Slot-Integrated Liquid-Cooled Stator for Higher Current Density
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Solution Overview
Problem
Existing liquid cooling methods for stators in electric motors and generators face challenges such as poor conductivity between the jacket and stator, limited cooling efficiency, complexity, and increased size due to cooling fluid paths, as well as issues with non-conductive fluids causing drag and complex manufacturing processes.
Innovation Solution
A novel design integrating a cooling manifold within the stator slot, using metallic vessels for ethylene glycol coolant, with brazed connections and conductive materials, and a configuration that accommodates both distributed and concentrated windings, ensuring efficient thermal management without performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling jacket is wrapped around the outside of the stator assembly, then cooling effectiveness is improved, but the design becomes limited by poor conductivity between the jacket and stator, stator lamination conductivity, slot liner conductivity, and winding-to-slot liner conductivity
Solution Approach 1:
The cooling manifold is nested within the stator slot, with coolant passages positioned between the stator teeth and windings. This nested configuration eliminates the need for external jackets and multiple interface connections, directly addressing the conductivity limitations by placing the cooling system inside the existing stator structure.
Solution Approach 2:
The slot liner serves as a thermal intermediary between the coolant passages and the stator teeth. The slot liner is thermally conductive and electrically insulating, mediating heat transfer from the stator teeth to the coolant while maintaining electrical isolation, thus solving the dual requirement of thermal conductivity and electrical insulation.
2Temperature
If cooling fluid passages are placed through the stator laminations or into slots cut into the stator laminations, then cooling is achieved, but the stator must get larger to accommodate the holes in the magnetic material
Solution Approach 1:
Cooling passages are placed locally in the slot space between the stator teeth and windings, rather than drilling holes through the entire stator lamination. This localized approach utilizes existing slot volume without compromising the magnetic path integrity or increasing overall stator dimensions.
3Temperature
If fluid is sprayed directly on the stator or the stator is submerged, then cooling is achieved, but the system becomes overly complex or the fluid causes drag between the rotor and the stator
Solution Approach 1:
The cooling system is self-contained within the stator slot structure, requiring no external spray mechanisms or submersion systems. The closed-loop coolant passages within the slot provide automatic cooling without adding external complexity or creating rotor-stator drag.
4Temperature
If a pipe or vessel is placed down through the slot with cooling fluid, then cooling is achieved, but non-conductive oil must be used with non-conductive connections to a manifold, increasing manufacturing complexity
Solution Approach 1:
The cooling manifold and passages are constructed from the same conductive material (aluminum or copper) as the stator structure, creating a homogeneous thermal path. This eliminates the need for non-conductive oil and complex non-conductive connections, allowing standard coolant materials and simpler manufacturing processes.
Solution Approach 2:
The cooling manifold is merged with the stator slot structure, forming an integrated assembly rather than separate components. This integration eliminates the need for separate non-conductive connections and manifolds, reducing manufacturing steps and improving thermal conductivity.
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 a compact, reliable, and cost-effective cooling solution with higher current density and torque density, utilizing ethylene glycol coolant and minimizing manufacturing complexity.
Implementation Method 1
This design cools the stator better than air, but is limited by i) the conductivity between the jacket and the stator, ii) the poor conductivity of the stator laminations, iii) the conductivity of the slot liners, and iv) the poor conductivity between the winding and the slot liners
Implementation Method 2
A novel design integrating a cooling manifold within the stator slot, using metallic vessels for ethylene glycol coolant
Data Source
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AI summary
A stator for a motor, generator or the like that is liquid cooled using glycol or similar fluid with the cooling applied directly in the winding slots of the stator in either concentrated wound or distributed wound configurations.