MOTORS

The fundamental driving force behind all electric motors, whether brushed or brushless, AC or DC, is magnetism. We've probably all played with magnets at some time or other, and have learned about them in science class in elementary school.

Recall that any magnet has a north pole and a south pole (it just so happens that the earth is a magnet whose poles happen to correspond very roughly to the geographical poles, hence the names for the magnet's poles). If you take two bar shaped magnets and line them up, they will be attracted to one another if one's north pole is next to the other's south pole. If you line them up north to north or south to south, they will repel each other. Opposites attract.

   

Induction motor

An induction motor (IM) is a type of asynchronous AC motor where power is supplied to the rotating device by means of electromagnetic induction. Another commonly used name is squirrel cage motor because the rotor bars with short circuit rings resemble a squirrel cage (hamster wheel). An electric motor converts electrical power to mechanical power in its rotor (rotating part). There are several ways to supply power to the rotor. In a DC motor this power is supplied to the armature directly from a DC source, while in an induction motor this power is induced in the rotating device. An induction motor is sometimes called a rotating transformer because the stator (stationary part) is essentially the primary side of the transformer and the rotor (rotating part) is the secondary side. Induction motors are widely used, especially polyphase induction motors, which are often used in industrial drives.