Liquid Cooled Electric Machine End Winding Cooling
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Solution Overview
Problem
Existing electrical machines with liquid-cooled stators face inefficiencies in cooling the rotor and end windings, particularly in compact designs where external air flow routing is complex and ineffective, leading to increased internal cooling air temperatures and reduced performance.
Innovation Solution
The solution involves directly coupling internal air flow to the liquid cooling system within the end winding space, using cooling pipe coils routed through the end windings and fan wheels to generate circulating air flows that pass through radial and axial air ducts, enhancing heat transfer without requiring an additional jacket housing, thus maintaining a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If internal air flow is generated by a fan and routed through free spaces in the machine housing, then end winding cooling is achieved, but an additional jacket housing with air ducts is required, increasing diameter and weight
Solution Approach 1:
The liquid cooling jacket serves multiple functions: it cools the stator core directly through liquid circulation and simultaneously acts as a heat exchanger for the air cooling circuit that cools the end windings and rotor. This multi-functionality eliminates the need for separate air ducting systems and additional housing structures.
Solution Approach 2:
The air cooling circuits for end windings and rotor are merged with the liquid cooling system by using the liquid cooling jacket as a common heat exchanger. Both air circuits convey heat to the same liquid-cooled components, consolidating the cooling system architecture and reducing overall system size and weight.
2Temperature
If cooling pipe coils are embedded in the end winding with cast resin, then contact between cooling tube and winding is improved, but the plastic material significantly limits heat conduction
Solution Approach 1:
Air is introduced as an intermediary cooling medium that flows directly over the end windings before reaching the liquid cooling circuit. This air cooling approach bypasses the need for direct thermal contact between cooling tubes and windings, eliminating the heat conduction limitation of plastic embedding materials while still achieving effective cooling.
3Temperature
If the machine housing has two shells with air ducts for routing internal air flow, then cooling is achieved, but the diameter and weight of the motor increase
Solution Approach 1:
The single machine housing simultaneously serves as the structural enclosure and as the cooling system infrastructure. The liquid cooling jacket integrated into the housing performs both stator cooling and heat exchange for rotor and end winding cooling, eliminating the need for a second jacket housing with dedicated air ducts.
Solution Approach 2:
The cooling system utilizes the radial and axial dimensions of the existing housing structure by integrating the liquid cooling jacket around the stator core and positioning air cooling circuits to utilize available spaces without requiring additional radial clearance or axial length.
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 approach achieves high-efficiency cooling of both the rotor and end windings with a space-saving design, improving heat transfer and maintaining machine performance without increasing diameter or weight, while allowing for countercurrent air flow through the rotor for enhanced cooling.
Implementation Method 1
The stator lamination can either be jacket-cooled with a cooling liquid such as oil or water
Implementation Method 2
the fan has two fan wheels, each assigned to one end winding space, for generating an air flow circulating within each end winding space
Implementation Method 3
the cooling pipe coils are routed through the end windings outside of the end windings and the fan has two fan wheels... which is conveyed by means of air ducts and/or air ducts in the respective winding space via the exposed cooling coils
Implementation Method 4
a liquid-cooled electric machine... in which a cooling liquid of a liquid cooling circuit is circulated through a jacket cooling
Data Source
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AI summary
The present invention relates to an electric machine with a machine housing in which a rotor and a stator winding are accommodated, the stator winding having winding heads arranged on opposite sides in a winding head space, and with a cooling device comprising a liquid cooling circuit with stator jacket cooling and cooling coils, as well as a fan connected to the rotor for air circulation in the machine housing. The invention further relates to a method for cooling such an electric machine.According to the invention, the cooling pipe coils are routed outside the winding heads through the winding head spaces, and the fan has two impellers, each assigned to a winding head space, to generate an airflow circulating within each winding head space. This airflow is guided by air ducts and/or guides in the respective winding space over the exposed cooling pipe coils and through the winding heads. By cooling the circulating internal air directly in or at the winding head space, highly efficient cooling of the winding head space can be achieved without sacrificing a compact design.