Variable Magnet Orientation in Permanent Magnet Electric Machines
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Solution Overview
Problem
Permanent magnet-type electric machines experience high losses at high motor speeds and low torque due to excess magnetic flux, leading to inefficiencies in motor performance.
Innovation Solution
The magnetic north-south pole orientations of permanent magnets are actively or passively adjusted to modify the magnetic flux between the rotor and stator, using an actuator to rotate rotatable magnets and optional flux-shunting elements, thereby reducing magnetic flux linkage and flux-related losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are used in a PM machine to generate torque, then torque generation efficiency is improved under low-speed/high-torque conditions, but flux-related losses increase at high-speed/low-torque operating points
Solution Approach 1:
The patent applies the dynamics principle by making the magnetic pole orientations adjustable rather than fixed. Rotatable magnets are incorporated into the rotor structure, allowing the magnetic field configuration to dynamically adapt to different operating conditions. At low-speed/high-torque conditions, the magnets maintain optimal orientation for torque generation, while at high-speed/low-torque conditions, the magnets can be repositioned to reduce magnetic flux and minimize associated losses, thus resolving the contradiction between torque efficiency and energy losses.
Solution Approach 2:
The patent implements parameter changes by varying the magnetic pole orientations through rotation of the magnets. By changing the angular position of the magnets relative to the stator, the magnetic flux density and distribution can be adjusted. This parameter change allows the system to optimize performance across different operating points, reducing flux-related losses at high speeds while maintaining effective torque generation at low speeds.
2Loss of energy
If magnetic pole orientations are adjusted to reduce flux-related losses, then energy efficiency is improved at high-speed operating points, but device complexity increases due to additional actuators and control mechanisms
Solution Approach 1:
The patent applies segmentation by dividing the rotor into modular components, specifically separating fixed magnets from rotatable magnets. This segmentation allows independent control of different magnet groups, enabling flux reduction in specific regions without requiring complete reconfiguration of the entire magnetic system. The actuator system is also segmented, with individual actuators controlling specific magnet groups, which simplifies the overall control architecture and reduces complexity.
Solution Approach 2:
The patent implements self-service through passive flux-shunting elements that automatically redirect magnetic flux paths without requiring active control. These elements utilize the inherent magnetic properties of materials to shunt excess flux away from the stator windings at high speeds, reducing flux-related losses passively. This self-service mechanism complements the active actuator system, reducing the control burden and overall system complexity.
3Adaptability or versatility
If rotatable magnets are introduced to modify magnetic flux paths, then flux control capability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent applies merging by integrating the rotatable magnets directly into the rotor structure, combining multiple functions into unified components. The rotatable magnets serve both as torque-generating elements and as adjustable flux control elements. Additionally, flux-shunting elements are merged with the rotor structure, eliminating the need for separate components and simplifying manufacturing. This integration approach maintains enhanced flux control capability while reducing manufacturing complexity and cost.
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 solution enhances the efficiency of the electric machine by reducing flux-related losses at high-speed/low-torque operating points without compromising structural integrity or packaging, improving motor performance across a wide range of operating conditions.
Implementation Method 1
The rotating electromagnetic field in turn interacts with the permanent magnetic fields of the rotor. Such field interaction occurs in a magnetic circuit in which magnetic flux paths extend across a small air gap from the rotor into the stator. Motor torque from the PM machine is thus generated by the interaction of the rotor's magnetic field, which is created by the magnets, with the stator's magnetic field
Implementation Method 2
Rotation occurs through an angular distance that is sufficient for changing the north-south magnetic pole orientations of the rotatable magnets to a desired extent. The reluctance, and thus the magnetic flux paths between the rotor and the stator, is modified in this manner, i.e., by modifying a level of magnetic flux linkage with stator windings across the air gap
Data Source
AI summary
A permanent magnet electric machine (PM machine) includes a rotor with rotatable magnets and a stator defining an air gap with the rotor. An actuator rotates the rotatable magnets at predetermined operating points through an angular distance sufficient for changing magnetic pole orientations of the rotatable magnets, and thus modifies magnetic flux linkage with stator windings across the air gap. Fixed magnets may be arranged around a circumference of the rotor. The actuator may be actively or passively driven. Flux-shunting elements are optionally disposed in the rotor to further modify the flux linkage. A gear set connected to torque transfer elements may be driven by the actuator to rotate the rotatable magnets. A vehicle includes drive wheels, a transmission, and the PM machine. A method controls magnetic flux linkage in the PM machine noted above.