Battery Disconnect Unit Two-Phase Cooling for SiC Power Electronics
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Solution Overview
Problem
Existing battery disconnect units (BDUs) for electric vehicles face challenges in efficiently cooling SiC-based semiconductor components due to high heat flux densities, leading to increased energy consumption, costs, and vehicle weight from high-capacity cooling systems and additional components required for leakage prevention.
Innovation Solution
A battery disconnect unit with a cooling device featuring a media-tight housing filled with a dielectric fluid, where the fluid absorbs heat from SiC components, undergoes boiling to enhance heat transfer, and the design allows for reduced pressure losses and energy consumption by using existing cooling plates and minimizing the need for high-efficiency cooling plates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional liquid cooling systems with high pump capacities are used to cool SiC semiconductor components, then effective heat dissipation is achieved, but energy consumption increases and vehicle weight increases
Solution Approach 1:
The patent utilizes the phase transition of dielectric fluid from liquid to gas (boiling) to absorb heat from SiC semiconductor components. The fluid boils at controlled temperatures (e.g., 80-150°C) creating vapor bubbles that rise and collapse, transferring heat efficiently to cooling channels without requiring high pump capacities, thus reducing energy consumption while maintaining effective heat dissipation
Solution Approach 2:
The patent employs a two-phase fluid system where dielectric liquid and vapor phases work together to transfer heat. The vapor phase rises to cooling channels where it condenses, creating a natural circulation loop that reduces reliance on high-power pumps while achieving effective cooling of the semiconductor components
2Temperature
If traditional liquid cooling systems with high pump capacities are used to cool SiC semiconductor components, then effective heat dissipation is achieved, but vehicle weight increases
Solution Approach 1:
By utilizing phase transitions of dielectric fluid, the system achieves high heat dissipation efficiency without requiring oversized cooling plates and high-capacity pumps. The phase change mechanism provides superior heat transfer coefficients that allow for more compact cooling system design, thereby reducing overall vehicle weight
Solution Approach 2:
The two-phase cooling system utilizes natural circulation driven by density differences between liquid and vapor phases. This self-circulating mechanism reduces or eliminates the need for high-power pumps, leading to a lighter cooling system while maintaining effective heat dissipation
3Power
If SiC semiconductor components are used for compact design, then high power density is achieved, but heat flux density increases requiring more complex cooling systems
Solution Approach 1:
The patent applies phase transition cooling directly to SiC semiconductor components through浸没式 (immersion) cooling. The dielectric fluid boils on the component surfaces, creating vapor bubbles that efficiently carry heat away. This approach handles the high heat flux density inherent in compact SiC designs without requiring complex external cooling infrastructure
Solution Approach 2:
The dielectric fluid acts as an intermediary between the SiC semiconductor components and the cooling system. It directly contacts the hot components, absorbs heat through phase change, and transports it to cooling channels. This intermediary approach simplifies the overall system by eliminating the need for complex heat transfer interfaces and intermediate cooling mechanisms
4Reliability
If additional components such as encapsulation and limiting frames are added to prevent leakage currents, then electrical safety is improved, but manufacturing costs increase
Solution Approach 1:
The patent uses a dielectric fluid with high electrical resistivity (greater than 10^12 Ω·cm) as the cooling medium. This fluid naturally prevents leakage currents and short circuits between closely spaced conductors, eliminating the need for additional encapsulation materials and limiting frames, thereby reducing manufacturing costs while maintaining electrical safety
Solution Approach 2:
The patent changes the electrical parameter of the cooling fluid by selecting dielectric fluids with extremely high resistivity. This parameter change allows the fluid itself to provide electrical insulation functionality, replacing the need for separate encapsulation components and reducing overall manufacturing complexity and cost
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 proposed solution effectively reduces energy consumption and costs by minimizing the need for high-capacity cooling systems, decreases vehicle weight, and maintains efficient heat dissipation through evaporative cooling and increased surface area, resulting in a more efficient and cost-effective cooling system.
Implementation Method 1
heat is transferred to the dielectric fluid, meaning that the dielectric fluid can initially absorb the heat of the at least one component directly
Implementation Method 2
the boiling of the dielectric fluid results in high turbulence in the area of the boiling bubbles, which leads to a very high heat transfer coefficient. This is also referred to as evaporative cooling and is a very efficient form of heat transport
Implementation Method 3
the dielectric fluid undergoes a phase change
Data Source
AI summary
A battery disconnect unit for separating a battery arrangement from at least one consumer of a drive system includes a cooling device having a media-tight housing. The housing includes a base plate and a cooling plate arranged opposite the base plate. The housing forms an internal volume at least partially filled with a dielectric fluid. The battery disconnect unit further includes at least one component of a power electronics system arranged on the base plate of the cooling device via at least one ceramic substrate. The at least one component of the power electronics system is covered with the dielectric fluid in the internal volume of the housing of the cooling device.