Abstract: An alternating current power electronic converter includes an alternating current chopper circuit including two pairs of switches, each switch of a pair connected in series and the two pairs of switches connected in parallel. Each switch of a pair is a uni-directional switch. The uni-directional switches of each pair are arranged in opposing directions, and the uni-directional switches of one pair of switches are arranged in an opposing configuration to the uni-directional switches of the other pair of switches. The circuit comprises a bridge connection between switches of each pair of switches. A controller is configured to control a sequence of operation of the switches, providing an overlap period whenever one of the switches of a pair changes from open to closed and the other switch of the pair changes from closed to open. During the overlap period the switch that is moving from closed to open remains closed.

Abstract: An alternating current power electronic converter includes an alternating current chopper circuit including two pairs of switches, each switch of a pair connected in series and the two pairs of switches connected in parallel. Each switch of a pair is a uni-directional switch. The uni-directional switches of each pair are arranged in opposing directions, and the uni-directional switches of one pair of switches are arranged in an opposing configuration to the uni-directional switches of the other pair of switches. The circuit comprises a bridge connection between switches of each pair of switches. A controller is configured to control a sequence of operation of the switches, providing an overlap period whenever one of the switches of a pair changes from open to closed and the other switch of the pair changes from closed to open. During the overlap period the switch that is moving from closed to open remains closed.

Abstract: An apparatus for inspecting an article includes a laser assembly which is operable to direct a laser beam against a series of locations disposed along a line which extends across discontinuities in a surface of the article. The position of at least of one location against which the laser beam is directed is detected. The at least one location is spaced from discontinuities in the surface of the article.

Abstract: An apparatus for inspecting an article includes a laser assembly which is operable to direct a laser beam against a series of locations disposed along a line which extends across discontinuities in a surface of the article. The position of at least of one location against which the laser beam is directed is detected. The at least one location is spaced from discontinuities in the surface of the article.

Abstract: A synchronous electrical machine having a plurality of phases, a detecting unit arranged to detect a fault in at least one of the phases of the synchronous electrical machine, an isolating unit arranged to isolate the at least one phase of the synchronous electrical machine with the fault, a phase shift unit arranged to produce a controlled phase shift between the voltage and the current within the remaining phases of the synchronous electrical machine to adjust the phase angle and magnitude of the second harmonic powers produced by the remaining phases of the synchronous electrical machine such that the vector sum of the second harmonic power vectors of the remaining phases of the synchronous electrical machine is zero.

Abstract: A synchronous electrical machine comprising a plurality of phases, detecting means arranged to detect a fault in at least one of the phases of the synchronous electrical machine, isolating means arranged to isolate the at least one phase of the synchronous electrical machine with the fault, phase shift means arranged to produce a controlled phase shift between the voltage and the current within the remaining phases of the synchronous electrical machine to adjust the phase angle and magnitude of the second harmonic powers produced by the remaining phases of the synchronous electrical machine such that the vector sum of the second harmonic power vectors of the remaining phases of the synchronous electrical machine is zero.