Which factors determine the power output of a permanent magnet alternator

[Fdtroya]

TL;DR

I have to design a permanent magnet motor (as an assignment) that should be able to power a relatively small load of around 1.5 Watts, and i would like to know where could i read and learn how to relate parameters such as rpm,coil turns, coil wire thickness, torque required to achieve a certain rpm, etc... With the power output in order to achieve an effective design.

To be more precise the generator has to be able to produce around 1.5 Watts from a person spinning its axis, which is why I was thinking of putting a gearbox in my design but I need to know how much Torque would it take to spin the axis and at what rpm would the generator be effective.

 

[anorlunda]

Welcome to PF. Sounds like a good project.

We are here to help you, but you have to do the work. So tell us what research you have done so far. Here are some tips.

1. Do not begin design until the requirements are well known. You did not show us the actual project statement including all requirements. In other words, what must it do to be declared a success?
2. [edit] I think you used the wrong words. You want to make a generator, not a motor. The generator should product 1.5 watts of electricity and perhaps light a LED. Correct?
   

 

[Fdtroya]

I'm very sorry for not explaining myself correctly.
The actual assignment goal is to make a toy very similar to the one in the attached file, the only difference between the one in the file and the one I am planning to make is that I will not be making a dynamo, but an alternator and rectifying the current with another circuit in order to power the toy cars.

 

[anorlunda]

So your dynamo is a generator, not a motor as you said in post #1. The motors are in the toy cars and are not part of your project. That is much clearer.

The specifications of the toy car motors should give you the required voltage and power. What do they say?

Permanent magnet alternators are used on small wind turbines, for example a wind generator to mount on a boat. It is actually a permanent magnet synchronous generator plus diodes.

This paper (starting on page 24) gives many helpful details on the generator design. See if you can understand that first, then come back with more questions. I fear it may be too advanced for your project.

http://www.diva-portal.org/smash/get/diva2:470652/FULLTEXT01
This youtube video may be more help.

This page discusses similar dynamos 3w instead of 1.5 watts, but they don't give design details.
https://www.cyclingabout.com/best-dynamo-hub-bicycle-touring-bikepacking/
By the way, doing it as a DC generator instead of an alternator is simpler. Old fashioned bicycle generators used simpler DC methods.

 

[anorlunda]

Whoops, @Baluncore informed me that I was wrong. That bicycle generator is not DC, it is an AC dynamo.