Wind Turbine Direct Drive Generator Stator Support

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Solution Overview

Problem

Existing wind turbine designs with direct drive generators face challenges in maintaining a constant air gap width between the rotor and stator due to unbalanced magnetic pull and load distribution, leading to heavy and expensive stator support structures, especially in large turbines.

Innovation Solution

A wind turbine design with a direct drive generator featuring an inner stator arrangement and outer rotor arrangement, supported by a stationary outer shaft and a rotatable inner shaft with two main bearings, where the stator is externally mounted and the rotor is indirectly attached to the inner shaft or hub, providing two-sided support and reducing the number of bearings needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a two-bearing arrangement with a stationary inner shaft is used to support the rotor, then the rotor can turn relatively to the stator, but the unilaterally supported stator structure makes it difficult to maintain constant air gap width and requires a large, heavy stator support structure

Engineering Contradiction:

Improverotor rotation capabilityVSAvoidstator support structure weight

Core Design Contradiction:

Ease of operationVSWeight of stationary object

Solution Approach 1:

The patent inverts the traditional bearing arrangement by placing the bearings on the rotor side (rotating side) rather than supporting the stator (stationary side). The rotor is supported by two bearings that allow it to rotate relative to the stator, while the stator is bilaterally supported by the turbine tower and bedplate. This inversion eliminates the need for a heavy stator support structure with multiple support arms.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The stator support structure in this patent serves multiple functions: it provides bilateral support for the stator, maintains constant air gap width through geometric design, and transfers loads to the turbine tower and bedplate. The support structure comprises a stator support ring and two support arms that are integrally connected, creating a unified structure that performs all these functions simultaneously.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If the stator structure is dimensioned to absorb and transfer all wind turbine rotor loads, then the air gap width can be maintained within tolerances, but the stator structure becomes very heavy and expensive on large wind turbines

Engineering Contradiction:

Improveair gap width toleranceVSAvoidstator structure weight

Core Design Contradiction:

Manufacturing precisionVSWeight of stationary object

Solution Approach 1:

Instead of having the stator structure absorb and transfer all rotor loads, the patent inverts the load path by having the rotor supported by bearings that carry the loads directly to the turbine bedplate through the torque arm. The stator support structure only needs to maintain positional stability and constant air gap width, not bear the full rotor loads.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The stator support structure uses local quality differentiation by having the stator support ring with varying thickness and the support arms with specific geometric designs that provide optimal stiffness and strength only where needed to maintain air gap width, rather than uniformly reinforcing the entire stator structure.

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If a four-bearing arrangement is used with separate main shaft bearings and generator bearings, then the main shaft and generator are independently supported, but a total of four bearings are required and the torque arm arrangement becomes substantial and heavy

Engineering Contradiction:

Improveindependent support of main shaft and generatorVSAvoidnumber of bearings and torque arm arrangement

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent merges the main shaft support function with the generator rotor support function into a single integrated bearing arrangement. The two bearings that support the generator rotor also serve as the main shaft bearings, eliminating the need for separate main shaft bearings and reducing the total bearing count from four to two.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The bearings in this patent perform multiple functions simultaneously: they support the rotor assembly, allow rotation of the main shaft, maintain generator air gap, and transfer torque loads. This multi-functionality eliminates the need for separate bearing arrangements for the main shaft and generator.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Device complexity

If a single bearing replaces the two-bearing arrangement, then the number of bearings is reduced, but the unilaterally supported stator structure drawback is not substantially changed

Engineering Contradiction:

Improvenumber of bearingsVSAvoidair gap width constancy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent uses asymmetric geometric design in the stator support structure, with the stator support ring and support arms configured to provide bilateral support symmetry while the bearing arrangement itself remains asymmetric with two bearings positioned to optimally support the rotor. This asymmetric design allows two bearings to provide effective bilateral support.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

By inverting the support arrangement to bear on the rotating rotor rather than the stationary stator, the patent achieves bilateral support functionality with fewer bearings. The two bearings on the rotor provide symmetric support that maintains constant air gap width without requiring a unilateral stator support structure.

Inventive Principle:

Principle #13The other way round (Inversion)

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 design simplifies and reduces the cost of the wind turbine by enabling a lightweight, compact stator structure while maintaining a constant air gap width, and addresses potential misalignment issues through a flexible front endplate, resulting in a more efficient and cost-effective solution.

Implementation Method 1

at least two main bearings support the rotatable inner shaft inside the stationary outer shaft

Methodology Applied

Scientific EffectBall bearing: Ball Bearing

Implementation Method 2

a flexible front endplate, resulting in a more efficient and cost-effective solution

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentEP2143942B1Wind turbine

Publication Date: 2016.01.06 SIEMENS AG

AI summary

The invention concerns a wind turbine (1) comprising a direct drive generator (2) comprising an inner stator arrangement (8) and an outer rotor arrangement (19), a stationary outer shaft (6) and a rotatable inner shaft (14) having a centre axis (A), wherein at least two main bearings (15, 16) support the rotatable inner shaft (14) inside the stationary outer shaft (6), the stator arrangement (8) is arranged on the outside of the stationary outer shaft (6) and the rotor arrangement (19) is substantially arranged around the stator arrangement (8) and on the front side at least indirectly attached to the rotatable inner shaft (14) and/or to the hub (17) of the wind turbine (1).