V-Shaped Permanent Magnet Motor Reduces Torque Ripple
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Solution Overview
Problem
Conventional permanent-magnet motors with multiplex multiphase armature windings experience interference voltages due to mutual inductances, leading to difficulties in converging motor currents and reducing torque ripple, resulting in increased vibration and noise.
Innovation Solution
A permanent-magnet motor design featuring a stator with teeth and slots and a rotor with embedded permanent magnets arranged in V-shaped pairs, where the distance between magnets at the outer radial direction is smaller than at the inner radial direction, reducing mutual inductances and torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiplex multiphase armature windings share a magnetic path in the air gap, then the motor structure is compact and simple, but large mutual inductances generate interference voltages that prevent current convergence and increase torque ripple
Solution Approach 1:
The patent divides the rotor core into multiple independent magnetic circuits by providing magnetic path separation structures. This segmentation isolates the magnetic paths of different phases, reducing mutual inductance between multiplex armature windings while maintaining the compact structure. The separation prevents interference voltages from propagating across phases, thereby improving current control stability.
2Manufacturing precision
If feedback response frequency is increased to cancel motor current ripple, then torque ripple reduction is improved, but interference voltages become larger and current convergence becomes difficult
Solution Approach 1:
The patent extracts and eliminates the source of interference voltages by reducing mutual inductance between phases through magnetic path separation. By removing the coupling mechanism that generates interference, the system can operate at higher feedback response frequencies without the interference voltages that would otherwise prevent current convergence. This enables effective torque ripple cancellation.
3Power
If permanent magnets are increased in amount to enlarge magnetomotive force, then motor output is improved, but magnetic path narrowing causes rotor core saturation and increases torque ripple
Solution Approach 1:
The patent addresses magnetic path narrowing by introducing a spatial dimension solution - magnetic path separation structures that create additional magnetic flux pathways. This allows increased permanent magnet content for higher output while preventing core saturation by distributing flux through separated magnetic circuits, thereby maintaining magnetic circuit stability.
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 achieves a significant reduction in torque ripple, enabling high-output electric power steering systems with reduced vibration and noise.
Implementation Method 1
permanent magnets for forming magnetic-field poles are incorporated in the rotor
Implementation Method 2
multiplex multiphase armature windings, in which multiplexed armature windings share a magnetic path in the air gap
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Each of a plurality of permanent-magnet pairs is configured with a pair of permanent magnets that are arranged in a v-shaped manner in such a way that the distance between the portions of the permanent magnets, facing each other at the outer side in the radial direction of the rotor core, is smaller than the distance between the portions thereof, facing each other at the inner side in the radial direction of the rotor core; a magnetic-field pole is formed of part, of the rotor core, that is situated between the adjacent permanent-magnet pairs.