Rotor Cooling Bar Structure for Demagnetization and Torque Loss
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Solution Overview
Problem
Conventional cooling methods for electric vehicle motors focus on stators and coils, neglecting the rotor, leading to increased rotor temperature, magnet demagnetization, and torque loss, especially with high rotation and current applications, and axial shafts hinder effective cooling due to fluid resistance.
Innovation Solution
A rotor assembly with a cooling structure that incorporates a cooling bar inserted axially into the rotor core, using thermally conductive materials like copper or aluminum, and supplemented by oil sprays to enhance heat dissipation, avoiding direct contact with the magnet region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hollow shaft with large cross-sectional area like SG2 is used for on-axis configuration, then shaft structural strength is improved, but the inside of the shaft cannot be used as a cooling channel due to fluid resistance
Solution Approach 1:
The shaft design incorporates local quality variations: the shaft has a hollow structure with optimized wall thickness and internal geometry. The shaft wall thickness is designed to provide sufficient structural strength while the internal cavity is configured to enable effective fluid flow for cooling, thus simultaneously achieving both strength requirements and cooling channel functionality.
2Power
If high rotation and high current are applied to meet increased motor specifications, then motor power output is improved, but heat generation in the rotor increases causing demagnetization
Solution Approach 1:
The design converts the harmful heat generated by high rotation and high current operations into a manageable thermal management challenge. By incorporating the rotor shaft as a heat conduction pathway with integrated cooling channels, the system transforms the previously problematic heat accumulation into an opportunity for efficient heat removal, allowing the motor to operate at high power levels without demagnetization risks.
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 cooling structure effectively reduces magnet demagnetization and torque loss by intensively cooling the rotor core, enhancing thermal conductivity and distributing heat uniformly, thereby improving motor efficiency.
Implementation Method 1
a cooling bar inserted in the rotor core and cooling the rotor core while conducting heat inside the rotor core in an axial direction
Implementation Method 2
The motor employs an oil cooling method that directly sprays oil onto the heat source
Data Source
AI summary
The disclosure relates to a rotor assembly, and more particularly to a rotor assembly with the cooling structure. The rotor assembly with the cooling structure according to the disclosure has been conceived to solve the foregoing problems, and the disclosure rotor assembly with the cooling structure has effects on cooling a rotor core more intensively as a cooling bar formed extending in an axial direction is inserted into the rotor core, reducing the torque loss of a motor significantly as the demagnetization of a magnet embedded in the rotor core is decreased, and cooling the rotor core without using the interior of a shaft when a motor shaft and a drive shaft have the same axis like an on-axis casing.