Series Current Limiter with Virtual Air Gap
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Solution Overview
Problem
Current high-power current limiters for electrical networks are bulky, expensive, and require maintenance, failing to effectively manage high-amplitude short-circuit currents which can damage networks.
Innovation Solution
A magnetic circuit that can be locally saturated using direct current to create a 'virtual air gap', allowing for adaptive control of current limiting without the need for replacement, utilizing a winding connected to a direct current source and featuring passive, active, or intelligent control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If known high-power protection devices (pyrotechnic fuses, static circuit breakers, superconductor limiters) are used, then fault current limiting capability is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex electronic control systems and superconducting materials with a purely magnetic field-based limiting mechanism. The magnetic circuit with saturated core and air gaps provides passive current limiting through magnetic reluctance changes, eliminating the need for power electronics, sensors, and control circuits while maintaining fault current limiting capability
Solution Approach 2:
The patent utilizes changes in magnetic circuit parameters (permeability, reluctance) through controlled saturation and air gap variations to achieve current limiting. By adjusting the magnetic circuit's saturation state and air gap size, the device dynamically changes its impedance to limit fault currents without complex control systems
2Reliability
If known high-power protection devices are used, then fault current limiting capability is improved, but device weight and volume increase
Solution Approach 1:
The patent eliminates heavy superconducting materials, power electronic components, and complex mechanical structures by using a simple magnetic circuit made of ferromagnetic materials. The current limiting function is achieved through magnetic field manipulation rather than heavy physical components, significantly reducing device weight
3Ease of manufacture
If fuses are used for fault protection, then cost is reduced, but maintenance requirements increase due to replacement needs
Solution Approach 1:
The magnetic circuit limiter provides automatic, self-resetting protection without requiring human intervention or component replacement. After a fault event, the magnetic circuit naturally returns to its normal state, allowing immediate resumption of protected operation, eliminating maintenance and replacement needs
Solution Approach 2:
Instead of discarding protective devices after use (like fuses), the patent recovers and reuses the same magnetic circuit components indefinitely. The magnetic core and air gaps are restored to their initial state after each fault event, enabling continuous operation without replacement
4Measurement precision
If magnetic saturation is achieved through controlled winding current, then current limiting precision is improved, but energy consumption and device complexity increase
Solution Approach 1:
The patent replaces active current control systems with passive magnetic field-based limiting. The magnetic circuit automatically adjusts its characteristics through saturation and air gap effects without requiring continuous energy input or active control, achieving precise current limiting with minimal energy consumption
Solution Approach 2:
The magnetic circuit operates in periodic cycles of saturation and desaturation corresponding to the AC current waveform. The magnetic field is saturated during fault conditions to limit current, then naturally desaturates when fault current decreases, creating a periodic automatic control action without continuous energy input
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 provides efficient current limiting with low voltage drop in normal operation and regains fault current limiting functionality without maintenance, reducing the need for superconducting materials and associated costs, while achieving high performance and low losses.
Implementation Method 1
The invention proposes to overcome at least one of these drawbacks, by implementing a magnetic circuit which it is possible to saturate locally by using a direct current. This procedure leads to what is called a virtual air gap (VE).
Implementation Method 2
a winding (3) connected to a source (5) of direct current, the winding (3) being wound between the holes (4) of each pair (40) of holes (4) in the magnetic circuit (2)... a magnetic circuit which it is possible to saturate locally by using a direct current
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
The invention relates to a current limiter (10) adapted to be connected in series between an AC current source (S) and a load (C). The limiter comprises a magnetic circuit (2) including a core (20) and at least one inductive coil (S) wound around the core (20) and connected to (i) the AC current source (S) and (ii) the load (C), said coil (1) having an impedance. The limiter is characterized in that it also comprises a virtual air-gap (EV) that includes: at least one pair (40) of holes (4) in the magnetic circuit (2); and a winding (3) which is wound between the holes (4) of each pair (40) of holes (4) and connected to a DC current source (5), said limiter (10) operating between at least two states.