IPM Rotor Gap Configuration for Demagnetization Control
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Solution Overview
Problem
Existing electric rotating machines with Interior Permanent Magnet (IPM) rotors face demagnetization issues due to concentrated demagnetizing magnetic fields, leading to increased magnet thickness and weight, which in turn increases costs.
Innovation Solution
The rotor design incorporates a configuration with first and second gaps between the permanent magnet's side surface and the rotor core, where the first gap is narrower than the second, preventing magnetic saturation and reducing the demagnetizing magnetic field strength, allowing for thinner magnets and reduced weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a gap is formed between the permanent magnet and rotor core to prevent demagnetizing magnetic field concentration, then demagnetization is prevented, but the rotor core volume is reduced causing magnetic saturation
Solution Approach 1:
The gap is divided into two distinct segments: a first gap between the radially outer end portion of the permanent magnet and the rotor core, and a second gap between the radially inner end portion and the rotor core. This segmentation allows each gap to serve specific functions in controlling magnetic flux distribution while maintaining sufficient rotor core volume.
Solution Approach 2:
Different regions of the gap are designed with different characteristics - the first gap has specific dimensions to control demagnetizing field at the corner portion, while the second gap is configured to manage overall magnetic flux distribution. This local differentiation optimizes both demagnetization prevention and magnetic saturation avoidance.
2Object-affected harmful factors
If the rotor core volume is reduced by the gap, then demagnetizing magnetic field concentration is prevented, but magnetic saturation occurs in the rotor core
Solution Approach 1:
The magnetic flux path is redirected into the permanent magnet itself by configuring the gap structure, utilizing the magnet's own volume as part of the flux path. This dimensional redistribution allows magnetic flux to bypass the constrained rotor core regions while maintaining adequate flux flow capability.
Solution Approach 2:
The permanent magnet acts as an intermediary medium that carries magnetic flux through its volume, compensating for the reduced rotor core volume. The magnet's high permeability and controlled remanence allow it to serve as an effective flux conduction path.
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 reduces the magnetically-saturated area in the rotor core, allowing smoother magnetic flux flow, decreases the demagnetizing magnetic field strength, and consequently reduces the thickness and weight of the permanent magnets, lowering the overall cost and weight of the rotor.
Implementation Method 1
an electric rotating machine which includes an Interior Permanent Magnet (IPM) rotor
Implementation Method 2
a plurality of permanent magnets 103 each of which is inserted in a corresponding one of the slots 102 of the rotor core 101
Implementation Method 3
it becomes difficult for the demagnetizing magnetic field to concentrate on the first corner portion 103a
Implementation Method 4
it becomes easy for magnetic saturation to occur in the rotor core 101 in the vicinity of the gap 105
Data Source
AI summary
A rotor includes a rotor core with a circumferential surface facing a stator and permanent magnets each received in a corresponding slot of the rotor core. Each of the permanent magnets has a first corner portion positioned closest to the circumferential surface of the rotor core and a first side surface that intersects an imaginary line, faces toward the stator side and makes up part of the first corner portion. The imaginary line extends in the magnetization direction of the permanent magnet through the center of the permanent magnet. Between the first side surface of the permanent magnet and the inner surface of the corresponding slot, there are formed a first gap, a second gap and an abutment area from the first corner portion side in this order. The first gap has a smaller width than the second gap in a direction perpendicular to the first side surface.