Abstract: A rotating electrical machine such as a generator has a rotor disposed within a rotor housing and an air flow path passing from the rotor housing to and through a silencer to an exhaust. The silencer comprises at least one air flow path disposed adjacent at least one sound absorbing column, the column comprising a first portion having a first sound absorbing material therein and a second portion having a microperforated panel (MPP) and a resonator cavity. The second portion comprises a reactive sound absorbing unit which can be specifically tuned to suppress aero-acoustic noise generated by ventilation slots in the rotor, typically peaks at 100 Hz or 120 Hz.

Abstract: A rotating electrical machine such as a generator has a rotor disposed within a rotor housing and an air flow path passing from the rotor housing to and through a silencer to an exhaust. The silencer comprises at least one air flow path disposed adjacent at least one sound absorbing column, the column comprising a first portion having a first sound absorbing material therein and a second portion having a microperforated panel (MPP) and a resonator cavity. The second portion comprises a reactive sound absorbing unit which can be specifically tuned to suppress aero-acoustic noise generated by ventilation slots in the rotor, typically peaks at 100 Hz or 120 Hz.

Abstract: Testing an engine having a rotary power output shaft by mechanically-coupling the output shaft of the engine to the rotor of a rotary electrical machine, operable alternatively in motor and generator modes, by connecting output/input conductors of the machine to conductors of an electrical supply main from which electrical power will be taken by the machine, when the machine is operating in the motor mode, and to which electrical power will be supplied by the machine, when the machine is operating in the generator mode, the electrical connections between the machine conductors and the supply main conductors being effected by a power converter including power-carrying devices of a semi-conductor type, e.g.