Rotor End Ring Bevel Prevents Coolant Backflow
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Solution Overview
Problem
Current electric motors experience coolant leakage back into the air gap between the stator and rotor, leading to spin losses due to the radial flow of coolant, which is not effectively distributed onto the stator end turn windings.
Innovation Solution
A rotor end ring with an annular disk-shaped body, featuring outlets for coolant flow, a recess to direct coolant radially outward, and a beveled outer circumference to prevent backflow, along with a ramped portion to enhance coolant dispersion onto the stator end turn windings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant flows radially outward through the rotor end ring, then cooling of the rotor is achieved, but coolant leaks back into the air gap causing spin losses
Solution Approach 1:
The rotor end ring is segmented into multiple functional zones: coolant outlets, a recessed coolant collection area, and a beveled outer circumference. This segmentation allows the coolant flow to be controlled and directed through distinct regions, preventing backflow into the air gap while maintaining cooling effectiveness.
Solution Approach 2:
The outer circumference of the rotor end ring is given a specific beveled geometry with a particular angle range (0-45 degrees) to create a local quality that prevents coolant backflow. This localized geometric feature addresses the backflow problem without affecting other parts of the rotor structure.
2Temperature
If coolant flows radially outward onto the end turn windings, then cooling of windings is achieved, but coolant distribution is localized and inefficient
Solution Approach 1:
The recess in the rotor end ring face creates a two-dimensional coolant collection area that gathers coolant from multiple outlets. This recessed structure allows coolant to accumulate and redistribute across a broader area before exiting radially, transforming the flow from localized point contact to a more distributed radial spray pattern.
Solution Approach 2:
The recess acts as an intermediary structure between the coolant outlets and the radial exit points. It mediates the coolant flow by collecting, redistributing, and directing the coolant across the beveled outer circumference, improving the overall distribution efficiency before the coolant contacts the end turn windings.
3Loss of energy
If the outer circumference is beveled to prevent coolant backflow, then spin losses are reduced, but manufacturing complexity increases
Solution Approach 1:
The beveled outer circumference is defined by a specific angular parameter range (0-45 degrees relative to the central axis). By specifying this parameter range, the design balances the need to prevent coolant backflow with the practical considerations of manufacturing. This parameter-based approach allows for optimization while maintaining ease of fabrication through standard machining operations.
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 prevents coolant leakage into the air gap and improves the radial distribution of coolant onto the stator end turn windings, enhancing cooling efficiency and reducing spin losses.
Implementation Method 1
As the rotor is spinning, circumferential forces cause the coolant to flow radially outward past the rotor
Implementation Method 2
coolant flowing through the outlets flows across the recess toward an outer circumference of the body
Data Source
AI summary
An electric motor comprises a housing, a stator mounted stationary within the housing and having end turn windings, a rotatable central shaft, a rotor mounted onto the central shaft for rotation within the stator, the stator, central shaft and rotor all positioned co-axially within the housing, a rotor end ring mounted onto the central shaft adjacent an axial end of the rotor, the rotor end ring including a body, a plurality of outlets adapted to allow coolant to flow from a back side to a face of the body, and a recess formed within the face of the body, wherein coolant flowing through the outlets flows across the recess toward an outer circumference of the body, and the outer circumference of the body is configured to prevent coolant from flowing into a circumferential air gap between the stator and the rotor.