DC Breaker Current Shunting to Reduce Fuse Heating
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Solution Overview
Problem
Conventional breaker apparatuses in photovoltaic power plants and high-power systems have low reliability due to excessive current flowing through fuses during normal operation, leading to premature heating and reduced service life, which can escalate faults and damage equipment.
Innovation Solution
A breaker apparatus with an overcurrent-automatic-disconnection unit and a current limiting unit, connected in series, and a controllable switch unit controlled by a controller to shunt current during normal operation, disconnecting the circuit when a fault occurs by exceeding the breaking current threshold, thereby reducing heat generation and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the breaker apparatus uses a fuse and relay connected in parallel with current shunting based on resistance proportion, then the circuit can be disconnected when fault occurs, but a considerable part of current flows through the fuse causing excessive heat generation and reduced service life
Solution Approach 1:
The patent introduces a current limiting unit as an intermediary component between the fuse and the circuit. This unit limits the current flowing through the fuse to a safe level during normal operation, preventing excessive heat generation while still allowing the fuse to perform its protective function when faults occur. The current limiting unit acts as a mediator that protects the fuse from harmful current levels without compromising the overall breaker apparatus reliability.
2Productivity
If the fuse is designed to handle full current during normal operation for reliable fault disconnection, then the breaking capability is ensured, but the fuse heats up excessively and service life is reduced
Solution Approach 1:
The patent applies partial action by having the current limiting unit restrict the current flow through the fuse to only what is necessary for its protective function. During normal operation, the fuse does not need to handle the full current - only a limited portion flows through it. This partial current flow is sufficient to maintain the fuse's breaking capability while preventing excessive heat generation that would reduce its service life.
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
The solution effectively reduces heat generation in the overcurrent-automatic-disconnection unit, extends its service life, and enhances the reliability of the breaker apparatus by ensuring safe disconnection of the electrical connection during faults.
Implementation Method 1
the overcurrent-automatic-disconnection unit is configured to be automatically disconnected when a current flowing through the overcurrent-automatic-disconnection unit exceeds a breaking current threshold
Implementation Method 2
the first current limiting unit is configured to limit a current on the first branch
Implementation Method 3
When the DC/DC conversion unit operates normally, a controller controls the relay to be closed. In this case, an output current of the photovoltaic string is shunted based on a proportional relationship between internal resistance of the relay and internal resistance of the fuse
Implementation Method 4
an output current of the photovoltaic string all flows through the fuse, and the fuse is blown passively
Implementation Method 5
a considerable part of the current flows through the fuse, causing the fuse to heat up
Data Source
AI summary
A breaker apparatus and an inverter system are configured to disconnect an electrical connection when a fault occurs in a protected circuit. The breaker apparatus is connected in series in a protected circuit, and is configured to disconnect the electrical connection when a fault occurs in the protected circuit. The breaker apparatus includes a first branch, and a second branch. The first branch includes an overcurrent-automatic-disconnection unit and a first current limiting unit that are connected in series, where the overcurrent-automatic-disconnection unit is configured to be automatically disconnected when a current flowing through the overcurrent-automatic-disconnection unit exceeds a breaking current threshold. The a second branch is configured to be open or closed under control of the controller. The controller is configured to control the first controllable switch unit to be closed when the protected circuit operates normally, and control the first controllable switch unit to be open when a fault occurs in the protected circuit.