Synchronous machines with contrarotating armatures: steady-state behaviour

A synchronous machine can be constructed with two armatures and one field. If the armatures contrarotate, the armature-reaction flux in the quadrature axis, ideally, is eliminated. The machine therefore operates with a high saliency ratio. The voltage regulation for a unity power-factor load is then only affected by winding resistance and leakage reactance. This unique feature allows the machine to have a peak power capability several times that of conventional machines of the same size. Two contrarotating machines have been designed and tested. One of the arrangements has steady-state behaviour approaching the expected ideal behaviour. The test machine built has three rotatable machine elements which allows the examination of a number of operating modes.