Electromotive Machine Stator Winding Harmonic Cancellation
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Solution Overview
Problem
Concentrated primary windings in electromotive machines produce large harmonic fields, leading to negative forces that detract from the desired positive force, especially when used in induction motors where conductors respond to any harmonic of the stator field.
Innovation Solution
The arrangement of primary windings on opposite sides of the rotor are offset by a specific wavelength or reversed, canceling out n-pole harmonics, resulting in a symmetrical waveform with only forward-traveling fields, reducing the impact of unwanted harmonics and improving machine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If concentrated primary windings are used in the stator, then the machine structure is simplified and manufacturing is easier, but large harmonic fields are produced that create negative forces reducing machine performance
Solution Approach 1:
The stator is divided into two separate groups of concentrated windings (first group and second group), each producing magnetic fields that interact to cancel harmonics. This segmentation allows the harmful harmonic effects from one group to be counterbalanced by the other group, maintaining the manufacturing simplicity of concentrated windings while eliminating their detrimental effects.
Solution Approach 2:
The two groups of concentrated windings are positioned asymmetrically on opposite sides of the rotor, with the second group displaced relative to the first group by a specific angle (such as 90 electrical degrees). This asymmetric positioning creates a phase difference in the magnetic fields produced, enabling harmonic cancellation while maintaining forward-traveling wave characteristics.
2Device complexity
If concentrated windings are used to simplify stator construction, then device complexity is reduced, but even harmonics are generated that travel in both directions causing performance degradation
Solution Approach 1:
The stator windings are segmented into two distinct groups positioned on opposite sides of the rotor. Each group generates magnetic fields with similar harmonic content, but the spatial displacement and phase relationship between groups cause the backward-traveling harmonic waves to cancel each other out, leaving only forward-traveling waves and a symmetrical waveform.
Solution Approach 2:
The second group of windings is positioned and phased such that its magnetic field production is effectively inverted relative to the first group. This inversion causes the backward-traveling harmonic components from one group to oppose and cancel the backward-traveling components from the other group, eliminating even harmonics and stabilizing the magnetic field composition.
3Device complexity
If coils on opposite sides of the rotor are aligned, then the structure is simpler, but n-pole harmonics are reinforced rather than cancelled
Solution Approach 1:
Instead of aligning the coils of the second group directly opposite the coils of the first group, the second group is displaced by a specific angle (such as 90 electrical degrees). This asymmetric displacement creates a phase difference that causes harmonic cancellation rather than reinforcement, as the magnetic field peaks and troughs from the two groups no longer coincide spatially.
Solution Approach 2:
The solution moves from a simple radial alignment (one-dimensional arrangement) to a two-dimensional positioning where both radial and tangential displacements are considered. By introducing angular displacement in addition to radial positioning, the patent creates a more complex spatial arrangement that enables harmonic cancellation through phase differentiation.
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 the effect of negative forces, enhancing the electromotive machine's efficiency and performance by eliminating even harmonics and ensuring fields travel in one direction, suitable for both permanent magnet and conductive rotor systems.
Implementation Method 1
the primary windings of each group comprise a plurality of coils which, in use, produce a magnetic field
Implementation Method 2
the coils of the second group are in a displaced position relative to the coils of the first group, so that corresponding coils of each group are not aligned and an n-pole harmonic of the magnetic field is substantially cancelled
Data Source
AI summary
An electromotive machine (200, 900) comprises a rotor (230; 800; 920) and a stator (210, 220; 500; 600; 700; 910, 920). The stator (210, 220; 500; 600; 700; 910, 920) comprises a first group of primary windings (260a, 240b, 240d; 520; 640a, 640b, 650a, 650b, 660a, 660b; 930a, 930b, 933a, 933b, 937a, 937b), which are concentrated windings, arranged on a first side of the rotor (230; 800; 920) and a second group of primary windings (240a, 250a, 240c; 530; 740a, 740b, 750a, 750b, 760a, 760b; 941a, 941b, 943a, 943b, 947a, 947b) that are concentrated windings arranged on a second, opposite, side of the rotor (230; 800; 920). The primary windings of each group comprise a plurality of coils that, in use, are supplied with current and produce a magnetic field. The windings of the second group (240a, 250a, 240c; 530; 740a, 740b, 750a, 750b, 760a, 760b; 941a, 941b, 943a, 943b, 947a, 947b) are displaced, relative to the windings of the first group (260a, 240b, 240d; 520; 640a, 640b, 650a, 650b, 660a, 660b; 930a, 930b, 933a, 933b, 937a, 937b) in order to cancel out an n-pole component of the magnetic field.