Capacitor Cooling in Vehicle Drive Systems
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Solution Overview
Problem
Existing vehicle drive systems with integrated rotating electric machines and electric devices lack an optimized cooling system for capacitors, leading to inefficiencies in heat management and mountability due to varying heat generation rates and inadequate electrical connection structures.
Innovation Solution
A vehicle drive system that utilizes two distinct cooling media for capacitors, with one capacitor cooled by flowing cooling medium and the other by stored oil, integrated with a cooler and housing to enhance heat dissipation and reduce system influence from differing heat generation rates, while optimizing wiring length for improved mountability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single cooling system is used for all capacitors, then the cooling system structure is simple, but it cannot effectively manage heat when capacitors generate different amounts of heat
Solution Approach 1:
The cooling system is segmented into two independent cooling circuits: a first cooling circuit for the inverter and first capacitor, and a second cooling circuit for the rotating electric machine and second capacitor. This segmentation allows each capacitor to be cooled according to its specific heat generation characteristics, resolving the contradiction between effective heat management and system simplicity.
2Ease of operation
If wiring length is not optimized, then electrical connection is simple, but mountability of the drive system onto the vehicle is poor
Solution Approach 1:
The electrical connection structure is optimized by positioning the second capacitor electrically closer to the power source than the first capacitor. This local optimization of wiring arrangement reduces the overall wiring length and improves mountability, while maintaining the functional integrity of the electrical connections.
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 reduces the overall system's heat management issues and improves mountability by using separate cooling media for capacitors, ensuring efficient heat dissipation even when one capacitor generates significantly more heat, and simplifies the electrical connection structure.
Implementation Method 1
a first cooling medium cooling the inverter
Implementation Method 2
a second cooling medium cooling the rotating electric machine
Implementation Method 3
the other of the first and second capacitors is cooled by the second cooling medium
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A vehicle drive system includes a battery (900), motor generators (MG1, MG2) driving the vehicle using electric power from the battery (900) or driven by the vehicle, a PCU (700) integrated with the motor generators (MG1, MG2), having inverters (720, 730) and controlling the motor generator (MG2), cooling water (1350) cooling inverters (720, 730), and oil (1050) cooling motor generators (MG1, MG2). The PCU (700) includes a smoothing capacitor (C2) and a filter capacitor (C1) provided electrically closer to the battery (900) than the smoothing capacitor (C2). Here, the smoothing capacitor (C2) is cooled by the cooing water (1350), while the filter capacitor (C1) is cooled by the oil (1050).