Electricity: motive power systems – Positional servo systems – Frequency- or phase-modulated systems
Patent
1995-06-30
1997-09-16
Masih, Karen
Electricity: motive power systems
Positional servo systems
Frequency- or phase-modulated systems
318798815-, 60325, 388929, G05B 102
Patent
active
056684576
ABSTRACT:
A hydraulic pump (16) is driven by an induction motor (14) from a source of multiphase alternating current (10) of either fixed or variable frequency. The pressure is applied to a hydraulic load, which may vary, and change the pressure. A pressure sensor coupled to the pump produces pressure signals. The motor includes plural windings, typically three, associated with a number of poles. Each motor winding is driven by a different phase of controlled alternating current. A rectifier (46) coupled to the multiphase AC source generates direct current, which is filtered to minimize DC ripple voltage. A controllable multiphase inverter (54) is coupled to the rectifier and to the motor windings, for converting the direct voltage into multiphase alternating motor drive voltages of controllable amplitude and frequency. An error signal generator (322) is coupled to the pressure sensor and to sources of signals representing reference pressures (310) and motor speeds (320), for generating a pressure-modified speed error signal. An inverter gate driver (66, FIG. 2) is coupled to the motor speed signal generator and to the inverter, for converting the motor speed signal into alternating drive signals for the windings of the motor. The drive signals have a fundamental frequency equal to the desired motor speed multiplied by one-half the number of the poles of the motor, and an amplitude which is normalized by the ratio of the fundamental frequency to a reference frequency. The alternating drive signals at the fundamental frequency include a component at the third harmonic of the fundamental frequency.
REFERENCES:
patent: 3753064 (1973-08-01), Agarwal et al.
patent: 3789355 (1974-01-01), Patton
patent: 5092824 (1992-03-01), Connett
patent: 5131507 (1992-07-01), Watanaabe
patent: 5436547 (1995-07-01), Nagai et al.
Checkovich P. J.
Martin Marietta Corporation
Masih Karen
Meise W. H.
Young S. A.
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