Design And Implement Of High-frequency High-voltage Transformer

High-frequency high-voltage switching power supply is widely used in electrostatic precipitator,military radar,electron beam welder,laser and other equipment because of its advantages of small size,light weight,safety and stability.As an important part of highfrequency high-voltage switching power supply,high-frequency high-voltage transformer plays a role in energy transfer,boosting,and isolation.Its stable and reliable operation has a decisive effect on the performance of the switching power supply.In this thesis,a 10 kV,12.5kHz,6kW high-frequency high-voltage transformer is designed.In this thesis,the equivalent model of the high-frequency high-voltage transformer and its simplified equivalent model are analyzed.The circuit structure and parameters of the series resonant capacitor charging power supply are given.The design parameters of the high-frequency high-voltage transformer are obtained through simulation of the charging power supply circuit.The design process of the high-frequency high-voltage transformer is introduced in detail from in four aspects: selection of the magnetic core,selection of the winding wire,determination of the winding structure,and design of the insulation.An ironbased nanocrystalline core with low core loss,high saturation magnetic flux density,and good temperature characteristics is used as the transformer core.Winding wires meeting the skin depth requirement are selected based on the current carrying density and the current flowing through the transformer.Coaxial winding of primary and secondary windings effectively reduces leakage inductance,the secondary winding adopts segmented layered winding to effectively reduce distributed capacitance.After completing the overall design of the high-frequency high-voltage transformer,the distribution parameters and losses are theoretically calculated.As a numerical analysis method,the finite element method is widely used to solve the electromagnetic field problems because of its high calculation accuracy.In this thesis,the finite element simulation software COMSOL is used to calculate the distributed capacitance,loss and temperature rise of the high-frequency high-voltage transformer.A twodimensional finite element model of the distributed capacitance is established.The corresponding distributed capacitances of the four secondary winding schemes are analyzed respectively.The optimal winding scheme is determined by the simulation analysis results,and the minimum distributed capacitance and the best transformer performance are achieved.A three-dimensional finite element model is established to analyze the loss of the transformer,by applying a circuit to stimulate and setting the magnetic field environment.The core loss and winding loss of the transformer are obtained.The solid-state heat transfer module and laminar flow module in the finite element are used to simulate the temperature field of the transformer.Through the simulation analysis,it is found that the temperature of the core is the highest when the transformer is working,and the maximum temperature rise is 44.2°C.The temperature rise meets the work requirements.In the end,the winding process of the high-frequency high-voltage transformer and the various components of the series resonant capacitor charging power supply prototype are introduced.The distribution parameters and losses of the high-frequency and high-voltage transformers are tested.The test results show that the distribution parameters of the transformer are small.It doesn’t cause much impact on the performance of the charging power supply.The loss of the transformer is also relatively small.The calculated transformer efficiency is as high as 98.43%.The high-frequency high-voltage transformer is used for the capacitor charging power source and the charging experiment is performed.The charging voltage rises to 10 kV within 3 s.The primary current is a typical resonant current waveform with the effective value of about 20 A.The voltage and current waveforms are good.It is verified that the high frequency and high voltage transformer designed in this thesis has good performance.