Analysis And Optimization Of Insulation And Thermal Conductivity Of Power Doubling Rectifier Module Of X-ray Generator High Voltage Power Supply

X-ray is widely used in industrial nondestructive testing,scientific research experiments,medical diagnosis and other fields.As a core component of X-ray generator,X-ray high-voltage power supply directly determines the quality and safety of X-ray imaging.High frequency,high voltage,and miniaturization are the development directions of X-ray high-voltage power supply in recent years.The insulation and heat dissipation characteristics of the corresponding high-voltage output module have become an important factor affecting the reliability of X-ray high-voltage power supply.This paper is derived from the "National Key Scientific Instruments and Equipment Development Project-X-ray High Voltage Power Supply" Aiming at the problem of high voltage withstand insulation and thermal conductivity that the voltage doubling rectifier module faces in the application of high voltage and small volume of X-ray high voltage power supply,this thesis studies the relationship between the composition of the solid potting material and the insulation and thermal conductivity,research material ratio,the thermal simulation optimization of Icepak,module testing and other work were carried out to achieve efficient heat dissipation of the voltage doubling rectifier module and improve the reliability of the power supply.The specific work is as follows:This thesis uses Saber software to simulate and analyze the bidirectional symmetric C-W full-wave voltage doubler rectifier circuit selected for the subject.The parameters such as voltage and current on the capacitor and diode are obtained,and the power consumption of the device is calculated.This thesis determines the addition of liquid silicone rubber as the matrix,aluminum nitride and boron nitride as Filler,thermally conductive and insulating composite materials were prepared and their thermal conductivity and electrical insulation properties were tested and analyzed.In order to reduce the exerimental cost and increase the efficiency,the orthogonal method is then used to analyze the optimal process for preparing the composite.The results show that the performance of the composite is optimal when the stirring time is 150 min,the curing time is 210 min,the silicon-hydrogen ratio is 1:1.8,and the mass ratio of AlN to BN is 8:2.The optimized process was applied to the preparation of composite materials with a doping concentration of 50wt%and tested.The experiment confirmed that the optimized composite thermal conductivity increased by 2.5 times,the volume resistivity increased by 2.1 times,and the breakdown strength increased by 1.3 times.On this basis,this thesis establishes a thermal simulation model of the voltage doubling rectifier module.The influence of the power device layout and potting structure in the voltage doubling rectifier module on the heat dissipation effect is analyzed,and the layout structure is optimized based on the design.The simulation results show that the thermal conductivity of the potting compound is 0.5 W/m·K,the overall volume of the voltage doubling rectifier module is 480×120×40mm3,and the heat dissipation is uniform and the effect is optimal under the layered potting structure.After conducting temperature test experiments with 8 points on the surface of the voltage doubling rectifier module of the 250kV/5kW experimental prototype,the results show that after half an hour of power supply,the standard deviation of the uniformity of the measured temperature field distribution is 0.98,the measured temperature is similar to the simulated temperature gradient distribution,and the maximum error is 8.57%.The results show that after the optimized layout,the temperature field distribution is more uniform and the overall temperature is obviously reduced,effectively improve the heat dissipation efficiency.In this thesis,the optimal insulating medium ratio and preparation process are determined through orthogonal experiments.The temperature field of the voltage doubling rectifier module is optimized through measures such as circuit simulation,device layout,and potting structure.Prototype experiments confirm that the design scheme can effectively ensure X-ray high-voltage power supply of high voltage,the high-power,small-volume(250kV/5kW)works normally and the thermal field distribution of the entire module is even.It has reached the national major scientific instrument and equipment development special project-X-ray high-voltage power supply project acceptance index requirements,which is of great significance.