Research On Electromagnetic Sensitivity Of Electromagnetic Relay Functional Module

Electromagnetic relays possess advantages of high sensitivity, lower power consumption, small size, fast action speed and high transfer depth. They have been widely used in aerospace, weapons and other industries. They are the most irreplaceable electric components in electric power system, communication and information system, automatic detection and remote control systems. The electromagnetic relay functional module is made of two or more completely independent relays in a shell for a special function. Research on the electromagnetic compatibility of the functional module is the key point to ensure the reliability of the whole system.In previous researches, experiment was the main method of studying the electromagnetic compatibility of the electromagnetic relay and there was a lack of theoretical model; the electromagnetic relay was usually considered as an interfering source, while few researches have been done on the anti-interference ability of the electromagnetic relay. In related standards, especially in national military standards, there has been no specification for electromagnetic relay's electromagnetic compatibility, which is a hidden danger for the armament system caused by the relay's compatible problem. In addition, manufacturers of the relay also have no definite electromagnetic compatibility index for their products. So the paper studies the interior electromagnetic interference of the relay module. Furthermore, the characteristics of the relay interfered by the outer magnetic field and conducted interference are studied and the theoretical model is established. It is quantitatively analyzed that how the different interference affects the characteristics of the electromagnetic relay.First of all, a mathematic model of the electromagnetic relay functional module is established. The electromagnetic interference between two relays is analyzed through attractive torque, operation time and interference torque for three working states of relays in three typical structures respectively. The experiment results are in accord with the simulation and the validity of the theoretical model is verified. To improve the working efficiency, a new method based on equivalent magnetic circuit is proposed to rapidly analyze the relay module's interior interference. This method is available for calculating the interfering torque between two relays and its calculation time is less than finite element method. So this method is useful for the engineering application. Secondly, aiming at the problem of electromagnetic relay functional module under interference of the outer magnetic field, a theoretic model of electromagnetic system of relay under interference of the outer magnetic field is established and a method for analyzing magnetic interference is given. The magnetic sensitive direction of the relay module is calculated. The effect of uniform constant magnetic field and power frequency magnetic field on relay's static and dynamic characteristics is studied. The critical value of magnetic field which the relay can endure is quantitatively calculated in different working states. And it is obtained that relationship between the outer magnetic field and characteristics of the relay, such as the electromagnetic torque, operation time, pick-up velocity and coil current.Thirdly, a mathematic model of relay functional module coupling with conducted interference is established. A method of analyzing effect of conducted interference on relay is proposed. The variation of the dynamic characteristics of the relay can be quantitatively obtained. Research indicates that the surge and short interruption could seriously interfere with the characteristics of the relay. With the enhancement of spike and voltage dips, the relay can be greatly interfered with too.Finally, the testing system of relay functional module's electromagnetic compatibility is built based on Ethernet. This system can solve the variety and complex problem of the electromagnetic compatibility test. The necessary device for the sensitive test of the electromagnetic relay is designed, such as the uniform constant and alternating magnetic field generator, and the spike generator. The anti-interference ability of the electromagnetic relay module is studied through the experiments. The validity of the theoretical analysis is verified by comparing the experiment with simulation results.This dissertation provides the necessary research method and basis for improving the quality of the electromagnetic relay design, electromagnetic compatibility and the reliability of electromagnetic relay functional module. The key methods and techniques in the paper can be extended to the design of other similar electric apparatus products.