Pulse-Forming Networks

The energy in magnetocumulative generators is stored in low value inductances, of the order of 10 nH, but the currents involved may reach tens and even hundreds of megaamperes. Transferring the corresponding large amount of energy into different types of loads poses a major problem, because the inductance of the MCG is smaller than that of the load. When the load is series connected to the MCG, efficient operation is only possible when the load parameters are matched to those of the generator. If pulse sharpening or matching devices are not used on the output of the MCG, it may still operate satisfactorily with an inductive load, provided that the inductance of the load is of the same order of magnitude as that of the MCG, i.e., several nanohenrys, or with an active resistance provided that its resistance is of the order of milliohms. To match the MCG to loads that do not meet these criteria, several methods have been developed to couple the energy from the MCG into the load. These methods include: • disconnecting the MCG from a circuit branch using an opening switch, followed by its connection to the load in a parallel circuit branch (Fig. 4.1). When the switch opens, a voltage pulse is delivered to the load, • using a transformer connected through an opening switch to the MCG and a closing switch to the load (Fig.4.2). When the opening switch is activated, energy is stored in the transformer. When the closing switch is activated, energy is delivered from the transformer to the load, • using an opening switch to shunt the current. When the switch opens, a closing switch simultaneously connects the load to the output of the MCG (Fig. 4.3).