Vernier Machine Shaped Permanent Magnet Groups
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Solution Overview
Problem
Vernier permanent magnet machines (VPMMs) suffer from a low power factor due to harmonic flux leakage caused by permanent magnets in the rotor, which affects torque production and efficiency.
Innovation Solution
The design incorporates a rotor with a greater number of magnetic poles than stator poles, utilizing permanent magnets with specific polarity arrangements and flux barriers to modulate the magnetic flux, creating two torque components: synchronous reaction torque and reluctance torque, thereby enhancing torque production while maintaining a high power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are added to the rotor to increase torque production, then torque density is improved, but power factor deteriorates due to harmonic flux leakage
Solution Approach 1:
The rotor magnets are segmented into multiple groups (first plurality and second plurality of magnets) with different polarities arranged in specific patterns. This segmentation allows the magnetic flux to be divided and modulated by stator teeth, creating synchronous reaction torque while reducing harmful harmonic flux leakage that degrades power factor.
Solution Approach 2:
Different regions of the rotor are assigned different magnet polarities (interior polarity facing other magnets, exterior polarity facing stator) to create specific magnetic field distributions. This local differentiation optimizes torque production in different zones while controlling flux leakage characteristics to maintain power factor.
2Power
If the number of rotor poles is increased to create synchronous reaction torque, then torque production is improved, but machine complexity increases
Solution Approach 1:
The rotor magnet arrangement serves multiple functions simultaneously: it generates synchronous reaction torque through the interaction with stator teeth, produces reluctance torque through magnetic anisotropy, and maintains acceptable power factor by controlling flux distribution. This multi-functionality reduces the need for separate components or complex control systems.
Solution Approach 2:
The machine operates by changing the effective number of poles dynamically through the Vernier effect, where the combination of rotor pole pairs and stator teeth creates a variable effective pole count. This allows torque optimization without physically increasing the number of magnet groups, thereby controlling complexity.
3Power
If permanent magnets are arranged with interior and exterior polarities to form rotor poles, then torque components are enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The magnet arrangement uses asymmetric polarity distribution with interior polarity facing adjacent magnets and exterior polarity facing the stator. This asymmetric configuration creates the desired torque components while providing tolerance to manufacturing variations, as the overall magnetic field pattern remains effective even with minor positioning deviations.
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 configuration achieves an approximately 80% improvement in torque density with a comparable power factor, making VPMMs suitable for direct-drive applications in industries requiring high torque at low speeds, such as wind turbines and marine propulsion.
Implementation Method 1
The torque is developed based on an interaction between stator current and magnetic flux contributed by rotor mounted permanent magnets
Implementation Method 2
The openings further include a first flux barrier formed by a first plurality of walls of each opening on a first side of each permanent magnet and a second flux barrier formed by a second plurality of walls of each opening on a second side of each permanent magnet
Data Source
AI summary
An electric machine includes a rotor, permanent magnets, a stator, and a stator winding wound about a plurality of teeth to form a number of stator magnetic poles. The rotor includes a rotor core and a plurality of walls that form openings in the rotor core. A permanent magnet is mounted in each of the openings formed in the rotor core. The plurality of permanent magnets are arranged to form a plurality of groups of permanent magnets that are equally circumferentially distributed around the rotor core with an interior polarity on a side of each permanent magnet facing other permanent magnets of the group of permanent magnets to which the permanent magnet is associated that is the same for all of the permanent magnets. Each permanent magnet is arranged to form a rotor pole, wherein a number of rotor poles is greater than the number of stator magnetic poles.