Embedded Magnet Rotor Opening Shape for Lower Cogging Torque
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Solution Overview
Problem
The presence of a top bridge in interior permanent-magnet rotors causes magnetic leakage flux, leading to decreased torque performance and generates noise due to cogging torque from rapid changes in magnetic reluctance.
Innovation Solution
The rotor core design includes a relaxing part with shaped opening tips to reduce the rapid change in magnetic reluctance, featuring inner and outer-side tip extensions that gradually decrease in thickness towards the opening, thereby smoothing the magnetic flux penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a top bridge is provided to mechanically support the rotor core and permanent magnet, then mechanical strength is improved, but magnetic leakage flux increases causing torque performance to deteriorate
Solution Approach 1:
The invention removes the top bridge component from the rotor core structure. By extracting this problematic element, the magnetic leakage flux path is eliminated, thereby improving torque performance while mechanical strength is maintained through alternative design approaches in the permanent magnet housing hole structure.
Solution Approach 2:
The invention converts the potential harm of the opening part (which causes rapid magnetic reluctance change) into a benefit by carefully designing its shape and position. The opening part is configured to communicate with the outer surface while its geometry is optimized to minimize cogging torque, thus transforming a potential problem into an acceptable solution.
2Power
If an opening part is provided to eliminate the top bridge, then torque performance is improved, but cogging torque increases causing noise to worsen
Solution Approach 1:
The invention applies local quality by creating a specific geometric configuration at the opening part of the permanent magnet housing hole. The opening part is designed with particular shape characteristics that differ from other portions of the rotor core, locally optimizing the magnetic flux distribution to reduce cogging torque while maintaining the benefits of the top bridgeless structure.
Solution Approach 2:
The invention changes geometric parameters of the permanent magnet housing hole, specifically the shape and dimensions of the opening part. By adjusting these parameters, the magnetic reluctance characteristics are modified to reduce the rapid change in magnetic flux, thereby decreasing cogging torque and associated noise while preserving torque performance.
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 design effectively reduces cogging torque and iron loss, improving the efficiency of the interior permanent-magnet rotor by suppressing harmonic components and maintaining torque values.
Implementation Method 1
relax a rapid change in a circumferential direction in magnetic reluctance with respect to a magnetic flux penetrating into the rotor core from the radially outer side of the rotor core
Data Source
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AI summary
According to an embodiment, an interior permanent-magnet rotor (10) includes: a rotor shaft; permanent magnets at least one of which is provided at each magnetic pole; and a rotor core (100) attached to a radially outer side of the rotor shaft and formed with permanent magnet housing holes (110) for storing the permanent magnets, respectively. Each of the permanent magnet housing holes has an opening part (114) in communication with a radially outer side of the rotor core and sandwiched between an opening-part circumferentially inner-side tip (112) and an opening-part circumferentially outer-side tip (113) of the rotor core. The rotor core (100) has a relaxing part (120) formed with shapes of the opening-part circumferentially inner-side tip (112) and the opening-part circumferentially outer-side tip (113).