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0000059856 Energy saver power factor controller for indudion motor / Mohd Hilmy AWullah Zawawi.

ENERGY SAVER POWER FACTOR

CONTROLLER FOR INDUCTION MOTOR

MOHD HILMY BIN ABDULLAH ZAWAWI

APRIL 2008

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"I hereby declared that I have read through this report and found that it has comply the

partial fulfillment for awarding the degree of Bachelor of Electrical Engineering (Power

Electronic and Drive)"

Signature . ..

. ALIAS B i b gtt4W5 Supervisor's name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Date : 3e/$[?.8.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ENERGY SAVER POWER FACTOR CONTROLLER

FOR INDUCTION MOTOR

MOHD HILMY BIN ABDULLAH ZAWAWI

This Report is Submitted In Partial Fulfillment Of Requirement For The Degree o f

Bachelor In Electrical Engineering (Power Electronic And Drive)

Faulti Kejuruteraan Elecktrik

Universiti Teknikal Malaysia Melaka

APRIL 2008

"I hereby declared that this report is a result of my own work except for excerpts that

have been cited clearly in the references"

Signature . . . . . . .

Name

Date

ACKNOWLEDGEMENT

In submitting this report, I would like to thanks Encik Alias Bin Khamis, my

Projek Sarjana Muda supervisor, for his guidance and participation in conducting my

project. His knowledge and insight were invaluable in identifying problem solving

solutions regarding to my project. I also would like to thanks all the lectures and my

friends who have been involving in sharing their knowledge and providing their

comments which I have took as important measure for me in completing this project.

ABSTRACT

The purpose of this project is to implement the energy saver power factor

controller for alternating current (AC) induction motor. Energy savings for induction

motor can be realized with adjustable speed operation. As the speed varies with load, the

power consumption characteristic of the motor will also varies.

The control of power consumption to save energy usage is done by using the

Variable Frequency Drive (VFD) or its other name, Variable Speed Drive. VFD is a

controller that varies the speed of an induction motors. It consists of a rectifier,

intermediate direct current (DC) circuit, an inverter, and a controller.

The operating speed of an induction motor which is connected to a VFD is

varied by changing the frequency of the motor's supply voltage. Output frequency and

voltage is controlled electronically by controlling the voltage pulse width to the motor.

These techniques require switching the inverter power devices ON and OFF many times

to generate proper RMS voltage level. This action allows continuous process speed

control. The power factor of variable frequency drive is discussed.

Tujuan projek ini adalah untuk mengaplikasikan penjimat tenaga pengawal

faktor kuasa untuk motor aruhan arus ulang alik. Penjimatan tenaga untuk motor jenis

ini boleh dilaksanakan dengan kaedah kawalan kelajuan motor. Apabila kelajuan

berubah mengikut beban motor, kadar penggunaan tenaga motor juga akan berubah.

Kawalan penggunaan kuasa elektrik untuk menjimatkan tenaga dapat dilakukan

dengan menggunakan 'Variable Frequency Drive (VFD)' atau dengan nama lainnya

'Variable Speed Drive'. VFD adalah pengawal yang mengubah kelajuan motor aruhan

mengikut keadaan. Ia terdiri daripada pengubah AC-DC, pengubah DC-AC, dan

pengawal.

Kelajuan operasi motor aruhan yang menggunakan VFD diubah dengan

mengubah frekuensi voltan masukan motor. Frekuansi dan voltan keluaran VFD dikawal

secara elektronik dengan mengawal kelebaran denyutan voltan masukan. Teknik ini

memerlukan operasi BUKA dan TUTUP berulang kali suis elekronik yang terdapat pada

VFD untuk menghasilkan tahap voltan keluaran yang sesuai. Proses ini membolehkan

kawalan kelajuan motor aruhan secara berterusan. Faktor kuasa motor dengan

menggunakan VFD akan dibincangkan dalam laporan ini.

