In-Wheel Motor Drive Unit Liquid Cooling
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Solution Overview
Problem
The existing in-wheel motor drive units have a cooling system that prioritizes cooling electromagnets over electronic components, leading to reduced operating lifetime due to inadequate cooling capacity for capacitors and power devices.
Innovation Solution
A motor drive unit with a housing design featuring a separation plate acting as a heat sink for capacitors and direct thermal contact for solid-state switching devices, along with DC bus bars that aid in heat transfer, ensuring efficient cooling of both components while minimizing assembly complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a cooling system with channels in a circumferential housing is used to cool both electromagnets and electronic components, then electromagnets are cooled effectively, but electronic components (capacitors and power devices) receive insufficient cooling capacity resulting in reduced operating lifetime
Solution Approach 1:
The cooling system is segmented into separate cooling paths: one for electromagnets and another dedicated cooling system for electronic components. The electronic components are cooled by a separate mechanism involving cooling channels in the stator core and thermal contact with the stator, dividing the cooling function to ensure adequate cooling capacity for each component type.
Solution Approach 2:
Different cooling approaches are applied to different locations: electromagnets are cooled by the circumferential housing channels, while electronic components are cooled by a dedicated system using stator core thermal contact. This local differentiation ensures each component receives appropriate cooling capacity for its thermal requirements.
2Loss of energy
If control electronics are integrated within the stator to minimize electrical losses, then electrical efficiency is improved, but thermal management becomes more complex due to proximity of heat-generating components
Solution Approach 1:
The control electronics are merged with the stator structure, with power devices mounted on the stator core and capacitors integrated into the stator assembly. This merging minimizes electrical losses by reducing bus bar lengths while the stator core itself serves as a thermal management pathway, conducting heat away from electronic components.
Solution Approach 2:
The stator core serves dual functions: electromagnetic function and thermal management function. The stator core's thermal conductivity is utilized to passively cool the integrated electronic components without requiring separate active cooling mechanisms, allowing the structure to serve itself thermally.
3Reliability
If a dedicated cooling system for electronic components is implemented, then operating lifetime is extended, but device complexity increases
Solution Approach 1:
The dedicated cooling system for electronic components is merged with the existing stator structure. Cooling channels are integrated into the stator core, and the stator itself serves as a heat sink, combining the cooling function with the electromagnetic structure rather than adding separate external cooling systems.
Solution Approach 2:
The stator structure is given multiple functions: electromagnetic operation, structural support, and thermal management. The stator core acts as both the electromagnetic component and the thermal conduction pathway, eliminating the need for separate dedicated cooling structures and reducing overall system complexity.
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
This design enhances the cooling efficiency of capacitors and solid-state switching devices, extends their operational lifetime, and simplifies maintenance by providing dedicated cooling where it is needed most, while maintaining a compact and efficient cooling system.
Implementation Method 1
the solid state switching device are arranged in the lower compartment between the bottom plate and the separation plate and in thermal contact with the bottom plate
Implementation Method 2
bottom plate is provided with cooling channels for receiving a liquid coolant
Implementation Method 3
the housing further comprises a separation plate covering the lower compartment, wherein the separation plate is in thermal contact with the sidewalls and with the one or more capacitors
Implementation Method 4
the separation plate is in thermal contact with the sidewalls and with the one or more capacitors
Implementation Method 5
the one or more capacitors are arranged at a side of the separation plate that faces away from the lower compartment and are mounted on and substantially supported by the DC bus bars
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Motor drive unit for an in-wheel motor, comprising a housing and one and capacitors and solid state switching devices arranged within the housing, the housing comprising: a lower compartment comprising a bottom plate, sidewalls which extend from the bottom plate, and end sides at the transverse ends of the sidewalls and bottom plate, wherein the bottom plate is provided with cooling channels for receiving a liquid coolant; a separation plate covering the lower compartment, wherein the separation plate is in thermal contact with the sidewalls and with the capacitors, and wherein the solid state switching devices are arranged in the lower compartment between the bottom plate and the separation plate and in thermal contact with the bottom plate, wherein the capacitors are connected to DC bus bars and are arranged at a side of the separation plate that faces away from the lower compartment.