Power Semiconductor Cooling with Integrated Bus-Bar Heat Spreading
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Solution Overview
Problem
Power semiconductors, particularly in solid-state circuit breakers, face challenges with heat dissipation due to their geometry mismatch with traditional two-phase thermosiphon cooling systems, leading to ineffective hot-spot configurations and prolonged cooling times, especially during repetitive operations and reclosing actions.
Innovation Solution
A configuration that incorporates a metallic heat spreader, such as copper or aluminum, between the power semiconductor and the base-plate of the cooling element, combined with a bus bar, to enhance heat spreading and reduce thermal resistance, allowing for efficient active cooling without excessive component oversizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional two-phase thermosiphon cooling systems are used, then cooling capability is provided, but the geometry mismatch between power semiconductors and base-plate results in ineffective hot-spot configuration
Solution Approach 1:
A heat spreader is introduced as an intermediary component between the power semiconductor device and the cooling base-plate. This heat spreader serves as a mediator that receives heat from the semiconductor and distributes it across the base-plate surface, resolving the geometry mismatch issue by providing a thermal coupling interface that adapts between the two components with different geometries.
Solution Approach 2:
The heat spreader transforms the point-source heat input from the semiconductor into a distributed two-dimensional heat distribution across the base-plate. By spreading heat laterally in the plane of the base-plate, the system converts a localized hot-spot problem into a distributed thermal field that is more effectively managed by the cooling system.
2Temperature
If heat spreaders are used to spread heat across the entire base-plate area, then cooling effectiveness is improved, but cost and complexity increase
Solution Approach 1:
The heat spreader and bus-bar are merged into a single integrated component. The bus-bar, which is already present for electrical connection, is designed to also serve as the heat spreader for thermal management. This consolidation eliminates the need for a separate heat spreader component, reducing part count and assembly complexity while maintaining effective heat distribution across the base-plate.
Solution Approach 2:
The bus-bar is designed to perform dual functions: electrical conduction and thermal conduction. By making the bus-bar also serve as the heat spreader, the system achieves multi-functionality where a single component handles both electrical and thermal management tasks, thereby reducing overall system complexity.
3Temperature
If natural convection cooling is used, then device simplicity is maintained, but cooling time exceeds 30 minutes during repetitive operation
Solution Approach 1:
The system employs liquid cooling through a closed-loop liquid cooling system with pumps and heat exchangers. The liquid coolant circulates through channels in the base-plate, providing forced convection heat removal that dramatically reduces cooling time compared to natural convection, enabling the circuit breaker to return to operating temperature within seconds rather than minutes.
Solution Approach 2:
The liquid cooling system utilizes phase transition of the coolant (liquid to vapor and back) in the heat exchanger to efficiently remove heat. The evaporative cooling process in the heat exchanger provides high heat transfer coefficients, enabling rapid cooling of the power semiconductor during and between operational cycles.
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 enables repetitive operation and reclosing functions in solid-state circuit breakers with increased power density, minimized surge arrester requirements, and improved thermal reliability, reducing thermal stress and maintaining high performance with lower costs.
Implementation Method 1
A metallic heat spreader (e.g., copper, aluminum, or a two-phase device) in between the power semiconductor and base-plate of the cooling element
Implementation Method 2
This is particularly critical when the circuit breaker has the requirement of multiple reclosing actions after a fault. The state of the art involves natural convection cooling of the surge arrester.
Implementation Method 3
Some products have used Cothex two-phase thermosiphon based cooling to provide greater power density than heat sinks without the auxiliary pumps required for liquid cooling.
Data Source
AI summary
Cooling arrangements are disclosed for solid state circuit breakers. In one arrangement, a MOV is disposed between two pulsating heat pipes. An IGCT is disposed on the other side of each pulsating heat pipe away from the MOV. In another arrangement, a bus bar is integral with a heat spreader disposed between a pulsating heat pipe and an IGCT.