DC Link Capacitor Charging Circuit with Segmented Switching
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Solution Overview
Problem
Existing circuit arrangements for charging DC link capacitors often require large and heavy switching elements to manage high currents, which is problematic in space-constrained applications like motor vehicles and wind turbines, as they can overload the charging battery and cause damage.
Innovation Solution
The use of two additional switching elements connected in series with the pre-charging resistor, one electronic and one electromechanical, allows for reduced installation space and weight by sequentially controlling the charging current through the resistor, preventing wear and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single switching element is used to connect the charging battery directly to the DC link capacitor, then the circuit is simple, but a high current flows that can overload and damage the charging battery
Solution Approach 1:
The single switching element is segmented into two switching elements (first switching element and second switching element) that operate in sequence. The first switching element connects the charging battery to the pre-charging resistor, while the second switching element connects the DC link capacitor to the pre-charging resistor, enabling controlled charge limiting during battery charging.
2Reliability
If a charging resistor with a further switching element is used to limit charging current, then the battery is protected from overload, but the installation space and weight increase due to the large switching element required for high voltage and current
Solution Approach 1:
The function of the single high-capacity switching element is segmented between two switching elements with lower individual ratings. Each switching element only needs to handle the pre-charging current through the resistor, not the full battery current, reducing individual component size and installation space.
Solution Approach 2:
The pre-charging resistor acts as an intermediary component that limits the charging current from the battery. By placing the resistor in series with the switching elements, it mediates the current flow, allowing the use of smaller switching elements that would not be capable of handling the full battery current directly.
3Reliability
If a pre-charging resistor is used to limit charging current, then the battery is protected, but heat generation occurs during the charging process
Solution Approach 1:
The pre-charging resistor is engaged only periodically during the initial phase of battery charging when current limiting is needed. Once the battery voltage approaches the DC link capacitor voltage, the switching elements open the pre-charging path, eliminating resistive heat generation for the remainder of the charging process.
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 configuration reduces the size and weight of the switching elements, preventing overloading and damage, while minimizing installation space requirements and heat generation within the battery control unit.
Implementation Method 1
a comparatively high current would flow from the charging battery to the DC link capacitor... In order to at least temporarily limit the charging current, the known circuit arrangements have a charging resistor
Implementation Method 2
a first switching element for optionally electrically connecting a first connection contact of the circuit arrangement for the charging battery to a second connection contact of the circuit arrangement for the DC link capacitor
Data Source
AI summary
A circuit arrangement for charging a DC link capacitor with electrical energy from a charging battery includes a first switching element. The first switching element can optionally electrically connect a first connection contact of the circuit arrangement for the charging battery to a second connection contact of the circuit arrangement for the DC link capacitor. The circuit arrangement also includes an electrical pre-charging resistor that can connect in parallel with the first switching element. The circuit arrangement also includes two second switching elements that can be connected in series with the pre-charging resistor and in parallel with the first switching element.