Variable Flux Bridge for Electric Machine Rotor
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Solution Overview
Problem
Electric machines in electrified vehicles face inefficiencies due to constant permanent magnet rotor fields, which optimize for either high or low torque conditions but not both, leading to high stator core losses and limited torque range.
Innovation Solution
Incorporating a rotor with a channel between magnets and a bridge assembly biased by a spring, allowing the bridge to translate between positions, altering the magnetic flux pattern based on rotational speed to optimize torque output across varying drive cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant permanent magnet rotor field is used, then the electric machine can operate reliably, but stator core losses increase and torque range is limited
Solution Approach 1:
The patent applies the dynamics principle by making the magnetic flux pattern variable rather than constant. A bridge element is introduced that can move between positions to alter the magnetic flux paths in the rotor. This dynamic adjustment allows the magnetic flux to be modulated based on operating conditions, enabling the system to reduce stator core losses while maintaining reliability across different torque demands.
Solution Approach 2:
The patent implements parameter changes by modifying the magnetic flux density distribution in the rotor. By moving the bridge element between different positions, the magnetic flux paths and their densities are changed. This allows optimization of the magnetic field parameters to reduce eddy current losses in the stator core while maintaining sufficient torque output, directly addressing the contradiction between reliability and energy losses.
2Device complexity
If a constant permanent magnet rotor field is used, then the magnetic field structure is simple, but torque output is limited to specific conditions
Solution Approach 1:
The dynamics principle is applied by introducing a movable bridge element that can dynamically adjust the magnetic flux paths. This adds controlled complexity to the magnetic field structure, enabling the system to adapt torque output to different operating conditions while maintaining a relatively simple overall rotor design. The bridge element's movement provides variable torque capability without requiring multiple magnet sets or complex control systems.
3Speed
If the bridge element moves radially away from the center, then magnetic flux pattern is optimized for high speed, but spring force increases
Solution Approach 1:
The preliminary action principle is applied through the spring element that is pre-biased to exert a centripetal force on the bridge element. This preliminary spring force positions the bridge element appropriately at different rotational speeds, enabling the magnetic flux pattern to be optimized for high-speed operation when the bridge moves radially outward. The spring's pre-established force field facilitates the speed optimization while managing the force requirements.
4Power
If magnets are positioned to optimize high torque, then high torque output is achieved, but efficiency at low torque conditions deteriorates
Solution Approach 1:
The parameter changes principle is applied by using the movable bridge element to dynamically alter the magnetic flux density distribution in the rotor. When high torque is required, the bridge position allows for stronger flux density; when low torque is needed, the bridge position adjusts to reduce flux density accordingly. This dynamic parameter adjustment optimizes the balance between torque output and stator core losses across different operating conditions, preventing excessive losses at low torque while maintaining high torque capability.
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 enables variable rotor flux, enhancing torque output and reducing stator core losses by adjusting magnetic flux paths, thus improving the electric machine's efficiency across high and low torque demands.
Implementation Method 1
a spring arranged to bias the bridge element toward a center of the rotor
Implementation Method 2
a spring arranged to bias the bridge element toward a center of the rotor such that the bridge element is disposed a first distance from the center of the rotor when the rotor is rotated at a first speed, and is disposed a second distance from the center of the rotor greater than the first distance when the rotor is rotated at a second speed greater than the first speed
Implementation Method 3
a rotor including a channel defined between a pair of magnets
Implementation Method 4
a bridge assembly disposed within the channel. The bridge assembly may include a bridge element and a spring arranged to bias the bridge element toward a center of the rotor such that the bridge element moves radially away from the center against a force of the spring to alter a magnetic flux pattern associated with the magnets
Data Source
AI summary
An electric machine includes a rotor including a channel defined between a pair of magnets and a bridge assembly within the channel. The bridge assembly includes a bridge element and a spring arranged to bias the bridge element toward a center of the rotor such that responsive to spinning of the rotor, the bridge element moves radially away from the center against a force of the spring to alter a magnetic flux pattern associated with the magnets.