Rotor Cooling Channel Design for Electric Machine Thermal Management
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Solution Overview
Problem
Electric machines face significant heat dissipation challenges, leading to thermal bearing loading, material fatigue, and reduced service life due to temperature differences between bearing rings, which affects the rotor shaft and overall machine performance.
Innovation Solution
A rotor design with a laminated core and an aluminum die-cast filler body, incorporating axial cooling channels and ventilation units to actively cool the rotor, reducing temperature differences and extending bearing life through efficient heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling of the rotor shaft or laminated rotor core is implemented, then bearing temperature and temperature difference are reduced, but device complexity increases
Solution Approach 1:
The cooling channels are integrated directly into the rotor core structure, merging the cooling system with the rotor assembly. This eliminates separate cooling components and reduces overall device complexity while achieving effective cooling of the rotor and bearing areas
Solution Approach 2:
The rotor itself serves as the cooling device through its integrated cooling channels. The rotor structure provides its own cooling capability without requiring external cooling systems, thereby reducing device complexity while maintaining effective temperature control
2Reliability
If bearings with greater bearing play are used to compensate thermal changes, then bearing preload is reduced, but electric machine performance deteriorates due to increased vibrations and axial tolerances
Solution Approach 1:
The cooling channels are positioned to cool the bearing areas before excessive temperature differences develop. By preemptively removing heat from the rotor and bearing regions, the system prevents thermal expansion issues without needing to overcompensate with larger bearing play, thus maintaining both bearing life and machine performance
3Loss of energy
If a shaft thermosiphon cooling system is used, then heat dissipation is improved, but apparatus complexity and cost increase significantly
Solution Approach 1:
The invention extracts only the essential cooling function needed for the rotor and bearing areas, implementing simplified cooling channels directly in the rotor core. This eliminates the need for complex shaft thermosiphon systems with evaporator and condenser units, achieving effective heat dissipation with minimal apparatus
Solution Approach 2:
The cooling channels are strategically positioned to provide localized cooling where heat is generated (rotor core and bearing areas). This targeted approach achieves efficient heat dissipation without the need for comprehensive complex cooling systems throughout the entire shaft assembly
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
The design achieves a longer service life for rolling bearings and improved electric machine performance by lowering average bearing temperatures and reducing material fatigue, while maintaining a low rotational mass moment of inertia for enhanced efficiency.
Implementation Method 1
a ventilation unit (18; 36, 37; 40; 60), wherein the filler body (5) connects the laminated rotor core (6) rotationally conjointly to the first shaft journal (3) and to the second shaft journal (4), the laminated rotor core (6) has a central axial bore (11) which is partially filled by the filler body (5) such that an axial cooling channel (16) for cooling air is formed within the central bore (11) of the laminated rotor core (6)
Data Source
AI summary
Various embodiments include a rotor for an electric machine comprising: a laminated rotor core; a filler body comprising an aluminum die-cast alloy cast onto the laminated rotor core; a first shaft journal having an air inlet opening; a second shaft journal having an air outlet opening; and a ventilation unit. The filler body connects the laminated rotor core rotationally conjointly to the shaft journals. The laminated rotor core includes a central axial bore partially filled by the filler body forming an axial cooling channel for cooling air within the central axial bore. The shaft journals drive the ventilation unit. Rotation of the ventilation unit draws an air stream in via the air inlet opening, conveys said air stream through the axial cooling channel, and discharges said air stream via the air outlet opening.