Motor Terms

AMPERE: a unit of intensity of electric current being produced in a conductor by the applied voltage.

FREQUENCY: the number of complete cycles per second of alternating current; e.g., 60 Hertz.

HORSEPOWER: the rate which work is done. It is the result of the work done (stated in pounds) divided by the time involved.

INERTIA: the property of physical matter to remain at rest unless acted on by some external force. Inertia usually concerns the driven load.

MOTOR EFFICIENCY: a measure of how effectively the motor turns electrical energy into mechanical energy. Motor efficiency is never 100% and is normally in the neighborhood of 85%.

POWER FACTOR: the ratio of the true power to the volt-amperes in an alternating current circuit or apparatus.

SERVICE FACTOR: a safety factor in some motors which allows the motor, when necessary, to deliver greater than rated horsepower.

SYNCHRONOUS SPEED & SLIP: the speed of an a-c motor at which the motor would operate if the rotor turned at the exact speed of the rotating magnetic field. However, in a-c induction motors, the rotor actually turns slightly slower. This difference is defined as slip and is expressed in percent of synchronous speed. Most induction motors have a slip of 1-3%.

TORQUE: that force which tends to produce torsion or rotation. In motors, it is considered to be the amount of force produced to turn the load. It is measured in lb.-ft.

VOLTAGE: a unit of electro-motive force. It is a force which, when applied to a conductor, will produce a current in the conductor.

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