basic difference between normal and servo motor?
A normal motor , either AC or DC does not run in position mode i.e. its position cannot be controlled. If you supply AC voltage to an AC motor ( or DC voltage to a DC motor ) , the motor will start rotating , and when you remove the voltage , the motor will stop. But the exact point at which it will stop cannot be controlled. A servomotor (servo) is an electromechanical device in which an electrical input determines the position of the armature of a motor. Input to a servomotor is in the form of pulses , and at every pulse , the motor will turn by a finite , exact amount. Servos are used extensively in robotics and radio-controlled cars, airplanes, and boats.
I would say that the definitions given in answer 1 are fine, but the latter applies more to a stepper motor than a servo. A feature of a servo is not that the pulse produces a specific step, but that the width of the pulse produces a definite displacement - in other words if pulse is 60 milliseconds wide it might produce a quarter turn and if 120 ms, a half turn. This is done with a potentiometer in the device which measures the turn. Servos come in partial turn and continuous and in the later the width controls the rotational speed and direction.
Difference Between Servo And Motor
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The two answers are right to some degree but my answer to the question would be as follows. Electric motors fall into to categories (industrial and servo) because the two types of motor have different performance requirements. The industrial machine is not normally required to have high acceleration and deceleration and is required to perform continuously for long periods. The servo motor is the GTI of the motor world and needs to have high accel/decel capability, good duty cycle performance. Both types of motors can have devices attached to give them extra capabilities. It is normal for a servo motor to have some form of rotor position measuring device (resolver or encoder). Industrial machines can also have simliar devices because with the advances in drive technology , modern drives can control the position of industrial machines. When looking at AC or DC in either category, generally DC motors have brushes that require maintenance every 2 years or so. AC motors do not have brushes. AC motors have the windings on the stator of the machine and heat can excape easily from the motor. DC machines generally have the high current carrying windings on the rotor and heat is difficult to extract without blowing air thorough the motor. AC machines should be generally considered as 1st choice for a new project in this century.
