Research Of Power Frequency Magnetic Field Generator Based On Inverter Technology

Power frequency magnetic field generator is one of the primary testing equipments for electromagnetic compatibility, which simulates power frequency magnetic field interferences produced by various equipments and power sources in various environments. As a main equipment of power frequency magnetic field immunity test, it has become an important instrument in the EMC design of the products with national compulsory certification put in practice. Power frequency magnetic field generators we can find in the market now all use the booster to adjust the voltage and then use the converter to convert the current to the proper number. They are mainly big in bulk, heavy in weight, high in cost and hard to control and improve the precision. The power frequency magnetic field generator introduced in this paper uses the power electronic convert technology to generate the current needed. It is easy to control, high in precision and also have advantages in bulk and cost.According to the voltage controlled current source principle, the design uses the AC-DC-AC topology. It follows the current feedback to alter the pulse width by change the dutycycle and consequently adjust and stabilize the output current. The structure of the main circuit is composed of the uncontrolled full-bridge rectifier, boost converter, full-bridge inverter and LC filter which changes the rectangle wave into sine wave. In the design of control system, the micro chip computer and appropriative chips are used to generate the pulse width modulation wave, collect, transform and disposal the signals. Integrated chips are more simple, reliable and easy to debug than discrete components. The use of common mode rejection circuits, optocoupler, watchdog and digital filter technologies improves the electromagnetic compatibility of the whole system and guarantee the system to work stable in complicated electromagnetic environment.The design idea and steps of the whole system are described in this dissertation. The power circuit topology suit for the current source and control strategy are introduced, the important formulas are deduced, the main parameters are calculated, and the idea of how to the write the program is illustrated in the dissertation. And in the last part, the design is proved to be feasible by emulate and test.