Wind Turbine Outer Rotor Cooling Channels for Permanent Magnets
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Solution Overview
Problem
Wind turbines face challenges in effectively cooling permanent magnets due to electrical losses and high ambient temperatures, leading to increased magnet temperatures and potential degradation of magnet properties.
Innovation Solution
The design incorporates a complex air path system with groove-like longitudinal and circumferential recesses in the rotor housing, allowing air to flow between the air gap and the magnet modules, enhancing cooling efficiency by creating a multi-directional air flow path that can be assisted by convection or an air pump, eliminating the need for gaps between magnet means and increasing the width of the cooling air flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If permanent magnets are arranged in rows on the inner surface of the rotor housing, then the magnetic field strength is improved, but heat accumulation occurs leading to magnet temperature rise above safe limits
Solution Approach 1:
The rotor housing inner surface is segmented into multiple longitudinal recesses that divide the magnet arrangement into separate cooling zones. Each recess creates an independent air channel that allows cooling air to reach individual magnet rows, preventing heat accumulation while maintaining magnetic field strength.
Solution Approach 2:
A pneumatic cooling system is implemented by creating air channels through longitudinal recesses in the rotor housing. Cooling air is supplied through these recesses to directly contact the permanent magnets, using pneumatic flow to remove heat generated by electrical losses and ambient temperature effects.
2Loss of energy
If cooling air is supplied to the air gap, then heat dissipation is improved, but the cooling air flow width is limited by the air gap dimensions
Solution Approach 1:
The cooling system transitions from a two-dimensional air gap cooling approach to a three-dimensional cooling structure by creating longitudinal recesses that extend into the rotor housing. This dimensional change allows cooling air to access magnets from multiple directions and increases the effective cooling surface area beyond the limitations of the air gap width.
Solution Approach 2:
The longitudinal recesses are nested within the rotor housing structure, creating internal cooling channels that are integrated into the existing rotor design. This nesting approach allows the cooling system to utilize the rotor housing itself as the cooling structure, maximizing the cooling air flow area without increasing the overall generator size.
3Temperature
If longitudinal recesses are created in the rotor housing, then cooling air access is improved, but the structural integrity of the rotor housing may be compromised
Solution Approach 1:
The rotor housing is designed with local quality variations where longitudinal recesses are created only in specific regions where cooling is most needed, while other regions maintain full structural thickness. This localized approach provides adequate cooling where required while preserving overall structural integrity of the rotor housing.
Solution Approach 2:
The rotor housing may utilize composite material construction that allows for the integration of cooling recesses without compromising strength. The composite structure can incorporate reinforcing elements or optimized material distribution that maintains structural integrity while accommodating the cooling channels needed for effective magnet cooling.
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 solution provides an enhanced cooling effect for the permanent magnets, reducing heat accumulation and maintaining magnet performance even in high-temperature conditions, thereby improving the reliability and efficiency of the electric generator.
Implementation Method 1
air can leave or enter the longitudinal recess at a position of the recess which is spaced apart from the facial front sides of the longitudinal recess, because otherwise a heat accumulation occurs at respective positions. Particularly, if air can enter the longitudinal recess only at openings which are located on the front end sides of the longitudinal recess, the resulting cooling effect is typically not sufficient for realizing an adequate cooling.
Data Source
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AI summary
Electric generator (7) for a wind turbine (1), comprising an inner stator (10) and an outer rotor (11) which is rotatably mounted around a rotation axis (6) which extends along a longitudinal direction (12) of the rotor (11), wherein an air gap (22) is provided between the stator (10) and the rotor (11), wherein the rotor (11) comprises a hollow cylindrical rotor housing (23) and a plurality of magnet means (24) being arranged at an inner surface of the rotor housing (23) in several rows extending along the longitudinal direction (12), wherein the inner surface comprises at least one groove like longitudinal recess (30) extending along the longitudinal direction (12) and being covered by the magnet means (24) of one of the rows, wherein the inner surface comprises at least one groove like circumferential recess (31) extending along the circumferential direction (14) and connecting the longitudinal recess (30) with the air gap (22).