Salient Rotor Structure for Sensorless Reverse-Rotation Prevention
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Solution Overview
Problem
Conventional surface permanent magnet (SPM) type motors with ultra-high speed rotor structures and air foil bearings require a rotor with saliency to prevent damage from reverse rotation, but existing designs lack the necessary saliency for effective sensorless control.
Innovation Solution
The proposed solution involves a rotor design with a sleeve part, a division part that divides the inner hole into two spaces, and two magnet parts with opposite polarities. This configuration creates a difference in inductances between the d-axis and q-axis, providing the necessary saliency for sensorless control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SPM type motor structure with uniform magnetic circuit configuration is used, then the motor structure is simple and easy to manufacture, but the inductances of d-axis and q-axis are the same resulting in no saliency which prevents sensorless control and causes reverse rotation damage to air foil bearing
Solution Approach 1:
The patent applies asymmetry by introducing a division part that creates different magnetic circuit paths for d-axis and q-axis, resulting in different inductances. This asymmetric configuration generates saliency which enables sensorless control and prevents reverse rotation damage to the air foil bearing, while maintaining relative structural simplicity
2Ease of operation
If a rotor with saliency is introduced to enable sensorless control, then reverse rotation can be prevented, but the rotor structure becomes more complex with additional division parts and magnet arrangements
Solution Approach 1:
The patent applies segmentation by dividing the rotor magnet structure into multiple magnet parts arranged in specific patterns. This segmentation creates the necessary saliency for sensorless control while organizing the complexity into manageable, modular components that can be systematically arranged
3Measurement precision
If high-frequency signal injection is used for location estimation in ultra-high speed rotation, then control precision is improved, but signal accuracy may deteriorate due to rotation-induced errors
Solution Approach 1:
The patent applies feedback by using the detected high-frequency current signals to continuously update and correct the rotor location estimation. This feedback mechanism compensates for signal accuracy losses due to ultra-high speed rotation, maintaining precise control despite the challenging operating conditions
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 rotor design with saliency enables effective sensorless control, allowing the rotor to be rotated only in a specific direction, thereby preventing damage to the air foil bearing during reverse rotation. Additionally, the high-frequency signal injection method enhances location estimation and current control performance.
Implementation Method 1
magnetic circuit configurations of the d-axis and the q-axis are the same configurations including a shaft 5, a permanent magnet 4, a sleeve 3, and a stator 2
Implementation Method 2
inductances of the axes
Implementation Method 3
a motor having an ultra-high speed rotor structure, to which an air foil bearing is applied, requires a rotor having a saliency
Data Source
AI summary
Disclosed is a rotor including a sleeve part having a shape corresponding to a cylinder extending in a reference direction, and having an inner hole extending in the reference direction, in an interior thereof, a division part disposed in the inner hole, and dividing the inner hole into a first space and a second space, together with the sleeve part, a first magnet part disposed in the first space, and a second magnet part disposed in the second space, and disposed to have an opposite polarity to that of the first magnet part when viewed along the reference direction.