Bench Test

This is a test bench procedure to see if any particular motor will work as an alternator, as not all will. The motor must be turning at around 1836 rpm. When the light shows normal luminance you can then connect it to a load. The battery must be removed just before you begin to turn the motor. If the light does not glow this motor will not work as an alternator.

Purchase a mechanical hand tach (no fuss, no muss, no setup) to make sure your generator will measure at least 2,000 rpm. The big boys use three phase induction motors in their wind turbines, but they are connected to the grid (with continuous load, within + or - 2%) on three phase lines and employ sophisticated electronics and or pitch mechanisms to maintain synchronous speeds. I wouldn't try using one in a small wind generator, as there are too many criteria to meet for reliable operation. You can use a horizontal shaft lawn mower engine, or a 2 hp. and above single phase motor for your driver. You can even use the power take off of a row crop tractor, as they operate at synchronous speed (1800 rpm.). You will not be able to test a motor that is the same size (hp.) or larger than your driver, and expect to get accurate results.

This will sound a little strange, but you can excite a three phase induction motor with an automotive battery (as long as it doesn't have an iron-aluminum composite rotor). It's best to have the motor set to operate on 220 or 240 volts. This means that each phase will produce 120 volts. Take the wires from one phase and connect this phase to an automotive battery for about 3-5 minutes. This imprints that region of the rotor next to the set of windings connected to the battery with a temporary magnetic field. Connect one of the other phases to a regular household light bulb (100 watts).

You need to be able to drive the motor you are going to use as a generator at about 5-7% above synchronous speed (this is the speed at which the line current revolves around the stator windings) - 1800 rpm. + 7% = 1826 rpm. Now after you exited the rotor, disconnect the battery and connect the two motors together and crank er' up. The light should begin to glow a little bit before the generator reaches 1826, at 1826 rpm. you should have normal luminance, if you don't, this motor won't work for power generation (this can happen for a multitude of reasons, but 8 times out of ten it will work).

You must be able to drive your generator under maximum load (data plate hp. rating x 746 watts. 5 hp x 746 = 3,930 watts). This is important because if you exceed this limit two things will happen. Depending on the design of the water wheel used (it will need to extract about 8 hp. from it's stream and no more for a 5 hp. generator) if this generator is continuously overdriven at maximum load it will eventually burn out the windings. If the water wheel can not drive the generator at 1826 rpm. it will drop out of current production. It's a precarious balance, but there are literally thousands of such applications here in the States. With proper electrical controls this system can be used in co-generation. As stated above it is intended for stand alone use.

Offered by Jay.