Fractional Slot Motor Tooth Width Optimization
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Solution Overview
Problem
Conventional three-phase permanent magnet-type synchronous motors with fractional slot configurations do not sufficiently reduce cogging torque, despite predetermined relationships between magnetic poles and slots.
Innovation Solution
A three-phase permanent magnet-type synchronous motor with a fractional slot configuration where the tooth width is approximately half of the slot pitch, and the tooth tip has curved corner portions, allowing for a uniform or larger cross-sectional shape from tip to root to facilitate winding and reduce cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a fractional slot motor is employed with predetermined relationship between number of magnetic poles and number of slots, then the motor structure is defined, but the cogging torque is not sufficiently reduced
Solution Approach 1:
The patent changes the geometric parameters of the motor by setting the tooth width to approximately half of the slot pitch, and configuring the tooth tip with curved corner portions. This parameter optimization significantly reduces cogging torque while maintaining the fractional slot structure, resolving the contradiction between structure definition and harmful factor reduction.
2Object-affected harmful factors
If the tooth width is set to approximately half of slot pitch, then the cogging torque is significantly reduced, but the winding occupation rate may be affected
Solution Approach 1:
The patent optimizes the tooth width parameter to approximately half of the slot pitch, which significantly reduces cogging torque. The curved tooth tip design further enhances this effect while maintaining adequate space for winding occupation, achieving a balance between reducing harmful factors and preserving electrical performance.
Solution Approach 2:
The patent introduces curved corner portions at the tooth tips, transforming the sharp corners into curved surfaces. This curvature design reduces magnetic concentration at the tooth tips, further decreasing cogging torque while maintaining the winding occupation rate by optimizing the overall tooth geometry.
3Object-affected harmful factors
If the tooth tip has curved corner portions, then the cogging torque is reduced and winding is facilitated, but the manufacturing complexity increases
Solution Approach 1:
The patent applies curvature to the tooth tip corner portions, which reduces cogging torque by eliminating magnetic concentration at sharp corners. The curved design also facilitates winding by providing a smoother surface. While this increases manufacturing complexity compared to straight edges, the benefits in performance and ease of winding make it a worthwhile trade-off.
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 design significantly reduces cogging torque to near zero, enabling efficient winding and higher winding occupancy within the slots, improving motor performance.
Implementation Method 1
a tooth width of the tooth in a circumferential direction is approximately 1/2 of a slot pitch of the stator or the rotator
Data Source
AI summary
A three-phase permanent magnet-type synchronous motor configured to significantly reduce cogging torque. The motor includes a rotator and stator each having either permanents magnets or teeth. The number of magnetic poles of the rotator or stator is P and a number of slots of the stator or rotator is N, and a fraction of 2N/3P has a value greater than zero and less than one. The tooth width of the teeth of the stator or rotator in a circumferential direction is ½ of the slot pitch of the stator or rotator.