Closed Magnetic Circuit Layout for Lower Coil Current
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Solution Overview
Problem
Magnetic field application devices require a relatively large current to increase the magnetic flux density in the magnetic working substance from zero to a desired level, as no magnetic field is applied when the coil is non-energized, leading to high coil current values.
Innovation Solution
Incorporating a permanent magnet and a yoke that forms closed magnetic circuits, allowing the magnetic flux to branch through these circuits even when the coil is non-energized, thereby reducing the current needed to achieve the desired magnetic flux density by pre-applying a magnetic field to the working substance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coil is used to generate the magnetic field from zero, then the magnetic field can be applied to the magnetic working substance, but a relatively large current is required to increase the magnetic flux density from zero to the desired level
Solution Approach 1:
The patent applies preliminary action by using a permanent magnet to pre-establish a magnetic flux density in the magnetic working substance before coil energization. The yoke structure with closed magnetic circuits ensures that magnetic flux from the permanent magnet is pre-applied to the working substance, so when the coil is energized, it only needs to adjust the field intensity rather than generate it from zero, significantly reducing the required coil current.
2Use of energy by moving object
If a permanent magnet and yoke with closed magnetic circuits are introduced, then the maximum coil current is reduced, but the device complexity increases
Solution Approach 1:
The patent merges the permanent magnet and yoke into an integrated magnetic circuit structure. The yoke forms closed magnetic circuits that connect both ends of the permanent magnet in its magnetization direction, creating a unified structure where the permanent magnet and yoke work together to establish the magnetic field, reducing overall system complexity while achieving current reduction.
3Temperature
If the magnetic flux density is increased from zero, then the desired magnetic field intensity is achieved, but copper loss in the coil increases
Solution Approach 1:
By using the permanent magnet to pre-establish the magnetic flux density in the magnetic working substance before coil energization, the coil only needs to provide the additional field intensity required to reach the desired level. This preliminary action significantly reduces the current through the coil, thereby minimizing copper loss while still achieving the target magnetic flux density.
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 configuration reduces the maximum coil current required, minimizes copper loss, and allows for a wider operation region by maintaining a magnetic flux density even when the coil is non-energized, enhancing the magnetocaloric effect and efficiency.
Implementation Method 1
a magnetic flux of the permanent magnet (28) is branched to flow through two or more of the closed magnetic circuits (44 to 46)
Implementation Method 2
the intensity of the magnetic field applied to the magnetic working substance (27) changes when the current is allowed to flow through the coil (47, 48), which makes the magnetic working substrate (27) cause a magnetocaloric effect
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A magnetic field application device (20) includes a yoke (30) that forms at least two closed magnetic circuits (44 to 46) each of which is a closed circuit that magnetically connects both ends in a magnetization direction of a permanent magnet (28). A magnetic field application unit (25, 26) is provided in at least one of the closed magnetic circuits (44 to 46). A coil (47, 48) capable of changing an intensity of a magnetic field applied to a magnetic working substance (27) is provided in at least one of the closed magnetic circuits (44 to 46). A magnetic flux of the permanent magnet (28) is branched to flow through two or more of the closed magnetic circuits (44 to 46) when the coil (47, 48) is non-energized. This can reduce the maximum value of a coil current of the magnetic field application device.