depends on the reliability of the operation mechanism of the circuit breaker. In addition, the severity of the consequences of the refusal of the miniature circuit breaker and the other two types of faults is also quite different.

According to the above-mentioned working characteristics and failure modes of small circuit breakers, we recommend that two reliability indicators be specified for the three types of faults, such as refusal, misoperation and operation faults. For refusal and misoperation faults, the protection success rate R can be used as the reliability index (success rate refers to the probability that the product completes the specified function under the specified conditions or the probability of the test being successful under the specified conditions); In terms of operation failure, the magnitude of the failure rate λ can be used as a reliability index (the failure rate refers to the probability of an operation failure of the product that has worked until time t within a unit time after time t). The protection of small circuit breakers on electrical equipment includes line overload protection and short circuit protection. In view of the fact that the damage to electrical equipment caused by short circuit faults on the circuit is more serious than that when overload occurs, and to avoid the reliability index system being too complicated and inappropriate, Too many reliability indicators are used to describe, so in this article we propose to mainly consider the protection characteristics of small circuit breakers when a short circuit occurs. Therefore, the instantaneous protection success rate R and the operation failure rate λ are used as the reliability of the small circuit breaker. Characteristic features, and the failure rate and success rate level are used as its reliability index.

We recommend that the maximum failure rate λmax be divided into three failure rate levels (level three, sub-fourth, and fourth level), and the value of unacceptable success rate R1 is divided into five success rate levels (level one. Level one). , Three, four, five).

Taixi Electric has extensive experience in the test industry, specializing in the development and manufacture of low-voltage circuit breaker characteristic test devices.