Study On Repetitive Nanosecond Pulse Generator Based On Pulse Magnetic Components

Pulse magnetic element is an important component in pulsed power system: with small volume and low cost, core-type pulse transformer is a widely- used step-up device in compact pulse generators; as one of the best repetitive switches, magnetic switch is of high stability. As a result, the repetitive pulse generator based on pulse magnetic elements has evident advantages in long- life, compact and high- repetition-rate operation.According to the circuit scheme of magnetic switch and saturable pulse transformer, the pulse forming process of the generator, including the reasonant charging based on core-type pulse transformer and the coordination between magnetic ele ments, is analyzed theoretically. For the design of magnetic elements, pulse magnetization characteristics of cores shall be tested and analyzed. The measurement of pulse magnetization characteristics of toroidal magnetic cores is studied. The magnetization characteristics of Mn-Zn ferrite core for magnetic switch is tested based on single-winding test circuit. As for the research on pulse magnetization characteristics of Fe-based nanocrystalline, the B-H curves of the cores with high and low remanence are obtained based on double-winding test, respectively. Besides, the pulse magnetization characteristics of the cores at different temperatures(from 25 to 150?) are tested, which indicates the fact that Fe-based nanocrystalline has better high- temperature pulse magnetization characteristic than ferrite.The loss on condition of pulse magnetization is different from that in cycling excitation. The initial energy loss on condition of pulse magnetization is defined, which contains both energy that is irreversibly transferred into heat and energy that is temporarily stored in magnetic energy. The initial energy loss and pulse cycling core loss of Fe-based crystalline at different magnetization rate are tested. The initial energy loss density is proportional to the product of two power functions of which the base numbers are the magnetization rate and magnetic flux swing. Besides, the pulse cycling core loss density is proportional to the equivalent frequency in this thesis.On the basis of theoretical analysis and experiments of pulse magnetic characteristics, the quantitative optimization design of the generator is presented through both theory results and simulation results from ATP-EMTP. The comparison of the results of theory, simulation and experiment illustrates the accuracy of the method of quantitative optimization design. The core loss of saturable pulse transformer in repetitive operation is also analyzed. Unlike traditional high- frequency operation in power electronics, the core loss of pulse transformer is mostly contributed b y the oscillated excitation after the generation of output voltage. Consequently, the power of core loss is proportional to the repetition rate of the generator, and a typical value of the power of core loss at 5000 pps is estimated at 175 W. The loss estimation is used in the Comsol simulation of temperature characteristic of the core. With the consideration of temperature rise, the oil- immersed prototype of the repetitive pulse generator is designed and constructed. The prototype can consequently work at the repetition rate of 5000 pps, and the static temperature at the surface of the core of pulse transformer is 80?. It can provide repetitive pulse with amplitude of approximately 42 k V, a full-width at half maximum duration of 198 ns, a rise time of 85 ns, and repetition rate ranges from 0 to 5 kHz.