Variable-speed drive for control of induction generators
First Claim
1. A power generating system comprising:
- an induction machine including an induction rotor and a stator;
mechanical drive means connected to said induction motor for driving said induction machine at a variable speed;
a synchronous excitation generator coupled mechanically with said induction machine by means of a variable-speed drive, whereby said synchronous excitation generator will provide a variable output voltage and frequency;
means for applying said variable output voltage and frequency to said stator of said induction machine; and
drive-logic control means for monitoring the speed and load data of said induction machine and for adjusting and maintaining the speed of said synchronous excitation generator so as to control the negative slip-frequency of said induction machine whereby said induction machine may operate in a generating mode with its output controlled in response to said speed and load data.
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Accused Products
Abstract
The invention is an aircraft power generation system which utilizes an induction-machine (G1) as a primary generator of variable-voltage/variable-frequency power. The induction-machine (G1) is directly driven by the engine (14) and is excited by an excitation-generator (G2) such that the induction-machine (G1) operates in a generating mode. A variable-speed drive (20), shown as a toroidal drive (30), controls the excitation frequency of the induction-machine (G1) such that the negative slip-frequency is controlled as a function of the input speeds (N1), (N2) and the electric load on the generator. Control of the toroidal drive (30) and thus speed (N2) is accomplished by a negative-slip control circuit which includes a drive control logic circuit (36), a proportional actuator (34), a control-start panel (48), and a steering mechanism (32).
In another aspect of the invention, the induction-machine (G1) operates in a start-mode to start the engine (14). In this mode of operation, after engine starting is initiated from control-start panel (48), a start-logic circuit (52) establishes a programmed voltage/frequency output from a start-power electronics source (46). The voltage/frequency output, programmed from a low value, against time, up to a predetermined high value is applied to the induction-machine (G1) field to bring the engine (14) up to speed.
53 Citations
20 Claims
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1. A power generating system comprising:
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an induction machine including an induction rotor and a stator; mechanical drive means connected to said induction motor for driving said induction machine at a variable speed; a synchronous excitation generator coupled mechanically with said induction machine by means of a variable-speed drive, whereby said synchronous excitation generator will provide a variable output voltage and frequency; means for applying said variable output voltage and frequency to said stator of said induction machine; and drive-logic control means for monitoring the speed and load data of said induction machine and for adjusting and maintaining the speed of said synchronous excitation generator so as to control the negative slip-frequency of said induction machine whereby said induction machine may operate in a generating mode with its output controlled in response to said speed and load data. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A power generation system for providing a source of variable-frequency/variable-voltage power comprising in combination:
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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 variable first 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 variable first rotational relationship; an induction generator having an induction rotor mechanically coupled to said drive shaft to rotate therewith in a fixed second 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 fixed 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 variable frequency and power characteristics in accordance with both said variable rotational speed of said drive shaft and said variable first rotational relationship. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification