The Meatgrinder: A Historical Perspective

The Meatgrinder Circuit was originally conceived in the Lawrence Livermore National Laboratory (LLNL) as an analog to the whip to enhance the energy transfer from inductor to inductor beyond the canonical maximum of 25%. The purpose was to miniaturize a MJ level Plasma Focus type system by introducing an intermediate inductive stage between a now much slower and lower voltage capacitor bank and the plasma focus inductance. At the time it was believed that it is impossible to transfer more than 25% of the energy from one inductor to another uncoupled inductor without the use of complementary energy storage elements such as capacitors, springs, or kinetic energy [1]. While originally the Meatgrinder papers [2] received considerable skepticism, a series of elaborate analytical papers followed by several experiments [3] slowly brought acceptance. In the original Meatgrinder concept, the source and load inductances occupied the same space but whose fields were orthogonal and thus uncoupled. That geometry resembled a “meatgrinder” and hence the name. Briefly, the basic circuit has two uncoupled inductances – storage (L1) and load (L2). The initial state has L1==L2 so a current flowing through both has most of the energy residing in L1. L1 is composed of a series of inductances in series where all are mutually coupled to one another but not to L2 (Figure 1). A series of switching operations using both opening and closing of switches are used to progressively reduce the cumulative size of L1. This process is energy invariant if the number of steps approach infinity. But even a system with very few steps results in substantial energy transfer. Even a one-step meatgrinder can be more than 35% efficient in comparison to the canonical 25% maximum efficiency of the classic circuit. Many variations of the circuit have been conceived over the years. They include the Ringer [4], the Stretch Meatgrinder [5] and various application for energizing EM guns [6] and various electronic converter circuits [7] to name a few. Over the last few years, the original published derivation has been read and referenced hundreds of times. It is also interesting that the same idea was conceived independently by Prof. Rioux [9] of in the same time frame. His derivation took a different methodology but with the same result. This paper will discuss the various Meatgrinder based circuits various applications and the historical background.