Series Z-Source Circuit Breaker for Low-Loss DC Fault Interruption
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Solution Overview
Problem
Existing series Z-source circuit breakers for DC circuits face challenges such as high resistive power losses, increased size and cost due to cooling requirements, and inability to interrupt faults immediately or effectively handle slow-rising fault currents.
Innovation Solution
The proposed series Z-source circuit breaker incorporates an electromechanical switch in parallel with the semiconductor switch, a delay circuit, and a capacitor configuration to manage fault currents, allowing for controlled switching and reduced power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor switch is used in a series Z-source circuit breaker for DC circuits, then the circuit breaker can interrupt fault currents, but high resistive power losses occur and cooling requirements increase size and cost
Solution Approach 1:
The circuit breaker is segmented into two distinct switching devices: a semiconductor switch for normal operation and an electromechanical switch for fault conditions. This segmentation allows each component to be optimized for its specific function, with the electromechanical switch handling high-current fault interruption without the resistive losses that plague semiconductor switches in this role.
Solution Approach 2:
A transfer switch serves as an intermediary device that facilitates the transition of current from the semiconductor switch to the electromechanical switch during fault conditions. This mediator enables the semiconductor switch to avoid direct exposure to high fault currents, thereby reducing resistive power losses while maintaining fault interruption capability.
2Reliability
If a semiconductor switch is used in a series Z-source circuit breaker, then fault currents can be interrupted, but cooling requirements increase device size and cost
Solution Approach 1:
By segmenting the switching function between semiconductor and electromechanical components, the semiconductor switch is relieved of the burden of handling high fault currents, allowing for a more compact design without extensive cooling infrastructure.
Solution Approach 2:
The electromechanical switch is designed as a robust, simple component that can handle fault currents without complex cooling systems. While electromechanical switches have mechanical wear limitations, they provide a cost-effective and space-efficient solution for fault interruption compared to heavily cooled semiconductor switches.
3Reliability
If the breaker semiconductor switch opens immediately upon overcurrent detection, then fault protection is provided, but the electromechanical switch does not have time to open and source power is lost
Solution Approach 1:
The control system is configured to close the semiconductor switch as a preliminary action before opening the electromechanical switch during fault conditions. This sequencing ensures that the semiconductor switch is already conductive and ready to carry current before the electromechanical switch opens, preventing power interruption.
Solution Approach 2:
The control logic maintains continuous power flow to the load by coordinating the switching actions to ensure that as one switch opens, the other is already closed and ready to carry the current. This continuity of useful action prevents power loss during the transition between normal and fault protection modes.
4Productivity
If a delay circuit is added to coordinate switching between semiconductor and electromechanical switches, then power continuity is maintained, but device complexity increases
Solution Approach 1:
The delay circuit is designed to automatically generate the required time delay using passive RC components without requiring external control signals or complex timing logic. The circuit self-regulates the timing based on the charging/discharging characteristics of the capacitor and resistor, eliminating the need for microcontrollers or complex timing circuits.
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 design enhances the ability to interrupt faults efficiently, reduces power losses, and provides improved fault handling capabilities, including effective management of slow-rising fault currents.
Implementation Method 1
A first capacitor is electrically coupled between the positive and negative buses at an output side of the breaker semiconductor switch
Implementation Method 2
A delay circuit is electrically coupled in series with the first capacitor between the positive and negative buses. The delay circuit is controlled to delay when reverse bias current is provided from the first capacitor to the breaker semiconductor switch
Data Source
AI summary
A series Z-source circuit breaker including a semiconductor switch that breaks source power being provided to a load in response to overcurrent. An electromechanical switch is electrically coupled in parallel with the semiconductor switch, a first capacitor is electrically coupled to an output side of the semiconductor switch, a second capacitor is electrically coupled in parallel with the semiconductor switch, and a delay circuit is electrically coupled in series with the first capacitor. The semiconductor switch is in an open position and the electromechanical switch is in a closed position when overcurrent is not present. Upon detection of overcurrent the semiconductor switch is closed, the electromechanical switch is opened and the delay circuit is controlled to delay when reverse bias current is provided from the first capacitor to the semiconductor switch to prevent source power from being provided to the load to give the electromechanical switch time to open.