DC Bias on Split-Core Transformer for Magnetic Force Stability
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Solution Overview
Problem
Existing power line monitoring systems using split-core current transformers face challenges in maintaining a consistent magnetic force between core halves due to alternating AC currents, leading to mechanical difficulties and noise issues during hot-stick deployment and operation.
Innovation Solution
Applying a DC bias to the split-core transformer using a circuit within the monitoring device to maintain a net positive magnetic force between the core halves, ensuring the magnetic force never equals zero during an AC cycle, and allowing secondary currents to have different magnitudes on each half-cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a split-core transformer is mounted on a distribution line using mechanical fastening, then the transformer can be installed and removed, but the magnetic force between core halves alternates between zero and peak force at twice the AC line frequency, causing vibration noise and mechanical challenges
Solution Approach 1:
The patent replaces the purely mechanical fastening system with an electromagnetic field-based solution. By introducing a DC bias current through the secondary winding, a static magnetic field is created that adds a constant attractive force between core halves, reducing reliance on mechanical fasteners and eliminating the zero-force periods that cause vibration and noise.
Solution Approach 2:
The patent changes the magnetic field parameters by superimposing a DC bias current on the AC current in the secondary winding. This creates a composite current waveform that produces a magnetic field with both AC and DC components, resulting in a net positive magnetic force that maintains core half attraction throughout the AC cycle.
2Ease of manufacture
If mechanical fastening is used to hold core halves together, then the transformer can be mechanically assembled, but additional mechanical components increase device complexity and deployment difficulty
Solution Approach 1:
The patent eliminates mechanical fastening components by substituting them with an electromagnetic field-based holding mechanism. The DC bias current creates a magnetic attraction force that replaces the function of mechanical fasteners, simplifying the device structure and reducing the number of parts required for assembly and deployment.
3Use of energy by moving object
If AC current alone is used in the secondary winding, then power harvesting is achieved, but the magnetic force alternates to zero twice per AC cycle, requiring mechanical holding mechanisms
Solution Approach 1:
The patent merges two current components (AC and DC) in the secondary winding to achieve dual functionality. The AC component continues to provide power harvesting through electromagnetic induction, while the added DC component provides a static magnetic field that maintains continuous attractive force between core halves, eliminating the zero-force periods.
Solution Approach 2:
The patent modifies the current parameter in the secondary winding by adding a DC offset to the AC current. This parameter change transforms the magnetic force waveform from one that periodically reaches zero to one that maintains a net positive value throughout the cycle, while preserving the AC component's power harvesting capability.
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 solution stabilizes the magnetic force, reduces vibration noise, and simplifies the mechanical requirements for holding the core halves together, enhancing the reliability and ease of deployment and removal of power line monitoring devices.
Implementation Method 1
Power harvesting using induction pick-up from the magnetic field surrounding a power distribution line
Implementation Method 2
applying a DC bias to the split-core transformer to maintain a net positive magnetic force between first and second core halves
Data Source
AI summary
A power distribution monitoring system is provided that can include a number of features. The system can include a plurality of monitoring devices configured to attach to individual conductors on a power grid distribution network. In some embodiments, a monitoring device is disposed on each conductor of a three-phase network and utilizes a split-core transformer to harvest energy from the conductors. The monitoring devices can be configured to harvest energy from the AC power grid and apply a DC bias to core halves of the split-core transformer to maintain a positive magnetic force between the core halves. Methods of installing and using the monitoring devices are also provided.