Perhaps this will help New ones to understand more about how 3-phase works.
The following is my basic understanding of the basic 3-phase alternator set-up.
With the basic 3-phase alternators we do here, you can ONLY choose a ratio of 4 mags per 3 coils, in order for it to be 3-phase and operate correctly. Inotherwords, you can only choose a 3-phase alternator with:
- poles (mags each rotor disc) to 6 coils. (2 coils per phase) OR,
- poles (mags each rotor disc) to 9 coils. (3 coils per phase) OR,
- poles (mags each rotor disc) to 12 coils. (4 coils per phase) OR,
- poles (mags each rotor disc) to 15 coils. (5 coils per phase) OR,
- poles (mags each rotor disc) to 18 coils. (6 coils per phase) And so on...
The PRINCIPLE of 3-phase is the SAME with all of these different combinations.
As a beginner, if you try and change any of these mag-to-coil numbers, it will, most likely cancel out your power potential greatly! (If it will even work at all)
To try and explain basic 3-phase, I am using the simple 8 pole (mags each rotor disc) to 6 coils. (2 coils per phase).
Here is how I Layout the set-up with 1/4" plywood:
Draw a bunch of random circles with your compass. This will help you determine the correct spacing of your magnets.
Next, draw your 'criss-cross' lines across the center point, according to how many magnets (poles) you have/need. In this case I need 8 lines (from the center point) (or;4 criss-cross lines) because I have 8 magnets. (or;poles)
My 8 magnets will be placed over each of the 8 lines.
Then, I use my protractor to mark out the spacing of my COILS.
In this case, since I will need 6 coils all together, I need 3 coils per side. So in this case, you simply divide up 180 degrees by 3. IT equals 60 degrees. Mark it on the plywood and draw it out. These 6 'pieces of the pie' are the spaces where my 6 coils will go later-- when I solder the coils together.
Since, in this case, my magnets are 1 inch diameter, I use 8 WASHERS which are exactly 1" diameter , to help my layout the correct spacing of my magnets. You MUST keep each of the 8 washers always in the center of each of the 8 designated lines. Simply slide the washers up and down each line until you get the right spacing between magnets.
The way I determine the SPACING of the magnets is to divide the width of each magnet in half. So since I have 1" (dia.)wide magnets, then the spacing between the magnets should be 1/2". I use the 1" washers to get my spacing right, and then draw a center point in the middle of each washer. This will be the center point of each magnet. I then DRILL 1/8" holes thru these 8 reference points to be used later to mark onto the 2 (dual) STEEL ROTORS. (or, just one single rotor if you so choose)
You can see in the photo I made a simulated plexy-glass magnet rotor to show how the magnets rotate across the coil phases.
Next, I cut out a simulated COIL from cardboard. I then traced it in the 6 spaces.
You can now see the 3 different phases. (2 coils per phase/ common colors)
The following are just 7 frames that show the plexy 'mag rotor' turning 1/4th of a revolution. The black arrow(s) are just for reference marks.
A couple of basic points I have learned:
If one magnet is exactly in the middle of a coil, it is NOT producing any voltage nor any current flow in the coil at that exact moment.
At least one magnet has to be rotating over one leg (side) of a coil in order for voltage and current to be induced in the coil at that moment.
And if a coil has a 'north' polarity magnet on one leg (side) of the coil and a 'south' polarity magnet on the other leg (side) of the SAME coil, it is producing close to MAXIMUM voltage and current flow in the coil.
I believe this is why they say 3-phase is better than single phase-- because you can get more 'magnet power' (2 magnets) over ONE coil, and thus, more power per revolution. Also, 3-phase rotates SMOOTHLY since the 'phases' that turn on and off are spread out around the circle. Single phase can have vibration problems due to the fact that ALL coils are turning on and off rapidly at the SAME TIME. But I don't think this is much of a problem with the smaller single phase alternators.
So what you DON'T want is to have either BOTH a 'north' polarity, or BOTH a 'south' polarity on BOTH legs (sides) of one coil. That would CANCEL OUT the current flow to a great extent in the coil.
Concerning the 7 frames above --- Notice I am turning the plexy-glass 'mag rotor' clockwise. The phase numbers work BOTH directions. You can number 1-2-3 clockwise,,, or 1-2-3 counter clockwise. The alternator works the same rotating BOTH directions.
You can see that the POLARITY and the 'TIMING' of the magnets are the SAME for the coils IN EACH PHASE at any one moment.
YOu can layout any of the other 3-phase combinations that I mentioned at the beginning, using the same basic method as the simple 8pole / 6 coil example I just did above.
For example,
If you want to do the 16 pole (mags each rotor) / to 12 coils alternator, then simply draw somewhat bigger circles and then draw your 16 lines (8 criss-cross lines) where the 16 mags will go, and then use your protractor (or, a ruler) to divide up each half of the circle into 6 equal spaces. (or, 12 equal 'pieces of the pie' in all, where the 12 coils will go)
The general rule I use is to make sure your magnet SPACING is HALF the WIDTH of your magnets. And I keep the width of each coil's 'center hole' , the same as the width of each magnet.
Make sure the WINDING DIRECTION of ALL your coils goes the same direction---and hook up the coils like DANB showed in his 3-phase wiring diagram.
If anyone sees something incorrect I've said -- PLease speak up!! 'Cause I'm no expert.
This is the simply method I use to layout 3-phase. I'm sure there are other methods also. This is based on my understanding of basic 3-phase after gathering 'bits and pieces' of info for about the last 3 years. I am just trying to help new ones since I remember how difficult it was. Like I said , it is difficult to explain with only words.
Any comments, questions, or corrections would benefit us all!!
