Elliptical Pole Head Contour for Synchronous Generator Torque Smoothing
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Solution Overview
Problem
Gearless wind turbines experience torque fluctuations due to discontinuous magnetic fields generated by pole stacks and gaps, leading to vibrations and potential damage from these vibrations and unwanted noise.
Innovation Solution
The pole assembly laminations of the synchronous generator are designed with an elliptical contour for the pole head area, which smooths out torque fluctuations by creating a continuous change in the magnetic field, reducing the difference in magnetic forces between pole stacks and gaps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pole stacks are arranged on the rotor with gaps between them, then the generator can generate magnetic excitation and produce electrical energy, but torque fluctuations and vibrations occur due to the discontinuous magnetic field
Solution Approach 1:
The pole head area is given an elliptical contour instead of a conventional straight or rounded shape. This curvature modification creates a continuous variation in the magnetic field strength as the rotor rotates, smoothing out the discontinuous magnetic field caused by gaps between pole stacks. The elliptical shape ensures that the magnetic flux density changes gradually, reducing torque fluctuations and vibrations while maintaining electrical energy generation capability.
2Force
If the pole head area is shaped to maintain a constant and narrow air gap, then magnetic forces are maximized for energy generation, but torque fluctuations increase due to the discontinuous magnetic field from gaps between pole stacks
Solution Approach 1:
The elliptical contour is applied specifically to the pole head area that faces the stator, while the pole shank area maintains its conventional shape for structural support and winding accommodation. This localized modification optimizes the magnetic field distribution in the critical air gap region without compromising the structural integrity or winding arrangement of the pole assembly.
3Ease of manufacture
If conventional pole head shapes are used, then manufacturing is simpler, but torque fluctuations cause vibrations that lead to system damage and unwanted noise
Solution Approach 1:
The elliptical contour of the pole head area can be manufactured using standard punching or cutting processes applied to the pole assembly laminations. The elliptical shape is defined by simple geometric parameters (major and minor axes) that can be easily programmed into manufacturing equipment, making the transition from conventional shapes to elliptical shapes straightforward and cost-effective while significantly improving system reliability.
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 significantly reduces torque fluctuations and associated vibrations, minimizing damage and noise while maintaining comparable torque levels with conventional systems.
Implementation Method 1
The pole shank areas of the pole stack laminations of the pole stacks arranged one behind the other are provided with a winding and an electrical excitation current is fed into this winding. As a result, a magnetic excitation is generated with the pole packages and the corresponding winding together with the excitation current.
Implementation Method 2
the contour of the pole head area on the side facing away from the pole shank area being elliptical or having an elliptical course... Such a contour of the pole head area influences the magnetic field generated by the pole stacks and the coils in such a way that the torque fluctuations are smoothed out.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a synchronous generator and a pole stack (10) for a rotor of a synchronous generator of a wind energy installation (100). The pole stack (10) has a plurality of pole stack sheets (22), each pole stack sheet (22) having a pole shaft region (20) and a pole head region (18). The pole head region (18) projects laterally beyond the pole shank region (20) and has a side (32) facing the pole shank region (20) and a side (30) facing away from the pole shank region (20). The contour of the pole head region (18) is elliptical at least on the side (30) facing away from the pole shank region (20).