Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
1998-09-29
2001-09-11
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S289000, C318S280000
Reexamination Certificate
active
06288517
ABSTRACT:
TECHNICAL FIELD
The present invention relates to motor control systems having multiphase sinusoidal AC signals. Motor control is provided for stepper motors, brushless DC-motors or three-phase induction motors such as those used in electrical vehicles. Other applications for the present invention include DC to AC power converters.
BACKGROUND OF THE INVENTION
Multiphase sinewave generators constructed using methods of prior art which require computer software and look-up tables to generate the required signals to drive multiphase systems are prone to system malfunctions. Software-based systems require a microprocessor, memory and interface logic, and have a start-up delay. Current technology limits current software-based systems to about 30 khz.
Multiphase sinewave generators constructed using methods of prior art which require capacitors and inductors cannot be fully integrated within a single LSI chip which unnecessarily limits reduction of the physical size of the required circuit. Capacitors and inductors limit the attainable circuit speed and at speeds approaching zero are unable to maintain the correct phase relationships.
Multiphase generators that produce triangular-shaped waveforms are easier to produce in hardware but have undesired harmonics.
SUMMARY OF THE INVENTION
Circuits constructed using methods of the present invention provide multiple-phase sinusoidal output signals which can be used to drive either two, three or five-phase stepper motors, brushless DC motors or three-phase induction motors such as those used in electrical vehicles. Other applications for the present invention include DC to AC power converters. Methods and apparatus described herein include a flexible basic design and variations. One embodiment provides for motor speed stabilization through precise motor speed control utilizing feedback. Another embodiment provides for manual control of motor speed and rotation direction. Methods taught herein provide for systems that control, to a high degree of precision, the degrees of a turn of a motor and provide for low harmonic distortion which prevents noise and oscillation in motors and power transformers. Methods are described for changing the circuit parameters to adjust the level and frequency of harmonic distortion of the sinusoidal output signals to meet the requirements of a range of applications.
The preferred embodiment of the present invention utilizes a synchronous-digital state machine to generate a plurality of analog signals having phase-shifted waveforms. A resistive-ring network shapes the waveforms to generate a plurality of phase-shifted differential signals, each having a waveform that approximates the shape of a sinusoid waveform. Instrumentation amplifiers amplify selected differential signals to provide a multiphase set of sinusoidal signals.
The teachings of the present invention provide for different specific embodiments which provide advantages not found in prior art such as: (1) enabling increased integration resulting in substantial reduction in physical circuit size greatly facilitating new applications such as applications involving nano-motors or micro-miniature motors, (2) elimination of capacitors and inductors to allow the circuit to be fully integrated within a LSI chip and to allow for higher output frequencies, (3) elimination of a computer memory and software resulting in substantial increase in the life of the circuit, increases the reliability of operation, lowers system cost, and allows reduction in the physical size of the generator.
REFERENCES:
patent: 3641566 (1972-02-01), Konrad et al.
patent: 4059789 (1977-11-01), Cocksedge
patent: 4377779 (1983-03-01), Plunkett
patent: 4405895 (1983-09-01), Gerst et al.
patent: 4459580 (1984-07-01), Furukawa
patent: 4862343 (1989-08-01), Nomura et al.
patent: 5283726 (1994-02-01), Wilkerson
Hollmann Joerg
Parker David C.
Lenzen, Jr. Glenn H.
Leykin Rita
Nappi Robert E.
Raytheon Company
Schubert William C.
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