Concentric-Winding Synchronous Machine With Cooled Wound Rotor
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Solution Overview
Problem
Synchronous electrical machines in boats face challenges with space constraints, torque mass ratio, reliability, and efficiency due to the complexity of permanent magnet rotors and higher thermal losses in wounded rotor machines, which limit their performance and require specific assembly procedures and cooling methods.
Innovation Solution
A synchronous electrical machine design featuring a stator with concentric winding and a wounded rotor, utilizing removable fastening means, non-magnetic shims for reduced losses, and optimized cooling channels to enhance torque density and efficiency, along with commutation means for speed variation without altering the supply frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If permanent magnet rotors are used, then torque density is improved, but assembly complexity and manufacturing difficulty increase due to requiring non-magnetic tools and specific assembly procedures
Solution Approach 1:
The patent replaces expensive permanent magnets with a wounded rotor design that uses conventional magnetic materials and winding techniques. The rotor windings can be easily replaced if needed, making the system more maintainable and less complex to manufacture while achieving comparable torque density through optimized cooling and magnetic circuit design.
Solution Approach 2:
The patent substitutes the permanent magnet system with an electromagnet system (wounded rotor) that uses electrical current to generate the magnetic field. This replacement eliminates the need for complex non-magnetic tooling and specialized assembly procedures required for permanent magnets, while maintaining torque performance through the described cooling and magnetic circuit optimizations.
2Device complexity
If wounded rotor synchronous machines are used, then assembly complexity is reduced, but thermal losses increase due to current circulating in the rotor winding
Solution Approach 1:
The patent segments the rotor into multiple independent magnetic circuits, each with its own cooling channel. This segmentation allows for more efficient heat dissipation from each individual winding section, reducing the overall thermal losses. The stator is similarly segmented with cooling channels positioned to optimize heat removal from high-loss areas.
Solution Approach 2:
The patent introduces a cooling fluid as an intermediary medium to transfer heat away from the rotor and stator windings. The cooling channels carry this fluid through strategic positions to extract thermal energy from the magnetic circuits, thereby reducing the thermal losses that would otherwise accumulate in the wounded rotor system.
3Temperature
If axial cooling is implemented, then stator cooling is achieved, but hotspots occur and torque density is limited due to cooling fluid passing only between adjacent coils
Solution Approach 1:
The patent transitions from a two-dimensional cooling approach (fluid passing between adjacent coils in the radial direction) to a three-dimensional cooling system. Cooling channels are positioned in multiple dimensions: radially between stator and rotor, axially along the magnetic circuits, and circumferentially around the pole cores. This multi-dimensional cooling eliminates hotspots and allows for higher torque density without thermal limitations.
Solution Approach 2:
The patent incorporates cooling channels in strategic positions before the magnetic flux paths are established, particularly in the stator yoke and rotor pole cores. This preliminary cooling arrangement ensures that heat is removed at its source before it can accumulate and create hotspots, allowing the machine to operate at higher power densities without thermal constraints.
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
The design improves torque density, reduces assembly complexity, and enhances cooling efficiency, allowing for higher performance and reliability in space-constrained applications like boats, while avoiding the limitations of permanent magnet rotors and thermal losses in wounded rotor machines.
Implementation Method 1
each magnetic stator pole core extending in a longitudinal direction of the stator comprises at least one cooling groove on a surface of the said magnetic stator pole core in contact with the stator frame and extending along the longitudinal direction so that the groove and the contact surface of the stator frame form a cooling channel
Implementation Method 2
The non-magnetic shim avoids Eddy-induced losses in the frame
Data Source
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AI summary
The synchronous electrical machine (8) comprises a stator (9) and a wounded rotor (10), the stator comprising a plurality of phases, each phase comprising coils (13) connected together and magnetic stator poles cores (12) fixed on a stator frame (11) and evenly distributed along a stator diameter, each coil being wounded around a different magnetic stator pole core to form a magnetic stator pole, each phase comprising a same number of magnetic stator poles, the magnetic stator poles of each phase being disposed in the stator frame to form a concentric winding stator. The rotor (10) comprises a plurality of magnetic rotor pole cores (14) evenly distributed around the rotor (10) and rotor coils (14), each rotor coil being wounded around a different magnetic rotor pole core to form a magnetic rotor pole.