| As an explosive power source that can output high current (MA) and high energy (MJ) on the inductance loads, the magnetic flux compression generators (MFCG, FCG or EMG) have been used to drive many kinds of pulse power devices, such as rail-gun, coil-gun, Z-pinch, 9 -pinch , dense plasma focus (DPF) and so on. Also, it can be used to drive the electrically exploding opening switch (EEOS) to produce high pulse voltage to simulate lightning discharge, and to drive microwave generators to radiate high power microwave and so on.There are many kinds of EMG where the helical generators whose explosive charge is initiated axially (CEMG), can output high current on a high inductance load with short pulse duration because of its high initial inductance and high velocity of magnetic compression. CEMG can raise the efficiency of energy transmitting from the generator's origin power source to the load as it can match the load better.The theoretical model and principal experiments of a CEMG with a high inductance load have been conducted in this paper. The model of the CEMG consists of 1-D model for explosion driven central tube (armature), a model for magnetic field distribution inside the helix, a model for magnetic force outside the center tube and the circuit model. A code (CEMG 1.0) was compiled then. With the aid of code CEMG1.0, four kinds of CEMG (*1, *2,*3 and #4) have been calculated separately, and the generator parameters have been optimized. Especially, the residual inductance of #1 CEMG induced from the magnetic force outside the central tube, the dependence of the residual inductance on the input energy and the load parameter, and the maximum output performance of #1 CEMG are given. Also, the calculated results of the code CEMG 1.0 have been compared with the experiments of the Institute of Chemical Physics (ICP, Russia) in this paper.Calculations of the four kinds of CEMG show that, the output current and pulse duration of CEMG can be enlarged as the distance between the central tube and the stator helix increases. The generator with smaller pitch of feed coil can output higher current on the load, and the generators with an aluminum tube can output shorter pulse duration than those with a copper tube. The calculated results of *1 CEMG show that, a generator with 120mm in stator coil diameter, 60mm in copper tube diameter, 2.5mm in tube thickness and initial current 3.5kA in feed coil can output pulse current 113kA on an inductance load of 1.26 u H , the rise-time less than 2u s. Using thecode CEMG1.0, the calculated results about the ICP's generator agreed well with the experimental results conducted in ICP.In terms of theoretical results, with a cylindrical electrically exploding metallic mesh as the initiator for the RDX explosive inside the central tube of density lg/cm3, a helical generator has been designed and tested. To measure the synchronism of the exploding mesh and the copper tube expansion, experiments of optical measurement were done firstly.Experimental results of high speed photography show that, the maximum initiation time difference for a cylindrical electrically exploding mesh with 10mm in diameter and 270mm in length (exploding point 21 X 6) is less than 0.18PS, the maximum break out time difference is less than 3.67 u s for a copper tube (60mm in diameter and 2.5mm in thickness) expanding to double origin diameter, and the average expansion cone of the copper tube is about 7. When the input energy is about 1.6kJ, CEMG with 5?conical helix of large diameter 135mm, and small diameter 125mm, length 195mm, can output pulse current 99kA and energy 6kJ on an inductance load of 1.26uH. The current derivative with time is 14GA/S, its pulse duration is 22 u s and the rise-time is 12 u s. When the flux losses of generator were taken into accounted, the calculation results with a revised code for the CEMGs with average cone shaped expanding tube and stator coil agree with the experimental results well.It is concluded that, the creative theoretical model and experiments of an... |
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