The Design And Control Software Realization Of 4Mev Solid-state Compact Modulator

With the continuous progress and development of radar and accelerator technology in recent years, higher requirements for pulse power equipment are putting forward. They not only require for higher power, higher voltage and better waveform, but also small volume, light weight, high efficiency, long life, and low cost. The disadvantages of conventional modulators like hydrogen thyratron, vacuum tube or tetrode are very obvious, that is longtime preheating, low efficiency, large volume, cumbersome, short lifespan, poor stability, high failure rate, and high cost,so they are being phased out. Solid state power pulse modulator is adopted to overcome the disadvantages mentioned above, so as to meet the requirements for modern pulse power electronic equipments. Especially after the appearance and commercialization of Insulated Gate Bipolar Transistor(IGBT) module, this opens a new chapter for pulsed power electronic equipments.The solid state compact pulse modulator introduced in this paper works in the topology of Marx, which is charged in parallel and discharged in series with four IGBTs, the capacitor charging power supply uses high frequency series resonant converter with constant current and low noise, and other auxiliary power supplies are also solid state. This modulator can output a rectangular pulse signal of 4.2μs、5MW、250Hz to supply for 4Mev electron accelerators, its efficiency is more than 85%, but the volume and weight is only 1/3 of the conventional modulators. This modulator has a wide range of applications in industrial CT and medical CT,which means stable market demand.For the fullest expression of the advantages of solid state switch, good use of switch modules is important, then we need well-designed circuit topology to the implementation of accurate monitoring and fast protection of the status of the circuit. Therefore, in this paper, we discuss the optimal design of the circuit, and simulate the discharge process of the switching circuit so as to obtain the parameters for the best working status. Based on the control system functional requirements of the modulator, software design for the modulator is analyzed and a PC control software and PLC control program is designed. Programmable controller PLC is used as main control program to do monitor, control and adjustment of the circuit’s work order, status and parameters, and to fast protect the switches while under a fault status of overvoltage or overcurrent, which ensures the long-term stable and reliable operation of the equipment. With optimized design and debugging of the PLC control program, the modulator with magnetrons loaded finally reaches the optimal running status. The GUI of PC control software is designed in the VB language, which is made up of several functional modules such as status indication, fault indication, operation introduction and data display, so as to implement observation and control of the modulator, in this way we realize the man-machine isolation and also save the cost.