| 摘要 |
A gas turbine engine for aircraft propulsion includes a variable pitch fan, pitch change of which is effected by providing a small D.C. excitation current to a selected one of two non-rotating field coils dependent upon the direction of pitch change desired. The field coils each form the static part of respective polyphase A.C. alternators, and the rotating armatures of the alternators connect to respective separate stator windings of a compound polyphase A.C. reversible induction motor rotating with the fan. An armature of the motor is relatively rotatable and couples with the fan blades to pivotally vary their pitch angle. An A.C. current is available from the non-excited alternator field coil, and may be rectified and controlled for use as the D.C. excitation current. Thus, all energy requirements of the pitch change apparatus may be extracted from the rotor of the fan engine.
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