DC Network Inverter Isolation Switch to Prevent Fuse Tripping
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Solution Overview
Problem
In direct current (DC) networks, a fault in a powerful inverter can cause the input capacitors of less powerful inverters to be overloaded, triggering their fuses and necessitating unnecessary replacements, as the fault current is not isolated effectively.
Innovation Solution
A power converter design with a protective circuit featuring a controllable power semiconductor switch and a controller that switches off the circuit breaker when current exceeds a threshold in a specific direction, preventing fuse tripping due to external faults, and includes a discharge circuit to manage excess energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fuse is used to protect the power converter, then fault protection is provided, but the fuse may trip due to external faults causing unnecessary device replacement
Solution Approach 1:
The protective function is segmented into two independent components: a fuse for severe fault protection and a circuit breaker for selective isolation. The circuit breaker handles external faults while the fuse remains protected from unnecessary tripping, dividing the protection responsibilities to eliminate the contradiction between reliability and ease of repair.
Solution Approach 2:
The circuit breaker acts as an intermediary device between the power converter and the fuse. It selectively isolates external faults before they reach the fuse, preventing the fuse from tripping due to external issues. This mediator allows the fuse to maintain its protective function while avoiding unnecessary replacement.
2Productivity
If the disconnect switch is always switched on, then normal operation is maintained, but external faults can cause current flow back to input capacitors triggering the fuse
Solution Approach 1:
The disconnect switch transitions from a static always-on state to a dynamic state that can be switched on or off based on operational needs and fault conditions. This dynamic behavior allows the system to maintain productivity during normal operation while providing reliability protection when faults occur, resolving the contradiction between continuous operation and protective isolation.
3Reliability
If the disconnect switch is always switched off, then fuse protection is maintained, but normal operation and energy efficiency are reduced
Solution Approach 1:
The disconnect switch is designed to be dynamically controllable, switching between on and off states based on operational requirements. During normal operation, it remains on to ensure productivity and energy efficiency. During fault conditions, it switches off to provide reliability protection, thus resolving the contradiction between continuous operation and protective isolation.
Solution Approach 2:
The disconnect switch operates periodically, switching between on and off states based on detected fault conditions. This periodic action allows the system to alternate between productive operation and protective isolation, maintaining both productivity during normal times and reliability when needed.
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
Prevents fuse tripping in less powerful inverters due to external faults, reduces energy loss, and safely manages excess energy, ensuring the converter operates without damage.
Implementation Method 1
a controllable power semiconductor switch (62), which opens if a current flowing from the input circuit to the DC voltage terminal exceeds a threshold value
Implementation Method 2
an input circuit with one or more capacitors (31, 32)
Data Source
Figure 1
Figure 2
AI summary
An inverter for connection to a DC supply network comprises a fuse and, in series therewith, a controllable isolating switch, wherein a controller is designed to switch off the isolating switch when the current flow through the isolating switch in the direction of the DC supply network exceeds a threshold value.