Introduction to Industrial Automation

Figure 2.1  Various types of actuators in industrial automation, (a) servo motor, (b) DC motor, 

(c) stepper motor, (d) linear motor, (e) pneumatic cylinder, (f) solenoid actuator.

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Hardware Components for Automation and Process Control 

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copper or aluminum bars. Since these conductors are directly shorted by an end ring, they form 

the rotor winding, which cuts the stator rotating magnetic field, causing the flow of electric cur-

rent through them. The attraction and repulsion between these two magnetic fields, according to 

Lenz’s law, causes the rotation of the rotor. For the case of a three-phase induction motor, switch-

ing two out of the three input voltage lines causes motor rotation in the opposite direction, as 

indicated in Figure 2.3. At this point, it should be highlighted that the alteration of three phases at 

the same time will result in no alteration of the magnetic flux, and thus the rotation of the motor 

will not change.

In both types of motors, the rotational movement of the rotor is transferred to a shaft and, 

subsequently, to a series of spindles, gears, pulleys, and smaller shafts in order to increase the 

output torque or to transform the rotary motion to a linear or reciprocating one. For example, the 

Stator

Coils

Motor shaft

Teethed north and

south magnetic rotor

N

N

N

S

S

S

Motor

casing

Stator poles

and coils

Rotor

(a)

(b)