Direct Liquid-Cooled Inductor for EV Core Hot Spot Control
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Solution Overview
Problem
Current cooling systems for inductors in electric vehicles are ineffective in cooling the core, which is the hottest spot and experiences increased energy losses due to the use of Silicon Carbide (SiC) MOSFET circuits, especially under high boost voltage conditions.
Innovation Solution
A cooling system where transmission fluid is circulated to directly contact the core and coils, flowing through channels on the surface of the core and windings to absorb heat, with an oil circulation system providing pressurized oil supply and drainage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional cooling systems (cold plate, thermal pad, oil splashing) are used to cool the inductor, then the coils can be cooled, but the core remains the hottest spot and is not effectively cooled
Solution Approach 1:
The cooling system is segmented into two separate cooling paths: one for the core and one for the coils. The core has dedicated cooling channels with oil flow passages that allow direct cooling, while the coils are cooled separately through end caps and thermal paths. This segmentation enables independent optimization of cooling for each component, effectively addressing the core temperature issue without compromising coil cooling.
Solution Approach 2:
Oil is introduced as an intermediary cooling medium that directly contacts both the core and coils. The oil circulates through channels in the core and absorbs heat, then continues to cool the coils. This liquid intermediary enables efficient heat transfer from both the core and coils, overcoming the limitation of conventional air or indirect cooling methods.
2Power
If Silicon Carbide (SiC) MOSFET circuits are used to increase switching frequency and maximum boost voltage, then converter performance is improved, but temperatures and core energy losses increase
Solution Approach 1:
The cooling system parameters are optimized to match the higher power density and temperature levels generated by SiC MOSFET circuits. The oil flow rate, channel dimensions, and thermal path configurations are adjusted to handle the increased heat loads from both the core and coils, enabling the system to operate at higher voltages and frequencies without overheating.
3Productivity
If the core is cooled indirectly through heated coils, then cooling is provided, but the cooling efficiency is low and the core remains substantially hotter than the coils
Solution Approach 1:
Oil serves as a direct intermediary cooling medium that contacts the core surfaces through dedicated channels, eliminating the need for indirect cooling through the coils. This direct liquid cooling path dramatically improves cooling efficiency and reduces the temperature difference between the core and coils by providing a separate, efficient heat removal path from the core.
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 solution effectively cools both the core and coils simultaneously, reducing temperature and energy losses, and is applicable to hybrid and other electric vehicles.
Implementation Method 1
oil flowing through the oil flow passage is in direct contact with both the windings and the core to absorb heat from the windings and the core
Implementation Method 2
transmission fluid is circulated to directly contact and cool both the core and coils of the inductor
Data Source
AI summary
An inductor for a converter of an electric machine includes a core defining a channel configured to receive transmission fluid on an outer surface of the core. Coils made of windings are wrapped on the core. The windings enclose an open side of the channel to define an oil flow passage, wherein oil flowing through the oil flow passage is in direct contact with both the windings and the core to absorb heat from the windings and the core.