Investigation Of An Ultra-low Impedance, Long Pulse Generator Based On Magnetic Switch And Strip Line

Defense and industrial applications have stimulated intense interests in pulsed power technology towards high repetition rate, high average power, all solid-state and compact structure. The long pulse, ultra-low impedance pulse generator based on magnetic switch and strip line investigated in this dissertation is an important candidate in this field.In this dissertation, a long pulse, ultra-low impedance pulse generator is developed based on the theoretical analysis, engineering designs, and experimental investigations of the two key subsystems which are a rolled strip pulse forming line (PFL) and a magnetic switch. These efforts are the ground for the development of a long pulse, ultra-low impedance and all solid-state pulse generator, and provide a significant reference for the research on this kind of pulse generator. The detailed contents and innovative work are as follows.1. A solid state, rolled strip pulse forming line with long pulse and ultra-low impedance is designed and is investigated both theoretically and experimentally. The characteristic impedance of the strip pulse forming line is obtained by using the conformal mapping methods. The design procedure of a rolled strip pulse forming line is worked out. And a rolled strip PFL with characteristic impedance of 0.5 ?, electric length of 115 ns was designed and manufactured. We use the DMD film and copper as the dielectric and conductor of the strip PFL separately. The dimension of the rolled strip PFL isΦ311mm×400 mm. A multi-channel rail gap switch for connecting to the strip PFL is designed and manufactured with the virtues of small volume and low inductance. In the PFL experiment, a quasi-square pulse of 17.8 kV, 270 ns (FWHM) on the matched load of 0.5 ? is obtained and the output power is 634 MW. A novel strip pulse forming line with a middle input structure is proposed. Compared with the conventional input structure, the middle input structure can reduce the duration of the charging and increase the electric strength of the strip line obviously on condition that the output pulse is a quasi-square wave.2. Based on the results of theoretical analysis and simulation, the design procedure of a toroidal magnetic switch is worked out. A 40 kV class magnetic switch is designed and manufactured according to the procedure. The core of the magnetic switch was stacked by the Fe-based amorphous magnetic rings. In the experiment, a pulse is compressed from 40 kV, 10μs to 39 kV, 2.36μs. And the magnetic switch can operate stably at 10 Hz repetition rate. A magnetic switch with low saturated inductance is designed and manufactured. The number of turns is one and made of copper plate. This structure can reduce the saturated inductance of the magnetic switch to about 30 nH. The magnetic switch is used as the main switch by replacing the rail gap switch to realize the solid state of the main switch.A novel testing method for the hysteresis cycle of the magnetic core has been proposed based on the single magnetic compression experimental platform. This method is applicable to the measurement of characteristic parameters and hysteresis cycle of magnetic material under the pulsed magnetization condition. In addition, this system can change the volt-second product of the output pulse conveniently by changing the parameters of the capacitor and inductor to measure the dynamical characteristics of the magnetic core in different magnetization condition.3. A novel long pulse, ultra-low impedance pulse generator with the advantages of solid state, high repetition rate and high average power is proposed. It comprises primary energy system, pulse transformer, magnetic switch, rolled strip PFL, main switch and load.In summary, based on the two key subsystems mentioned above, the long pulse, ultra-low impedance pulse generator is developed. The pulse generator is investigated by circuit simulation and experiment. On a 0.5 ? matched load, it can generate an output pulse with voltage of 17.8 kV, duration (FWHM) of 270 ns and rise time about 20 ns in the single shot mode. In the rep-rate mode, the experimental results show that the pulse generator can operate stably at 7 Hz repetition rate, with the output pulse of 14 kV, duration (FWHM) of 285 ns.