Eddy Current Linear Actuator for Fast Switching
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Solution Overview
Problem
Existing electromechanical transfer switches have slow response times due to high inertia armatures, limiting switching speeds and transfer times, while solid-state switches face issues with heat dissipation, control power redundancy, and unpredictable switching behavior, leading to increased costs and complexity.
Innovation Solution
A linear electromagnetic actuator with a lightweight, non-ferrous driven coil and a ferromagnetic center pole, capable of fast switching speeds, is used in conjunction with a biasing element to achieve rapid position changes, eliminating the need for complex control circuits and heat management systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a traditional electromechanical actuator with a heavy armature is used, then the switch can handle high power applications, but the response time is slow due to high inertia
Solution Approach 1:
The patent replaces the traditional heavy armature with a lightweight non-ferrous driven coil that is actuated by electromagnetic forces. The driven coil is attracted to the ferromagnetic center pole when the drive coil is energized, providing mechanical motion without the inertia of traditional armatures. This substitution of mechanical components with electromagnetic actuation achieves fast switching speeds while maintaining the ability to handle high power applications.
Solution Approach 2:
The patent changes the material parameters of the moving component from ferromagnetic (heavy) to non-ferrous (lightweight). The driven coil is made of non-ferrous material that is electrically conductive and magnetically attracted to the ferromagnetic center pole, but has significantly lower density and inertia. This parameter change enables rapid acceleration and deceleration, achieving switching times of less than 5 milliseconds.
2Speed
If solid-state switches are used, then switching speed is fast, but heat dissipation becomes a problem requiring complex cooling systems
Solution Approach 1:
The patent replaces solid-state semiconductor switches with an electromechanical contactor that uses electromagnetic actuation to open and close electrical contacts. This mechanical switching approach avoids the heat dissipation problems inherent in solid-state switches, as the electromagnetic actuator itself does not conduct the high power current and therefore generates minimal heat. The contacts handle the power current separately from the control current that actuates the mechanism.
3Speed
If solid-state switches are used, then switching speed is improved, but control power redundancy and unpredictable behavior increase system complexity
Solution Approach 1:
The electromagnetic actuator is inherently self-latching through its magnetic circuit design. When the drive coil is energized, it creates a magnetic field that attracts the non-ferrous driven coil to the ferromagnetic center pole, closing the electrical contacts. The magnetic flux path through the ferromagnetic materials provides stable holding force without requiring continuous control power or complex feedback circuits. The system naturally maintains its state through magnetic attraction, eliminating the need for redundant control power supplies and complex control logic.
4Loss of time
If a lightweight non-ferrous driven coil is used, then switching time is reduced to less than 5 milliseconds, but the magnetic field strength must be increased to compensate for lower magnetic permeability
Solution Approach 1:
The patent employs a composite magnetic circuit structure combining ferromagnetic and non-ferrous materials. The ferromagnetic center pole and yoke provide high magnetic permeability and concentrate the magnetic flux, while the non-ferrous driven coil provides lightweight, fast-response moving mass. The drive coil is wound around the ferromagnetic center pole, creating a concentrated magnetic field that efficiently acts on the non-ferrous driven coil. This composite approach allows the lightweight driven coil to be actuated rapidly while the ferromagnetic components provide the necessary magnetic field concentration and strength.
Solution Approach 2:
The patent applies different material properties to different parts of the magnetic circuit: the center pole and yoke are made of ferromagnetic material with high permeability to concentrate and guide magnetic flux, while the driven coil is made of non-ferrous material with low permeability but high electrical conductivity and low density. The drive coil windings are positioned to create a localized magnetic field of high intensity at the air gap where the driven coil is attracted. This local optimization of material properties achieves fast switching without requiring excessive overall magnetic field strength.
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 enables switching times of less than 5 milliseconds, reducing operational costs and complexity, while ensuring reliable and efficient power transfer without the drawbacks of solid-state switches.
Implementation Method 1
A linear electromagnetic actuator with a lightweight, non-ferrous driven coil and a ferromagnetic center pole, capable of fast switching speeds
Implementation Method 2
eddy current inductive drive electromechanical liner actuator
Data Source
AI summary
The present invention is directed to an inductively driven electromagnetic linear actuator arrangement employing eddy currents induced by a fixed drive coil to drive its armature. Eddy current focusing fields are employed to direct the eddy currents using Lorentz forces to maximize armature speed. The armature includes a shorted driven coil in a DC magnetic field. This can be supplied by a permanent magnet. When current is applied, a force is felt by the coil in a direction perpendicular to the magnetic field. Such an actuator is well suited for electrical switching applications including transfer switching applications, circuit breaker applications, and ground fault interrupter applications.