What is meant by Electrical Drives?
- Systems employed for motion control are called as Drives.
- It may employ any of the prime movers (Diesel engines, steam turbines and electric motors) for supplying mechanical energy for motion control.
- Drives employing electric motors are called as Electrical Drives.
- In other words,
A Drive is a combination of various systems combined together for the purpose of motion control.
Advantages of Electrical Drives:
- Do not pollute the environment.
- Unlike other prime movers there is no need to refuel or warm-up the motor.
- They are available with wide range of torque, speed and power.
- Electric braking can be employed. Therefore they are having flexible control characteristics.
- In the past, Induction and synchronous motors were employed mainly in constant speed drives.Variable speed drives uses dc motor.
- Now a days AC motors also used in variable speed drives due to development of semiconductor converters.
- The reason is due to the presence of commutator and brushes, DC motors have number of disadvantages.
Application (Traction motors):
One of the major application of electric drives is Electric Traction. ie to transport men and materials from one place to another. Various types of Electric Traction are
(i) Electric trains
(ii) Electric buses
(iii) Trams(tramways) & trolleys
(iii)Battery driven solar-powered vehicles
In India, 25kV, 50Hz single phase supply is used for traction.
Classification of Electrical Drives:
Generally electrical drives are classified as follows:
 Group drive
 Individual Drive
 Multi motor drive
In addition to this drives are further classified,
Based on supply:
AC drives and DC drives
Based on running speed:
Constant speed(single speed) Drives and Variable speed drives
Based on number of motors:
Single motor drives and Multi motor drives
Based on control Parameter:
Constant torque drives and Constant power drives