Rotor Shaft Segmentation for Cooling Fluid Containment
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Solution Overview
Problem
Existing electric machine cooling systems lead to undesirable drag losses due to cooling fluid infiltration into the air gap between the rotor and stator, reducing performance and risking demagnetization of permanent magnets, especially under high-load conditions.
Innovation Solution
A rotor assembly with a separation element that separates the shaft into distinct portions, creating a closed cooling circuit within the shaft to prevent cooling fluid from entering the machine housing and the air gap, using a network of cooling channels and fluid-guiding elements to efficiently cool the permanent magnets without the need for rare earth materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling channels are extended into the machine housing to cool permanent magnets, then cooling efficiency is improved, but cooling fluid infiltration into the air gap causes drag losses and performance reduction
Solution Approach 1:
The shaft is segmented into a first shaft portion and a second shaft portion by a separation element, creating distinct cooling circuits. The first cooling channel is confined to the first shaft portion and the second cooling channel to the second shaft portion, preventing cooling fluid from entering the air gap while maintaining effective cooling of the permanent magnets.
Solution Approach 2:
The separation element acts as an intermediary component that divides the shaft interior and prevents cooling fluid from the first and second cooling channels from mixing or escaping into the machine housing, thereby eliminating drag losses while preserving cooling functionality.
2Temperature
If cooling fluid is used to cool permanent magnets under high-load conditions, then thermal management is improved, but the risk of demagnetization increases if cooling is insufficient
Solution Approach 1:
The cooling channels are pre-configured within the shaft structure, with the first cooling channel extending axially through the first shaft portion and the second cooling channel through the second shaft portion. This preliminary arrangement ensures that cooling fluid can immediately and effectively reach the permanent magnets when the machine operates under high-load conditions, preventing temperature rise that could lead to demagnetization.
Solution Approach 2:
The cooling channels provide continuous cooling paths through the shaft portions, ensuring uninterrupted cooling of the permanent magnets during operation. The fluidically connected first and second cooling channels maintain continuous cooling action even under varying load conditions, thereby preventing demagnetization.
3Ease of manufacture
If a simple shaft structure is used, then manufacturing ease is improved, but cooling efficiency and power density are reduced
Solution Approach 1:
The shaft is divided into functional segments (first shaft portion with first cooling channel, second shaft portion with second cooling channel) separated by a separation element. This segmentation allows for targeted cooling of different regions while maintaining a relatively simple overall shaft structure that can be manufactured using conventional techniques, thereby achieving high power density without excessive manufacturing complexity.
Solution Approach 2:
The shaft serves multiple functions: it provides mechanical support for the rotor core, contains integrated cooling channels for thermal management, and incorporates a separation element for fluid circuit division. This multi-functionality increases power density by combining structural and cooling functions in a single component without significantly complicating manufacturing.
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 enhances the electric machine's efficiency and power density by preventing drag losses and allowing the use of more economical permanent magnets with lower demagnetization temperatures, while maintaining effective cooling and mechanical stability.
Implementation Method 1
a cooling channel arrangement which is formed within the rotor assembly and comprises a first cooling channel (14), which extends within the shaft (4), a second cooling channel (15), which is fluidically connected to the first cooling channel (14) and extends in the radial direction along an end face (16) of the rotor core (2), and a third cooling channel (17), which, adjoining the second cooling channel (15), extends in the axial direction through the clearances (7) in the magnet pockets (7a-7d)
Implementation Method 2
The cooling channels are designed to guide a liquid cooling fluid, for example oil, water or a glycol-water mixture. However, it is also conceivable that the cooling channels are deigned to guide a gaseous cooling fluid.
Implementation Method 3
a separation element (5), which separates an interior of the shaft (4) into a first shaft portion (8), in which the first cooling channel (14) extends, and into a second shaft portion (9)
Data Source
AI summary
A rotor assembly for an electric machine includes a rotor core, a plurality of permanent magnets, which are arranged within a magnet pocket each, formed in the rotor core, with a clearance extending in the axial direction, and a shaft connected to the rotor core for conjoint rotation. A cooling channel arrangement is formed within the rotor assembly, and includes a first cooling channel extending within the shaft, a second cooling channel fluidically connected to the first cooling channel and extending in the radial direction along an end face of the rotor core, and a third cooling channel, which, adjoining the second cooling channel, extends in the axial direction through the clearances in the magnet pockets. The arrangement further includes a separation element, which separates an interior of the shaft into a first shaft portion, in which the first cooling channel extends, and into a second shaft portion.