Performance study of inductive output cryotronic converters

A matrix method of electric circuit analysis was used for the theoretical performance study of a converter based on both a fullwave rectifier and a cyclic superconducting transformer with two cryotrons. The solution for the loop current matrix allows to calculate the transient commutation process in any cryotronic converter under any shape of supply voltage. Expressions are given for the converter maximum current under load conditions. The experimental study of the commutation processes was conducted on the model of a cyclic-superconducting-transformer-based cryotronic converter at the working current of 800 A in the secondary coil ratio of the primary and secondary 800:1, of the superconducting transformer without a ferromagnetic core. In the cylindrical cryotrons the switching element is made of a bifilaly wound Pb-3.8% Sb tape and is placed between the control winding and the superconducting shield. In resistive state the valve resistance is 5.5 × 10^-3Ω at 4.2 K. A superconducting solenoid consisting of four disk coils connected in parallel served as the converter load, its inductance being 0.15 × 10^-3H. The measurements of currents in the secondary circuits and voltage drops on the cryotron valves were made by Hall probes and potential probes, respectively. The commutation processes were studied in conditions of pumping the current into inductive load and energy recuperation accumulated in the load through the superconducting transformer into its primary. The paper offers current oscillograms for the windings of control and voltage drops on the valves of both cryotrons, and also oscillograms for the transformer´s primary and secondary and the load.