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.