CRDM Coil Bobbin Cut-Off Grooves for Eddy Current Elimination
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Solution Overview
Problem
The existing electromagnetic coil assemblies in reactor control rod drive mechanisms (CRDM) face limitations in high-temperature resistance, leading to asymmetric magnetic fields and subsequent eccentric wear and movement issues due to poor high-temperature resistance of high molecular materials and single-cut-off-groove metal bobbins.
Innovation Solution
A cylindrical electromagnetic coil bobbin structure comprising an inner and outer shell with multiple uniformly distributed cut-off grooves and insulating connection strips, which eliminates induced eddy currents and ensures a symmetric magnetic field by canceling out asymmetric electromagnetic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If high molecular materials are used for the electromagnetic coil bobbin, then ease of manufacture is improved, but high-temperature resistance deteriorates (temperature resistance grade can only reach around 250°C)
Solution Approach 1:
The patent employs a composite structure consisting of an inner bobbin made from high molecular material and an outer shell made from metal material. This composite design combines the manufacturing advantages of high molecular materials with the high-temperature resistance of metal, enabling the electromagnetic coil assembly to withstand temperatures above 300°C while maintaining ease of manufacture through modular construction.
2Object-generated harmful factors
If a single cut-off groove is provided on the metal bobbin, then induced eddy current is reduced, but magnetic field symmetry deteriorates (asymmetric electromagnetic forces cause eccentric wear)
Solution Approach 1:
The patent introduces multiple cut-off grooves (at least two) uniformly distributed around the inner bobbin and outer shell, creating a symmetric pattern of asymmetries. This configuration cancels out asymmetric electromagnetic forces by distributing the eddy current disruption evenly around the circumference, thereby maintaining magnetic field symmetry and preventing eccentric wear while still reducing induced eddy currents.
3Temperature
If metal material is used for the bobbin, then high-temperature resistance is improved, but device complexity increases (single cut-off groove design creates asymmetric forces)
Solution Approach 1:
The patent divides the metal bobbin structure into segmented components: an inner bobbin and an outer shell, both with multiple uniformly distributed cut-off grooves. This segmentation approach simplifies the overall design by creating modular, easily manufacturable components that can be assembled together, reducing device complexity while maintaining high-temperature resistance and magnetic field symmetry.
4Reliability
If forced ventilation cooling is used, then reliable operation at high temperature is achieved, but reactor head cover structure complexity increases
Solution Approach 1:
The patent changes the material parameter of the bobbin from high molecular material to a composite of high molecular material and metal material. This parameter change raises the temperature resistance grade from around 250°C to above 300°C, allowing the electromagnetic coil assembly to operate reliably in high-temperature environments without requiring forced ventilation cooling, thereby simplifying the reactor head cover structure.
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 design enhances the high-temperature resistance and movement performance of CRDM by reducing eccentric and excessive wear, maintaining reliable operation and extending the life of the CRDM components.
Implementation Method 1
the cut-off grooves on the inner bobbin and the outer shell are used to cut off the inner bobbin and the outer shell... so as to avoid generation of induced eddy current
Implementation Method 2
CRDM electromagnetic coil assembly... essential functions... high temperature resistance grade, excellent insulating property, radiation resistance
Data Source
AI summary
The invention discloses an electromagnetic coil bobbin used in reactor as well as an inner bobbin and an outer shell thereon, wherein more than one cut-off grooves are provided on the inner bobbin and the outer shell and uniformly distributed on corresponding inner bobbin or outer shell such that the inner bobbin and the outer shell of which the material of the main body is metal have excellent high-temperature resistance and avoid generation of induced eddy current, and such that the electromagnetic coil can generate a more uniform magnetic field while operating, thus achieving technical effects of reducing or avoiding eccentric wear, reducing or avoiding partial excessive wear, etc., and realizing the objectives of improving and raising movement performance of CRDM.