Current-impulse-displacement thyristor commutation with controlled trapped energy

The paper considers the fundamental operating principles of a number of current impulse displacement commutation techniques used in thyristor DC choppers and inverters. In each case the optimum commutation pulse is considered and the conditions for unpredictable and undesirable operation due to trapped-energy `runaway¿ are analytically specified. A simple solution exists, preventing undesired operation, whereby the trapped energy is not fed back into the supply or dissipated in resistors. The energy is safely retained and used to optimise LC commutation-circuit values. The resultant commutation circuit has a higher current commutating ability for given LC values and can result in circuits with lower losses and shorter commutation cycle times than those circuits of conventional design.