Means for stabilizing an a-c electric motor drive system
First Claim
1. An improved stabilizing scheme for an a-c electric motor comprising a stator and a rotor and provided with a source of excitation comprising electric power conversion apparatus that supplies a-c power of variable frequency to said stator, said motor being capable of developing electromagnetic force tending to move the rotor relative to the stator due to the interaction of current and flux in the motor when excited, wherein the improvement comprises:
- a. first means coupled to said motor for deriving an angle feedback signal representative of the actual phase angle between said interacting current and flux in the motor when excited; and
b. second means responsive to said angle feedback signal for controlling the motor excitation as a function of said angle feedback signal.
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Abstract
For use with an adjustable speed a-c electric motor having a stator adapted to be coupled to a source of variable frequency excitation and a rotor in which torque is developed when the motor is excited, the strength of said torque being dependent on interacting current and flux in the motor, a scheme is provided that comprises means for deriving an angle feedback signal representative of the actual phase angle between the aforesaid current and flux and means responsive to said angle feedback signal for controlling the source of variable frequency excitation so as to control the frequency of stator excitation as a function of the angle feedback signal.
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Citations
29 Claims
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1. An improved stabilizing scheme for an a-c electric motor comprising a stator and a rotor and provided with a source of excitation comprising electric power conversion apparatus that supplies a-c power of variable frequency to said stator, said motor being capable of developing electromagnetic force tending to move the rotor relative to the stator due to the interaction of current and flux in the motor when excited, wherein the improvement comprises:
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a. first means coupled to said motor for deriving an angle feedback signal representative of the actual phase angle between said interacting current and flux in the motor when excited; and b. second means responsive to said angle feedback signal for controlling the motor excitation as a function of said angle feedback signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. An improved method of stabilizing an a-c electric motor having a stator adapted to be coupled to a source of variable frequency excitation and a rotor in which torque is developed when the motor is excited, the magnitude and relative direction of said torque being dependent on interacting current and flux in the motor, wherein the improvement comprises the steps of:
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a. deriving an angle feedback signal representative of the actual phase angle between said interacting current and flux in the motor when excited; and b. controlling the motor excitation as a function of said angle feedback signal. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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Specification