Generate AC/DC w/o Contact Brushes: Is It Possible?

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    Generators Motors
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Discussion Overview

The discussion revolves around the feasibility of generating AC or DC electricity without the use of contact brushes, particularly focusing on induction motors and alternative designs for generators. Participants explore various mechanisms and configurations that could achieve this goal.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a permanent magnet spinning near or within a coil could generate electricity without brushes, questioning if kinetic motion alone can produce a magnetic field.
  • Another participant confirms that most AC generators operate on inductive principles.
  • A third participant describes motorcycle alternators as brushless, detailing their design with a stator field coil and a steel rotor, indicating that this design avoids the need for brushes.
  • A later reply explains that standard AC induction motors can be converted into AC generators, noting that all motors can act as generators under certain conditions. The participant mentions the importance of adding a capacitor to the output to facilitate this conversion.

Areas of Agreement / Disagreement

Participants express various viewpoints on the topic, with some agreeing on the principles of induction and brushless designs, while others explore different configurations and mechanisms. No consensus is reached on the best method or the feasibility of the initial proposition.

Contextual Notes

Some claims depend on specific configurations and assumptions about motor operation and design, which may not be universally applicable. The discussion does not resolve the technical details or limitations of the proposed methods.

FulhamFan3
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I just saw a demonstration of an induction motors and was wondering if its possible to build an AC or DC generator without contact brushes? The only way I can think of is if you have a permanant magnet spinning near or within a coil or wire. Is there anyway to produce a magetic field with just kinetic motion? I've searched the net and haven't found any explanation. If you have a link please include it.
 
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Most motorcycle alternators have no brushes. There is a stator field coil held in place from one side, a steel rotor comprised of 2 halves with a zigzag separation cantilevered in from the other side, and pickup coils on the outside. It works the same as an automotive unit except that since it only has a bearing on one side, the field coil can come in from the other and needs not rotate. In the automotive unit, there are bearings on both sides so slip rings and brushes are needed to activate the field coil.
 
Originally posted by FulhamFan3
I just saw a demonstration of an induction motors and was wondering if it's possible to build an AC or DC generator without contact brushes?

Yes, and you can even convert a standard AC induction motor into an AC generator. All motors act as generators (that's why a motor uses more energy when you ask it to perform more work, and why a motor stops drawing energy if allowed to spin frictionlessly.) AC induction motors are a little weird, but since they already are generators inherently, there must be a way to use them as stand-alone generators.

The secret: add a capacitor across the output. Then, as the rotor spins, a large AC voltage builds up and a large current exists between the motor coil and the capacitor. Spin the motor fast enough, and choose the right value of capacitor, and you'll have a 120VAC 60Hz generator.

See: http://www.qsl.net/ns8o/Induction_Generator.html
 

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