Assembly

Reworking the rotor was the hard part. Assemble the rotor, stator and case, thread your red, white, blue and black stator wires up through their respective holes and re-install the rubber terminal insulators. Rotate the rotor by hand to make sure that it isn't dragging on anything, and if it is take things apart and correct the problem.

You should notice that the rotor is a bit harder to turn since the rebuild, and you may want to put the pulley back on, at least temporarily. This increased resistance is from eddy currents in the stator laminations that are produced by the now much stronger magnetic field. To get an idea of exactly how much more current this machine is now capable of, get a friend to short all the stator leads together while you turn the rotor by hand. You should be very pleased to find it MUCH more difficult to turn while the leads are shorted, even at this very low RPM. That is because when the leads are shorted current is flowing, and that takes power to produce.

If an oscilloscope is available, connect the black stator lead to the ground of the oscilloscope and any of the colored leads to the input. Give it a spin and you should see a nice sine wave on the scope. Do each of the colored leads in turn and you should see a similar sine from all of them.

If you find that shorting the output leads makes the rotor much harder to turn, and all of the colored output leads give consistent sine waves, and you can test each stator lead against the case ground with a multimeter and you find no shorts, then the odds are good that you have just made yourself an alternator with a permanent magnet field. Congratulations! You aren't done yet, though.

There are actually several ways to use this alternator, but let me describe the simplest. Replace the diodes in the alternator (I'm assuming they are good), but before you do you need to decide if you want to go to the bother of isolating the output from the case. At this point the stator leads should be isolated (you tested this, right?), but the diodes will short the negative output to the case if you just bolt them back on. In most cases this isn't a problem, but if it is for whatever system you envision, you can slip some insulating material between the diode bridge and the mounting bolts, or simply mount it in some other fashion. I leave that problem to you. Assuming, then, that you are not concerned with this issue, mount the diode bridge as before and replace the metal cover on the back end of he alternator. This part is now done!

If you now mount some blades on this alternator, put it up on a pole and attach a battery you will be open for business . . . assuming you have some wind. As long as the alternator is rotating at a rate too low to overcome the diode voltage drop and the battery voltage there should be very little load on the alternator and it should spin up quickly. As soon as the output voltage from the alternator exceeds the battery voltage and the diode voltage drop, current will flow into the battery and the alternator spin rate will be constrained by this load. Thus such a system becomes self-regulating with one exception: if the battery becomes completely charged the battery voltage will rise and the energy from the alternator will start to break down the water in the battery into hydrogen and oxygen, thus "burning" it off. The solution to this problem is to use a voltage comparator to detect when the battery voltage exceeds, say, 13.8 volts, and close a relay that applies an additional (sometimes called a "diversion") load to the system sufficient to absorb this extra power. Something useful would be good to use for that load, like a hot water heater, some additional lights or a pump.

Below is a circuit diagram for a simple voltage regulator you can construct from Radio Shack parts and an automotive relay. I haven't tried this circuit myself, so let me know if you try it and have any problems with it so I can make any necessary corrections (and I'd like to know if it works too).

Here is a list of the major parts, all available from Radio Shack except the relay. You should be able to get a relay from any auto parts store.

In addition to the above, you will need some resistors as shown, a circuit board to build the circuit on, a box or whatever to put it in and protect it from the elements, and if your relay coil has a DC resistance less than about a thousand ohms you will need a heatsink for the TIP42G.

After you build the voltage regulator circuit you will have to adjust it to operate the relay at the voltage you choose, probably 13.8 volts. If I didn't screw something up here, the circuit is supposed to work like this: The top of the 5.1 volt zener diode is a voltage reference for the positive input of the LM339 voltage comparator at pin 9. As the battery voltage increases a fraction of that voltage will be present at the wiper of the 10 Kohm trimpot, because the trimpot and the 5.6 Kohm resistor in series with it form an adjustable voltage divider with a range between ground and roughly 2/3 the battery voltage. The pins on the LM339 number counter-clockwise from the top left on the chip (looking down on it) so the trimpot wiper is connected to LM339 pin 8. Once the voltage at LM339 pin 8 (the inverting input) exceeds the voltage at pin 9, the comparator output at pin 14 will change state to a "low" value. The output of this comparator is actually an open collector type, which means that it only has an active low, no active high. Anyway, when the output at pin 14 goes low it will pull the base voltage of the 2N3906 transistor toward it's collector voltage through the 6.8 Kohm resistor thus turning it "on." The 2N3906 transistor is connected between the Base and Collector of the TIP42G, so when the 2N3906 becomes conductive, that allows current to flow from the Base to the Collector of the TIP42G as well, so it also becomes conductive. This configuration is known as a "Darlington pair," by the way, and is used to increase the current gain. When the TIP42G is conductive, current will flow through the relay coil, thus energizing it. The 1N4004 diode serves to snub out the inductive kickback from the relay coil when the TIP42G turns off.

This circuit can be set by powering it up with a DC voltage source set to the set point you are trying to achieve, for example 13.8 volts, and adjusting the trimpot until the relay just operates. A convenient source of 13.8 volts (or something close) is a fully charged automobile battery with the engine running to maintain that charge.

That's all I have so far on this subject, I hope you find it useful. If you spot something stupid that I have done please use the contact link below and let me know so I can fix it! Also, if anyone wants to offer to jump in and provide machining or make blades or mounts or whatever for those not blessed with the right equipment, let me know and I will add that information to the "Resources" section. What I have in mind is your name, address, contact phone, what you want to do (like machine the rotor claws) and how much you want for the service. I'll also make some space for user comments on the services you offer to provide feedback for others.

I've been having quite a bit of fun with this, I hope you do too!

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