NMR Electromagnet Alternating Winding Field Homogeneity
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Solution Overview
Problem
Current NMR-based moisture content measurement devices are hindered by the high cost, weight, and size of magnets required for producing homogeneous and strong magnetic fields, particularly for large sample volumes, and existing solutions have poor energy efficiency and require liquid cooling.
Innovation Solution
The development of an electromagnet with conductor wire stacks wound in alternating directions to minimize radial currents and spurious effects, allowing for precise positioning and efficient energy use, resulting in a smaller, lighter, and more energy-efficient magnet with improved field homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conductor wire stacks are positioned far from the sample volume to achieve homogeneous magnetic field, then field homogeneity is improved, but magnet size and weight increase and energy efficiency deteriorates
Solution Approach 1:
The patent transitions from a conventional configuration with wire stacks positioned far from the sample volume to a configuration where wire stacks are wound in grooves on the inner cylindrical surface of the magnet frame, bringing them much closer to the sample volume. This dimensional repositioning reduces the radial distance between the conductor and sample, improving energy efficiency while maintaining field homogeneity through the alternating winding direction pattern.
Solution Approach 2:
The patent employs asymmetric winding patterns where adjacent wire stacks are wound in opposite directions (clockwise vs. counterclockwise). This asymmetric arrangement creates alternating current directions in adjacent stacks, which generates opposing magnetic field contributions from radial currents that cancel each other out, thereby maintaining field homogeneity despite the reduced distance between stacks and sample volume.
2Manufacturing precision
If conductor wire stacks are positioned far from the sample volume to achieve homogeneous magnetic field, then field homogeneity is improved, but magnet size increases
Solution Approach 1:
The patent repositions the wire stacks from a distant radial arrangement to a configuration where they are wound in grooves on the inner cylindrical surface, bringing them close to the sample volume. This reduces the overall radial dimension of the magnet while maintaining field homogeneity through the alternating winding pattern that compensates for the reduced distance.
3Use of energy by moving object
If wire stacks are positioned close to sample volume to improve energy efficiency, then power consumption is reduced, but field homogeneity deteriorates due to positioning tolerances
Solution Approach 1:
The patent uses asymmetric alternating winding directions in adjacent stacks to create opposing radial current patterns. This asymmetry causes the magnetic field contributions from radial currents to cancel each other, compensating for potential inhomogeneities that would otherwise arise from positioning tolerances when stacks are placed close to the sample volume.
Solution Approach 2:
The patent converts the potentially harmful effect of radial currents that cause field inhomogeneity into a beneficial cancellation effect. By winding adjacent stacks in opposite directions, the radial currents flow in opposite directions and their magnetic field contributions cancel each other out, transforming what would be a source of inhomogeneity into a mechanism that maintains field uniformity despite close positioning.
4Ease of manufacture
If wire stacks are wound in single direction to simplify construction, then manufacturing is easier, but radial currents create spurious effects on field homogeneity
Solution Approach 1:
The patent implements alternating winding directions in adjacent stacks, creating an asymmetric current pattern where radial currents flow in opposite directions. This asymmetry causes the spurious magnetic field effects from radial currents to cancel each other, maintaining field homogeneity. While this increases manufacturing complexity compared to single-direction winding, it is still more manageable than conventional designs and achieves superior field uniformity.
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 approach enables the creation of a compact, low-cost NMR magnet that achieves high field homogeneity with minimal power consumption, eliminating the need for forced cooling and allowing for accurate moisture content measurements in large sample volumes.
Implementation Method 1
an electromagnet (100) for producing a magnetic field into a measurement volume
Implementation Method 2
winding the wire of the wiring substacks alternatively in clockwise and counterclockwise directions to reduce the effect of effective radial currents to the field homogeneity
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The invention relates to an electromagnet and a method manufacturing the same. The electromagnet comprises a frame (1) having a volume (4) within, and a conductive wiring (7) wound around the frame (1). In accordance with the invention the magnet includes at least two circular grooves (5) having two walls parallel to the each other and perpendicular to the longitudinal axis of the frame, at least two wire stacks (7) each comprising at least one substack (7a, 7b), wherein the wire has a cross section,at least one of the walls (6) separating the two circular grooves (5), and jump wiring (10) interconnecting the stacks so that contributions from jump wires (10) of the adjacent stacks to total axial directional current are cancelled in average by the current of the return current wire, such that their contribution to the resulting magnetic field at the sample volume is minimized.