Phase-Change Winding Cooler for High-Current Electrical Machines
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Solution Overview
Problem
Existing cooling systems for high-power electrical machines, particularly in constrained environments, fail to adequately cool windings due to the distance between phase-change materials and areas of thermal stress, leading to increased winding temperatures and Joule losses.
Innovation Solution
A new winding cooling structure using a heat sink with separate hollow parts containing phase change material, positioned close to the windings to absorb excess heat rapidly, minimizing temperature rise and reducing Joule losses without increasing conductor space requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If phase change materials are used in constrained environments, then cooling capability is improved, but the distance between phase-change material and windings increases leading to insufficient heat absorption
Solution Approach 1:
The heat sink is integrated within the slot structure, nesting the phase-change material cooling system inside the existing machine geometry. The heat sink comprises a first part and a second part that fit together within the slot, allowing the phase-change material to be positioned in close proximity to the windings without increasing the overall machine dimensions.
Solution Approach 2:
A thermal conductive material is introduced as an intermediary between the heat sink and the windings to improve heat transfer efficiency. This mediator ensures effective thermal coupling while allowing for practical assembly and positioning, bridging the gap between the phase-change material and the heat-generating conductors.
2Temperature
If direct cooling to coil heads is implemented, then heat transfer is improved, but oil may enter the air gap causing friction losses and insulation damage
Solution Approach 1:
The cooling function is extracted from the traditional liquid spray system and transferred to a solid-phase change material system. The heat sink with phase-change material absorbs heat through conduction and phase transition without requiring fluid circulation, eliminating the risk of oil contamination while maintaining effective cooling of the coil heads.
Solution Approach 2:
The mechanical spray cooling system (requiring pumps, nozzles, and fluid circulation) is replaced with a passive thermal conduction system using phase-change material. This substitution eliminates the mechanical complexity and associated risks of fluid injection while achieving superior thermal management through direct contact heat transfer.
3Temperature
If conventional cooling systems are used, then heat dissipation is achieved, but the system complexity increases with pumps and heat exchangers
Solution Approach 1:
The phase-change material cooling system is self-regulating and requires no external control or mechanical components. The material automatically absorbs heat when temperature increases and releases it when temperature decreases, providing passive cooling without pumps, valves, or control systems. This self-service approach dramatically simplifies the cooling system architecture.
Solution Approach 2:
The cooling mechanism utilizes the phase transition properties of the phase-change material (melting and solidification) to store and release thermal energy. This phase-based thermal management provides effective cooling with minimal system complexity, as the material's inherent thermodynamic properties perform the cooling function without requiring mechanical intervention.
4Power
If current density is increased for high power applications, then power output is improved, but Joule losses and winding temperature increase
Solution Approach 1:
The phase-change material provides continuous thermal management throughout the operating cycle, continuously absorbing heat generated by high current density operations. This continuous cooling action enables sustained high-power operation without the temperature excursions that would otherwise force reduction of current density, maintaining both power output and efficiency.
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 winding temperatures and Joule losses, allowing higher current densities and simplified cooling systems without additional mass or volume, while maintaining efficient heat transfer.
Implementation Method 1
a phase change material having the capacity to absorb an excess quantity of heat when the conductors of the winding are subjected to an increase in their current density
Implementation Method 2
the heat sink is made up of at least two separate hollow parts that fit together and are intended to receive the phase change material
Implementation Method 3
an assembly comprising a winding and a cooler in contact with conductors of this winding
Data Source
Figure 1A
Figure 1B~1C
Figure 2~3
AI summary
An assembly comprising a winding (20) and a cooler in contact with the conductors of the winding, the cooler comprising a container (26) forming a thermal dissipator and comprising a phase-change material (28) having the ability to absorb a surplus amount of heat when the conductors of the winding experience an increase in their current density and the thermal dissipator is formed by at least two hollow parts (26A, 26B) that are separated and are nestable and are intended to accommodate the phase-change material.