Oscillating Heat Pipe Cooling for Electric Motor Stator Windings
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Solution Overview
Problem
Traditional cooling methods for electric motors, such as liquid cooling and external fins, often result in hot spots and high thermal resistance due to poor bulk thermal conductivities and interfacial resistances, which limit the effective cooling of stator windings, especially in high-power density applications.
Innovation Solution
The integration of oscillating heat pipes within the stator windings, with an evaporator section near the heat source and a condenser section in a cooling channel, utilizes fluid flow to enhance heat transfer and mitigate thermal resistance, aligned with the primary direction of vibration to optimize cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional liquid cooling jackets are used to cool the stator, then cooling is provided on the radial and axial periphery of the stator core, but hot spots occur at the axial centerline of the stator core due to inadequate cooling coverage
Solution Approach 1:
The cooling system is segmented into multiple independent cooling channels distributed throughout the stator core. Each channel provides localized cooling to specific regions, ensuring uniform temperature distribution and preventing hot spots at the axial centerline while maintaining a relatively simple overall structure.
Solution Approach 2:
The cooling approach transitions from surface-level cooling (radial and axial periphery only) to volumetric cooling by embedding cooling channels within the stator core. This three-dimensional cooling distribution eliminates thermal gradients and prevents hot spot formation throughout the entire stator volume.
2Temperature
If nn-slot cooling is used to directly cool electric motor windings, then lower temperatures are achieved, but poor bulk thermal conductivities and interfacial resistances result in high overall thermal resistance
Solution Approach 1:
A thermal interface material or optimized contact structure is introduced between the cooling channels and the windings to reduce interfacial thermal resistance. This intermediary enhances heat transfer efficiency from the windings to the cooling fluid, achieving lower winding temperatures without compromising thermal reliability.
Solution Approach 2:
The thermal properties of the cooling system are optimized by adjusting parameters such as cooling fluid flow rate, channel geometry, and contact pressure between cooling elements and windings. These parameter changes reduce both bulk thermal resistance and interfacial resistance, enabling effective heat removal from the windings.
3Power
If high power density is achieved in electric motors, then more intense heat generation occurs in stator and rotor windings, but traditional cooling methods become insufficient to manage the heat
Solution Approach 1:
The cooling system is divided into multiple distributed channels that segment the heat removal process across different locations in the stator core. This segmentation enables proportional heat dissipation from high-power-density windings, preventing localized overheating while supporting higher overall motor power density.
Solution Approach 2:
The cooling architecture transitions from external surface cooling to internal volumetric cooling with channels embedded throughout the stator core. This three-dimensional cooling distribution provides sufficient heat removal capacity to manage the intense heat generation from high power density windings, enabling higher motor power density without thermal limitations.
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 effectively reduces thermal resistance and prevents hot spots by efficiently transferring heat away from the stator windings, improving cooling performance and power density in electric motors, particularly in vibration-sensitive applications like aviation-class motors.
Implementation Method 1
one or more oscillating heat pipes disposed at least partially in the at least one winding
Implementation Method 2
an evaporator section and a condenser section and wherein the evaporator section is disposed in the at least one winding and the condenser section is disposed in the cooling channel
Implementation Method 3
The at least one winding is held apart from the stator slot base so that a cooling channel is defined between an inner winding portion of the at least one winding and a portion of the one or more oscillating heat pipes
Data Source
AI summary
A stator and a motor including a stator. The stator includes a stator hub, a plurality of stator teeth extending from the stator hub that define a stator slot having a stator slot base, at least one winding disposed in the stator slot, and one or more oscillating heat pipes disposed at least partially in the at least one winding. The at least one winding is held apart from the stator slot base so that a cooling channel is defined between an inner winding portion of the at least one winding and a portion of the one or more oscillating heat pipes is disposed in the channel so cooling fluid can be passed between the stator slot base and the inner winding portion to cool the inner winding portion via at least operation of the one or more oscillating heat pipes.