Enclosed Electric Machine Rotor Cooling via Segmented Airflow
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Solution Overview
Problem
Existing encapsulated electrical machines face challenges in efficient cooling, particularly in limited spaces, leading to increased thermal resistance and reduced performance due to the heat dissipation limitations between the rotor and stator, which are typically air-cooled and liquid-cooled respectively.
Innovation Solution
The implementation of air guiding elements to create a separate closed cooling air flow for the rotor, connected via end shields with hose or pipe connections to the stator's cooling channels, allowing for independent thermal management of the stator and rotor, and the use of cooling channels in end shields to dissipate heat efficiently using a common cooling fluid system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a double-walled housing with cooling channels is used to cool the stator, then the stator can be liquid-cooled, but the thermal resistance increases and heat dissipation from the rotor is impaired
Solution Approach 1:
The cooling system is segmented into two independent circuits: a liquid cooling circuit for the stator and an air cooling circuit for the rotor. This segmentation allows each component to be cooled by the most suitable method without interfering with the other, eliminating the thermal resistance problem caused by combined cooling channels while maintaining effective heat dissipation for both stator and rotor.
2Temperature
If the rotor is air-cooled and the stator is liquid-cooled using a double-walled housing, then both components can be cooled, but the space required increases and the design becomes more complex
Solution Approach 1:
The air cooling circuit for the rotor is merged with the existing liquid cooling system by using the same housing structure. Cooling air is introduced through the liquid cooling channels of the double-walled housing, allowing the air cooling circuit to utilize the available space without requiring additional external housing volume. This combining approach maintains compact design while enabling dual cooling methods.
3Temperature
If cooling channels are added to the stator for liquid cooling, then the stator can be effectively cooled, but the manufacturing complexity and cost increase
Solution Approach 1:
The liquid cooling channels in the stator serve dual functions: they provide liquid cooling for the stator and simultaneously serve as air inlets for the rotor's air cooling circuit. This multi-functionality eliminates the need for separate air inlet channels, reducing manufacturing complexity and maintaining ease of production while achieving effective temperature control for both components.
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 enables the electrical machine to operate at higher performance with the same size or achieve the same performance in a smaller size, by reducing thermal resistance and optimizing heat dissipation, making it suitable for high-performance applications like locomotive generators.
Implementation Method 1
cooling channels for guiding a cooling fluid... cooling channels in the at least one bearing shield are connected in parallel or in series with the cooling channels in the stator
Implementation Method 2
a fan is provided on the rotor... cooling channels are arranged in the rotor laminated core which are connected to corresponding return lines in the rotor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to an encapsulated electric machine with a stator arranged in a housing tube (3) with a stator lamination stack (1) with a stator winding (16) and with cooling channels (2) for guiding a cooling fluid, and with a rotor with a rotor lamination stack (5) connected to a rotor shaft (24) in a rotationally fixed manner and permanent magnets (6a) or short-circuit bars (6b) arranged therein, and with bearing shields (13, 14) arranged on both sides.To improve cooling, a fan (12) is provided on the rotor, cooling channels (7) are arranged in the rotor lamination stack (5) which are connected to corresponding return lines, air guide elements (22a, 22b) are provided to separate the cooling airflow (20) from the stator, so that a closed cooling airflow (20) is formed over the bearing shields (13, 14) separate from the cooling of the stator, and cooling channels (17) for guiding a cooling fluid are arranged in at least one bearing shield (13, 14), which cooling channels (17) are connected to the cooling channels (2) in the stator in parallel or in series via hose or pipe connections (28).