Laminated Magnetic Core for Flowmeter Inductance Reduction
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Solution Overview
Problem
Magnetic flowmeters with small diameter flowtubes face challenges in maintaining accurate measurements due to high Q and inductance values, leading to oscillations and phase lag, which introduce errors in fluid velocity calculations.
Innovation Solution
A magnetic flowtube assembly with a plurality of orthogonally oriented, planar laminations of magnetically permeable material reduces inductance and quality factor, allowing for precise control of the magnetic circuit's load and frequency response, thereby stabilizing the excitation current and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a magnetic flowtube assembly with small diameter flowtube is used, then the device can measure flow in compact applications, but high Q and inductance values cause oscillations and phase lag leading to measurement errors
Solution Approach 1:
The magnetic core is divided into multiple planar laminations stacked together, with each lamination electrically insulated from others. This segmentation reduces eddy current losses and lowers the Q factor and inductance values, eliminating oscillations and phase lag while maintaining accurate flow measurements in small diameter flowtubes
Solution Approach 2:
The magnetic core uses composite construction with multiple layers of magnetically permeable material separated by electrical insulators. This composite structure maintains the necessary magnetic field strength for small diameter applications while reducing electromagnetic oscillations through the insulating layers, resolving the contradiction between compact size and measurement accuracy
2Power
If traditional magnetic core design is used, then the magnetic field is generated, but high inductance and Q values lead to oscillations and phase lag
Solution Approach 1:
The magnetic core is segmented into multiple planar laminations with electrical insulation between layers. This reduces eddy currents and lowers inductance and Q values, stabilizing the excitation current by eliminating oscillations while maintaining sufficient magnetic field generation for accurate flow measurement
Solution Approach 2:
The magnetic core design changes physical parameters including lamination thickness, number of layers, and insulation material properties to optimize the balance between magnetic field strength and electrical losses, achieving stable excitation current with reduced oscillations and phase lag
3Measurement precision
If multiple layers of magnetically permeable material are used, then inductance and Q values are reduced, but device complexity increases
Solution Approach 1:
The magnetic core is constructed from multiple thin planar laminations stacked together, each electrically insulated from others. This segmentation reduces inductance and Q values to eliminate measurement errors while maintaining a relatively simple overall structure that can be manufactured using standard techniques
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 enables a robust current control loop with improved stability and reduced power dissipation, enabling accurate and repeatable flow measurements with lower Amp-Turn requirements, suitable for low-power operation and high-frequency sampling.
Implementation Method 1
A coil is disposed to generate a magnetic field having field lines that are substantially orthogonal to the plane of each layer
Implementation Method 2
A magnetic core is mounted relative to the flowtube and includes a plurality of layers of a magnetically permeable material
Implementation Method 3
Magnetic flowmeters measure flow by application of Faraday's Law, an electromagnetic effect. An electromotive force (EMF) is generated by the flowing process fluid crossing through the magnetic field
Data Source
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AI summary
A flowtube assembly (200) for a magnetic flowmeter (102) is provided. The flowtube assembly (200) includes a flowtube (202) configured to receive a flow of process fluid. A magnetic core (224) is mounted relative to the flowtube (202) and includes a plurality of layers (300) of a magnetically permeable material. Each layer (300) is substantially planar and is electrically insulated from others of the plurality of layers (300). A coil (216) is disposed to generate a magnetic field having field lines that are substantially orthogonal to the plane of each layer (300).