Magnetic Shielded Current Transformer for Watt-Hour Meter
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Solution Overview
Problem
Current transformers in watt-hour meters are susceptible to errors due to external magnetic fields, leading to inaccurate current detection and potential 'stealing electricity' issues, particularly in developing countries, and existing solutions to mitigate this, such as increasing distance, result in larger device sizes which are impractical.
Innovation Solution
A magnetically shielded current transformer design featuring a ring-shaped magnetic core module, a bobbin, and a coil surrounded by a cylindrical shielding member made of inexpensive iron, which forms a magnetic path to block external magnetic fields, allowing for compact and cost-effective manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sufficient distance is secured between the current transformer and the outer case to block external magnetic field influences, then measurement precision is improved, but the device size increases
Solution Approach 1:
A magnetic shielding member is introduced as an intermediary component between the current transformer and the external environment. This shielding member, positioned within the outer case, actively blocks external magnetic fields from reaching the current transformer, thereby maintaining measurement precision without requiring increased distance and thus preventing device size expansion.
2Reliability
If the distance between the current transformer and the outer case is increased to prevent electricity theft, then reliability is improved, but device complexity and size increase
Solution Approach 1:
The magnetic shielding member serves as a mediator that maintains reliable current detection by blocking external magnetic interference, thereby preventing electricity theft without requiring structural modifications that would increase device complexity. The shielding member integrates seamlessly into the existing device structure.
3Measurement precision
If a magnetic shielding member is added to block external magnetic fields, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The magnetic shielding member is constructed from inexpensive materials such as iron or iron-based alloys, which are cost-effective and readily available. This approach enables the production of magnetically shielded current transformers at lower manufacturing costs while maintaining measurement precision, making the solution economically viable for widespread deployment.
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
The solution effectively blocks external magnetic fields, reducing manufacturing costs and enabling the production of smaller, accurate watt-hour meters without the need for increased device size, thus preventing electricity theft and ensuring precise power measurement.
Implementation Method 1
a shielding member which is configured to surround an outer circumferential surface and both side surfaces of the magnetic core module... and is formed of iron
Implementation Method 2
the shielding member... is formed of iron
Implementation Method 3
a coil configured to be wound along an outer circumferential surface of the bobbin... detects a current by transforming a high current from a power supply into a low current
Data Source
AI summary
A magnetically shielded current transformer is provided, which includes a magnetic core module including a core formed in a ring shape by winding plate shape ribbon a plurality of times, a bobbin configured to accommodate the core, and a coil configured to be wound along an outer circumferential surface of the bobbin; a shielding member which is configured to surround an outer circumferential surface and both side surfaces of the magnetic core module, includes through-holes at centers of the both side surfaces, and is formed of iron; and an outer case configured to protect the magnetic core module and the shielding member. Accordingly, a magnetic path is formed by an external magnetic field, which is applied from the outside, via the shielding member and thus the external magnetic field is prevented from being transferred to the magnetic core module, thereby stably blocking influences caused by the external magnetic field.