System for supression of underdamped oscillations in ac power drawn by synchronous motors driving Ward-Leonard generators
AssigneeThe Broken Hill Proprietary Company Limited
InventorsNoel R. Godfrey, Larry S. Parkes, Richard H. Treacy
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Abstract
A method and apparatus for reducing oscillations in input electrical power to a Ward-Leonard drive system which is subject to variations in mechanical loading, the technique utilizing a notch filter in the feedback path to the dc generator, the notch filter being turned to match the resonant frequency of the synchronous motor.
Claims10
A method of reducing the amplitude of oscillations in input electrical power to a drive system, the system including a synchronous motor the output shaft of which is coupled to drive a dc generator which is in turn coupled electrically to a dc motor, the output shaft of which is coupled to a mechanical load, said generator including a generator field exciter, said method including the steps of generating a control signal for controlling said generator field exciter, at least one component of the control signal having been derived from the dc motor and related to its instantaneous power and is passed through a notch filter the frequency response of which generally provides reciprocal compensation for the frequency response of the ratio of input electrical power to the synchronous motor to the mechanical power on its output shaft, and applying the control signal to said exciter to thereby reduce oscillations in input electrical power to the synchronous motor.
An electric drive system comprising a synchronous motor for coupling to an ac mains supply, a dc generator coupled to be driven by the output shaft of the synchronous motor and including a field exciter, a dc motor coupled to be electrically driven by the dc generator, the output shaft of the dc motor being coupled in use to a mechanical load, said drive system including control means for controlling power output on said output shaft, said control means including a control circuit for controlling the field exciter of the dc generator, a notch filter the frequency response of which generally provides reciprocal compensation for the frequency response of the ratio of input electrical power to the synchronous motor to the mechanical power on its output shaft, said circuit including means for generating at least one control siganl related to the instantaneous power of the dc motor, said control signal being coupled to the notch filter and the output thereof being coupled to control the field exciter of the dc generator.
Dependencies are inferred from the claim text.