AC motors are used worldwide in many residential, commercial, industrial, and utility applications. Motors transform electrical energy into mechanical energy. An AC motor may be part of a pump or fan, or connected to some other form of mechanical equipment such as a winder, conveyor, or mixer. AC motors are found on a variety of applications from those that require a single motor to applications requiring several motors.
Before discussing AC motors it is necessary to understand some of the basic terminology associated with motor operation. Many of these terms are familiar to us in some other context. Later in the course we will see how these terms apply to AC motors.
In simple terms, a force is a push or a pull. Force may be caused by electromagnetism, gravity, or a combination of physical means.
Net force is the vector sum of all forces that act on an object, including friction and gravity. When forces are applied in the same direction they are added. For example, if two 10 pound forces were applied in the same direction the net force would be 20 pounds.
If 10 pounds of force were applied in one direction and 20 pounds of force applied in the opposite direction, the net force would be 10 pounds and the object would move in the direction of the greater force.
If 10 pounds of force were applied equally in both directions, the net force would be zero and the object would not move.
Torque is a twisting or turning force that causes an object to rotate. For example, a force applied to the end of a lever causes a turning effect or torque at the pivot point. Torque (τ) is the product of force and radius (lever distance).
τ = Force x Radius
In the English system torque is measured in pound-feet (lb-ft) or pound-inches (lb-in).If 10 lbs of force were applied to a lever 1 foot long, for example, there would be 10 lb-ft of torque.
An increase in force or radius would result in a corresponding increase in torque. Increasing the radius to two feet, for example, results in 20 lb-ft of torque.
Before discussing AC motors it is necessary to understand some of the basic terminology associated with motor operation. Many of these terms are familiar to us in some other context. Later in the course we will see how these terms apply to AC motors.
In simple terms, a force is a push or a pull. Force may be caused by electromagnetism, gravity, or a combination of physical means.
Net force is the vector sum of all forces that act on an object, including friction and gravity. When forces are applied in the same direction they are added. For example, if two 10 pound forces were applied in the same direction the net force would be 20 pounds.
If 10 pounds of force were applied in one direction and 20 pounds of force applied in the opposite direction, the net force would be 10 pounds and the object would move in the direction of the greater force.
If 10 pounds of force were applied equally in both directions, the net force would be zero and the object would not move.
Torque is a twisting or turning force that causes an object to rotate. For example, a force applied to the end of a lever causes a turning effect or torque at the pivot point. Torque (τ) is the product of force and radius (lever distance).
τ = Force x Radius
In the English system torque is measured in pound-feet (lb-ft) or pound-inches (lb-in).If 10 lbs of force were applied to a lever 1 foot long, for example, there would be 10 lb-ft of torque.
An increase in force or radius would result in a corresponding increase in torque. Increasing the radius to two feet, for example, results in 20 lb-ft of torque.
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