Electric Machine Cooling via Oil-Coolant Heat Exchange
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Solution Overview
Problem
Existing cooling arrangements for hybrid vehicles with electric power units face inefficiencies in cooling the electric machine and power electronics, as they require different temperature ranges and rapid thermal management, leading to suboptimal performance and energy consumption.
Innovation Solution
A cooling arrangement featuring an oil circuit with an oil radiator and a heat exchanger, along with a control unit to manage the cooling of both the oil and coolant circuits, allowing for two-step temperature adjustment of the oil before it reaches the electric machine, and separate coolant circuits for the electric energy storage and power electronics, optimized by ambient temperature and sensor feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single coolant circuit is used to cool both power electronics and electric machine, then the cooling system is simpler, but it cannot provide different temperature ranges required by different components
Solution Approach 1:
The cooling system is divided into two separate coolant circuits: a first coolant circuit for cooling power electronics and a second coolant circuit for cooling the electric machine. This segmentation allows each circuit to be optimized for the specific temperature requirements of different components, resolving the contradiction between system simplicity and temperature adaptability.
2Device complexity
If the electric energy storage is cooled by ambient air when temperature is low, then cooling is simple, but the electric machine cannot be heated when ambient temperature is low
Solution Approach 1:
The first coolant circuit serving power electronics is designed to perform multiple functions: it can cool the power electronics, and through the heat exchanger, it can also heat the oil in the oil circuit when ambient temperature is low. This multi-functionality resolves the contradiction between system simplicity and heating capability.
3Reliability
If a large coolant radiator is used to provide sufficient cooling capacity, then cooling performance is improved, but the thermal inertia reduces responsiveness to rapid cooling demand changes
Solution Approach 1:
The cooling system is segmented into multiple circuits with different thermal characteristics. The oil circuit with smaller thermal mass can respond rapidly to cooling demands of the electric machine, while the first coolant circuit with larger thermal inertia provides stable cooling for power electronics. This segmentation resolves the contradiction between cooling performance and thermal response speed.
4Reliability
If the oil is cooled directly by a large oil radiator, then cooling capacity is sufficient, but energy consumption and noise increase
Solution Approach 1:
The first coolant circuit acts as an intermediary between the ambient air (via coolant radiator) and the oil in the oil circuit. Heat is transferred from the oil to the coolant through a heat exchanger, allowing indirect cooling that reduces the size and power requirements of the oil radiator, thereby reducing energy consumption and noise while maintaining sufficient cooling capacity.
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 provides stable and efficient cooling for the electric machine and power electronics, minimizing energy consumption and noise, while ensuring the electric energy storage operates within its optimal temperature range, even under varying ambient conditions.
Implementation Method 1
a heat exchanger in which heat is transferred between the coolant in the first coolant circuit and the oil
Implementation Method 2
an oil radiator in which the oil is cooled by air
Data Source
AI summary
A cooling arrangement for an electric machine (2) and at least one further component (4, 5) of an electric power unit: The cooling arrangement comprises an oil circuit (16), an oil pump (46) circulating oil to the electric machine (2), a first coolant circuit (6) configured to cool the further component (5) of the electric power unit, and coolant radiator arrangement (8a, 8b) in which the coolant in the first coolant circuit (6) is cooled by air, The oil circuit (16) comprises an oil radiator (46), an oil radiator fan (47) configured to provide an adjustable air flow through the oil radiator (46) and a heat exchanger (15) in which heat is transferred between the coolant in the first coolant circuit (6) and the oil in the oil circuit (16).