The design of nanosecond high-current generators is usually one of three schemes: a high voltage microsecond pulse voltage generator and pulse forming line; a relatively low-voltage pulse voltage generator and inductive energy storage in vacuum; or the switching of energy into a load with the help of a plasma-erosion opening switch. The use of an inductive storage (IS) of energy with an electro-explosive opening switch (EEOS) allows charging of a pulse forming line in about 100 ns; this ensures insulation of high electrical strength and reduces overall dimensions and weight of the line. Optimisation of various designs that include an EEOS is usually performed by examining a large number of experimental data for RLC circuit models. We consider a theoretical RLC-circuit model of a particular device, the magnetic- ux compression generator (MCG). The energy conversion in the IS circuit occurs in two stages. Initially, the energy is stored in the inductance, with a partial loss for fuse heating; this stage is simultaneously one of heating and of accumulation of magnetic energy. At the second stage, the fuse resistance is determined mainly by the density of expanding metal and grows by a few orders of magnitude in a short time (explosion stage), when the magnetic field energy of increasing power is released into the fast-rising resistance of the fuse. We discuss the MCG detonation procedure, how the energy efficiency varies with respect to inductance and the EEOS parameters, and how the energy is released to the load.