Research On The Technology Of Short-Circuit Breaking For AC Contactor

The widely-used contactor is an important control electrical appliance. Currently, all contactors, in the domestic and overseas, can switch on and off the circuit frequently, but do not have the capacity to break short-circuit fault. With the development of smart grid construction, the demand for performance and functionality of intelligent appliance increases. As it is known, contactor is used as control electrical appliance and low voltage breaker is used as protective apparatus to control and protect the load at low voltage distribution system. To meet the requirements of the smart grid, the paper proposes the physical model based on new contactor, the contact structure, the technology of early short-circuit fault detection, and the concept of new contactor integrated control and protection function. The morphologic wavelet and current change slope are combined as double criterion of early short-circuit fault detection, and the mechanical model achieve fast motion with the eddy current repulsion. Not only the characteristic value of short-circuit fault signal can be extracted with noise interference in low voltage system effectively depressed, but also faulty circuit can be switched off quickly to protect low voltage system.1. From the point of view of the research significance and background, this paper introduce the short-circuit protection mode and significance of the electric system. Then expound the development status and trends of the short-circuit protective electric devices in the low-voltage system, the application of the morphological wavelets in the electric system fault signal and the application of eddy current repulsion mechanism in the high-speed switch.2.The short-circuit early detection model based on the morphological filter, wavelets analysis and current slope detection theory is proposed, the filtering effect of arithmetic, the veracity and rapidity of the fault characteristic value are verified through the design and test of the early detection system.3. The high-speed switch model with eddy current repulsion mechanism based on the principle of eddy current repulsion is proposed. The eddy current repulsion mechanism model is built by ANSYS and ADAMS, the rapidly breaking character is verified by software simulation and prototype test.4. The researching of the ac contactor short-circuit breaking technology consists of two parts, respectively, the breaking test of short-circuit current early detection and the test of 50kA short-circuit current.Simulating and testing results have shown that the short-circuit early detection model combining morphological wavelets with current slope can not only effectively suppress the noise jamming in the low-voltage distribution system, but also can validly extract the characteristic value of the short-circuit fault signal and reach the purpose of early detection of short-circuit. The fast switching model with eddy current repulsion mechanism with the fast breaking characteristics has great research significance and practical vale for the detection and breaking of short-circuit in the low-voltage system. The prototype has passed the test of 50kA short-circuit current at Fu jian Inspection and Reasearch Institute for Product Quality, from the view of the last test waveforms, it can break the short-circuit current even the short-circuit current is low. Therefore, the use of the institution and implementation can even break higher than 80kA short-circuit current.