Research On Closed Loop Control Contactor And Its Dynamic Performance

Alternating current contactors as low-voltage electrical products are largely used.Arc which is produced during opening process and two bounces which are produced during closing process of AC contactor’s contacts are the main factor influencing a contactor’s life.At present,adopting intelligent ways to achieve break arc is used widely,such as segmenting DC excitation or getting the zero point of the primary circuit’s current through the current transformer,then setting off delay and breaking electromagnetic system,so zero off is realized,and so on;and the speed of contacts in the closing process is regulated by intelligent control mode.However,these methods can not avoid the effect of dispersion of operating mechanism and the environment,and many uncertain factors.In this regard,the proposed modular asynchronous contactors can achieve each contact individually closed-loop controlled.The zero current splitting technique is used to achieve no arc breaking.This is a new idea in the field of structural design and control of contactors and closed-loop control can eliminate the influence that dispersion of operating mechanism and many other uncertain factors put on the accuracy breaking on the zero point of current,so it can achieve no jump closure.Firstly,the combination of double E type DC electromagnet is chosen as the electromagnetic mechanism of contactor,which controls spring reaction force and electromagnetic attraction respectively.The structure size and the circuit parameters of the electromagnetic system are designed and the simulation design is carried out by setting the working stroke,the mechanical counterforce characteristics and the required electromagnetic suction.In order to understand the two bounce of contact closure better,in this paper,based on the vibration theory,the recovery coefficient and the wave equation,the two bounces is analyzed in detail,and a new speed measuring device is designed for measuring the real-time speed of the contact.The simulation model is established and its effectiveness is verified,and the speed planning curve of the closed-loop control system is designed.In view of the fact that the traditional current transformer can not be well applied to the contactor,a method of quick report and current transformer to detect the zero point of alternating current is proposed,and a simulation model is established to determine its feasibility,and the measurement can be made regardless of current saturation or not.At last,the control system of closed loop control contactor is put forward,and the current acquisition module,speed acquisition module,conversion module,signal amplification module,drive module and power module are designed in detail.