Dual-Loop Motor Cooling for Electrically Driven Compressors
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Solution Overview
Problem
Existing cooling systems for electrically driven compressors, particularly in aircraft, face inefficiencies in cooling high-power density electrical motors/generators, with air cooling being insufficient for stators and wet-liquid cooling increasing manufacturing costs and reducing efficiency due to sealing issues and larger gaps between rotor and stator.
Innovation Solution
A dual cooling system comprising a closed liquid coolant loop for dry-liquid cooling of the stator's iron stack and winding, and a compressed gas loop for cooling the rotor and bearings, with an external heat exchange system to optimize thermal management and reduce pressure losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cooling system is used for both rotor and stator, then device complexity is reduced, but cooling effectiveness deteriorates due to inability to separately manage thermal loads
Solution Approach 1:
The cooling system is divided into two independent loops: a first cooling loop for the stator and a second cooling loop for the rotor. Each loop can be optimized separately for its specific thermal requirements, allowing independent management of thermal loads and improving overall cooling effectiveness without excessive complexity
2Temperature
If wet-liquid cooling is used for the stator, then heat extraction effectiveness is improved, but system reliability deteriorates due to sealing breakdown and manufacturing cost increases
Solution Approach 1:
The system uses a liquid coolant in a closed-loop hydraulic system with the stator, but employs heat exchangers and vaporization techniques to prevent liquid contact with rotating components. The coolant circulates through channels in the stator and is cooled externally, combining liquid cooling effectiveness with the reliability of sealed systems
3Temperature
If a larger gap is used between rotor and stator for wet-liquid cooling, then cooling effectiveness is improved, but motor efficiency deteriorates due to increased losses
Solution Approach 1:
The system employs a controlled liquid cooling system where coolant flows through sealed channels within the stator structure, maintaining effective thermal contact without requiring increased rotor-stator gap. This preserves motor efficiency while achieving adequate cooling through internal heat transfer pathways
4Temperature
If end turns are potted for cooling, then cooling coverage is improved, but system reliability deteriorates due to potting material separation and motor seizure
Solution Approach 1:
The end turns are extracted from the traditional potted configuration and instead cooled through extended cooling channels that directly reach the end turn regions. This eliminates the potting material entirely, removing the reliability issues associated with material separation while maintaining cooling coverage through direct thermal pathways
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 approach enhances cooling efficiency, reduces manufacturing costs, and maintains motor efficiency by separating and optimally distributing thermal loads, resulting in a more compact and lightweight compressor design.
Implementation Method 1
a closed liquid coolant loop... dry-cools the stator's iron stack and winding
Implementation Method 2
The first cooling loop extracts heat from an iron stack and winding of a stator
Implementation Method 3
a separate compressed gas loop cools the rotor and bearings, with an external heat exchange system
Implementation Method 4
an external heat exchange system to optimize thermal management and enhance cooling efficiency
Data Source
AI summary
A cooling system for an electrical motor or generator includes a first cooling loop, a second cooling loop, and a heat exchange system. The first cooling loop may extract heat from an iron stack and winding of the electrical motor or generator. The second cooling loop may extract heat from end turns of the stator winding, the rotor, and the bearings independently from and simultaneously to the first cooling loop. At least the first cooling loop may pass through the heat exchange system. A liquid coolant may circulate in the first cooling loop and a compressed gas, such as compressed air or compressed refrigerant in vapor form, may circulate in the second cooling loop. The cooling system and method for an electrical motor or generator may be suitable for, but not limited to, applications in the aircraft and aerospace industries, such as driving a cabin air compressor of an aircraft.