Dual-Circuit Cooling for EV Inverters and Electric Motors
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Solution Overview
Problem
Existing cooling systems for electric motor vehicles and plug-in hybrid vehicles often operate at high coolant temperatures, limiting the maximum current that can be sustained by semiconductor switches in power electronics devices, such as IGBTs, which restricts torque and drive power.
Innovation Solution
Implementing a separate second coolant circuit with a lower maximum temperature for the power electronics device, allowing it to be cooled independently of the electric motor, thereby enabling higher currents and torques by maintaining semiconductor switches at lower temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power electronics device is cooled in the same cooling circuit as the electric motor with high coolant temperature, then the electric motor can operate at lower friction, but the maximum current in the pulse inverter is limited
Solution Approach 1:
The cooling system is divided into two separate cooling circuits: a first cooling circuit for the electric motor and a second cooling circuit for the power electronics device. This segmentation allows each component to be cooled at its optimal temperature independently, resolving the contradiction between motor friction reduction (requiring higher temperature) and inverter current capacity (requiring lower temperature).
Solution Approach 2:
The power electronics device is extracted from the motor cooling circuit and placed in a separate cooling circuit. This extraction enables the power electronics device to be cooled to lower temperatures (50-65°C) while the motor cooling circuit can operate at higher temperatures for reduced friction, thereby increasing the maximum sustainable current in the pulse inverter.
2Productivity
If the coolant temperature for the power electronics device is reduced from 75°C to lower temperatures, then higher currents can be sustained in the pulse inverter, but this requires a separate cooling circuit
Solution Approach 1:
The cooling system is segmented into two independent circuits with different temperature levels. The second cooling circuit for power electronics operates at lower temperatures (50-65°C) to enable higher current capacity (up to 580 A for 10 seconds), while the first cooling circuit for the motor operates at higher temperatures to reduce friction.
Solution Approach 2:
The coolant temperature parameter is changed for different components: the second cooling circuit maintains coolant temperature between 50-65°C for the power electronics device to maximize current capacity, while the first cooling circuit uses higher temperatures for the motor. This parameter differentiation resolves the contradiction between current capacity and system complexity.
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 allows for higher maximum currents in the pulse inverter, specifically up to 580 A for 10 seconds, compared to 480 A at higher temperatures, enhancing drive power without risking component destruction and reducing friction in the electric motor.
Implementation Method 1
the power electronics device is cooled in a second cooling circuit, which is separate from the first cooling circuit, using coolant of a second maximum temperature in the supply flow, which is lower than the first maximum temperature
Data Source
AI summary
A motor vehicle comprises a drive train with an electric motor, to which a traction battery and a power electronics device comprising at least one pulse inverter are associated, and a cooling device for cooling the electric motor, the power electronics device and the traction battery, wherein the electric motor is cooled in a first cooling circuit with coolant of a first maximum temperature in the supply flow, wherein the power electronics device is cooled in a second coolant circuit, which is separate from the first coolant circuit, using coolant of a second maximum temperature in the supply flow, which is lower than the first maximum temperature.