DC Bus Capacitor Discharge via Dynamic Switching
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Solution Overview
Problem
In power conversion systems with floating ground configurations, the conditioner capacitor often remains charged for a long time after shutdown due to the absence of a dedicated discharge resistor, posing safety risks and requiring manual intervention for discharge.
Innovation Solution
A discharge circuit with a monitor circuit and power supply is activated when the DC bus voltage drops below a threshold, connecting a discharge resistor between the conditioner capacitor and the reference node to automatically discharge the capacitor, ensuring safe and timely access to the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a dedicated discharge resistor is permanently connected to the conditioner capacitor, then the capacitor can be discharged quickly after shutdown, but the system complexity increases and leakage current problems arise in floating ground configurations
Solution Approach 1:
The discharge resistor is connected dynamically through a switching circuit only when needed (after shutdown), rather than being permanently connected. The switch transitions from open during operation to closed after shutdown, enabling discharge only when required. This resolves the contradiction by providing quick discharge capability without permanently increasing system complexity or creating continuous leakage current paths in floating ground configurations.
Solution Approach 2:
The control circuit detects shutdown conditions in advance and activates the switching circuit to connect the discharge resistor before the capacitor voltage becomes hazardous. This preliminary action ensures the discharge path is established timely without requiring permanent connection, balancing safety requirements with system simplicity.
2Device complexity
If no discharge resistor is connected to the conditioner capacitor, then the system remains simple and leakage current is minimized, but the capacitor remains charged for a long time after shutdown creating safety risks
Solution Approach 1:
The system uses its own control circuit and power supply to automatically activate the discharge circuit after shutdown. The control circuit monitors system state and self-activates the discharge function without external intervention, eliminating safety hazards while maintaining system simplicity during normal operation. The discharge occurs automatically when needed, providing safety without permanent complexity.
Solution Approach 2:
The control circuit detects shutdown conditions and activates the discharge resistor in advance before capacitor voltage reaches hazardous levels. This preliminary activation ensures safety is addressed proactively rather than reactively, eliminating safety hazards while avoiding permanent circuit complexity.
3Device complexity
If manual intervention is required to discharge the conditioner capacitor, then the system remains simple without additional discharge circuits, but operational safety is compromised and maintenance time increases
Solution Approach 1:
The system automatically performs the discharge function through its control circuit and switching mechanism without requiring manual intervention. The control circuit detects shutdown and autonomously activates the discharge resistor, eliminating both manual time loss and the need for complex manual discharge procedures. The system serves itself by automatically managing capacitor discharge safety.
Solution Approach 2:
The control circuit acts as an intermediary between system shutdown and capacitor discharge, automatically coordinating the discharge action without human intervention. This intermediary function eliminates manual time loss while keeping the discharge circuit simple and integrated into the existing 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 solution effectively and automatically discharges the conditioner capacitor, reducing safety hazards and eliminating the need for manual intervention, particularly in marine applications where a dedicated discharge resistor is undesirable.
Implementation Method 1
connect a discharge resistor between the first reference node and a DC bus terminal of the DC bus circuit to at least partially discharge the terminals of the conditioner capacitor through the discharge resistor
Data Source
AI summary
Power conversion systems, discharge circuits and methods are disclosed for discharging a DC bus conditioner capacitor connected between a neutral node and a first reference node in a DC bus circuit of a power conversion system, in which a DC bus voltage of the power conversion system is monitored, and a discharge control DC power supply is activated in response to the DC bus voltage transitioning below a first threshold voltage to activate a switching circuit to connect a discharge resistor between the first reference node and a DC bus terminal of the DC bus circuit to at least partially discharge the conditioner capacitor through the discharge resistor.