Electric Motors
The process industry uses electric motors to operate pumps, generators,
compressors, fans, blowers, and other equipment. Electric motors are
either direct current (DC) or alternating current (AC). The operation of an
electric motor is based on three principles: Electric current creates a magnetic
field; opposite magnetic poles attract each other, and like magnetic
poles repel each other; and current direction determines the magnetic
poles. An electric motor consists of a stationary magnet (stator) and a moving
conductor (rotor). A permanent magnetic field is formed by the lines of
force between the poles of the magnet. When electricity passes through
the conductor in a DC motor, the conductor becomes an electromagnet
and generates another magnetic field. The twin fields increase in intensity
and push against the conductor. The direction of rotation in a motor is
determined by these strong magnetic fields.