AC motors are divided into two major classes: synchronous and asynchronous.
The principal difference from the first second is that in induction motors, you can change the speed of the output shaft end, which allows increase the life of equipment and reduce energy costs. One of the most important characteristics of any motor, be it synchronous or asynchronous, is its power. The power of the motor, normally indicated in its technical passport.
If the document was lost or not given this important feature, then define the capacity can be according to the stator core. The product of a constant depending on the dimensions of the machine, and its speed, square of the inner diameter of the stator, its length (including ventilation ducts), synchronous speed (determined by using the tachometer) to ten to the minus sixth degree is the required amount of power to the motor.
Another way to determine capacity is similar to a school science lab. Includes motor, measure it voltage and current of each phase with a voltmeter and ammeter, respectively (devices must be connected in series). Then calculate full capacity for a very simple formula. Found the voltage multiplied by the sum of currents in phases.
You can also take the measurements of the motor (length, shaft diameters) and define the directory to which series is your engine. Knowing the series, you will learn and the powerthat is given in this Handbook.