Electric Machine Cooling Jacket and Rotor Channels
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Solution Overview
Problem
Conventional electric machine cooling methods, such as passing a coolant around the perimeter, lead to reduced heat rejection efficiency due to high interface and convection resistances, particularly affecting the stator and rotor assemblies, which can result in reduced bearing life and ineffective heat rejection.
Innovation Solution
An electric machine module with a housing featuring a coolant jacket that circumscribes the stator assembly, a coolant sump, and coolant channels that facilitate fluid communication, allowing for the circulation of a first coolant to absorb heat and a second coolant to enhance convection through centrifugal pumps and channels, improving heat transfer and rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a coolant is passed around the perimeter of the electric machine, then cooling is provided to the machine, but heat rejection efficiency is reduced due to high interface and convection resistances
Solution Approach 1:
The cooling system is segmented into multiple independent coolant channels positioned at different locations within the housing, allowing separate coolant flows to target specific heat-generating components (stator, rotor, bearings) independently, thereby overcoming the limitations of a single perimeter coolant path
Solution Approach 2:
Different regions of the housing are equipped with customized cooling solutions - coolant channels are strategically positioned near the stator assembly, rotor assembly, and bearings to provide localized cooling where heat generation is highest, rather than uniform perimeter cooling
2Loss of energy
If heat is conducted through the rotor assembly shaft and bearings, then heat transfer occurs, but bearing life is reduced and conduction resistance is high
Solution Approach 1:
The heat extraction function is separated from the bearing support structure. Instead of relying on the shaft and bearings to conduct heat away from the rotor, dedicated coolant channels are positioned to directly cool the rotor assembly and bearings separately, extracting heat through the housing walls rather than through the bearing components
Solution Approach 2:
A coolant fluid serves as an intermediary heat transfer medium between the rotor assembly/bearings and the housing. The coolant absorbs heat directly at the source through positioned channels and transfers it to the housing, eliminating the need for heat conduction through the bearing structures
3Loss of energy
If heat is lost by forced convection to internal air within the housing, then heat rejection occurs, but convection resistance is high making it ineffective
Solution Approach 1:
The system transitions from gas-phase (air) convection to liquid-phase (coolant) heat transfer. Coolant channels positioned within or near the rotor assembly enable direct liquid cooling, which provides superior heat transfer coefficients compared to air convection, effectively overcoming the high convection resistance of internal air
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 increases heat convection from the stator and rotor assemblies, reduces cooling requirements, and enhances the durability and efficiency of the electric machine by effectively transferring heat energy to the coolant, thereby maintaining lower operating temperatures and reducing system costs.
Implementation Method 1
The coolant extracts heat from portions of the electric machine
Implementation Method 2
increases heat convection from the stator and rotor assemblies
Implementation Method 3
a second coolant to enhance convection through centrifugal pumps and channels
Data Source
AI summary
Embodiments of the invention provide an electric machine module including a housing. In some embodiments, the housing can include a sleeve member coupled to at least one end cap. The housing can include an inner wall at least partially defining a machine cavity, a coolant sump, and at least one coolant channel positioned between the inner wall and an outer wall of the housing. In some embodiments, the coolant channel can be in fluid communication with the coolant sump. In some embodiments, an electric machine can be positioned in the machine cavity. The electric machine can comprise a stator assembly including stator end turns and a rotor assembly. In some embodiments, a coolant jacket can be at least partially defined by the housing and can be positioned so that to at least partially circumscribe a portion of the stator assembly.