Coreless Alternator for Bicycle Lighting
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Solution Overview
Problem
Conventional low-power alternators used in bicycle lighting and flashlights have high resistive torque, significant weight, and high no-load losses, making them inefficient and requiring additional mechanical effort from cyclists, which can compromise safety by delaying lighting activation.
Innovation Solution
A low-power alternator design featuring a permanent magnet with orthogonal magnetization and a winding without an iron core, with coils arranged at a dihedral angle of less than 75 degrees and extending over a quarter to half of the magnet's diameter, providing polyphase power through multiple angularly offset sets of coils, optimizing voltage production and minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If magnetic cores are provided at the stator level, then the concentration and use of the magnetic field is optimized, but the alternator has high resistive torque and significant weight
Solution Approach 1:
The invention extracts and removes the iron magnetic cores from the stator assembly, retaining only the copper windings. This eliminates the weight penalty and resistive torque associated with magnetic cores while preserving the essential electromagnetic generation function through the permanent magnet rotor and air-core stator configuration.
2Use of energy by moving object
If magnetic cores are provided at the stator level, then the concentration and use of the magnetic field is optimized, but the alternator has high no-load losses
Solution Approach 1:
By removing the iron magnetic cores from the stator, the invention eliminates the hysteresis and eddy current losses that occur in ferromagnetic materials during alternating magnetic field cycles. The air-core design allows the magnetic field to pass through air rather than iron, dramatically reducing no-load energy losses while maintaining sufficient magnetic field concentration for effective power generation.
3Use of energy by moving object
If conventional alternator design is used, then magnetic field concentration is improved, but additional mechanical parts are required for actuation
Solution Approach 1:
The simplified alternator design removes the need for complex mechanical actuation systems by creating a permanently coupled, always-active generator. The air-core, coreless stator design reduces friction and mechanical resistance, allowing the alternator to be permanently mounted and continuously driven by the bicycle wheel without requiring switches, clutches, or other actuation mechanisms.
4Use of energy by moving object
If conventional alternator design is used, then magnetic field concentration is improved, but the cyclist must provide additional effort
Solution Approach 1:
By eliminating the iron magnetic cores, the invention removes the source of high resistive torque that opposes rotor rotation. The air-core design creates minimal magnetic resistance and friction, allowing the bicycle wheel to drive the alternator with negligible additional effort, making the system transparent to the cyclist during normal operation.
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
The solution results in a high-efficiency, lightweight alternator with negligible no-load losses, allowing permanent mechanical coupling and efficient power generation, reducing the effort required from cyclists and enabling continuous recharging of batteries.
Implementation Method 1
Alternators are considered here, that is to say electrical generators supplying an alternating voltage... a rotor made up of a permanent magnet and a stator made up of a winding
Implementation Method 2
in order to optimize the concentration and use of the magnetic field generated by the rotor
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
The invention relates to an alternator comprising a permanent magnet (1) mounted for rotation, the direction of magnetization of the magnet being orthogonal to the axis of rotation, and a coreless iron winding (10) surrounding the magnet and whose turns are in a plane substantially parallel to a plane containing the axis of rotation, the winding extending over a dihedral angle from the axis of rotation of less than 75 degrees and, radially, over a distance between one-quarter and one-half of the diameter of the magnet.