Rotor Rectifier Cooling in Externally Excited Synchronous Machines
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Solution Overview
Problem
The waste heat generated during the rectification of the coil current in externally excited synchronous machines limits their performance, particularly in high-performance applications such as motor vehicle drives, due to inefficient indirect cooling methods.
Innovation Solution
Integrating at least one electrical structural component of the rectifier circuit within a cooling volume through which a cooling fluid directly contacts and cools the components, eliminating the need for large heat sinks and reducing thermal gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If indirect cooling via heat sink and circuit board is used, then the structural components are cooled, but the thermal path is long and heat transfer efficiency is reduced
Solution Approach 1:
The patent extracts the electrical structural components from the traditional circuit board mounting arrangement and places them directly within the cooling volume. This eliminates the intermediate heat sink and circuit board thermal path, allowing direct thermal contact between the components and cooling fluid, thereby resolving the contradiction between cooling efficiency and device complexity
Solution Approach 2:
The cooling fluid serves as a direct intermediary between the electrical structural components and the thermal management system. By eliminating the heat sink and circuit board as thermal intermediaries, the patent achieves superior thermal coupling and heat transfer efficiency
2Reliability
If larger heat sinks are used for indirect cooling, then thermal reserves are improved, but weight and space requirements increase
Solution Approach 1:
The patent removes the traditional heat sink component entirely by placing electrical structural components directly in the cooling volume. This extraction eliminates the need for large, heavy heat sinks while maintaining or improving thermal management effectiveness, thus resolving the contradiction between reliability and weight
Solution Approach 2:
The patent changes the thermal management approach from passive heat sink-based conduction to active fluid-based convection cooling. This parameter change in the cooling mechanism allows for more efficient heat removal with reduced component size and weight
3Temperature
If indirect cooling is used, then cooling is provided, but thermal gradients are high and service life is reduced
Solution Approach 1:
By extracting components from the indirect cooling path and placing them directly in the cooling fluid flow, the patent eliminates thermal gradients that would otherwise develop across heat sinks and circuit boards. This direct thermal coupling improves component reliability and service life
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 direct cooling method enhances thermal coupling, enabling higher rotor currents, faster field formation, and deactivation, reduces material costs, and increases robustness and service life, while achieving higher performance and power density.
Implementation Method 1
the at least one electrical structural component directly contacts the cooling fluid... achieve significantly improved thermal coupling of the at least one electrical structural component with the cooling fluid
Implementation Method 2
a cooling volume through which a cooling fluid flows in at least one operating state of the synchronous machine
Data Source
AI summary
An externally excited synchronous machine is disclosed and may include a stator, a rotor rotatably mounted on a stator and having a rotor winding for generating a rotor magnetic field, and an inductive energy transfer circuit for energizing the rotor winding. The rotor may include a cooling volume through which a cooling fluid flows in at least one operating state of the synchronous machine. The inductive energy transfer circuit may include a stator-side primary winding, a rotor-side secondary winding, and a rectifier circuit for rectifying an alternating current provided by the secondary winding for energizing the rotor winding. The rectifier circuit may include at least one electrical structural component arranged within the cooling volume of the rotor such that the at least one electrical structural component directly contacts the cooling fluid at least in the operating state of the externally excited synchronous machine.