Solid-State Circuit Breaker Soft Switching for Inrush Current
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Solution Overview
Problem
Solid state circuit breakers face issues with inrush currents during initial load start-up, leading to complex configurations and increased size due to the need for an initial charging circuit, and they struggle to differentiate between transient and normal currents.
Innovation Solution
A solid state circuit breaker with a semiconductor switch unit and control unit that controls the semiconductor switch to repeat turn-on and turn-off during a preset initial operation time, mitigating inrush currents without an initial charging circuit, using a hardware trip function and soft trip functions to manage current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical solid state circuit breaker includes a separate initial charging circuit to prevent circuit interruption by inrush current, then the circuit breaker can avoid false tripping during initial start-up, but the configuration of the circuit becomes complicated and its size increases
Solution Approach 1:
The patent extracts and eliminates the separate initial charging circuit from the solid state circuit breaker design. Instead of including a dedicated RC circuit with charging resistor and bypass switch, the invention uses the existing semiconductor switch and control unit to detect and manage inrush current conditions, thereby simplifying the overall circuit configuration while maintaining the ability to prevent false tripping during initial start-up
Solution Approach 2:
The patent makes the semiconductor switch and control unit perform multiple functions: they not only control normal circuit operation but also detect inrush current conditions and manage the initial charging phase. By integrating these functions into existing components rather than adding separate dedicated circuits, the design achieves multi-functionality without increasing complexity
2Speed
If a solid state circuit breaker uses high-speed current detection, then the circuit can be interrupted at high speed, but transient inrush current is detected and causes circuit breaking
Solution Approach 1:
The patent implements dynamic control of the semiconductor switch during initial start-up by repeatedly turning it on and off under control of the control unit. This dynamic operation allows the system to gradually charge the load capacitance while monitoring current conditions, enabling the circuit to distinguish between harmful fault currents and normal inrush current, thereby preventing false tripping while maintaining high-speed response capability
Solution Approach 2:
The patent employs periodic on/off cycling of the semiconductor switch during the initial operation period. This periodic action allows the circuit to gradually build up voltage and charge the load capacitance in controlled steps, preventing excessive inrush current while maintaining the ability to quickly detect and respond to actual fault conditions
Data Source
AI summary
The present disclosure relates to a solid state circuit breaker, comprising: a semiconductor switch unit including a semiconductor switch that electrically connects or disconnects a power system and a load according to a voltage applied to a gate terminal; and a control unit that, when the semiconductor circuit breaker is turned on, controls the semiconductor switch to repeat turn-on and turn-off operations for a predetermined initial driving time so as to gradually alleviate the magnitude of inrush current caused by an initial connection between the power system and the load.