Cascaded harmonic synchronous machine

In a number of applications of generating and motoring, a low shaft speed is required. The usual way of providing this low speed is either through large diameter multipole machines or through high-speed machines in conjunction with a gearbox. A novel machine has been designed which can interface the mains to a low-speed shaft without the necessity for a large number of poles. The principle of operation is based on a stationary DC magnetic field, a short-circuited rotor winding and a stator winding connected to the supply through a set of filters. The rotation of the rotor causes circulation of harmonic currents in the stator. The filters are designed to allow these circulations, but to divert the 50 Hz current into the mains. This effect provides a speed gearing, the level of which depends on the number of harmonies permitted to circulate. The principle can be applied to a single or 3-phase design. The operational characteristics are those of a synchronous machine possessing a distinct number of synchronous speeds