Variable Flux Permanent Magnet Generator Using Saturable Shunts
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Solution Overview
Problem
Traditional permanent magnet (PM) electric generators lack a convenient means to alter magnetic flux for regulating output, which is essential for applications requiring highly regulated electrical output at varying angular velocities, leading to increased weight, cost, and complexity due to the need for reduction gearboxes or complex hybrid designs.
Innovation Solution
A PM electric generator with directly controllable field excitation using magnetically saturable ferromagnetic shunts and saturation control coils, where DC control current is applied to the coils to adjust the magnetic flux linkage between the PMs and stator coils, allowing for regulation of electromagnetic force across a range of angular velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a wound field synchronous machine (WFSM) is used to enable easy adjustment of rotor current for regulating electrical output, then electrical output regulation is improved, but the angular velocity limitation requires a reduction gearbox which increases weight, cost and complexity
Solution Approach 1:
The patent changes the magnetic flux parameter by introducing saturable ferromagnetic shunts with control coils that can magnetically saturate the shunts to alter the magnetic circuit reluctance. This allows continuous adjustment of magnetic flux and electrical output without requiring a reduction gearbox, enabling direct coupling to high-speed prime movers while maintaining output regulation capability
Solution Approach 2:
The patent replaces the mechanical reduction gearbox with a magnetic field control system using saturable shunts and control coils. Instead of mechanically reducing speed to match generator capabilities, the system uses magnetic saturation control to regulate output at high angular velocities, substituting a mechanical transmission system with an electromagnetic control system
2Device complexity
If a permanent magnet (PM) machine is used to achieve much higher angular velocity and direct coupling to the prime mover, then weight, cost and complexity are reduced, but traditional PM machines have no convenient means to alter magnetic flux for regulating output
Solution Approach 1:
The patent introduces saturable ferromagnetic shunts as intermediary elements between the permanent magnets and the stator teeth. These shunts act as magnetic flux mediators that can be controlled via control coils to adjust the amount of magnetic flux reaching the stator, providing a convenient means to regulate output while maintaining the simple PM machine structure with direct coupling capability
Solution Approach 2:
The patent makes the magnetic circuit dynamically adjustable by incorporating control coils that can magnetically saturate the ferromagnetic shunts. This dynamic control capability allows the magnetic flux to be altered in real-time, enabling output regulation without changing the mechanical structure or adding complex gear systems
3Ease of operation
If hybrid electric machines with PMs and field excitation control winding are used to achieve flux control, then output regulation is improved, but the design becomes relatively complex with increases in size, weight and expense
Solution Approach 1:
The patent extracts and isolates only the essential flux control components (saturable shunts and control coils) from the complex hybrid machine design. By removing unnecessary components and focusing on the core magnetic saturation mechanism, the design achieves flux control capability while minimizing increases in size, weight and expense compared to traditional hybrid machines
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 solution enables efficient regulation of electromagnetic force at lower angular velocities, reducing the need for gearboxes and complex designs, thereby minimizing weight, cost, and complexity while maintaining consistent output across varying speeds.
Implementation Method 1
application of a control current Ic to the control coils at least partially magnetically saturates the shunts to reduce shunting of air gap magnetic flux Φg
Implementation Method 2
increasing magnetic flux linkage ΨM between the PMs and the stator coils and increasing generated electromagnetic force (EMF)
Implementation Method 3
multiple saturable ferromagnetic shunts, each shunt coupling adjacent distal ends of the stator teeth to shunt air gap magnetic flux Φg
Implementation Method 4
multiple saturable ferromagnetic shunts, each shunt coupling adjacent distal ends of the stator teeth to shunt air gap magnetic flux Φg
Data Source
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AI summary
A permanent magnet electric generator (2) with directly controllable field excitation control comprises: a drive shaft (4); a permanent magnet rotor assembly (6) with multiple permanent magnets (8) arranged around an outer annular periphery of the rotor assembly; a stator assembly (12) comprising a ferromagnetic stator yoke (16), multiple ferromagnetic stator teeth (14) mounted to the stator yoke with distal ends proximate the outer annular periphery of the rotor assembly and separated therefrom by an air gap and multiple stator coils mounted between the stator teeth; multiple saturable ferromagnetic shunts (22), each shunt coupling adjacent distal ends of the stator teeth to shunt air gap magnetic flux generated by the permanent magnets across the air gap through the distal ends of the stator teeth; and multiple saturation control coils (24), each saturation control coil being wrapped about a saturable region of an associated one of the shunts; wherein application of a control current to the control coils at least partially magnetically saturates the shunts to reduce shunting of air gap magnetic flux, thereby increasing magnetic flux linkage between the permanent magnets and the stator coils and increasing generated electromagnetic force.