Interior Magnet Machine Angled Slots Torque Ripple
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Solution Overview
Problem
Interior magnet machines suffer from lower power density, significant torque ripple, higher inductance, and cogging torque issues, which affect noise, vibration, and drive costs, and existing solutions either reduce power density or increase complexity.
Innovation Solution
The introduction of angled slots between the magnet surface and the rotor outside diameter, which alter the rotor flux distribution from trapezoidal to sinusoidal, reducing harmonic distortion and cogging torque while maintaining or increasing back-emf and average torque production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If interior magnet machines use traditional perpendicular slot designs, then manufacturing is simpler, but power density is lower and torque ripple is significant
Solution Approach 1:
The patent applies asymmetry by positioning slots at non-perpendicular angles (e.g., 45 degrees) relative to the rotor radius rather than using traditional perpendicular slot designs. This asymmetric slot configuration transforms the rotor flux distribution from trapezoidal to sinusoidal, thereby increasing power density while reducing torque ripple and cogging torque.
Solution Approach 2:
The patent changes the geometric parameter of slot orientation from perpendicular (90 degrees) to angled (e.g., 45 degrees) relative to the rotor radius. This parameter modification fundamentally alters the flux distribution characteristics, enabling higher power density and improved torque smoothness without compromising manufacturability.
2Device complexity
If interior magnet machines use traditional perpendicular slots, then structural simplicity is maintained, but torque ripple and cogging torque increase
Solution Approach 1:
By introducing asymmetric slot angles (non-perpendicular to rotor radius), the patent modifies the magnetic flux distribution pattern. This asymmetry in slot positioning smooths the flux transitions, thereby reducing torque ripple and cogging torque while maintaining relatively simple rotor construction.
Solution Approach 2:
Changing the slot orientation parameter from perpendicular to angled configuration transforms the flux distribution from trapezoidal to sinusoidal, which inherently reduces harmonic content and minimizes torque ripple and cogging effects without significantly increasing structural complexity.
3Stability of the object's composition
If interior magnet machines use traditional designs, then inductance is higher providing stability, but power factor decreases and drive costs increase
Solution Approach 1:
The patent modifies the slot orientation parameter to reduce the average inductance of the machine. By positioning slots at angled orientations rather than perpendicular to the rotor radius, the magnetic path is altered, resulting in lower inductance values that improve power factor and reduce the complex power (VA) requirement from the drive system.
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 enhances power density by allowing for smaller motor or generator sizes, reduces drive costs, and minimizes torque ripple and cogging torque, achieving a balance that is typically not possible with existing methods.
Implementation Method 1
a trapezoidal air-gap flux distribution is usually generated by a interior magnet rotor... The introduction of angled slots between the magnet surface and the rotor outside diameter, which alter the rotor flux distribution from trapezoidal to sinusoidal
Implementation Method 2
The winding current in a fixed bus voltage system is limited by the back-emf and machine resistance and inductance... A rotor geometry that results in higher back-emf or lower inductance allows the number of turns to be adjusted
Implementation Method 3
Interior magnet machines have the following characteristics... many interior magnet machines have lower power density than surface mounted magnet machines... interior permanent magnet machine
Data Source
AI summary
An interior permanent magnet machine having angled slots.