Design And Control Of 30kW Solid-state Modulator

The traditional modulator can’t meet the current user demand due to its disadvantages of large volume, low efficiency and poor reliability. With the emergence of high power semiconductor switches, it is quite possible that study of the solid state modulator can replace the traditional modulator. The solid state modulator has the advantages of small-size, light-weight, easily adjustable pulse width and high reliability, which lead to a broad market. It can be used in the industries like cargo inspection system and NDT of pipeline. The solid state modulator greatly improves stereo imaging quality of testing items and color imaging quality. On health care, both CT machines and radiotherapy equipment require high reliability and high precision solid state modulator. In addition, the solid state modulator can be used in areas like field testing and environmental dust. Some foreign companies like e2 v, North Star, ABB and CERN have entered into this area very early and put their products in the market. While in domestic market, the study of the solid state modulator began late and the technology is not mature. In order to meet the demand of the future market and to increase the self-innovation ability and market competence, the study of the solid state modulator can meet future demand and can improve domestic capability as well.This paper provides a topology structure of the solid state modulator main circuit, which the Marx generator with pulse transformer is used, and the advantages of this design is to reduce the primary voltage and circuit design complexity. 1、 The paper introduces the hardware circuit design of 30 kW solid state modulator.The hardware circuit includes the series resonant inverter power supply design, driving pulse, and the design of discharge circuit and arcing protection. 2、 The main softwares used are VB software, serial debugging software and circuit simulation software Multisim. 3、 The paper illustrates the control and the implementation of the solid state modulator, which can achieve good human-computer isolation. Siemens 200 series PLC is used as the controller of the whole system and VB as software operation control software.The VB control interface communicates with PLC in control unit by optical fiber converter, all the fault indication, status indication and operating order are displayed on the VB control interface and the condition of this system can be easily grasped and observed in the operating room. 4、 The paper introduces various technical difficulties encountered in the modulator system during debugging process, and how to solve these technical problems through a lot of experiments.Upper computer and the PLC of Siemens are used in the control of whole system to achieve the remote control. This can not only work out the problem of interference among complicated electromagnetic environment, but also achieve the man-machine isolation. Meanwhile both the reliability of system and the safety of human-being can be greatly improved. Technology like driving power isolation supply, fast arcing protection and layered winding of pulse transformer used in hardware circuit design of the system are of great significance to the further design of the high voltage pulse modulator. 30 k W solid state modulator designed has been successfully used in laser plasma laboratory of Shanghai Jiao Tong University. The modulator mainly is used in scientific experiments of optical electron diffraction. High reliability and good technical indicator of the modulator in operating peried win the good evaluation from users.