Ferrite Magnet Stepping Motor d/D Ratio Optimization
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Solution Overview
Problem
Conventional permanent-magnet stepping motors rely on expensive rare-earth magnets, limiting the use of cost-effective ferrite magnets while maintaining performance.
Innovation Solution
A permanent-magnet stepping motor design with a rotor and stator yoke configuration where the ratio of rotor outer diameter to stator yoke outer diameter is greater than 0.6, utilizing ferrite magnets to achieve performance equivalent or superior to rare-earth magnet systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ferrite magnets are used instead of rare-earth magnets, then material cost is reduced, but magnetic force and performance deteriorate
Solution Approach 1:
The invention changes the geometric parameter of the motor by setting the ratio of rotor outer diameter to stator yoke outer diameter greater than 0.6. This parameter change compensates for the weaker magnetic force of ferrite magnets by increasing the magnetic interaction area, thereby maintaining performance while using lower-cost ferrite materials
Solution Approach 2:
The invention employs a composite structure combining ferrite magnets with a specific stator-rotor geometric configuration. The composite approach integrates the low-cost ferrite material with an optimized structural design (d/d > 0.6) to achieve overall performance comparable to expensive rare-earth magnet systems
2Reliability
If the ratio of rotor outer diameter to stator yoke outer diameter is increased to greater than 0.6, then performance with ferrite magnets is improved, but stator yoke size increases
Solution Approach 1:
The invention optimizes the d/D ratio parameter to be greater than 0.6, finding the optimal balance point where performance with ferrite magnets is maximized while controlling stator yoke size. This parameter optimization ensures that the motor achieves sufficient torque and performance without excessive dimensional increases
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 enables superior torque characteristics and reduced material costs by using ferrite magnets, maintaining high performance across various drive frequencies and reducing material usage and weight.
Implementation Method 1
rotation and stop are controlled by a relationship between magnetic force of the rotor magnet and magnetic force generated at the stator core by excitation
Implementation Method 2
magnetic force generated at the stator core by excitation
Data Source
AI summary
A stepping motor uses a low-cost ferrite magnet instead of an expensive rare-earth magnet. The stepping motor has characteristics equivalent or superior to those of a conventional stepping motor. The stepping motor is provided with a rotor 300, a stator yoke 200, and bearings 501 and 502 which rotatably hold the rotor 300 with respect to the stator yoke 200. The rotor 300 has a columnar shape and has plural magnetic poles arranged in the circumferential direction of the outer circumferential surface. The stator yoke 200 has an outer cylindrical portion and an inner circumferential portion which surrounds the rotor 300 and which has plural first pole teeth and plural second pole teeth. The outer diameter “d” of the rotor 300 and the outer diameter “D” of the stator yoke 200 are set so that the ratio of “d/D” is greater than 0.6.