Lecture 01

Advanced Electrical Machines and Drives

Semester 2 (MEET)

Dr. Muhammad Humza

Email : engr.humza7@gmail.com

Department of Electrical Engineering

Institute of Southern Punjab

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Contents

1. Introduction

2. Need for Drives

3. Conventional Electrical Drives

4. Components of Modern Electrical Drives

5. Summary
Course Introduction

Credit hours

➢ Advanced Electrical Machines and Drives

➢ 3 semester credit hours

Objective

➢ To get the knowledge about electrical drives

➢ To understand the concept of different types of machines

and their performance

➢ To study the different methods of starting and control of

different machines
Grading Policy

Sessional 25%
Midterm Exam 25%
Final Exam 50%
Books

➢ Electric Machinery by Fitzgerald.

➢ Electric Motor Drives Modeling, Analysis and control, By

R._Krishnan, 2002

➢ Electric motors and drives by Austin Hughes

➢ Electrical Machines and Drives by Jan A Malkebeek

➢ Fundamental of Electrical Drives by G.K Dubay

➢ Power electronics by M.H Rashid

Introduction

Electrical Drives

➢ System employed for motion control are called drives.

➢ Prime movers are required in drive system to provide the

movement. Such as diesel engine, electric motors

➢ Drives that uses electric motors as prime movers are called

electrical drives

➢ Used for variable torque/speed applications such as wind

generators and robots etc.
Need for drives
➢ Electrical motors are used to drive mechanical loads by converting
electrical energy.

➢ Traditionally motors were operated uncontrolled running at constant

speed even in applications where efficient control over speed could
be very advantageous

➢ For example process industry where flow rates of gases and fluid
need often be controlled

➢ Where pumps are driven at constant speed and throttling valves are
used to control the flow rates

➢ The mechanism of throttling valves is more complicated and

inefficient to implement.

NOTE: A throttling valve is any device that reduces, increases, starts, or stops flow of a fluid.
Example

System without drive System with Drive

Power out Power Power out

Power In
In

Power loss

Power loss
Mainly in valve

➢ Improves the energy utilization in electric motors and give a

large impact to the overall energy consumption
Conventional Electrical Drives

A Conventional drive system: Via control of DC generator

3-phase
power supply

Fixed speed Variable DC Variable speed

AC DC DC
Load
motor Generator Motor

Change the field current

▪ Bulky size
▪ Inefficient
▪ inflexible
Why electronic control in electrical drives ?

➢ Operation with high efficiency and energy saving.

➢ Speed and position control may be essential to the process

➢ Some processes are enhanced if speed control is available

➢ Reduction of transients and stresses due to abrupt motion and

ON/OFF operations

➢ Matching motor and load characteristics

Advantages of modern 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

➢ Adaptable to most operating conditions

Choice of electrical drives
The choice of an electrical drive depends on a number of factors.
Some important factors are as follows:
➢ Steady-state operation requirements (nature of speed-torque
characteristics, speed regulation, speed range, efficiency, duty
cycle, quadrants of operation, speed fluctuations, rating, etc.).
➢ Transient operation requirement (values of acceleration and
deceleration, starting, braking, speed reversing).
➢ Requirement of sources (types of source, its capacity,
magnitude of voltage, power factor, harmonics, etc.).
➢ Capital and running cost, maintenance needs, life periods.
➢ Space and weight restrictions.
➢ Environment and location.
➢ Reliability.
Modern Electrical Drives

3-phase Motor
Input power Load

~ Power
Processor
Unregulated
DC or AC

References Control Unit

Speed, torque, Feedback
position Voltage, current,
speed, etc.

▪ Easy to control ▪ Small

▪ wide range of speed ▪ Efficient

▪ clean ▪ Flexible
Continue
Power Source

➢ The power source: provides the energy to the drive system

Input power DC Batteries Special type of applications

(airplanes)

Unregulated
DC or AC
AC Utility Grid
Commonly used
1-ph, 3-ph
Renewable Sources

Power source requirment

Type, capacity, voltage magnitude, voltage fluctuations, power factor,

harmonics and its effect on loads, ability to accept regenerated power

*Nearly 2/3rd of all electrical power is utilized by electrical machines

in the form of electric drives.
Continue

Processor Unit
Power
Processor

➢ Since electrical sources are normally uncontrollable it is

therefore necessary to be able to control the flow of power to
the motor, this is achieved by using power processor or power
modulator.

➢ With controllable sources (output of power processor) motor

can operate with variable speed.

➢ Classical methods used such as variable impedance or relays

to shape the voltage and current that is supplied to motor, are
inflexible and inefficient

➢ Power electronics converters are more

▪ efficient : As no losses occur in power electrics devices
▪ Flexible: Voltage and current can be shaped by simply
controlling switching function
Continue
Converters for Motor Drives
(some possible configurations)

DC Drives AC Drives

AC Source DC Source AC Source DC Source

DC-AC-DC DC-DC

AC-DC AC-DC-DC AC-DC-AC AC-AC DC-AC DC-DC-AC

Const. Variable FCC

NCC
DC DC
NCC: Naturally commutated cycloconverter
FCC: Forced commutated cycloconverter
Continue
AC DRIVES
AC-DC-AC

control
AC-DC DC-AC

Motor

The common PWM technique: CB-SPWM with ZSS

carrier based PWM with zero sequence signal

Continue

Motors
3-phase
Motor

➢ Motors obtain power from electrical source.

➢ They convert energy from electrical into mechanical therefore

motors regarded as called energy converters.

➢ There are several types of motors used in electrical drives,

choice of type used depends on applications and electrical
sources available.
Motors

DC Motors AC Motors

▪ Wound / permanent magnet ▪ Induction motor

▪ Synchronous motor
▪ Reluctance motor
▪ PM motors
Continue

Control Unit

Control Unit

Scalar Control Vector Control

▪ Microprocessor/Microcontroller based ▪ Trend: DSP- based, FPGA

▪ Less computational requirement ▪ High computational
▪ Low-medium performance requirement – real time
torque, flux estimations
▪ High performance

Control unit: supervises the operation of the whole system to

ensure stability and enhance the overall performance
Continue

Feedback Unit

Feedback Unit

Sensors

Torque Rotor Speed Phase Currents DC link voltage

▪ Torque Sensor ▪ Hall Effect Sensor ▪ Hall Effect Sensor

▪ Speed Sensor
▪ Control & protection ▪ Control & protection

Observer

▪ Torque and Speed

Summary of lecture

➢ Drive , its requirement with the help of two examples?

➢ Conventional drives,

➢ Advantages of modern drive

➢ Choice of Drive

➢ Components of Modern Electrical drive ,

➢ Power sources, Power processors, motors, load, feedback
system, control unit etc.
Assignment # 01

➢ What are electrical drives and discuss the importance of

drives with at least two examples?

➢ Explain the different components of drives in details.

THANK YOU