Study On High Voltage Power Supply Technology Based On Insulated Core Transformer

E-beam irradiation processing industry has been developing rapidly in recent years and it made a great contribution to the development of national economics. High voltage electron accelerator shows its superior performance in the producing of wire and cable, heat shrinkable tubing, foam, plastic, and semiconductor device surface coating, rubber crosslinking, food storage, medical and health products sterilizing, industrial wastes treatment. Compared to the high demand of the low-energy accelerators market, their developments are still slow. Therefore, it is imperative to solve this problem.High voltage accelerator consists of electron acceleration system and high voltage (HV) power supply, and the later is the most important component. The insulated core transformer (ICT) power supply is usually used in the accelerators with the energy of0.3～3MV. In low-energy region, the ICT takes advantages of high power, high efficiency and reliability. It is significant for irradiation industry to developed high performance ICT with new technology.Segmented core structure of the ICT is convenient to insulation. However, because of it, the excitation current and magnetic flux leakage increase, power transmission ability reduces and vibration and noise intensify. Magnetic flux leakage leads to inconformity of disk voltage and high load regulation of the power supply.In this paper, based on a350kV/50mA power supply design and development, the theories and key techniques of the ICT power supply is studied deeply; design process is summarized; some optimization design methods are presented as well. Physical and engineering design of the power supply and prototype development have been performed.The method of optimization for the thickness of the insulation gap, the disk output voltage and the number of disks is proposed. It has considered the relationship of dielectric strength and insulation thickness, the surface roughness of core, and the performance of rectifiers, etc. The total thickness of air gap is reduced and the efficiency of power supply is improved by using the insulation materials sufficiently. The limitations of the lowest height of disks are summarized either.The flux leakage magnetic circuit model and the simplified equivalent circuit model of the ICT are presented respectively. The relationship between their parameters is derived, so that the function of power loss and the magnetic circuit parameters is obtained. The magnetic circuit parameters can be optimized through the function. The single-turn mutual inductance matrix of coils is obtained through magnetic field numerical calculation. Based on it, a circuit simulation model of the power supply is established, and it is more accurate for simulating the power supply. The eddy current loss on primary coil is researched deeply and the power loss is calculated while the power supply is under no load and full load condition. Thus the design of primary coil is optimized correspondingly.The existed methods are cleared up and summarized systematically. Based on it, a combined method and an improved turns compensation method are proposed. The turns of secondary coils can be optimized by applying the improved turns compensation method, and the average inconsistency of disks can be reduced by more than50%compared with the traditional turns compensation method. The inconsistency of the disks output voltage caused by magnetic flux leakage can be overcome very well by the combined method. The consistency of disk output voltage remains a high level within the entire operating range of the power supply. The utilization of the rectifier components, the uniformity of electric field and the output voltage of the power supply are increased while the power supply is more compact.The control model of the power supply is presented, and the compensation network is optimized. Control simulation model of the power supply is established. Steady voltage output and voltage dynamic adjustment of the power supply are simulated under closed loop control. Simulation results show that the performance of the power supply is greatly improved and the design targets are achieved.At last, compensation experiment of the disk output voltage tests of the closed loop performance of the power supply and high voltage experiment with no load are carried out. After compensating, the maximum relative error of the disk voltage is lower than3.5%, the relative error of the disk output voltage between simulation results and experiment is lower than2.5%. Output voltage rising linearly as well as load open experiments demonstrate that the performance closed loop control has reached the design requirements.