Wound-Rotor Motor Pole Shoe Curvature for Torque Ripple Reduction
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Solution Overview
Problem
In belt-driven starter generators, the spatial limitations and current constraints limit the increase in torque, and the application of ideal curves to rotors results in increased air gap and decreased counter electromotive force, hindering motor performance.
Innovation Solution
A rotor design for wound-rotor motors featuring a rotor core with a hollow central portion, radially formed teeth, and arc-shaped pole shoes with specific imaginary circles and rotation angles, which optimize the winding regions and air gaps to maintain counter electromotive force while reducing total harmonic distortion and torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the number of coil windings or current is increased to increase torque, then torque is improved, but spatial limitations and current constraints prevent further increase
Solution Approach 1:
The patent changes the geometric parameters of the pole shoe outer side surface by defining it with multiple imaginary circles (first, second, and third imaginary circles) instead of conventional simple arc shapes. This parameter optimization allows for improved magnetic flux distribution and torque characteristics without increasing the overall motor volume, resolving the contradiction between torque enhancement and spatial constraints
2Device complexity
If an ideal curve such as inverse cosine is applied to the rotor, then the rotor structure is simplified, but the air gap increases exponentially and the magnitude of counter electromotive force decreases
Solution Approach 1:
The patent applies curved imaginary circles to define the pole shoe outer side surface, optimizing the air gap distribution through carefully selected radii (R1, R2, R3) and center positions. This curvature optimization maintains a relatively uniform air gap that prevents exponential increase while preserving the magnitude of counter electromotive force, avoiding the drawbacks of ideal curve applications
3Power
If the pole shoe outer side surface is optimized to reduce air gap, then counter electromotive force is maintained, but total harmonic distortion increases
Solution Approach 1:
The patent optimizes multiple geometric parameters simultaneously including the radii (R1, R2, R3) of the three imaginary circles, their center positions, and the arc angle ranges. This multi-parameter optimization achieves a balanced design that maintains counter electromotive force magnitude while minimizing total harmonic distortion through improved magnetic flux distribution
4Ease of manufacture
If conventional rotor designs are used, then manufacturing is simpler, but torque ripple is higher and motor performance is limited
Solution Approach 1:
The patent defines the pole shoe outer side surface using three imaginary circles with specific radii and center positions, creating an optimized curved profile that reduces torque ripple through improved magnetic flux distribution. The arc segments are defined by specific rotation angles, providing a manufacturable curved geometry that outperforms conventional straight or simple arc designs
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
The design enhances torque output, reduces torque ripple, and maintains a low total harmonic distortion, preventing an increase in motor size while sustaining counter electromotive force, thereby improving motor performance.
Implementation Method 1
a rotor for a wound-rotor motor including: a rotor core including a hollow formed in a central portion thereof and coupled to a shaft; a teeth portion radially formed on an outer side surface of the rotor; and a pole shoe formed to extend from an end portion of the teeth portion
Data Source
AI summary
Disclosed herein is a rotor for a wound-rotor motor. The rotor for a wound-rotor motor includes: a rotor core including a hollow formed in a central portion thereof and coupled to a shaft; a teeth portion radially formed on an outer side surface of the rotor; and a pole shoe formed to extend from an end portion of the teeth portion in one direction and including a part of a cross section of an outer side surface formed in an arc shape of a first imaginary circle (C1) having a first radius (r1) which is a distance from a central point (CP1) of the hollow to an outermost position (P1) thereof.