Synchronous Machine Lamination Cooling for Compact Marine Propulsion
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Solution Overview
Problem
Existing electrical rotating machines, particularly in propulsion-oriented drive devices for boats, face inefficiencies in cooling, leading to increased volume, mass, and hydrodynamic losses due to limited heat exchange surfaces and the need for high-power converters in induction motors, while synchronous machines with wounded rotors suffer from hot spots and reduced efficiency in forced air cooling systems.
Innovation Solution
A synchronous electrical machine design featuring a stator with stacks of laminations and channels for fluid flow, separated by spacers to form extraction ducts, and a rotor with permanent magnets arranged in U or V shapes, utilizing a bilateral cooling system to inject and extract fluid through the machine housing for enhanced thermal management, reducing volume and improving hydrodynamic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the machine diameter is increased to improve cooling, then thermal losses are reduced, but volume and mass increase deteriorating hydrodynamical efficiency
Solution Approach 1:
The stator is segmented into multiple laminations stacked together, with cooling channels formed between adjacent laminations. This segmentation allows heat to be dissipated through multiple distributed channels rather than requiring a single large cooling surface, thus reducing the need for increased machine diameter while maintaining effective thermal management.
Solution Approach 2:
The cooling approach transitions from external surface cooling (requiring larger diameter) to internal volumetric cooling through channels embedded within the lamination structure. By utilizing the internal dimension of the stator core, the patent achieves enhanced heat dissipation without increasing the external dimensions of the machine.
2Temperature
If induction motor is used with forced air cooling, then cooling is achieved, but electrical efficiency is low requiring high-power converters
Solution Approach 1:
The patent employs a liquid cooling system instead of forced air cooling. Liquid coolant flows through channels formed between stator laminations, providing superior heat transfer efficiency compared to air. This eliminates the need for high-power converters required by inefficient air-cooled induction motors, as the synchronous motor operates at higher electrical efficiency.
3Temperature
If synchronous machine with wounded rotor is cooled by forced air, then cooling is provided, but hot spots appear reducing efficiency
Solution Approach 1:
The cooling channels are strategically positioned between specific laminations to target high heat generation zones. The liquid cooling system provides localized cooling where thermal loads are highest, preventing hot spot formation in the stator core while maintaining overall thermal balance and electrical efficiency.
Solution Approach 2:
Liquid coolant replaces forced air as the cooling medium. The liquid flows through channels between laminations, providing continuous and uniform cooling that prevents hot spots. This hydraulic cooling approach is more effective than pneumatic (air) cooling in eliminating localized thermal peaks that reduce motor efficiency.
4Loss of energy
If stator is shrunk into housing for conduction cooling, then cooling is achieved, but heat exchange surface is limited
Solution Approach 1:
The stator is divided into multiple thin laminations with cooling channels between them. This segmentation creates multiple internal heat exchange surfaces distributed throughout the stator volume, dramatically increasing the total heat exchange area compared to external housing conduction alone. Heat is transferred from the core to the coolant through these distributed interfaces.
Solution Approach 2:
A liquid coolant serves as an intermediary heat transfer medium, flowing through channels between laminations to carry heat away from the stator core. This intermediary system provides a large effective heat exchange surface area within the confined stator structure, overcoming the limitations of direct housing conduction.
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 solution effectively reduces thermal losses, minimizes machine volume, and enhances torque density by combining bilateral cooling with conduction-based heat transfer, improving hydrodynamic efficiency and maintaining overall system efficiency despite potential electrical efficiency losses.
Implementation Method 1
a fluid injected in the air gap at the ends of the stator flows in the extraction duct and in the channel, and is extracted from the machine through the opening to cool the stator and the rotor
Implementation Method 2
combining bilateral cooling with conduction-based heat transfer
Implementation Method 3
the machine housing being configured to dissipate thermal losses generated by the stator
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The synchronous electrical machine (8) comprises a machine housing (26) including a stator (27) and a rotor (28) lodged in the stator, the rotor being separated from the stator by an airgap (29), the machine housing being configured to dissipate thermal losses generated by the stator. The stator comprises stacks (30) of laminations (300) and at least one channel (36) extending along a longitudinal direction of the stator and formed in the laminations, two adjacent stacks of laminations being separated by pins or spacers (31) to form an extraction duct (32) connected to the channel, the machine housing further comprising an extraction opening (21) so that a fluid injected in the air gap at the ends of the stator flows in the extraction duct and in the channel, and is extracted from the machine through the opening to cool the stator and the rotor.