Stator Winding Design for Electric Machine Eddy Current Reduction
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Solution Overview
Problem
Fractional Slot Concentrated Winding (FSCW) electric machines experience significant eddy current losses due to lower order sub-harmonics, leading to reduced efficiency, increased noise, and vibration in large electric machines, particularly in those with solid back iron yokes.
Innovation Solution
The electric power system employs a stator arrangement with electric windings connected in parallel to a power converter system, reducing eddy currents in rotor permanent magnets and solid back yokes by optimizing the winding topology and power converter configuration, thereby minimizing noise and vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If FSCW machines use conventional winding topologies (even or odd), then the winding factor can be maximized, but lower order sub-harmonics penetrate into the rotor inducing eddy current losses
Solution Approach 1:
The patent divides the conventional single winding per phase into multiple windings per phase (e.g., two windings A1 and A2 for phase A). These segmented windings are connected in parallel through a dual three-phase converter system, allowing independent control of each winding group. This segmentation enables cancellation of lower order sub-harmonics while maintaining the beneficial winding factor of FSCW topology.
2Strength
If a solid back iron yoke is used in the rotor, then mechanical strength is sufficient, but eddy current losses increase significantly
Solution Approach 1:
The patent introduces a dual three-phase converter system as an intermediary between the stator windings and the grid/load. This converter system processes the electrical output to cancel lower order sub-harmonics before they reach the rotor, thereby protecting the solid back iron yoke from excessive eddy current losses while maintaining its mechanical strength benefits.
3Loss of energy
If lower order spatial harmonics are present, then eddy current losses increase, but also generator noise and vibration levels increase
Solution Approach 1:
The dual three-phase converter system continuously monitors and controls the electrical output from the two winding groups. By using feedback control, the system adjusts the current in each winding group to cancel lower order spatial harmonics, thereby simultaneously reducing eddy current losses and the associated noise and vibration effects.
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 configuration significantly reduces eddy current losses, enhances thermal performance, and improves overall efficiency, while also lowering noise and vibration levels in electric machines.
Implementation Method 1
Fractional Slot Concentrated Winding (FSCW) is a known approach for spatially arranging and electrically connecting a plurality of stator windings of an electric machine which can be a motor or a generator
Implementation Method 2
In a FSCW machine having a rotor with permanent magnets (PM) exhibits a sinusoidal back electro motive force (emf) waveform and a low cogging torque. In a known manner cogging torque results from the magnetic interaction between the PM of the rotor and the stator slots
Implementation Method 3
The comparatively long wavelengths of these lower order sub-harmonics will penetrate into the rotor inducing eddy current losses in particular within the rotor PM and within a rotor iron yoke
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
It is described a stator arrangement (110, 210, 510) for an electric machine (105, 305, 505), in particular for a generator of a wind turbine. The stator arrangement (110, 210, 510) comprises (a) a frame structure (112) which is formed around a center axis; (b) a plurality of stator teeth (114) which are arranged equally spaced apart along a circumference of the frame structure (112), wherein each stator tooth (114) extends in a radial direction with respect to the center axis; (c) a plurality of electric windings, each electric winding being wound around one stator tooth (114); and (d) an electric interface (120) for connecting the plurality of electric windings with a power converter system (360, 460). Each electric winding is assigned to one electric phase of a multi-phase current which is associated with an operation of the electric machine (105, 305, 505), and the electric interface (120) is configured in such a manner that two neighboring electric windings being assigned to one and the same electric phase are connectable in parallel with the power converter system (360, 460). It is further described an electric machine (105, 305, 505) and an electric power system (300, 400) which both comprise the described stator arrangement (110, 210, 510).