Magnetically Saturable Inrush Current Limiter Circuit
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Solution Overview
Problem
Radiation-hardened inrush current limiter circuits for space applications are expensive and have long lead times, necessitating the development of cost-effective and readily available solutions.
Innovation Solution
The implementation of magnetically saturable components, specifically inrush current limiter circuits with a saturable resistor and transformer, where the impedance of the resistor is reflected across the transformer to limit inrush current until the magnetic core saturates, reducing peak inrush current and protecting electronic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radiation-hardened components are used for inrush current limiter circuits in space applications, then reliability is improved, but cost increases and lead time increases
Solution Approach 1:
The circuit is segmented into two functional parts: a radiation-hardened transformer that provides the magnetic coupling and impedance transformation, and a standard resistor that provides the current limiting function. This segmentation allows only the critical radiation-exposed components to be hardened while using inexpensive standard components for the rest of the circuit.
Solution Approach 2:
The transformer acts as an intermediary device that couples the primary and secondary circuits magnetically. By placing the resistor on the secondary side and using the transformer's reflected impedance, the circuit achieves radiation hardening without requiring the resistor itself to be radiation-hardened, thus reducing cost while maintaining reliability.
2Reliability
If radiation-hardened components are used for inrush current limiter circuits in space applications, then reliability is improved, but lead time increases
Solution Approach 1:
The circuit is segmented into two functional parts: a radiation-hardened transformer that provides the magnetic coupling and impedance transformation, and a standard resistor that provides the current limiting function. This segmentation allows only the critical radiation-exposed components to be hardened while using inexpensive standard components for the rest of the circuit.
Solution Approach 2:
The transformer acts as an intermediary device that couples the primary and secondary circuits magnetically. By placing the resistor on the secondary side and using the transformer's reflected impedance, the circuit achieves radiation hardening without requiring the resistor itself to be radiation-hardened, thus reducing cost while maintaining reliability.
3Object-generated harmful factors
If a saturable resistor is used in the inrush current limiter circuit, then inrush current is reduced, but device complexity increases
Solution Approach 1:
The saturable resistor automatically limits inrush current based on the magnetic saturation state of the transformer core. During power-on, the unsaturated core reflects the resistor's impedance to limit inrush current. As the core saturates, the reflected impedance disappears and normal current flows. This self-regulating mechanism eliminates the need for complex control circuits, switches, or additional active components.
Solution Approach 2:
The circuit exploits the non-linear parameter change of the transformer core's magnetic permeability as it transitions from unsaturated to saturated state. This parameter change naturally produces the current limiting effect without requiring external control, simplifying the overall device complexity while effectively reducing inrush current.
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 approach significantly reduces inrush current, is cost-effective, and utilizes radiation-hardened components that are inexpensive and readily available, addressing the high cost and lead time issues of traditional rad-hard solutions.
Implementation Method 1
a transformer including a primary winding, a secondary winding and a saturable magnetic core shared therebetween, a resistor connected in parallel with the secondary winding, wherein an impedance of the resistor is reflected across the transformer when a voltage is applied across the primary winding
Implementation Method 2
the saturable magnetic core is not saturated... when the saturable magnetic core saturates
Data Source
AI summary
Embodiments described herein are directed to inrush current limiters having a transformer. In one embodiment, an inrush current limiter includes a transformer including a primary winding, a secondary winding and a saturable magnetic core shared therebetween, a resistor connected in parallel with the secondary winding, wherein an impedance of the resistor is reflected across the transformer when a voltage is applied across the primary winding and the saturable magnetic core is not saturated, and a diode connected between the primary winding and ground.