As per my knowledge a VFD(variable frequency drive) is used to control speed/velocity of 3 phase induction motor. A variable frequency drive controls the frequency of incoming supply to the motor & hence controls the rpm of motor.
If i am right, then i have a doubt regarding servo drives.

1)What is the exact use of servo drive?
2)What may be the possible applications of same?

Thank you for your kind support & awaiting your valuable replies..

 

You're correct about VFDs.

http://en.wikipedia.org/wiki/Servo_drive

A servo drive receives a command signal from a control system, amplifies the signal, and transmits electric current to a servo motor in order to produce motion proportional to the command signal. Typically the command signal represents a desired velocity, but can also represent a desired torque or position. A sensor attached to the servo motor reports the motor's actual status back to the servo drive. The servo drive then compares the actual motor status with the commanded motor status. It then alters the voltage frequency or pulse width to the motor so as to correct for any deviation from the commanded status.

 

You have it right on VFD drives--I will add that they are used for general purpose motoring applications and may be used with any 3 phase motor--speed regulation is not all that accurate (e.g. 5%) because velocity feedback is generally not used--common power range is up to about 100kW--cost effective drive control

Servo drives are generally used for precise speed and position control (both while motoring and when stopped)--used for specific applications--generally sold with a special motor--velocity and position feedback is via encoder--high loop gain and often difficult to set up--power range generally does not exceed about 2kW--relatively expensive drive control

 

As per my knowledge a VFD(variable frequency drive) is used to control speed/velocity of 3 phase induction motor. A variable frequency drive controls the frequency of incoming supply to the motor & hence controls the rpm of motor.
If i am right, then i have a doubt regarding servo drives.

1)What is the exact use of servo drive?
2)What may be the possible applications of same?

Thank you for your kind support & awaiting your valuable replies..

consider VFD as a method, then consider servo as an application of that method. Servo is a command/feedback regime, that can employ any and all means of drive technologies. Size or power is not implied.