Hybrid Permanent Magnet Motor Cogging Torque Reduction
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Solution Overview
Problem
Permanent magnet motors face inefficiencies due to high cogging torques and linear speed-to-torque relationships, which are not effectively addressed by existing control methods that increase motor size and weight, negating the benefits of using permanent magnets.
Innovation Solution
A permanent magnet electro-mechanical device with a shaft-mounted salient pole rotor, control coils, and a novel arrangement of permanent magnets in the stator, allowing for low cogging forces and high efficiency through controlled magnetic flux manipulation, enabling operation as either a single-phase or multi-phase motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnets are used to replace field coils or armature coils, then power density and efficiency are increased, but high cogging torques and linear speed-to-torque relationships are introduced
Solution Approach 1:
The stator is divided into multiple stator segments with permanent magnets positioned between them, creating a segmented magnetic flux path that reduces cogging forces while maintaining high power density
Solution Approach 2:
Permanent magnets are strategically positioned between stator segments rather than uniformly distributed, creating localized magnetic fields that optimize both power density and reduce cogging effects in specific regions
2Loss of energy
If electronic control is used to modify the linear speed to torque relationship, then efficiency at peak power is improved, but motor size and weight increase
Solution Approach 1:
The motor achieves hyperbolic speed-to-torque relationship through geometric parameter optimization of rotor and stator poles and spacing relationships, eliminating the need for electronic controllers that would increase weight
Solution Approach 2:
The patent replaces electronic control systems with a mechanically optimized pole geometry and spacing arrangement that inherently produces the desired hyperbolic speed-to-torque relationship, reducing overall system weight
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 solution achieves low cogging torque, high efficiency, and high power density by allowing 100% field weakening without air gap magnetic flux, enabling efficient operation and peak power production without increasing motor size or weight.
Implementation Method 1
each of which has north and south pole faces and is positioned between a different pair of stator segments among the plurality of stator segments... the permanent magnets are serially arranged along the magnetic flux path defined by the plurality of stator segments
Implementation Method 2
a permanent magnet electro-mechanical device that functions as a motor or generator
Data Source
AI summary
An electro-mechanical device that functions as a motor or a generator and methods for constructing and using such electro-mechanical device are provided. The electro-mechanical device features permanent magnets placed in a magnetically attracting manner and inter-dispersed between control coils. The control coils are energized to create a flux opposing the flux of the permanent magnets and to create a rotational torque on the poles of a salient pole rotor before those poles align with the poles of the energized control coil stator segment. Power can be generated by placing the flux of the control coils in a steady state and mechanically rotating the salient pole rotor. The electro-mechanical device provides little or no cogging forces, high-efficiency operation, and a high power density.