How to wire the coil for your Alternator / Generator.

How you wire your coil will determine how much magnetic flux you cut along with the voltage and current your alternator / generator will produce. The number of windings and the gage of the wire will directly effect your output. If you have been reading from the beginning there is a common theme you have been hearing over and over and that is that such and such will determine the output of your alternator / generator. That's because just about everything talked about is equally important when it comes to output. How you wire your coil is important because it's the relationship between your coil and the magnet that causes an electrical current flow.

How to Wire Your Coil

The type of wire used in motors and alternators is called magnetic wire. This type of wire has a varnish type of isolation. .If you have ever seen the windings on a transformer you know what I mean.

The length and gage of the wire used in your coils will greatly effect your output. The greater the number of turns in the coil will increase the amount of magnetic flux cut by the coil which will increase the electrical output. Also the thicker the wire the more amps the wire will produce.

But here's what happens, very thin wire can have a greater number of turns per amount of space then thick wire and the closer each winding will be to the magnet. The closer the windings to the magnet the greater the amount of flux which will be cut. But the more thin the wire the less amps you can get from the wire with out cooking it. But the thicker the wire the farther the outer turns will be from the magnet i.e. less output per wire turns. -- Large companies have spent millions in R&D to over come these problems by employing magnetic circuits. In other words they put a core in their coils that will evenly distribute the magnetic flux to the windings. These magnetic circuits require a good working understanding of the science involved as well as software to model the design and the ability to have the cores manufactured to be effective; Something a home brewer may not have at his disposal. That why I'm going for simple but max output on the design.

In the design of your unit it must be taken into account that just an inch from the magnet one looses as much as 90% of the magnetic flux found on the surface of the magnet. There are ways of increasing the flux that flows through your coil. Soft iron laminates or even other permanent magnets can be used to draw more flux through the magnets. This will involve a lot of experimenting to see what ways can be used in your design to draw more flux through the coil but will increase the output and lower the losses to inefficiency.

Current flow inside an alternator.

If you notice the diagram above you will notice that the current on one side of the coil is flowing in one direction relative to the magnets and in the opposite direction on the other side of the coil. This allows the current to flow in one direction through the whole coil. This is accomplished by having one side of the coil traveling in one direction and the other side traveling in the other direction.

The wrong way to pass a magnet over a coil.

If you were to just run the magnet over the coil or vic versa the current, as the magnet passed over the center, would push against itself. So whether the coil will be turned or the magnets it must be setup so as to have one side of the coil cutting the flux in one direction and the other side of the coil cutting the flux in the opposite direction.

Internal current flow of a Dynamo.

Above is an example with the magnet rotating with a stationary coil. A better design can be found in the photo below.

Graph of the current running through an alternator

With the design above you could ether have the coil on the inside turning as displayed or have the magnets on the inside rotating with the coil on the outside and stationary.

The left-hand rule for the motor effect and the right hand rule for a dynamo.

These hand rules will help you determine the direction of current in a generator and the direction of force in a motor. The direction of the field is the magnetic flux from north to south poles.

Both forces are in play whether it's a motor or a generator. In a perfect generator the force applied to the shaft to turn the rotor of the generator would be met with equal & opposite force from the magnetic field created by the current in the coil's winding . Theoretically no force would be great enough to turn the shaft. The same would hold true for a motor, once an initial current was applied to the windings of a motor it would spin for ever without needing additional current. We just don't live in a perfect world.

I use the TI-89 Graphing Calculator for all my calculations
which has symbolic manipulation ability.

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