This document discusses electric drives and AC motor drives. It defines electric drives as systems that use 50% of electrical energy produced and can operate equipment at constant or variable speeds. The main components of electric drives are motors, including DC and AC types, and power sources like batteries or utilities. It also summarizes different types of single-phase and three-phase DC drives classified by their converter configurations. For AC drives, it explains that speed and torque can be controlled through stator voltage, rotor voltage or frequency control. It concludes that variable speed AC drives can increase system efficiency from 15-27% compared to constant speed operation.

1. S.Sumalatha
G.Lakshmi prasanna
BY

2. Introduction:
 In some countries nearly 65% of the total electric
energy produced is consumed by electric motors.
 DC motors play a significant role in modern industrial
drives.
 DC motors can provide a high starting torque.

3. ELECTRIC DRIVES - A DEFINITION
About 50% of electrical energy produced is used in
electric drives today.Electric drives may run at
constant speed or at variable speed

4. Block diagram of Electrical drive:
• Small
• Efficient
• Flexible

5. Components in electric drives
 Motors
• DC motors - permanent magnet – wound field
• AC motors – induction, synchronous , brushless DC
 Power sources
• DC – batteries, fuel cell, photovoltaic - unregulated
• AC – Single- three- phase utility, wind generator -
unregulated

6. • DC drives can be classified, in general, into three types:
 1. Single-phase drives
 2. Three-phase drives
 single-phase drives may be subdivided into:
 Single-phase half-wave-converter drives.
 Single-phase full-converter drives.
 Single-phase dual-converter drives.

7. Single-Phase Half-Wave-Converter Drives:
The applications of this drive are limited to the 0.5 kW
power level.

8. Single-Phase Full-Wave-Converter Drives
 It is a two-quadrant drive, and is limited to
applications up to 15 kW.

9. • Three-phase drives may also be subdivided
into:
-Three-phase half-wave-converter drives.
– Three-phase full-converter drives.

10.  A three phase half wave converter drive operates in
first quardant and is limited to applications upto
40kw.
 A three-phase full-wave-converter drive is a two-
quadrant drive without any field reversal, and is
limited to applications up to 1500 kW.

11. Introduction: AC Motor Drives
• There are two types of ac drives:
– Induction motor drives
– Synchronous motor drives
• Ac drives are replacing dc drives and are used in
many industrial and domestic applications

12. • The speed and torque of induction motors can be
controlled by
– Stator voltage control
– Rotor voltage control
– Frequency control

13. Stator Voltage Control:
• The stator voltage can be varied by three-phase
– ac voltage controllers,
– pulse-width modulation (PWM) inverters
• They are used mainly in low-power applications, such as
fans, blowers, and centrifugal pumps, where the starting
torque is low.

14. Rotor Voltage Control:
• The typical torque-speed characteristics for variations
in rotor resistance

15. Frequency Control:
 The torque and speed of induction motors can be
controlled by changing the supply frequency.
 At low frequency, the reactances decrease and the
motor current may be too high. This type of frequency
control is not normally used.

16. Energy/Cost Savings
 System efficiency can be increased from 15% to 27% by
introducing variable-speed drive operation in place of
constant-speed operation.
 For a large pump variable-speed drive, payback period
~ 3-5 years whereas operating life is ~ 20 years

17. DC DRIVES Vs AC DRIVES
Advantages:
 Ac motors are less expensive as compared to dc
motors.
 Ac motors require low maintenance as compared to dc
motors.
Disadvantages:
 Power converters for ac drives are complex.
 Power converters for ac drives generates harmonics in
the supply system & load circuit

18. Conclusion:
 In India, we are using three phase,50hz ac supply as an
input. There so many applications that require higher
frequency and phases for better operations of
industrial equipments. Even though we are with same
frequency for particular applications keeping economy
in point of view.