Rotor Shaft Cooling Channel Layout for Permanent Magnet Heat Removal
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Solution Overview
Problem
Existing cooling systems for electric machine rotors, particularly those using liquid cooling, face challenges in efficiently cooling permanent magnets due to indirect heat exchange and mechanical losses, leading to reduced performance and lifespan.
Innovation Solution
A rotor design with longitudinal cooling channels at the periphery of the rotor shaft and a sleeve arrangement that increases the diameter, allowing for closer proximity to permanent magnets and simplified production, enhancing heat exchange and reducing mechanical losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If cooling channels are positioned close to the rotor shaft to facilitate supply and minimize pump demands, then the pump capacity requirements are reduced, but the number of channels is limited thereby reducing heat exchange capacity
Solution Approach 1:
The patent transitions from radial positioning of cooling channels (close to the shaft) to longitudinal positioning along the rotor shaft axis. This dimensional change allows multiple cooling channels to be arranged in series along the length of the rotor shaft, increasing the total number of channels and heat exchange surface area without significantly increasing the radial distance from the shaft, thus maintaining reasonable pump capacity requirements while enhancing heat exchange capacity.
2Quantity of substance
If cooling channels are positioned far from the rotor shaft to increase heat exchange capacity, then more channels can be accommodated, but the back pressure in the heat transfer fluid increases due to centrifugal speed
Solution Approach 1:
The patent arranges cooling channels longitudinally along the rotor shaft rather than radially outward from it. This longitudinal arrangement allows the channels to extend along the axis of rotation, maximizing their length and heat exchange capacity without increasing their radial distance from the shaft. Consequently, the channels benefit from both increased heat exchange capacity and reduced back pressure, as the fluid does not need to overcome high centrifugal forces over long radial paths.
3Quantity of substance
If radial supply solutions are used to position channels away from the shaft, then heat exchange capacity can be increased, but dynamic seals are required which induce mechanical losses and require replacement
Solution Approach 1:
The patent extracts the cooling channels from the radial supply system and integrates them directly into the rotor shaft structure as longitudinal channels. This eliminates the need for dynamic seals and radial supply mechanisms, removing the source of mechanical losses and wear. The cooling fluid is supplied axially through the rotor shaft, and the longitudinal channels are formed directly in or on the rotor shaft, eliminating intermediate components and improving reliability.
4Quantity of substance
If complex rotor shaft designs with drilling and specific shapes are used, then cooling channels can be positioned optimally, but the manufacturing complexity increases
Solution Approach 1:
The patent simplifies manufacturing by adopting longitudinal cooling channels that run parallel to the rotor shaft axis, rather than requiring complex radial drilling and curved pathways. These longitudinal channels can be formed using standard machining operations such as milling or boring, which are much simpler than creating radial channels that would require precise drilling at various angles and positions. The longitudinal arrangement allows for straightforward tooling and process planning, significantly reducing manufacturing complexity while still achieving optimal cooling channel positioning.
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 design achieves effective cooling of permanent magnets, improving the thermal resistance and performance of electric machines while reducing the need for complex production and mechanical stress.
Implementation Method 1
Heat exchange is indirect between the magnets and the fluid, with heat transferred by conduction from the permanent magnets to the iron, then by conduction from the iron to the rotor shaft, and finally to the cooling fluid
Implementation Method 2
the cooling fluid circulates in the central part of the rotor... heat transferred by conduction from the permanent magnets to the iron, then by conduction from the iron to the rotor shaft, and finally to the cooling fluid
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention relates to a rotor (1) comprising a rotor body and a stack of laminations (2) shrink-fitted onto the rotor body. The rotor body comprises a rotor shaft (3), a first sleeve (4), and at least one first cooling channel (5). Each first cooling channel (5) is longitudinal and is arranged between the rotor shaft (3) and the first sleeve (4). Furthermore, the first channel (5) is arranged on the periphery of the rotor shaft (3).