Rotor End Member Venting for Cooling Without Airgap Friction
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Solution Overview
Problem
Electric machines in vehicles face heat-related issues due to resistance, hysteresis, and mechanical friction, leading to thermal limitations that can cause demagnetization of rotor magnets and thermal fatigue in stator windings, reducing performance and potentially terminating the machines.
Innovation Solution
A rotor assembly with a ring-shaped end member featuring venting grooves and openings that facilitate airflow and direct cooling using oil-spray, preventing oil-contaminated air from entering the airgap and reducing friction losses, while incorporating a fan unit to enhance airflow and maintain low friction within the airgap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If direct cooling using oil-spray is implemented, then cooling efficiency is improved, but oil-contaminated air may enter the airgap causing friction losses
Solution Approach 1:
The end member is segmented with multiple venting grooves and openings that create separate airflow channels. These segmented structures guide oil-spray cooling airflow through specific paths while preventing contaminated air from entering the airgap, thus resolving the contradiction between cooling efficiency and friction losses
Solution Approach 2:
The venting grooves and openings act as intermediary structures between the oil-spray cooling system and the airgap. They mediate the airflow by directing cooled air through controlled paths and filtering out oil-contaminated air before it can reach the airgap, maintaining both effective cooling and low friction
2Power
If rotor magnets operate at high temperature, then power output may increase, but demagnetization occurs reducing performance
Solution Approach 1:
The venting grooves and openings are pre-configured in the end members to establish cooling airflow paths before the rotor operates at high temperature. This preliminary structural arrangement ensures that when high power operation generates heat, the cooling system is already in place to prevent demagnetization, thus protecting reliability while allowing power output
3Power
If stator windings operate at high temperature, then efficiency may improve, but thermal fatigue cracks occur causing machine termination
Solution Approach 1:
The venting grooves and openings create continuous cooling airflow through the rotor assembly, maintaining constant temperature control of stator windings during operation. This continuous cooling action prevents thermal fatigue cracks from developing, allowing the machine to maintain high efficiency operation without reliability degradation
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 cools the rotor assembly, reduces friction losses, and prevents thermal damage, thereby enhancing the performance and reliability of electric machines by maintaining low temperatures and minimizing the risk of demagnetization and thermal fatigue.
Implementation Method 1
The venting groove and the venting opening are in fluid communication with ambient air. Such ring-shaped end member may facilitate an airflow throughout the rotor body
Implementation Method 2
direct cooling using oil-spray provided towards end-windings of the rotor assembly
Implementation Method 3
incorporating a fan unit to enhance airflow
Data Source
AI summary
A ring-shaped end member for a rotor assembly, a rotor assembly including such ring-shaped end member and an electric machine including such rotor assembly. The ring-shaped end member includes at least one venting groove, at least one venting opening, a front surface and a rear surface. The venting groove extends from an interior to an outer circumference at the front surface. The venting opening extends from the front surface of the rear surface. The venting groove and the venting opening are in fluid communication with ambient air.