Variable frequency induction generator

An aircraft electric power system comprising:

• an aircraft engine;
• an induction machine, said induction machine including an induction rotor mounted on a first shaft;
• a synchronous permanent magnet generator electrically attached to said induction machine for exciting said induction machine and causing it to operate in a generating mode, said permanent magnet generator comprising a tandem synchronous generator including first and second synchronous permanent magnet generators, each said first and second synchronous permanent magnet generators having a permanent magnet rotor mounted on a second shaft;
• and
• mechanical drive means driven by said engine, said drive means including first and second gear elements secured to said first and second shafts, respectively, whereby said induction machine rotor is driven at a greater speed relative to said permanent magnet generator rotors and said induction machine is driven above its synchronous speed.

A power generation system for providing a variable-frequency/variable-voltage power comprising in combination:

• a drive shaft adapted to be rotated at a variable speed by a source of mechanical power;
• a synchronous generator having a synchronous rotor mechanically coupled to said drive shaft so as to rotate therewith in a first predetermined rotational relationship and also having a synchronous stator connected to a first set of electrical terminals, the output of said synchronous generator at said first set of terminals having a variable frequency characteristic in accordance with said variable speed of said drive shaft and said first rotational relationship;
• an induction generator having an induction rotor mechanically coupled to said drive shaft to rotate therewith in a second predetermined rotational relationship and also having an induction stator connected to a second set of electrical terminals, the output of said induction generator having a variable voltage characteristic in accordance with said variable speed of said drive shaft and said second rotational relationship, a frequency characteristic determined by the frequency characteristic of an excitation input applied to said second set of terminals, and a power characteristic determined by the percentage difference between said excitation input frequency characteristic and a synchronous frequency, said synchronous frequency being directly related to the rotational speed of said induction rotor;
• and
• means for effecting respective direct electrical connections between respective ones of said first and second sets of terminals so that said output of said synchronous generator will serve as said excitation input for said induction generator and the output of said induction generator will thereby have a variable frequency characteristic in accordance with said variable rotational speed of said drive shaft and said first rotational relationship.