Monitorable Pre-Charging Circuit for DC Bus Capacitor Inrush Control
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Solution Overview
Problem
High inrush currents during connection of backup capacitors to a DC bus in power distribution networks cause technical difficulties and reduce the service life of components, and existing pre-charging circuits are not optimally matched with support capacitors, especially after replacement, leading to thermal issues and excessive pre-charging cycles.
Innovation Solution
A two-pole arrangement with a monitorable electrical component as a capacitor and a pre-charging circuit, where a control processor with a measuring device monitors and evaluates operational variables like DC current and voltage to ensure optimal matching and prevent overload, integrating sensors for temperature and switching cycle monitoring, and using microstructuring for high integration and parallel charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If backup capacitors are connected directly to the DC bus, then the connection is simple and fast, but high inrush currents occur that damage components and reduce service life
Solution Approach 1:
The patent applies preliminary action by pre-charging the backup capacitor through a pre-charging circuit before connecting it to the DC bus. The pre-charging circuit charges the capacitor to a predetermined voltage level (e.g., 80% of nominal voltage) before the main connection is made, thereby eliminating the inrush current that would otherwise occur during direct connection.
Solution Approach 2:
The patent uses an intermediary element - a pre-charging resistor - that is temporarily inserted between the DC bus and the backup capacitor during the pre-charging phase. This resistor limits the charging current to a safe level, and is subsequently removed or bypassed once the capacitor is fully charged, allowing full power connection without inrush current.
2Ease of manufacture
If pre-charging circuits are installed far from support capacitors, then installation is easier, but signal transmission becomes difficult and matching after capacitor replacement is problematic
Solution Approach 1:
The patent merges the pre-charging circuit and the support capacitor into a single integrated module or assembly. This combination ensures that the pre-charging circuit is always optimally matched with its corresponding capacitor, eliminates signal transmission issues over long distances, and simplifies installation as a pre-assembled unit that maintains proper electrical connections and signal integrity.
3Productivity
If pre-charging cycles are not monitored, then the system operates continuously, but the pre-charging resistor overheats and component lifespan decreases
Solution Approach 1:
The patent implements feedback control by monitoring the temperature of the pre-charging resistor and the number of pre-charging cycles performed. When the resistor reaches a predetermined temperature threshold or a maximum number of cycles is reached, the system automatically inhibits further pre-charging operations until the resistor has cooled down, preventing thermal damage and extending component lifespan while maintaining system availability.
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 ensures pre-charging circuits are always optimally matched with backup capacitors, reduces thermal stress, and allows for efficient monitoring and control of pre-charging cycles, extending component lifespan and maintaining system performance.
Implementation Method 1
The electrical component according to the invention with at least one functional orientation as a capacitor can be monitored by the higher-level control processor, which monitors the electrical component via a measuring device that is preferably additionally used or integrated in the control processor
Implementation Method 2
Hard connection to a completely discharged capacitor results in high inrush currents that are technically difficult to control and also have a negative impact on the service life of the components used (capacitors, switch elements, terminals, lines, capacitors, etc.). For protection, a resistor is placed in series with the power path
Data Source
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AI summary
The invention relates to a monitorable electrical component with at least one functional orientation as a capacitor (4) within a topology of a pre-charging circuit in the vicinity of a power distribution network, a circuit diagram, in particular within a power distribution network, comprising a 2-pole arrangement with a monitorable electrical component having at least one functional orientation as a capacitor (4) and with a pre-charging circuit, a power distribution network with a circuit diagram as an intermediate circuit, comprising at least one 2-pole arrangement with at least one monitorable electrical component having at least one functional orientation as a capacitor (4) and with at least one pre-charging circuit, a method for operating a monitored pre-charging circuit in the form of an intermediate circuit comprising a pre-charging circuit and a monitorable electrical component having at least one functional orientation as a capacitor (4),in particular in an application in a power distribution network, as well as the use of a monitorable electrical component with at least one functional orientation as a capacitor in automation systems, drive technology, or power electronics. The invention is characterized in that the monitoring, in particular for protection against overload, is implemented by a control processor (7) which acquires and evaluates measured values.