Classification of Electric Drive:
Main classification of electric drives are :
1. DC drives and
2. AC drives
DC drives :
A dc motor speed can be controlled by using a power converter. Here motor is coupled with load.
An AC motor speed can be controlled by power converter. Here motor is coupled to the load.
The main purpose is to vary the motor speed.
Comparison between DC and AC drives:
DC drives AC drives
1. Power circuit and control circuit is simple
2. Frequent Maintenance.
3. Commulator makes bulky , costly and heavy.
4. Speed and design rating are limited due to commutation.
5. This is used in certain location
6. Fast response and wide speed range smooth achieved by conventional and solid state control
7. Poor PF, harmonic distortion of the current.
8. Power / weight ratio is small.
1. Power and Control circuit is
2. Less Maintenance.
3. Problems are not there, particularly squirrel cage motor.
4. Ratings have no upper limits.
5. Used in all location
6. In solid state control speed range is wide and conventional method it is stepped and limited.
7. For Regenerative drives the line pf is poor, for non-regenerative drives the line PF is better.
8. Power / weight ratio is large.