Alternator Rotor Claw Pole Angular Opening Optimization
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Solution Overview
Problem
Existing rotating electrical machines, such as alternators, face inefficiencies due to the third harmonic being perceived as a disturbance, which lowers charging efficiency, and there is a need to optimize machines to exploit the third harmonic for better battery charging.
Innovation Solution
A rotor design with alternately formed north and south poles and a specific angular opening of the claw-shaped magnetic poles, optimized to maximize the electromotive force peak, including a central external surface with a constant angular opening and peripheral surfaces with discontinuities, to enhance the third harmonic contribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotor uses conventional claw-shaped poles without optimized angular opening, then the structure is simple and easy to manufacture, but the third harmonic is perceived as a disturbance that lowers charging efficiency
Solution Approach 1:
The patent optimizes the angular opening of the claw-shaped magnetic poles by defining it as a function of the angular pole pitch (Obe = K × Theta, where K is between 0.4 and 0.8). This parameter change transforms the third harmonic from a disturbance into a useful component that contributes to battery charging, thereby improving charging efficiency without fundamentally changing the rotor structure.
Solution Approach 2:
The patent introduces a central external surface on the claw-shaped poles with specific angular opening characteristics, while peripheral surfaces may have discontinuities. This local differentiation of surface properties allows the third harmonic to be exploited while maintaining overall structural simplicity and manufacturability.
2Power
If the claw-shaped poles have optimized angular opening Obe=K×Theta with central external surface, then the electromotive force peak is maximized and third harmonic is exploited, but the manufacturing precision requirements increase
Solution Approach 1:
The patent defines the angular opening Obe as a proportional function of the angular pole pitch Theta (Obe = K × Theta), where K is a coefficient between 0.4 and 0.8. This parametric relationship allows the optimal angular opening to be determined through calculation rather than requiring complex trial-and-error manufacturing processes, thus maximizing electromotive force peak while keeping manufacturing precision requirements manageable.
3Power
If the rotor coil is fully covered by claw-shaped magnetic poles, then the magnetic flux transmission is optimized, but the air gap distance increases
Solution Approach 1:
The patent specifies that the radial distance from the central external surface of the claw-shaped poles to the stator should be less than three times the air gap. This local optimization ensures adequate magnetic flux transmission coverage while preventing excessive air gap distance, thereby maintaining both power transmission efficiency and compact machine dimensions.
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 optimizes the electromotive force peak for both the fundamental and third harmonic, ensuring the third harmonic is in phase with the fundamental and maximizes the charging efficiency by maintaining a constant flux transmission to the stator.
Implementation Method 1
a rotor coil for generating a magnetic flux upon passage of an electric current; and a pair of pole wheels composed of: a cylindrical portion on which said rotor coil is wound
Implementation Method 2
said stator surrounding said rotor and an air gap is defined as the minimum distance between the stator and the rotor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention mainly relates to a rotating electrical machine, for example an alternator, comprising a rotor (4) and a stator having slots for receiving a winding. In this invention, the rotor comprises north (N) and south (S) poles formed alternately in a direction of rotation of the rotor, said rotor having an angular pole pitch (Theta) equal to 2π divided by 2P, P being the number of pole pairs of the rotor; and said rotor (4). Each claw-shaped magnetic pole (61, 62, 71) comprises a first external surface (712) facing said slots. The first external surface (712) has an angular opening in a cutting plane of one of the claw-shaped poles, said maximum angular opening (Obe) for all the cutting planes of one of the claw-shaped poles is equal to Obe = K x Theta, with K between 0.4 and 0.8.