Motor System with Opposing Stator Rotor Currents for Torque Control
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Solution Overview
Problem
Existing motor technologies face challenges in achieving high torque output with high power efficiency, particularly in electric vehicles, where they require larger torque at lower rotation speeds and higher-speed rotation with weakened field control, leading to increased size, cost, and efficiency losses due to armature reactions and conflicting magnetic flux control requirements.
Innovation Solution
A motor design with multiple-phase stator windings and rotor windings, where stator and rotor currents are oppositely directed to cancel out magnetomotive forces, reducing armature reactions and allowing for concentrated magnetic flux at the airgap, enabling higher torque output and precise field weakening control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If larger torque is generated at lower rotation speeds, then torque output is improved, but power factor decreases and motor size increases
Solution Approach 1:
The patent segments the motor system into two independent current control paths: stator current control for field magnetic flux generation and rotor current control for torque generation. This segmentation allows independent optimization of power factor (through stator field current) and torque output (through rotor current), resolving the contradiction between improving torque while maintaining power factor.
Solution Approach 2:
The patent inverts the conventional motor architecture by placing field windings on the stator and armature windings on the rotor, opposite to traditional DC motor design. This inversion enables the stator to generate the main field magnetic flux independently while the rotor provides torque current, allowing separate control of excitation and torque to resolve the power factor-torque contradiction.
2Force
If field magnetic fluxes are increased for larger torque, then torque output is improved, but motor size and production cost increase
Solution Approach 1:
The patent changes the operational parameters by enabling independent control of field current and torque current magnitudes. The field current can be optimized to produce sufficient magnetic flux density without excessive current, while torque current is separately controlled to match load requirements. This parameter independence allows achieving required torque with smaller, more efficient motor dimensions.
3Speed
If weakened field control is performed for higher-speed rotation, then high-speed performance is improved, but torque output decreases
Solution Approach 1:
The patent implements dynamic control where the field current magnitude can be adjusted in real-time based on operating conditions. During high-speed operation, the field current is reduced (weakened field control) to prevent excessive back-EMF and voltage requirements, while torque current is simultaneously adjusted to maintain required torque output. This dynamic adjustment of both field and torque currents resolves the speed-torque trade-off.
4Force
If armature reaction is generated during large torque generation, then torque current is improved, but field magnetic flux distribution becomes nonuniform
Solution Approach 1:
The patent extracts the field magnetic flux generation function from the torque generation function by placing field windings on the stator and armature windings on the rotor. This separation removes the armature reaction effect from the field flux distribution, as the rotor currents no longer directly affect the stator field magnetic flux. The field flux distribution remains uniform and stable while torque current can be freely controlled.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves higher torque density, improved power factor, and reduced motor size and weight, while maintaining efficient operation across varying speed and torque demands, enhancing performance and reducing manufacturing costs.
Implementation Method 1
a motor (1) and a control device (2) are provided. The motor (1) includes: multiple-phase stator windings (SW) arranged in a stator (11); rotor windings (RW) arranged in a rotor (12); stator current supplying means (MSC) for supplying a current (SIG) to the stator windings (SW); rotor current supplying means (MRC) for supplying a current (RIG) to the rotor windings (RW); and current control means (MCC) for controlling the current (SIG) to the stator windings (SW) and the current (RIG) to the rotor windings (RW).
Implementation Method 2
The motor (1) and the control device (2) are characterized in that a flowing direction of the current (SIG) and a flowing direction of the current (RIG) are relatively, in part or all of the current, opposite to each other.
Data Source
AI summary
A motor is provided with stator windings arranged on a circumference of stator. Multiple-phase currents are supplied to the stator windings. A current is supplied to rotor windings. The multiple-phase currents include torque current components, which are arranged to be opposite in directions to torque current components of the current. By this mutually opposite-directional current arrangement, a sum of both torque current components results in a magnetomotive force of zero. It is also possible to reduce influence of the torque current components on the field magnetic fluxes of the motor. In the motor, circumferential magnetic flux components can be concentrated on an airgap and a portion near therearound, so that a larger amount of torque can be obtained, and constant output control can be performed more easily.