Design And Magnetic Saturation Characteristics Of Pulse Transformer Based On Field-circuit Coupling

Linear transformer drive source(FLTD)is a new type of drive source in pulse power technology.Because of its small size,low cost and can directly output high voltage,fast front,low jitter characteristics,it has been widely used in high energy density physics,radiation environment simulation,flash photography and other pulse power fields.The three-electrode field distortion switch in the form of ultraviolet preionization is a kind of gas switch commonly used in FLTD devices.Its trigger output pulse amplitude is about 100 k V,and it needs to have the characteristics of fast front and low jitter.Pulse transformer has the advantages of simple structure,small volume,easy frequency repetition and high reliability.In order to achieve faster pulse front,steepened gas switch is often connected behind secondary capacitor.The performance of pulse transformer will directly affect the overall structure design and output of the driving source,so its performance is particularly critical.At present,the design of pulse transformer is mainly based on theoretical calculation and engineering experience,there is a large error between the experimental results and the theoretical output performance.Therefore,it is of great engineering significance to study a more accurate and practical design method.The main research contents and results are as follows:Firstly,the pulse transformer is studied theoretically,and the calculation formula of the pulse amplitude and the pulse front is calculated.According to the formula,the influence law of the parameters of the pulse transformer working loop on the output front and amplitude is summarized,and the problems which should be paid attention to in the design are put forward.Then,the magnetic saturation process of magnetic core under pulse condition is analyzed,the factors affecting magnetic core saturation are summarized,and the influence of magnetic saturation on the performance of magnetic core is analyzed,which provides a theoretical basis for the design of magnetic core.Secondly,based on the above research,the magnetic core,primary winding and insulation structure of the pulse transformer are designed respectively,and the double-winding magnetic core test circuit is set up.The J-A parameters of the magnetic core are pseudo-combined and extracted in matlab.The magnetic core J-A model is introduced into COMSOL software,and the electromagnetic field model of the pulse transformer is built.The simulation of the designed pulse transformer is carried out by coupling its peripheral circuit.The results show that with the increase of primary voltage,the pulse front will gradually decrease and the ratio will decrease.When the primary voltage is 1.5k V,the output voltage can reach 100 k V and the leading edge is about 5us.Based on the B-H curve of magnetic hysteresis,the magnetic saturation process of pulse transformer is analyzed,and the reason of the linear decline of output waveform after the first peak is explained.The energy transmission efficiency of pulse transformer is analyzed,and it is found that the magnetic core saturation will lead to the rapid increase of magnetic core loss.According to the simulation results of primary current,the type selection of pulse thyristor is carried out.Finally,a pulse transformer is wound.The inductance and mutual inductance of the primary stage are measured.The ideal ratio is 67.7.The experimental platform is built and the output voltage and primary current under different primary loop states are tested.The influence of changing capacitance and primary voltage on amplitude,ratio and front edge is analyzed.It is found that the conclusions are consistent with those obtained by theory and simulation.The experimental results at the primary capacitance of 6μF are compared with the simulation results.The experimental results show that the errors of the field-route coupling method are less than10% and the waveform is consistent,while the errors of the circuit method are large,which verifies the feasibility of the design method.When the primary voltage is 1.5k V,the output amplitude of the pulse transformer is 100 k V,and the leading edge is 5μs.The output front of the pulse transformer was steepened by a three-electrode gas switch,and the related performance of the trigger was tested.After the steepening,the pulse amplitude reached108.5k V,the leading edge was 6ns(10%-90%),and the steepness reached 14.3k V/ns,which can work stably and has been applied to the FLTD gas switch test platform.