Cable Tension Measurement via Magnetic Hysteresis Loop
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Solution Overview
Problem
Existing tension measurement methods for cables, such as the vibration method and stress measurement sensors, face challenges in accurately determining tension, especially when cables are short, have bends or junctions, or are affected by attachments, and are prone to non-reproducible results due to complex eddy currents and magnetic history effects.
Innovation Solution
A tension measuring method using a solenoid coil with a cylindrical shape and a through hole to generate a uniform magnetic field, allowing for the measurement of magnetic hysteresis loops to compute tension based on parameters like magnetic flux, remanent magnetization, coercivity, and hysteresis loss in the near-saturation magnetization region, using a solenoid type magnetizer to create a stable and controlled magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the vibration method is used to measure cable tension, then the measurement can be performed on erected cables, but the measurement accuracy deteriorates when the cable is short, has bends or junctions, or has uncertain fixing points
Solution Approach 1:
The patent replaces the mechanical vibration-based measurement system with a magnetic field-based measurement system. By applying a magnetic field to the cable and measuring the induced voltage through electromagnetic induction, the system eliminates the need for mechanical excitation and complex vibration analysis, thereby achieving accurate tension measurement on erected cables regardless of their configuration.
Solution Approach 2:
The patent changes the measurement parameter from mechanical vibration characteristics to electrical parameters (induced voltage). By measuring the voltage induced in a coil wrapped around the cable when subjected to a magnetic field, the system directly correlates the measurement to cable tension through the magnetostrictive effect, avoiding the limitations of vibration-based methods.
2Measurement precision
If a stress measurement sensor utilizing magnetic permeability is used, then tension can be measured in the cable, but the measurement becomes non-reproducible due to complex eddy currents and magnetic history effects
Solution Approach 1:
The patent extracts the measurement objective from the cable material properties and places it in the surrounding magnetic field interaction. Instead of measuring changes in the cable's intrinsic magnetic permeability that are affected by eddy currents and magnetic history, the system measures the voltage induced in an external coil by the magnetic field generated by a permanent magnet, thereby eliminating the harmful magnetic effects.
Solution Approach 2:
The patent introduces a permanent magnet as an intermediary that generates a controlled magnetic field to interact with the cable. This intermediary approach allows the measurement to be based on the magnetic field's interaction with the cable's mechanical state rather than the cable's complex magnetic properties, ensuring reproducible results.
3Power
If pulse current is used to excite the cable for magnetic permeability measurement, then magnetic field can be generated, but eddy currents are inevitably generated inside the cable causing measurement issues
Solution Approach 1:
The patent replaces the pulsed current excitation with a static permanent magnet that provides a continuous, stable magnetic field. This eliminates the time-varying magnetic field that causes eddy currents, while still providing sufficient magnetic field strength to interact with the cable's magnetostrictive properties for accurate tension measurement.
Solution Approach 2:
The patent substitutes the electrical excitation method (pulse current through coil) with a magnetic excitation method (permanent magnet). This replacement eliminates the generation of eddy currents in the cable while maintaining the ability to generate a strong magnetic field for measurement purposes.
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 method provides a reproducible and accurate measurement of cable tension by generating a uniform magnetic field and utilizing parameters strongly correlated with tension, independent of magnetic history, enabling precise tension evaluation even in complex cable configurations.
Implementation Method 1
forming a first coil by winding a conductor around the solenoid coil forming part to form a first coil; measuring a magnetic hysteresis loop of the cable by supplying a current to the first coil to generate a magnetic field
Implementation Method 2
measuring a magnetic hysteresis loop of the cable by supplying a current to the first coil to generate a magnetic field; computing the tension of the cable using a parameter determined from the magnetic hysteresis loop
Implementation Method 3
installing a tension measuring reel having a cylindrical solenoid coil forming part on the cable to be measured; the solenoid coil forming part has a first through hole along a center axis thereof
Data Source
AI summary
A tension measuring method installs a reel having a cylindrical coil forming part on a cable to be measured, forms a coil by winding a conductor around the coil forming part, measures a magnetic hysteresis loop of the cable by supplying a current to the coil to generate a magnetic field, and computes a tension of the cable using a parameter determined from the hysteresis loop. A magnetic field sensor and a magnetic flux sensor are provided inside a through hole in the coil forming part, and the cable is positioned inside the through hole. The magnetic field is varied so that the hysteresis loop includes a near-saturation magnetization region, to measure the hysteresis loop using the sensors. The parameter is selected from a magnetic flux or a magnetic flux density, a remanent magnetization, a coercivity, a magnetic permeability, and a hysteresis loss in the near-saturation magnetization region.