Ferrite Core Overcurrent Limiting With Isolated Fault Detection
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Solution Overview
Problem
Existing technologies face challenges in effectively limiting short-circuit currents in DC networks due to high rise times and the need for fast and robust detection methods, while also avoiding invasive measurement methods that introduce additional losses.
Innovation Solution
The proposed solution involves an overcurrent limiting unit and detection unit that utilizes a ferrite core saturated by permanent magnets, with a network coil and a detection coil wound around the ferrite core. The detection coil is galvanically isolated and detects the transition from a saturated to an unsaturated region of the ferrite core, triggering the switching off of the electric network current through the network coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If inductances are used to limit current rise, then the switch can switch off at lower currents, but the switching time increases and more energy is converted due to additional inductively stored energy
Solution Approach 1:
The permanent magnets are pre-installed on the ferrite core to establish a preliminary magnetic flux that saturates the core during normal operation. This preliminary magnetic state enables the core to rapidly transition to an unsaturated state during faults, providing fast current limitation without requiring additional switching time
Solution Approach 2:
The ferrite core's magnetic permeability is dynamically changed by transitioning from a saturated state (during normal operation) to an unsaturated state (during faults). This parameter change is triggered by the interaction between the permanent magnet flux and the fault current, enabling rapid current limitation while minimizing switching time and energy loss
2Loss of energy
If non-invasive measurement methods are used for current detection, then additional losses are avoided, but a large delay occurs due to the needed interference immunity
Solution Approach 1:
The detection coil serves as an intermediary that magnetically couples to the network coil through the ferrite core. This intermediary detects the transition from saturated to unsaturated state via induced voltage, providing non-invasive measurement without the delays associated with electronic interference immunity requirements
Solution Approach 2:
The detection system exploits the phase transition of the ferrite core between saturated and unsaturated magnetic states. This physical phase transition produces a detectable voltage signal in the detection coil that immediately indicates fault conditions, eliminating detection delays while maintaining non-invasive measurement
3Extent of automation
If additional wiring blocks are used to combine detection and current limitation, then integrated protection is achieved, but device complexity increases
Solution Approach 1:
The detection coil and network coil are merged into a single magnetic circuit around the ferrite core, eliminating the need for separate wiring blocks. The permanent magnets are also integrated directly onto the core, creating a compact unified structure that provides both detection and current limitation functions without additional complexity
Solution Approach 2:
The ferrite core serves multiple functions simultaneously: it provides the magnetic path for the network coil (current limitation), the magnetic coupling for the detection coil (detection), and the saturation transition mechanism (signal generation). This multi-functionality eliminates the need for separate dedicated components for each function
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 allows for non-invasive and automatic detection of overcurrents, enabling immediate switching off of the network current without time delay, thus effectively limiting current rise and ensuring component protection.
Implementation Method 1
a magnetic flux caused by the at least one permanent magnet flows against a magnetic flux caused by the network coil during the operation of the overcurrent limiting unit and detection unit
Implementation Method 2
a ferrite core that is brought into a saturated region with regard to its magnetic conductivity by arranging at least one permanent magnet
Implementation Method 3
a detection coil, which is galvanically isolated from the network coil, is wound around a part of the ferrite core and is configured to detect a transition from the saturated region of the ferrite core to an unsaturated region of the ferrite core by detecting a detection voltage at the detection coil
Data Source
AI summary
An overcurrent limiting and detection unit includes a ferrite core that is brought into a saturated region with respect to its magnetic conductivity by arranging at least one permanent magnet to effect magnetic non-conductivity of the ferrite core, a network coil that is wound around a part of the ferrite core and that is configured such that, during operation of the overcurrent limiting unit and detection unit, an electric network current flows through it, the at least one permanent magnet being arranged on the ferrite core such that a magnetic flux caused by the at least one permanent magnet flows against a magnetic flux caused by the network coil during operation, wherein a detection coil being galvanically isolated from the network coil, is wound around a part of the ferrite core and is configured to detect a transition from the saturated region to an unsaturated region.