IPM Rotor Gaps Equalize Magnetic Flux to Reduce Cogging Torque
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Solution Overview
Problem
IPM synchronous motors experience cogging torque ripple due to variations in magnetic attraction force caused by differing magnetic flux densities across various magnetic paths, leading to pulsating torque when no current is applied.
Innovation Solution
A rotor structure with a rotor core and permanent magnets, featuring slits aligned radially outside magnet insertion apertures and additional axial gaps on one side of the magnetic paths to adjust magnetic resistance, ensuring equivalent magnetic flux densities across paths and reducing flux variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If slits are formed in the rotor to align with magnetic flux from permanent magnets, then torque generation is improved, but magnetic flux distribution becomes uneven across different magnetic paths, causing cogging torque ripple
Solution Approach 1:
The patent introduces gaps at specific locations (radially inner side of magnet insertion apertures) to create non-uniform magnetic resistance distribution. This local modification adjusts magnetic flux density in specific magnetic paths without affecting the overall rotor structure, thereby reducing cogging torque ripple while preserving torque generation capability
Solution Approach 2:
The patent modifies magnetic resistance parameters by introducing gaps of specific widths and positions. By changing the magnetic resistance in predetermined magnetic paths, the magnetic flux distribution is adjusted to achieve more uniform flux density across different magnetic paths, reducing cogging torque ripple
2Ease of operation
If the rotor structure includes multiple slits and magnetic paths, then motor functionality is achieved, but variation in magnetic resistance across magnetic paths causes unequal magnetic flux distribution, leading to torque pulsation
Solution Approach 1:
The patent applies local quality by introducing gaps only in specific magnetic paths (those with higher magnetic flux density) rather than uniformly across all paths. This selective modification creates targeted adjustment of magnetic resistance, balancing the magnetic flux distribution across different magnetic paths while maintaining motor functionality
Solution Approach 2:
The patent aims to achieve equipotentiality in magnetic flux distribution by adjusting magnetic resistance through gap introduction. The gaps are designed to equalize the magnetic flux density across different magnetic paths, creating a more uniform magnetic field distribution that reduces torque pulsation
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 adjusted magnetic resistance and flux distribution minimize cogging torque ripple by maintaining consistent magnetic flux between adjacent paths, thereby reducing torque fluctuations.
Implementation Method 1
Each permanent magnet 3 is disposed in each magnet insertion aperture MS. Specifically, the permanent magnet 3 is oriented such that its magnetic poles are directed in the diameter direction of the rotor 1
Implementation Method 2
a current applied to the wire in the slot 5 generates a torque in the rotor 1 in accordance with the position of the magnetic pole of the rotor 1, according to Fleming's left-hand rule
Implementation Method 3
The slits 7 are formed parallel with the magnetic flux generated from the permanent magnet 3. The slits 7 and the magnetic flux from the permanent magnet 3 constitute an N-pole or S-pole magnetic pole of the rotor 1
Implementation Method 4
a gap formed on an opposite side from one or more predetermined magnetic paths across the permanent magnet to adjust magnetic resistance of the predetermined magnetic paths for making a change in magnetic flux between adjacent magnetic paths small
Data Source
AI summary
A rotor of a synchronous motor has a rotor core and a permanent magnet. The rotor core has a plurality of magnet insertion apertures and a plurality of slits. The permanent magnet is disposed in each of the magnet insertion apertures such that the magnetic poles of the permanent magnets are directed in a diameter direction. The slits are formed on an radially outer side of the magnet insertion aperture so as to align with intervals along a side of the permanent magnet. Magnetic paths are defined between adjacent slits. A gap that is a slot open in the axial direction of the rotor core is formed on the opposite side from a plurality of magnetic paths across the permanent magnet to adjust the magnetic resistance of the magnetic paths for making a change in magnetic flux between adjacent magnetic paths small.