Multi-winding set fractional slot synchronous machine
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Solution Overview
Problem
Conventional fractional slot concentrated windings in electrical machines produce undesired harmonics, leading to increased losses, torque ripple, and thermal demagnetization, particularly in large generators like those used in wind turbines.
Innovation Solution
A dual three-phase fractional slot synchronous machine with a combined star-delta configuration for two winding sets, each wound around stator teeth, and a phase-shifted converter system to minimize harmonics and torque ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fractional slot concentrated windings are used, then ease of manufacture and fault tolerance are improved, but unwanted MMF harmonics increase causing losses and torque ripple
Solution Approach 1:
The patent divides the stator winding into multiple independent winding sets (first and second three-phase winding sets) with different slot assignments. Each winding set generates MMF harmonics independently, and their superposition can be controlled to cancel unwanted harmonics while maintaining the manufacturing simplicity of fractional slot concentrated windings
Solution Approach 2:
The patent introduces asymmetric phase shifting between winding sets (30 degrees for first sub-space harmonics, 15 degrees for seventh harmonics) to achieve harmonic cancellation. This asymmetric configuration allows selective elimination of specific harmonic orders while preserving the fundamental torque production
2Loss of energy
If dual three-phase configuration with 30° phase-shift is used, then first sub-space winding MMF harmonic is eliminated reducing rotor losses, but device complexity increases
Solution Approach 1:
The patent combines two three-phase winding sets into a unified stator structure with shared magnetic circuit and rotor. The winding sets are configured to work together harmonically, eliminating the need for separate magnetic circuits or complex control systems while achieving loss reduction through harmonic cancellation
3Object-generated harmful factors
If multi-layer windings are used, then MMF harmonics are substantially reduced, but winding complexity increases
Solution Approach 1:
Instead of adding layers in the vertical dimension (multi-layer windings), the patent introduces a new dimension of phase shifting between independent winding sets. This approach achieves harmonic reduction through spatial and temporal phase relationships rather than through increased winding layers, maintaining manufacturing simplicity
4Object-generated harmful factors
If stator shifting with doubled slots is used, then harmonics are minimized through phase-shift, but manufacturing complexity increases
Solution Approach 1:
The patent applies local phase shifting only to specific winding sets rather than redesigning the entire stator slot structure. Each winding set maintains its own phase characteristics, allowing harmonic cancellation at specific harmonic orders without requiring a complete stator redesign or doubling of slot numbers
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
Reduces unwanted harmonics, losses, and torque ripple, enhancing efficiency and reducing the risk of thermal demagnetization in generators, particularly in large wind turbine applications.
Implementation Method 1
the non-overlapping windings may result in a less sinusoidal MMF (magneto-motive force) distribution with a large number of loss producing harmonics
Data Source
AI summary
An electrical machine is provided, in particular a dual three-phase fractional slot synchronous machine, including: a stator providing plural slots between plural teeth; a first multi-phase winding set; and a second multi-phase winding set, wherein the first winding set and the second winding set are both provided as star-delta connection and at least partially arranged in the slots and wound around the teeth.