Individual-Tooth Winding Spacers for Electric Machine Cooling
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Solution Overview
Problem
Concentrated windings in electric machines, such as those in hybrid electric aircraft, generate step-shaped field waves causing eddy current losses and temperature rises, leading to potential insulation damage and fire risks due to inductive coupling and high current densities, which limits power and torque density.
Innovation Solution
The use of individual-tooth windings with spacers to space apart turns, creating larger cooling channels and increasing the exposed surface area for heat dissipation, allowing for efficient direct cooling and reducing the risk of thermal and mechanical damage, thereby enhancing operational reliability and overload capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If concentrated windings are used to achieve high power and torque densities, then power density and torque density are improved, but eddy current losses increase causing temperature rises that risk insulation damage and fire
Solution Approach 1:
The patent divides the stator winding into multiple independent individual-tooth windings, each occupying a separate slot and electrically isolated from others. This segmentation prevents eddy current paths between adjacent turns, reducing eddy current losses and temperature rises while maintaining high power density through concentrated winding configuration
Solution Approach 2:
The patent introduces an insulating barrier (such as mica tape or resin coating) between adjacent individual-tooth windings and between turns within each winding. This intermediary material blocks eddy current paths caused by the step-shaped field wave, reducing eddy current losses and associated temperature rises
2Temperature
If current density is limited to avoid excessive coil temperatures, then temperature control is improved, but power output is reduced
Solution Approach 1:
By segmenting the winding into electrically isolated individual-tooth windings, the patent eliminates harmful eddy currents between turns, allowing higher current densities without excessive temperature rises. Each isolated turn experiences minimal induced voltages from adjacent turns, enabling higher power output at controlled temperatures
3Area of stationary object
If individual-tooth windings are placed close together to maximize space utilization, then space efficiency is improved, but potential differences between adjacent windings cause short circuit risks
Solution Approach 1:
The patent places an insulating barrier between adjacent individual-tooth windings, serving as an intermediary that prevents electrical short circuits while allowing the windings to be positioned close together. This maintains high space utilization in the stator while ensuring electrical isolation between windings with different potentials
4Temperature
If cooling channels are added to dissipate heat, then temperature control is improved, but device complexity increases
Solution Approach 1:
The patent combines the cooling function with the structural support function by integrating cooling channels into the stator core structure itself. The stator yoke and teeth are designed with internal cooling passages that utilize the existing structural material, eliminating the need for separate cooling system components and reducing overall device complexity
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 solution effectively reduces the risk of insulation failure and short circuits, enabling higher current densities and overload capacities while maintaining high power and torque densities, thus improving the reliability and safety of electric machines in hybrid electric aircraft.
Implementation Method 1
The spaces between the individual conductors of the individual-tooth winding may be used as cooling channels
Implementation Method 2
a significantly higher exposed surface is obtained, which contributes linearly to the level of heat flow that may be transmitted
Implementation Method 3
Owing to the inductive coupling of the rotor field into the stator, power losses disadvantageously occur in the coils
Implementation Method 4
Concentrated windings, however, generate a step-shaped field wave, which causes eddy current losses in permanent magnets of the rotor
Data Source
AI summary
An electric machine includes at least one stator having at least one individual-tooth winding carrier that has at least one spacer configured to space apart turns of an individual-tooth winding mounted on the individual-tooth winding carrier. A hybrid electric aircraft has an electric machine of this kind.