Drives Lecture 1

8/2/2019 Drives Lecture 1

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Chapter 1. Introduction

Design of

Electronic Drivesfor AC Machines

Dr. Umar T. Shami


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Introduction

Text Book


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1.1 The need for Variable speed drives

1.2 Fundamental Principles

1.4 Types of Variable Speed Drives

1.8.4 Electrical variable speed drives forDC motors (DC drives)

1.8.5 Electrical variable speed drives

for AC motors (AC drives)

2.1 The 3-Phase Induction Motor

Chapter 1 Introduction

CONTENTS


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1.1 The need for Variable speed drives

In general, variable speed drives are used to:

Match the speed of a drive to the process requirements Match the torque of a drive to the process requirements Save energy and improve efficiency


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The following is a review of some of the fundamental principles

associated with variable speed drive applications.

1.2 Fundamental principles

Forward direction

Forward direction refers to motion in one particular direction.

The Forward direction is designated as being positive (+ve).

Reverse direction

Reverse direction refers to motion in the opposite direction. The

Reverse direction is designated as being negative (ve).

Force

Motion is the result of applying one or more forces to an object.

Motion takes place in the direction in which the resultant force is

applied. So force is a combination of both magnitude and direction.


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Linear velocity (v) or speed (n)

Linear velocity is the measure of the linear distance that a movingobject covers in a unit of time.

In SI units, this is usually measured in meters per second (m/sec).

Kilometers per hour (km/hr)

Angular velocity () or rotational speed (n)

Although a force is directional and results in linear motion, many

industrial applications are based on rotary motion.

TorqueThe force used for rotating is known as torque.

In SI units, torque is measured in Newton-meters (Nm).


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TorqueThe force used for rotating is known as torque.

In SI units, torque is measured in Newton-meters (Nm). Linear acceleration (a)

Linear acceleration is the rate of change of linear velocity, usually in

m/sec2.



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Rotational acceleration (a)

Rotational acceleration is the rate of change of rotational velocity,usually in rad/sec2.

PowerPower is the rate at which work is being done by a machine. In SI

units, it is measured in watts.



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Energy

Energy is the product of power and time. In SI units it is usuallymeasured as kiloWatthours (kWh).



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1.4 Types of Variable Speed Drives

(a) Typical mechanical VSD with an AC motor as the prime mover

(b) Typical electrical VSD with a DC motor and DC voltage converter;

(c) Typical electrical VSD with an AC motor and AC frequency

converter;


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1.8 Electrical Variable Speed Drive Methods

1.8.2 Ward-Leonard system


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The fundamental principles of a DC variable speed drive


1.8.3 Electrical Variable Speed Drive For DC Motors


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1.8.4 Electrical Variable Speed Drive For AC Motors

This is what we will study in detail (InshaALLAH).


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Chapter-2Three-Phase AC Induction Motors

The Induction Motor was invented by Nikola Tesla In 1888.

Nikola TeslaThe early induction motor


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The AC induction motor consist of :

Stationary part called the stator



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Rotating part called the rotor,supported at each end on

bearings



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2.2.1 The stator

The stator is the outer stationary part of the motor, which consists

of: The outer cylindrical frame of the motor,

The magnetic path,

A set of insulated electrical windings.


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2.2.1 The rotor

This is the rotating part of the motor. The rotor can be either:

Wound rotor type,

Squirrel cage rotor type


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The stator and rotor


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Drives Lecture 1

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