AC Line Protection Coil for DC Current Diversion
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Solution Overview
Problem
Existing AC devices connected to AC lines are vulnerable to damage from direct currents flowing from adjacent DC lines, particularly when the AC line is not grounded or has no power transformer, leading to magnetic saturation and thermal overload.
Innovation Solution
A protective device with current diverting coils and magnetic cores, including air gaps, is connected in parallel with the AC device to divert and reduce direct currents, preventing magnetic saturation and protecting the AC device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If AC lines run adjacent to DC lines for efficient layout, then space utilization is improved, but ion currents flow to the AC line causing DC currents that can damage AC devices
Solution Approach 1:
A protective device is introduced as an intermediary component between the AC line and the harmful ion currents from the adjacent DC line. The protective device includes a current diverting coil connected in parallel with the AC device, which acts as a mediator to redirect the harmful DC currents away from the AC device through a magnetic core with air gaps, thereby protecting the AC device while allowing the AC and DC lines to run adjacent for space efficiency.
2Device complexity
If the AC line is connected to an inductive voltage transformer without grounding or power transformer, then system complexity is reduced, but DC currents flow via the primary winding driving the transformer into magnetic saturation causing thermal overload and destruction
Solution Approach 1:
The protective device with the current diverting coil is installed in advance on the AC line before any potential DC current issues occur. The coil is connected in parallel with the AC device and the magnetic core with air gaps is pre-configured to provide a preferred path for DC currents. When DC currents from adjacent DC lines attempt to flow into the AC line, the protective device already in place immediately redirects these currents, preventing magnetic saturation and thermal overload of the voltage transformer without requiring complex grounding systems or additional power transformers.
3Ease of manufacture
If magnetic cores without air gaps are used in protective devices, then manufacturing simplicity is improved, but magnetic saturation occurs at lower field strengths requiring significantly larger core cross-sections
Solution Approach 1:
Instead of using a uniform magnetic core design throughout, the invention introduces air gaps at specific locations within the magnetic core structure. These localized air gaps are strategically placed to control the magnetic flux distribution and prevent saturation in critical areas. This local modification allows the use of smaller overall core cross-sections while maintaining protective functionality, optimizing both the quantity of magnetic material used and the effectiveness of the protection against DC current-induced saturation.
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 reduces direct currents flowing through AC devices, preventing damage and ensuring safe operation during high-voltage DC transmission.
Implementation Method 1
at least one current diverting coil (19) connected to the alternating current line (5) in parallel with the AC device (11) and, for each current diverting coil (19), a magnetic core (21) with a first magnetic core section (21.1) around which the current diverting coil (19) runs
Implementation Method 2
Each magnetic core is preferably designed such that it is not driven into magnetic saturation even at relatively small direct currents
Implementation Method 3
at least one magnetic core has at least one air gap. In particular, the first magnetic core section of at least one magnetic core can have at least one air gap
Data Source
Figure 1
Figure 2
AI summary
The invention relates to the protection of an AC device, in particular an inductive voltage converter (11), electrically connected to an AC line (5), from damage caused by direct currents flowing in the AC line (5). In this case, at least one current transfer coil (19), which runs around a magnetic core section (21.1) of a magnetic core (21), is connected to the AC line (5) in parallel with the AC device.