Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
2000-07-17
2002-07-30
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S807000, C318S448000
Reexamination Certificate
active
06426605
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates generally to the field of motor drive systems and more specifically to a multi-phase induction motor drive system and method.
BACKGROUND OF THE INVENTION
The need for efficient motors has led to the demand for improved multi-phase induction motor drive systems and methods. Engineers are faced with the problem of designing motors that yield greater power and torque density. For example, motors powered by inverters often do not achieve high power output. Inverters impress rectangular voltage or current output on motors that are typically designed to receive sinusoidal input, thus reducing the power capabilities of the motors. Additionally, motors designed to receive sinusoidal input typically produce low torque output. Accordingly, designing motors that yield greater power and torque density has posed a challenge for engineers.
SUMMARY OF THE INVENTION
While known approaches have provided improvements over prior approaches, the challenges in the field of drive systems have continued to increase with demands for more and better techniques having greater effectiveness. Therefore, a need has arisen for a multi-phase induction motor drive system and method.
In accordance with the present invention, a multi-phase induction motor drive system and method are provided that substantially eliminate or reduce the disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the present invention, a multi-phase induction motor drive system is disclosed. The system comprises a motor having at least five phases and comprising a stator and a rotor. For each phase, the motor receives a command current to power the motor, where the command current has a fundamental frequency. A processor determines, for each phase, at least one harmonic component of a signal indicative of the fundamental frequency, generates a command current from the harmonic component and the fundamental frequency, and supplies the command current to the stator.
According to another embodiment of the present invention, a method for operating a multi-phase induction motor drive system is disclosed. A first command current is supplied to a motor having at least five phases, where the first command current powers the motor. The first command current has a fundamental frequency, and the motor comprises a stator and a rotor. For each phase, at least one harmonic component of a signal indicative of the fundamental frequency is determined. A second command current is generated from the harmonic component and the fundamental frequency. The second command current is supplied to the stator.
Embodiments of the invention may provide numerous technical advantages. For example, a technical advantage of one embodiment is that the power density of a motor may be improved by enhancing the motor's ability to utilize rectangular current input. Another technical advantage of one embodiment is that a combination of harmonic components of a fundamental frequency may be used to increase torque density. Another technical advantage of one embodiment is that a multi-phase motor may be able to operate under loss of one or more phases, increasing the reliability of the motor. Another technical advantage of one embodiment is that the flux of the multi-phase motor may be more evenly distributed than that of known motors, thus decreasing the torque pulsation and lowering acoustic noise in the motor.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.
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Shi Ruhe
Toliyat Hamid A.
Xu Huangsheng
Baker & Botts L.L.P.
Ro Bentsu
The Texas A&M University System
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