A linear induction motor is made up of an inductor which is made of individual cores with a concentrated polyphase. Linear motors can be directly substituted for ball screw drives, hydraulic drives, pneumatic drives, or cam drives.
A linear induction
motor is basically what is referred to by experts as a “rotating squirrel cage”
induction motor. The difference is that the motor is opened out flat. Instead
of producing rotary torque from a cylindrical machine it produces linear force
from a flat machine. The shape and the way it produces motion is changed,
however it is still the same as its cylindrical counterpart. There are no
moving parts, however and most experts don’t like that. It does have a silent
operation and reduced maintenance as well as a compact size, which appeals many
engineers. There is also a universal agreement that it has an ease of control and
installation. These are all important considerations when thinking about what
type of device you want to create. The linear induction motor thrusts ratio
varies depending mainly on the size and rating. Speeds of the linear induction
motor vary from zero to many meters per second. Speed can be controlled.
Stopping, starting and reversing are all easy. Linear induction motors are
improving constantly and with improved control, lower life cycle cost, reduced
maintenance and higher performance they are becoming the choice of the experts.
Linear motors are simple to control and easy to use. They have a fast response
and high acceleration. Their speed is not dependent on contact friction so it
is easier to pick up speed quickly.
Stepper motors are
a special kind of motor that moves in discrete steps. When one set of windings
is energized the motor moves a step in one direction and when another set of
windings is energized the motor moves a step in the other direction. The advantage
of stepper motors that the position of the motor is "known". Zero
position can be determined, if the original position is known.
Stepping motors
come in a wide range of angular resolution and the coarsest motors typically
turn 90 degrees per step. High resolution permanent magnet motors are only able
to handle about 18 degrees less than that. With the right controller stepper
motors can be run in half-steps, which is amazing.
The main complaint
about the stepper motor is that it usually draws more power than a standard DC
motor and manoeuvring is also more difficult.
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