Study On Breaking Current-phase Control And Electric Life Of Ac Contactor Under The Condition Of AC-4

As a frequent on-off switching device, AC contactors are widely used in various power systems. Its electrical life is smaller than the other use categories when AC contactor working under the condition of AC-4 that on and off six times the current at the rated voltage. The main reason for this phenomenon is that the intense arc generated by contactor breaking ablated contacts, which has become the primary source of electric life of AC contactors. The wear of contactor contact has a great relationship with arcing energy when breaking, and its breaking current-phase has a direct impact on the arcing energy. Therefore, CJX8-65 for example, this article studied the subject in terms of the test platform design, controller design and test research.First, set up a test platform under the condition of AC-4. Through theoretical analysis and experimental research methods, AC sinusoidal excitation and DC excitation were compared and analyzed to determine the final AC contactor exciting program, which will help phase control while reducing the impact of the closing of the test results. Symmetrical three-phase load used in the main three-phase circuit and the wire and load parameters are calculated. Multi-channel data acquisition is designed to collect the current waveform of the main circuit and the port voltage waveform, which will help post-theoretical analysis and research.Second, breaking current-phase control and test was achieved. Hardware of the controller was designed, including some circuits of signal condition, embedded control and switch control. Software was also designed, including some functions of signal acquisition, data processing and logic control. The controller was stable in the test platform and error control.Finally, the test results were analyzed and studied. The mass loss of contacts obtained in different breaking phase. The mass loss curve was depicted within a half current waveform and the breaking phase was found where can be minimal loss. This article proposed a mathematical model of contact wear, combined with theoretical analysis and experimental results obtained the correlation of contact wear and arc current. This study effectively improved the electric life of AC contactors.