Armature Windings for Rotating Machines Reducing Harmonic Vibration
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Solution Overview
Problem
In synchronous machines with fractional-number slots, specific harmonics generated in the armature magnetomotive force lead to vibration and noise due to resonance with natural vibration frequencies, particularly in multipolar machines with a large number of poles.
Innovation Solution
The armature windings are designed with a 3-phase winding of two layers having an electrical phase difference of 60°, where at least one coil piece in either the upper or lower coil pieces is replaced with a coil piece from an adjacent different phase, reducing the specific harmonic that causes core vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fractional-number slots are used to improve waveform quality and design flexibility, then waveform quality and design freedom are improved, but harmonics are generated in the armature magnetomotive force causing vibration and noise
Solution Approach 1:
The patent applies local quality by selectively replacing only one coil piece (either upper or lower, but not both) in each phase belt with a coil piece from an adjacent different phase. This localized modification targets specific harmonic components while preserving the overall fractional-number slot structure and its design flexibility benefits.
Solution Approach 2:
The patent converts the harmful effect of harmonics generated by fractional-number slots into a beneficial outcome by strategically replacing coil pieces to eliminate specific harmonic components. The coil replacement technique transforms the inherent harmonic problem of fractional-number slots into an opportunity to reduce vibration and noise while maintaining the design freedom advantages.
2Object-affected harmful factors
If the armature core structure is enlarged to reduce harmonics and vibration, then vibration and noise are reduced, but the machine size and weight increase
Solution Approach 1:
The patent extracts and eliminates specific harmonic components from the armature magnetomotive force through selective coil piece replacement. By removing the harmful harmonic elements (particularly sub-synchronous harmonics with denominators of 4 or greater) from the system, the need for larger armature core structures is avoided, thus preventing increases in machine weight and size.
3Object-affected harmful factors
If coil arrangement is carried out by replacing one coil piece in a phase belt with a coil piece in an adjacent different phase (interspersed one coil windings), then harmonics such as fifth-order and seventh-order are reduced in integral-number slots, but sub-synchronous harmonics in fractional-number slots are not effectively reduced
Solution Approach 1:
The patent applies parameter changes by modifying the coil arrangement parameters specifically for fractional-number slot configurations. The replacement of one coil piece per phase belt with a coil piece from an adjacent different phase changes the magnetomotive force distribution pattern, effectively targeting and reducing sub-synchronous harmonics (with denominators of 4 or greater) that were not addressed by conventional interspersed winding techniques designed for integral-number slots.
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 effectively reduces the specific harmonic responsible for core vibration, preventing the need to enlarge the armature core structure while maintaining the fundamental wave flux, thus addressing the vibration and noise issues associated with fractional-number slots.
Implementation Method 1
a harmonic called a sub-synchronous (or fractional) harmonic of a case where the number of slots per pole per phase (number of slots or coils per each pole per each phase), which is referred to as Nspp, includes a fractional number
Implementation Method 2
A state where a frequency of the electromagnetic force based on such a harmonic and fundamental wave is close to a natural vibration frequency is called a resonance, and this becomes a cause of vibration of the armature core
Data Source
AI summary
According to one embodiment, there is provided armature windings of a rotating electrical machine, in which a 3-phase winding of two layers including upper and lower layers is constituted of phase belts having an electrical phase difference of 60° in between, pairs of upper coil pieces and lower coil pieces are contained in slots, the number of slots per pole per phase includes a fractional number, and a denominator thereof is an integral number greater than or equal to 4, wherein coil arrangement is carried out such that at least one coil piece in either of the upper or lower coil pieces included in two layers of upper and lower layers in one phase belt is replaced with a coil piece of an adjacent different phase.