Semiconductor Circuit Breaker with Current Limiter for Surge Control
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Solution Overview
Problem
Semiconductor circuit breakers using semiconductor switches like thyristors or triacs cut off current only at the zero point of an alternating current, leading to potential surge voltages when cutting off load currents, especially in induction loads, necessitating large switches or parallel connections, increasing size and cost.
Innovation Solution
A semiconductor circuit breaker with a semiconductor switch unit controlled by a control signal, an accident detection unit, and a zero point detection unit, which cuts off current either upon accident detection or at the current zero point, and a current limiter connected in parallel with the master switch to manage power supply currents during accidents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a semiconductor switch controlled by a control signal is used to cut off current quickly when an accident occurs, then the response speed is improved, but a high surge voltage may be generated when cutting off load current at non-zero points, damaging the semiconductor switch
Solution Approach 1:
A current limiter is introduced as an intermediary component connected in parallel with the semiconductor switch. During normal operation, the current limiter has high impedance and does not affect the circuit. When the semiconductor switch cuts off current quickly during an accident, the current limiter activates to limit the surge voltage, protecting the semiconductor switch from damage while maintaining the fast response capability
Solution Approach 2:
The current limiter is designed to provide beforehand cushioning by being pre-connected in parallel with the semiconductor switch. When surge voltage is anticipated during fast current cutoff, the current limiter automatically activates to absorb or limit the voltage spike, providing protective cushioning before the surge voltage can damage the semiconductor switch
2Reliability
If a semiconductor switch with large withstand current or multiple parallel switches is used, then the reliability is improved, but the size and cost increase
Solution Approach 1:
The invention changes the operating parameters of the semiconductor switch by introducing a current limiter that modifies the voltage-current characteristics during fault conditions. This allows the use of semiconductor switches with lower withstand current ratings while maintaining reliability, as the current limiter prevents excessive voltage spikes that would otherwise require oversized switches
Data Source
AI summary
The semiconductor circuit breaker includes a semiconductor switch unit connected to an AC circuit, and a phase control unit that controls conduction and non-conduction of the semiconductor switch unit by the control signal. The phase control unit includes an accident detection unit to detect an accident based on a current detected from the AC circuit, a zero point detection unit to detect a current zero point based on the current detected from the AC circuit, and a control signal output unit to output the control signal for setting the semiconductor switch unit to be non-conductive when the accident detection unit detects the accident or when the zero point detection unit detects the current zero point in response to a command to cut off the current.