Dual-Fluid Electric Machine Cooling for Winding Head Lubrication
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Solution Overview
Problem
Existing electric machines face challenges in simultaneously achieving high levels of cooling, lubrication, and oxidation protection, often requiring tradeoffs that do not fully exploit the machine's potential.
Innovation Solution
The electric machine incorporates a dual cooling system, with a first cooling system using water-based fluid for efficient cooling in the stator stack section and a second cooling system using oil-based fluid with spray nozzles or bores directed at the stator winding heads for additional cooling and lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cooling system is used, then the device complexity is reduced, but the ability to provide high-level cooling, lubrication, and oxidation protection simultaneously deteriorates
Solution Approach 1:
The cooling system is divided into two separate systems: a first cooling system using water-based fluid for cooling the stator lamination stack, and a second cooling system using oil-based fluid for cooling and lubricating the stator winding heads. This segmentation allows each system to be optimized for its specific function without compromise.
Solution Approach 2:
Different cooling fluids are applied to different regions of the electric machine based on local requirements: water-based fluid is used where high cooling capacity is needed (stator lamination stack), while oil-based fluid is used where both cooling and lubrication are needed (stator winding heads).
2Temperature
If water-based cooling fluid is used, then cooling efficiency is improved, but lubrication capability deteriorates
Solution Approach 1:
The cooling fluid system is segmented into two separate fluid circuits: one using water-based fluid for cooling, and another using oil-based fluid for lubrication and cooling. This allows each fluid to perform its optimal function without the limitations of the other.
Solution Approach 2:
The oil-based cooling fluid in the second cooling system serves dual functions: it provides cooling to the stator winding heads and simultaneously provides lubrication to the interior of the electric machine, eliminating the need for a separate lubrication system.
3Ease of operation
If oil-based cooling fluid is used, then lubrication is improved, but cooling power deteriorates
Solution Approach 1:
The thermal management system is segmented into two independent fluid circuits with different fluid types, allowing each circuit to be optimized for its primary function. The water-based system handles high cooling power requirements, while the oil-based system handles lubrication and supplementary cooling.
Solution Approach 2:
The second cooling system merges the cooling and lubrication functions into a single oil-based fluid circuit, so that the same fluid performs both cooling of the stator winding heads and lubrication of the machine interior, eliminating the need for separate systems.
4Device complexity
If a single cooling system is used, then the device complexity is reduced, but oxidation protection deteriorates
Solution Approach 1:
The oil-based cooling fluid creates an inert atmosphere in the machine interior, displacing oxygen and preventing oxidation of electrical components. The oil-based fluid circuit allows the machine interior to be filled with oil vapor, which protects sensitive components from oxidative degradation.
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 dual cooling system enables high-level simultaneous cooling, lubrication, and oxidation protection, maximizing the potential of the electric machine by optimizing thermal management and reducing oxidation risks.
Implementation Method 1
a first cooling system based on a first cooling fluid around the stator lamination stack
Implementation Method 2
a first cooling channel of the first cooling system, wherein the first cooling channel is formed between the inner housing part and the outer housing part
Implementation Method 3
a second cooling system based on a separate second cooling fluid, wherein the separate second cooling system comprises spray nozzles or bores, which are directed towards at least one of the stator winding heads
Implementation Method 4
in addition the stator winding heads can be cooled and a lubricant can be brought into the interior of the electric machine
Implementation Method 5
the separate second cooling system comprises spray nozzles or bores, which are directed towards at least one of the stator winding heads
Implementation Method 6
By the proposed measures, also unwanted oxidation can be avoided in the interior of the electric machine
Data Source
AI summary
An electric machine includes a machine housing, a stator and a rotor. Stator windings include a stack section, in which they run within the stator lamination stack, and stator winding heads, where they run out of the stack section. The machine housing includes a first cooling system based on a first cooling fluid around the stator lamination stack and a separate second cooling system based on a separate second cooling fluid. The separate second cooling system comprises spray nozzles or bores, which are directed towards at least one of the stator winding heads. A vehicle may include the electric machine.