Electric Drive Unit Cooling via Rotor-Shaft Coolant Spray
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Solution Overview
Problem
The thermal load on power electronics in electrical machines limits their continuous power and thermal availability, necessitating a more effective cooling method.
Innovation Solution
A liquid cooling system is integrated within the motor housing, where coolant is sprayed through a channel in the rotor shaft and guided against an inner cooling surface of a heat sink of the power electronics, effectively cooling both the power electronics and the electrical winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If coolant is sprayed only onto the winding overhang, then the electrical winding is cooled effectively, but the power electronics thermal load remains unaddressed and limits continuous power
Solution Approach 1:
The cooling system is segmented into multiple cooling zones: one for the electrical winding (via spray openings in the rotor shaft) and another for the power electronics (via coolant channels in the inverter housing). This allows independent optimization of cooling for each component, enabling the power electronics to be cooled effectively without compromising winding cooling performance.
Solution Approach 2:
The cooling approach transitions from a single-dimension spray system to a multi-dimensional cooling architecture. The inverter housing incorporates integrated coolant channels that provide three-dimensional cooling paths around the power electronics modules, adding spatial complexity to the cooling system to address thermal loads that a simple spray cannot handle.
2Volume of moving object
If power electronics are positioned close to the winding overhang for common cooling, then installation space is saved, but thermal management complexity increases
Solution Approach 1:
The inverter housing is merged with the cooling system structure, integrating coolant channels directly into the housing that serves as the mounting structure for power electronics. This consolidation eliminates the need for separate cooling plates or heat sinks, reducing overall space while managing thermal complexity through integrated design.
Solution Approach 2:
The inverter housing serves multiple functions simultaneously: it provides mechanical support and mounting for power electronics, acts as a structural component of the motor assembly, and functions as a thermal management system with integrated coolant channels. This multi-functionality reduces the number of separate components needed.
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 cooling method allows for efficient heat dissipation from the power electronics and electrical winding, enabling higher continuous power operation and improved thermal management of the electric drive unit.
Implementation Method 1
the power electronics, together with the electrical winding of the stator and optionally together with the rotor, can be effectively cooled by the liquid coolant
Implementation Method 2
the coolant is sprayed through a channel in the rotor shaft through a radial passage in the rotor shaft in the radial direction and/or in the axial direction into the motor interior and guided against an inner cooling surface of a heat sink of the power electronics
Data Source
Figure 1
Figure 2
AI summary
The invention relates to an electric drive unit (10) and to a method for operating such a unit, in particular for a traction drive of a motor vehicle, comprising a stator (12) having a stator base body (14) on which an electrical winding (20) is arranged, which forms a winding head (22) at the axial end of the stator base body (14), and power electronics (51) with a cooling surface (52) are arranged axially adjacent to the winding head (22), and comprising a rotor (30) arranged radially inside the stator base body (14) and having a rotor shaft (32), wherein an axial cavity (34) is formed inside the rotor shaft (32), and the rotor shaft (32) has at least one radial feedthrough (36) through which coolant (44) can be conducted from the cavity (34) against the cooling surface (52) of the power electronics (51).