The document defines electrical drives as systems that use electric motors as prime movers for motion control. It discusses the advantages of electrical drives such as flexible control, wide speed and torque ranges, and high efficiency. It describes conventional ward-leonard drive systems and modern drive systems. Modern systems are more compact, efficient, and flexible due to use of power electronic converters and control units. The basic components of electrical drives are described as the power source, motor, power processing unit, control unit, and mechanical load. Different motor types, power sources, and the functions of the power processing and control units are also summarized.

1. Definition of Electrical Drives
• Drives – system employed
for motion control
• Motion control requires
prime movers
• Electrical Drives – Drives
that employ Electric
Motors as prime movers Electrical Drives -> Electric
Motor as Prime Mover
Prime Mover
Drives -> Motion Control

2. Advantages of Electrical Drives
 Flexible control characteristic
 particularly when power electronic converters are
employed
 Wide range of speed, torque and power
 High efficiency – low no load losses
 Low noise
 Low maintenance requirements, cleaner operation
 Electric energy easily transported
 Adaptable to most operating conditions
 Available operation in all four torque-speed quadrants

3. Conventional Electric Drives
 Ward-Leonard system – introduced in 1890s
 Disadvantage :
 Bulky,
 Expensive,
 Inefficient,
 Complex

4. Modern Electric Drives
Power Source Power Processing Unit Motor Load
Control
Reference
Control
Unit
feedback
 Small (compact)
 Efficient
 Flexible
 Interdisciplinary

5.  Power Source
 Motor
 Power Processing Unit (Electronic Converter)
 Control Unit
 Mechanical Load
Basic Components of Electric Drives
Electrical
Energy Motor
Mechanical
Energy
• Obtain power from electrical sources
• DC motors - Permanent Magnet or wound-field (shunt, separately excited,
compound, series)
• AC motors – Induction, Synchronous (wound –rotor, IPMSM, SPMSM), brushless DC

6. Basic Components of Electric Drives –
Power Source
• Provides energy to electric motors
• Regulated (e.g: utility) or Unregulated (e.g. : renewable
energy)
• Unregulated power sources must be regulated for high
efficiency – use power electronic converters
• DC source
• batteries
• fuel cell
• photovoltaic
• AC source
• single- or three- phase utility
• wind generator

7. Basic Components of Electric Drives –
Power Processing Unit
• Provides a regulated power supply to motor
• Enables motor operation in reverse, braking and variable
speeds
• Combination of power electronic converters
Controlled rectifiers, inverters –treated as ‘black boxes’
with certain transfer function
More efficient – ideally no losses occur
Flexible - voltage and current easily shaped through
switching control
Compact
Several conversions possible: AC-DC , DC-DC, DC-AC, AC-
AC

8. Basic Components of Electric Drives – Power
Processing Unit
1. DC to AC

9. 2. DC to DC

10. 3. AC to DC

11. 4. AC to AC

12. Basic Components of Electric Drives –
Control Unit
• Supervise operation
• Enhance overall performance and stability
• Complexity depends on performance requirement
• Analog Control – noisy, inflexible, ideally infinite bandwidth
• Digital Control – immune to noise, configurable, smaller
bandwidth (depends on sampling frequency)
• DSP/microprocessor – flexible, lower bandwidth, real-time
• DSPs perform faster operation than microprocessors
(multiplication in single cycle), complex estimations and
observers easily implemented

13. Basic Components of Electric Drives –
Component Selection
• Several factors affecting drive selection:
• Steady-state operation requirements
• nature of torque-speed profile, speed regulation, speed range,
efficiency, quadrants of operations, converter ratings
• Transient operation requirements
• values of acceleration and deceleration, starting, braking and
reversing performance
• Power source requirements
• Type, capacity, voltage magnitude, voltage fluctuations, power
factor, harmonics and its effect on loads, ability to accept
regenerated power
• Capital & running costs
• Space and weight restrictions
• Environment and location
• Efficiency and reliability