
105
5
AC and DC Motors
Of the total electrical energy generated worldwide, about 58% is used by all motors
combined, about 7% for lighting, and the remaining 35% for heating and other uses.
Major types of motor are the synchronous motor, induction motor (also known as
asynchronous motor), and dc motor. All have two sets of coils with different cur-
rents, say, I
1
and I
2
. The electromagnetic interaction between two currents produces
motor torque T K I I
m
1 2
. If the motor shaft has a load torque T
Load
< T
motor
, the motor
would accelerate to a speed at which T
Load
= T
motor
, where it would stop accelerating
and run at steady speed. The motor armature ...