Research On The Electricalwear For Contact Of Miniature Circuit Breaker In Switching Process

The contact is the execution unit of the miniature circuit breaker. The voltage andcurrent wave of the contact is the most direct reflection of the circuit breaker’s operatingperformance and protection features. During the miniature circuit breaker’s breakingprocess the waveforms of the current and voltage on the contact change dynamically. Andthe waveforms can not only reflect the dynamical behavior of the contacts, but also reflectthe phenomenon of the arcing and contact wear. Therefore, it will contribute to research theelectrical and mechanical wear on the contact, the performance degradation of the circuitbreaker to study the current and voltage waveform monitoring technology on MCB contact.It has a very important significance. This article mainly studies the miniature circuit breakercontact electrical performance test technology. And then further study the measurement ofcontact electrical wear.First, conduct research on the hardware part of the MCB contact current and voltagedynamic monitoring system. The hardware of the test system is mainly consisted of: theanalog load control circuit, the data acquisition circuit and the detection circuit of thevoltage and current. In the analog load control circuit, ACSSR is used as a high-speedswitching device so that it can switch the multiple resistances quickly to produce thedesired current. The detection circuit of the voltage and current consists of filter circuit andsensors. The data acquisition circuit selects Advantech PCI-1742U cards for high-speedsampling and transmitted data in high-speed by DMA.Second, conduct research on the software part of the MCB contact current and voltagedynamic monitoring system. The software of the test system is designed by LABVIEW,including the control program of the analog load, the data collection procedures and theprogram of data processing (display and storage). In the control program, the systemcontrols the ACSSR actions through the operation on I/O ports of the PCI-1750to producethe test current that is desired by contact load circuit. In the data acquisition and processingprogram the Producer-Consumer structure mode is adopted, which carries out thehigh-speed data acquisition and processing synchronously. Due to the large amount of thedata and high sampling speed in the test system, TDMS data stream format is used to saverelated data. It can derive and calculate the delay time, arc time and the arc energy through themeasured records miniature circuit breaker on-off process contact current voltagewaveform and the analysis of breaking properties of miniature circuit breaker. With theincrease of current level, the delay time decreases, the arc time increases, so does arc energy.We can calculate the energy loss in the three parts of bimetallic strip, electromagnetic tripand contact in the process of miniature circuit breaker on-off, and can put forward themeasurement method of Contact electrical wear.