Rotor Cooling Channel Layout for Higher Fluid Fill Under Centrifugal Force
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Solution Overview
Problem
High-voltage electric motors, such as those used in traction for vehicles, generate excessive heat due to eddy current losses, which affects efficiency and can lead to demagnetization and motor failure, and existing cooling systems are not sufficient to address this issue effectively.
Innovation Solution
A rotor assembly with an internal fluid cooling system that includes cooling channels and end plate channels, where the radially innermost position of the outer wall is arranged inward of the inner wall, enhancing the filling level of cooling fluid and thus improving cooling efficiency, particularly under centrifugal force conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cooling systems are used in high-voltage electric motors, then the motor can operate, but excessive heat from eddy current losses causes demagnetization and motor failure
Solution Approach 1:
The cooling system is segmented into multiple cooling channels distributed across the rotor core, with each channel independently guiding cooling fluid through specific regions. This segmentation allows targeted cooling of high-heat areas while maintaining overall system reliability
Solution Approach 2:
The cooling channels are nested within the rotor core structure, with the fluid cooling pathway integrated into the existing rotor assembly. The downstream end plate channel is nested within the end plate, creating a compact nested configuration that maximizes cooling efficiency within limited space
2Device complexity
If the downstream end plate channel is positioned radially outward, then the structure is simpler, but the filling level of cooling fluid decreases under centrifugal force
Solution Approach 1:
Instead of positioning the downstream end plate channel radially outward as conventional design, the invention inverts this arrangement by positioning it radially inwards. This inversion counteracts the centrifugal force effect, allowing cooling fluid to maintain higher filling levels in the channels during motor operation
3Power
If cooling fluid filling level is increased, then cooling power improves, but the radial positioning of channel walls becomes more complex
Solution Approach 1:
The invention changes the radial position parameter of the downstream end plate channel from outward to inwards, and adjusts the radial extent parameter to extend beyond the cooling channel radius. This parameter modification enables increased cooling fluid filling level while maintaining manufacturable channel wall positioning
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 enhanced fluid cooling system increases cooling power and efficiency, reducing heat-related issues and improving the performance of electric machines by maintaining a higher filling level of cooling fluid within the channels, effectively addressing heat generation in high-voltage applications.
Implementation Method 1
Particularly in operating conditions where the centrifugal force is higher than the gravity force the filling level of cooling fluid in the at least one cooling channel can be increased
Implementation Method 2
The at least one fluid cooling pathway (110) is configured to guide cooling fluid through the rotor (30)
Implementation Method 3
The downstream end plate channel (125, 128) is restricted radially outwards by a radially outer wall portion (125a, 128a)
Data Source
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AI summary
The present disclosure relates to a rotor assembly (10) for an electric machine (1). The rotor assembly (10) comprises a rotating shaft (20), a rotor (30) and a fluid cooling system. The rotor (30) is fixed to the rotating shaft (20). The rotor (30) comprises a rotor core (32), a first end plate (34) and a second end plate (36). The first end plate (34) is provided at a first axial end (32a) of the rotor core (32). The second end plate (36) is provided at a second axial end (32b) of the rotor core (32). The fluid cooling system (100) comprises at least one fluid cooling pathway (110) provided internally in the rotor (30). The at least one fluid cooling pathway (110) is configured to guide cooling fluid through the rotor (30), and comprises at least one cooling channel (124, 126) and a downstream end plate channel (125, 128).The at least one cooling channel (124, 126) extends through the rotor core (32) from the first axial end (32a) to the second axial end (32b). The downstream end plate channel (125, 128) is fluidically connected to a downstream end of the at least one cooling channel (124, 126). The downstream end plate channel (125, 128) is restricted radially outwards by a radially outer wall portion (125a, 128a). The at least one cooling channel (124, 126) is restricted radially inwards by a radially inner wall portion (124a, 126a). A radially innermost position (125b, 128b) of the radially outer wall portion (125a, 128a) is arranged in a range about or at or radially inwards of a radially innermost position (124b, 126b) of a radially inner wall portion (124a, 126a).