Frameless Traction Motor Cooling Layout for Low-Floor Rail Vehicles
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Solution Overview
Problem
Low-floor rail vehicles face space constraints due to large drive motors and cooling systems, limiting power density and increasing floor height, which hinders passenger transport in urban areas.
Innovation Solution
A housing-less electric traction machine with a stator laminated core and rotor laminated core design, featuring heat sinks with cooling channels and a unique arrangement to reduce dimensions, allowing for efficient heat dissipation and high power density, suitable for low-floor rail vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a housing is added to the electric traction machine for structural support and cooling system integration, then structural strength and cooling efficiency are improved, but the overall size and weight of the machine increase
Solution Approach 1:
The press plates serve dual functions: they provide structural support as end caps for the stator core assembly and simultaneously serve as mounting surfaces for the cooling system components. The tension strips are integrated into the press plate structure, creating a unified load-bearing and cooling system assembly that eliminates the need for separate housing structures.
Solution Approach 2:
The press plates are designed to perform multiple functions: mechanically securing the stator core, providing mounting surfaces for heat sinks, serving as structural end caps, and facilitating coolant flow distribution. This multi-functionality reduces the need for additional structural components that would increase weight.
2Temperature
If cooling fins are integrated into the stator core for heat dissipation, then cooling efficiency is improved, but the machine dimensions increase
Solution Approach 1:
Instead of extending cooling fins radially outward from the stator core (which would increase radial dimensions), the heat sinks are mounted axially on the press plates at the ends of the stator core. This axial arrangement allows heat dissipation in a different dimension, maintaining the compact radial profile of the machine while still providing effective cooling surface area.
Solution Approach 2:
The press plates serve as intermediary mounting surfaces between the stator core and the heat sinks. This allows the cooling system to be coupled to the stator core through the press plates, enabling efficient heat transfer from the stator core to the heat sinks without requiring direct integration that would increase machine dimensions.
3Temperature
If the electric machine is designed with larger dimensions to accommodate cooling systems, then cooling capacity is improved, but the power density decreases
Solution Approach 1:
The cooling system is arranged axially along the length of the machine rather than radially, allowing effective cooling capacity to be achieved without increasing the radial dimensions. This maintains a high power-to-volume ratio by keeping the machine compact while still providing adequate cooling surface area through the heat sinks mounted on the press plates.
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 enables a compact, high-power electric machine with optimal heat dissipation, achieving high speeds and reducing floor height, thus enhancing spatial efficiency and passenger accessibility in low-floor rail vehicles.
Implementation Method 1
heat sinks, each with at least one cooling channel for guiding a cooling fluid
Implementation Method 2
cooling channels for guiding a cooling fluid
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to an unenclosed electric traction machine (1), comprising a stator (2) formed by a stator lamination stack (3) and a rotor shaft (4) with a rotor (5) secured thereon and formed by a rotor lamination stack (6), wherein the stator lamination stack (3) is arranged between two external press plates (7, 8) and at least one bearing plate (29, 30) having a respective bearing (24) for the rotor shaft (4), and tension bars (9) are arranged between the press plates (7, 8). In order to create an electric traction machine (1) that is as space-saving as possible, yet still powerful, in particular for driving low-floor rail vehicles, at least two cooling elements (10) having a respective at least one cooling channel (11) for guiding a coolant (K) are arranged opposite one another on the surface of the stator lamination stack (3) along a portion of the circumference of the stator lamination stack (3) between the press plates (7, 8), such that the unenclosed electric traction machine (1) has a reduced height (h) relative to the width (b).