Abstract: In a direct AC/AC converter, fault protection is performed with a minimal number of fault detecting devices and the rating of such fault detecting devices is reduced while still being able to respond quickly to a fault current. This is achieved by using a current sensor in common to at least all the current lines of one group of switches and by combining the operation of such common current sensor with the operation of one current sensor associated with the related output phase line. In another embodiment, all the current lines connected to a switch, for all the groups of switches, are passed through a common and single current sensor.

Abstract: A three-phase matrix converter including switches having snubber circuits associated thereto, is provided with a common voltage clamp capacitor for limiting the voltage applied to the snubber capacitor, and energy is accumulated in the clamp capacitor which is controllably dissipated, in particular by providing energy to auxiliary elements of the overall system.

Abstract: The N converters of a UFC bridge system interconnecting an N-phase voltage source to N output loads, comprise each N bilateral switches connected to one end of the associated output load and (N-1) bilateral switches connected to the other end thereof. The (N-1) bilateral switches of the respective converters build up a polygonal assembly between the output loads which is selectively connected to the respective phases of the voltage source by selective control of the N groups of N switches and of the (N-1) groups of switches.