Internal Slot Jacket Cooling for E-Machine Winding Heat Dissipation
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Solution Overview
Problem
Existing internal cooling systems for electric machines, particularly AC electric motors, face limitations in thermal convection coefficients and contact area between coolants and conductors, leading to reduced power density and efficiency due to high thermal resistances.
Innovation Solution
The proposed internal cooling system incorporates an internal slot jacket with ducts featuring high thermal conductivity materials like alumina, BeO, or AlN, and optimized fins to increase thermal contact area and convection coefficients, along with an external head winding jacket to evacuate losses, using dielectric fluids such as mineral oil or silicon oil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional internal cooling systems are used, then the structure is simple, but the thermal convection coefficient and contact area between coolant and conductors are insufficient, leading to high thermal resistance
Solution Approach 1:
The internal slot jacket is nested within the stator slots, containing ducts that are integrated into the slot structure. This nesting approach allows the cooling system to occupy space within existing structural elements, reducing overall device complexity while improving thermal contact area between the coolant and conductors.
Solution Approach 2:
The cooling system transitions from conventional surface-level cooling to three-dimensional internal cooling by creating ducts within the slot jacket that penetrate deep into the winding regions. This dimensional expansion increases the contact area between coolant and heat-generating components without significantly increasing external dimensions.
2Temperature
If high thermal conductivity materials like alumina, BeO, or AlN are used in the slot jacket, then thermal convection coefficient increases, but manufacturing complexity and cost increase
Solution Approach 1:
High thermal conductivity materials are applied locally in critical heat transfer zones such as the internal slot jacket and duct regions, rather than throughout the entire machine. This localized application optimizes thermal convection where most needed while reducing overall manufacturing complexity and cost.
Solution Approach 2:
The cooling system employs composite construction combining high thermal conductivity materials (alumina, BeO, or AlN) in the slot jacket with conventional materials in other components. This composite approach achieves high thermal convection coefficients in critical areas while maintaining ease of manufacture for the overall system.
3Temperature
If the internal slot jacket encapsulates stator slot winding turns, then thermal contact area increases, but electrical insulation requirements become more stringent
Solution Approach 1:
The internal slot jacket acts as an intermediary component between the coolant and the windings, providing thermal contact while maintaining electrical insulation. The duct structure and jacket material serve as a thermal bridge that is electrically isolated, allowing heat transfer without compromising insulation reliability.
Solution Approach 2:
The system changes the thermal parameters of the slot jacket material to achieve high thermal conductivity while maintaining appropriate electrical insulation properties. By carefully selecting materials with specific thermal and electrical parameter combinations, the design maximizes thermal contact area while ensuring insulation requirements are met.
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 system enhances heat dissipation by reducing thermal resistance and increasing the thermal convection coefficient, thereby improving the power density and efficiency of electric machines.
Implementation Method 1
an internal slot jacket configured to encapsulate the stator slot winding turns in the stator slots and comprising a plurality of ducts configured to conduct the coolant in contact with the stator slot winding turns
Implementation Method 2
optimized fins to increase thermal contact area and convection coefficients
Implementation Method 3
using dielectric fluids such as mineral oil or silicon oil
Data Source
AI summary
An internal cooling system for an electric motor including a stator with stator laminations and stator slots, a motor winding including head windings and stator slot winding turns in the stator slots, the internal cooling system including an internal slot jacket configured to encapsulate the stator slot winding turns in the stator slots. The internal slot jacket and/or the internal slot jacket outside the plurality of ducts includes a plurality of ducts configured to conduct coolant in contact with the stator slot winding turns in the stator slots to extract winding losses. Each of the ducts includes a plurality of features to reduce thermal resistance.