DC Voltage Precharge Circuit with Dynamic Inductor Control
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Solution Overview
Problem
High-power DC voltage electrical systems face issues with current spikes and overvoltage during contactor closure due to parasitic inductance and capacitance, leading to potential damage to contactors and electronic components, and existing precharge circuits suffer from energy losses and fuse sizing challenges.
Innovation Solution
A DC voltage electrical power supply system with a precharge circuit that includes a contactor in series with a high-power resistor, where a switch and inductor form a second connection branch to precharge the decoupling capacitor, allowing controlled current regulation and reduced energy losses, and using multiple diodes for breakdown resistance and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precharge circuit with high-power resistor is used to charge the decoupling capacitor, then current spikes are reduced, but energy losses increase due to heat dissipation in the resistor
Solution Approach 1:
The patent applies dynamics by making the precharge resistance variable rather than fixed. The resistance value changes over time during the precharge process, starting high to limit current and gradually decreasing to transfer energy to the capacitor. This dynamic adjustment optimizes both current limitation and energy efficiency throughout the charging process.
Solution Approach 2:
The patent changes the resistance parameter during operation. By varying the resistance value as a function of time or capacitor voltage, the system adapts to different charging stages, reducing energy losses while maintaining effective current spike suppression. This parameter change allows the precharge circuit to be more efficient than a fixed resistor approach.
2Reliability
If the precharge duration is extended to fully charge the capacitor, then current spikes are minimized, but the time to supply power to the load increases
Solution Approach 1:
The patent applies partial action by determining when precharging is sufficient rather than waiting for complete charging. The control unit monitors capacitor voltage and decides when to stop precharging and close the contactor, balancing protection needs with time efficiency. This avoids unnecessary extended precharge time while maintaining adequate protection.
Solution Approach 2:
The patent uses feedback by continuously monitoring the capacitor voltage during precharging. The control unit adjusts the precharge duration based on the actual charging state, stopping when sufficient voltage is reached. This feedback mechanism optimizes the trade-off between protection and time by adapting to real-time conditions.
3Reliability
If a fuse is added in series with the precharge resistor for protection, then component safety is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies multi-functionality by designing the control unit to perform multiple functions: monitoring capacitor voltage, controlling the precharge process, determining when precharging is sufficient, and controlling contactor closure. This integrated approach provides protection without adding separate protective components like fuses, reducing overall system complexity.
Solution Approach 2:
The patent applies self-service by using the control unit's existing monitoring and control capabilities to provide protection during precharging. The system uses its own resources (voltage sensing and control logic) to prevent overcurrent conditions, eliminating the need for additional protective devices and simplifying the overall system architecture.
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 system effectively reduces energy losses and minimizes the risk of component damage by controlled precharging, allowing for efficient and safe power supply to electrical loads with improved component reliability and reduced costs.
Implementation Method 1
A capacitor stores energy in electrostatic form
Implementation Method 2
A capacitor stores energy in electrostatic form. The smoothing capacitor, also called a decoupling capacitor, allows an energy reserve to be kept as close as possible to the components used for the switching operations
Implementation Method 3
The wiring circuit between the power supply system and the decoupling capacitor forms a series resonance circuit. The inductance is that of the wiring circuit, conventionally of the order of 1 μH per meter of length. The capacitance is essentially defined by the decoupling capacitor
Implementation Method 4
The precharge circuit typically includes a contactor connected in series with a high-power resistor. When the contactor of the precharge circuit is closed, a large current flows through this circuit in order to charge the decoupling capacitor. A heavy load is then suddenly placed on the high-power resistor during charging and it must be capable of transiently storing the energy in the form of heat
Data Source
AI summary
The invention concerns an electrical system that comprises: —an electrical charge (42, 43); —a decoupling capacitor (41); —a DC voltage power supply system, comprising first and second terminals (321, 322), including: —a DC voltage source (2) comprising first and second poles; —a first branch including a first contactor (51); —a second branch including first and second switches (302, 303) and an inductor (305) connected in series in order to selectively connect the DC voltage source to the first terminal (321) of the power supply system; —a unidirectional conducting device (307, 308, 309) for conduction from the second terminal of the DC power supply system to a connection node (323) between the second switch (303) and said inductor (305); —a control circuit (304) comprising —a mode for supplying electrical load (42, 43); —a mode for charging the decoupling capacitor (41).