Transport Refrigeration Capacitor Discharge Using Existing Loads
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Solution Overview
Problem
Transport refrigeration units with high voltage capacitors pose safety risks during service or inspection, as existing solutions like dedicated discharge systems add weight, complexity, and generate heat, which are undesirable in refrigeration systems.
Innovation Solution
A refrigeration transport system that uses existing demand components to actively discharge capacitor voltage by communicating voltage status to a controller, which directs the components to operate until the voltage is reduced below 60 volts, thereby safely managing power flow and reducing system-wide voltage within 5 seconds of shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated discharge system (resistors) is used to discharge capacitor voltage, then voltage discharge is achieved, but weight and device complexity increase
Solution Approach 1:
The patent makes existing demand components perform an additional function: voltage discharge. These components normally consume power during operation, but after shutdown they are repurposed to discharge capacitor voltage. This multi-functionality eliminates the need for dedicated discharge resistors, reducing system complexity and weight while maintaining safety.
Solution Approach 2:
The system uses its own existing components (demand components with capacitors) to discharge their stored voltage, rather than requiring external discharge equipment. The demand components serve themselves by converting their stored electrical energy into operational function temporarily, achieving discharge without additional systems.
2Reliability
If a dedicated discharge system (resistors) is used to discharge capacitor voltage, then voltage discharge is achieved, but heat is generated which is undesirable in refrigeration systems
Solution Approach 1:
The patent converts the potentially harmful stored voltage in capacitors into a useful function by operating demand components. Instead of dissipating voltage as heat through resistors, the electrical energy is converted into mechanical or operational work by the demand components, eliminating harmful heat generation while achieving voltage discharge.
Solution Approach 2:
The patent replaces the thermal discharge mechanism (resistors converting electrical energy to heat) with a mechanical/operational discharge mechanism (demand components converting electrical energy to work). This substitution eliminates the harmful thermal effect while achieving the same voltage discharge goal.
3Device complexity
If demand components are used to actively discharge capacitors, then weight and complexity are reduced, but voltage must be monitored and controlled
Solution Approach 1:
The patent implements a feedback control system where the controller monitors capacitor voltage status and adjusts demand component operation accordingly. The controller receives voltage status information, determines whether discharge is needed, and controls the timing and duration of demand component operation to achieve target voltage levels, ensuring safe discharge while maintaining simplicity.
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 approach effectively and safely reduces capacitor voltage to a safe level without adding weight or heat, enhancing operational safety and efficiency by utilizing existing components for voltage discharge.
Implementation Method 1
a capacitor, the demand component being operably coupled with the capacitor. Halting operation of the transportation refrigeration system may leave an undesirable voltage in one or more capacitors
Data Source
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AI summary
A refrigeration transport system (200) including a power source (512) providing a power flow to a demand component (26, 42, 44, 48), wherein the demand component (26, 42, 44, 48) is operatively coupled to a capacitor; and a controller (30) configured to actively discharge the capacitor when the power flow is interrupted.