CONTENTS

CHAPTER TOPIC PAGE

ACKNOWLEDGEMENT

ABSTRACT

CONTENTS

LIST OF FIGURES

LIST OF TABLES

LIST OF APPENDIX

1 INTRODUCTION

1.1 Problem Statement

1.2 Project Objectives

1.3 Project Scopes

1.4 Project Planning

2 LITERATURE REVIEW

-2.1 Introduction

2.2 Introduction to Power Factor

2.3 Induction Motor

2.4 Energy Saving for Induction Motor

2.5 Variable Frequency Drive (VFD)

2.5.1 Applications of VFD

2.6 Other Energy Saving Power Factor Correction Method

2.6.1 Installing Capacitor banks to improved System power factor

2.6.2 Selecting Suitable Motor

1

. . i1

iv

vi i

xi

xii

2.6.3 Minimize operation of idling or lightly loaded 18 motor

2.7 Summary 18

3 THEORETICAL ANALYSIS

3.1 Introduction

3.2 Induction Motor Construction

3.3 Basic Operation of Induction Motor

3.4 Induction Motor Equivalent Circuit

3.5 Components of Variable Frequency Drive (VFD)

3.5.1 Rectifier

3.5.2 DC Bus (Filter)

3.5.3 Inverter

3.5.4 Drive Controller

3.5.5 Pulse Width Modulation (PWM) Signal

3.6 Variable Frequency Drive (VFD) Control Methods

3.6.1 Volts/Hertz Control

3.6.2 Vector Control

3.7 Summary

4 METHODOLOGY

4.1 Project Development

4.2 Simulation Part Process

4.3 Software

4.3.1 MATLab

4.3.2 Orcad PSpice 9.1

4.4 Simulation

4.4.1 Induction Motor Torque Speed Characteristic Curve

4.4.2 Pulse Width Modulation (PWM)

4.4.3 Three Phase Pulse Width Modulation (PWM)

4.4.4 Simulation of induction motor with VFD

4.4.5 Simulation of induction motor operation without

using VFD 4.4.6 Single Phase Uncontrolled Bridge Rectifier 5 8

4.5 Hardware Development 60

4.5.1 Hardware Testing 63

4.6 Experiments 63

4.7 Summary 64

5 RESULT AND DISCUSSION

5.1 Induction Motor Torque Speed Characteristic

5.1.1 Variable Voltage Fixed Frequency Control Analysis

5.1.2 Fixed Voltage Variable Frequency Control Analysis

5.1.3 Variable Voltage Variable Frequency Control Analysis

5.2 Pulse Width Modulation (PWM)

5.3 Three Phase Pulse Width Modulation (PWM)

5.4 Simulation of induction motor with VFD

5.5 Simulation of induction motor operation without 76

5.6 Single Phase Uncontrolled Bridge Rectifier 78

5.7 Hardware Testing

5.8 Experiment

5.8.1 Power Factor As a hnction of Mechanical Load 82 Torque Experiment

5.8.2 ABB ACS550-01 Low Voltage AC Drive 83

5.9 Summary 8 5

6 CONCLUSION 86

6.1 Recommendation 8 7

REFERENCE 8 8

APPENDIXA : VARIABLE FREQUENCY DRIVE A1 AND POWER FACTOR

APPENDIX B : DSP APPROACH B1

LIST OF FIGURES

Figure Title Page

Power triangle 6

Power factor improvement power triangle 15

Induction motor construction 19

Induction motor stator construction 20

Induction motor rotor construction 2 1

Equivalent circuit of induction motor 23

Equivalent circuit of induction motor referred to stator 24

Variable Frequency Drive Circuit 26

Three-phase Uncontrolled Bridge Rectifier 27

Source voltage and resultant DC waveform 28

Inverter circuit 30

Basic PWM generation method 32

PWM Signal 33

Three phase PWM generation, Phase voltage (Van and Vbn), and 34

Line voltage (Vab)

Block diagram of Vector Controlled VFD 37

Project methodology flowchart 3 9

Simulation part flowchart 4 1

MATLAB window 43

m-file window 44

Simulink project window 44

Orcad Capture CIS project window 4 5

Basic PWM signal generation block diagram 5 1

Simulation Parameters

Three phase PWM generation block diagram

Sine wave generator configuration

Simulink Block Diagram of VFD driving Induction Motor

(a) Asynchronous Machine Parameter

(b) Universal Bridge Parameter configurations

Simulink Discrete 3-phase PWM Generator block

Simulation Configuration Parameters

Simulink block diagram of induction motor simulation

AC Voltage source configuration

PSpice model of Uncontrolled Bridge Rectifier with filter

capacitor

PSpice model of Uncontrolled Bridge Rectifier without filter

capacitor

(a) SG3525A PWM generator circuit

(b) PCB layout for SG3525 PWM generator circuit

DC-to-AC inverter circuit

PCB layout for AC-to-DC converter and DC-to-AC inverter

circuit

(a) Ferric Chloride acid (right) and PCB developer - thiner

(b) Etching process

Constructed hardware board

(a) SG3525A PWM Generator

(b) AC-to-DC converter and DC-to-AC inverter board

Hardware testing setup

ABB ACS550-01 Low Voltage AC Drive

Nameplate of induction motor used in the experiment

(a) Voltage versus frequency for VVFF.

(b) Variable voltage fixed frequency torque-speed curve

(a) Voltage versus frequency for VFVF

(b) Fixed voltage variable frequency torque-speed curve

(a) Voltage versus frequency for VVVF

(b) VVVF torque-speed characteristics

PWM simulation output waveforms

(a) Sine input and high frequency carrier signal waveforms

(b) Compared signal waveforms

(a) PWM switching signal

(b) PWM output waveforms

Filtered output waveforms

Fundamental Vab and Ia curve

Vab, Rotor speed (om), and Torque (Te) curve

Torque at steady state curve

PWM switching signal to phase A

Currents in IGBT Switches phases A

Timer parameter configuration

(a) Motor operating condition at different load condition

(b) Motor active and reactive power at different load condition

(a) Stator supply voltage waveform

(b) Vab, Rotor speed (om), and Torque (Te) curve

(a) Motor operating condition at different load condition

(b) Motor active and reactive power at different load condition

Non-filtered output voltage and source voltage waveforms

Non-filtered average output voltage waveform

Filtered output voltage and source voltage waveforms

Filtered average output voltage waveform

SG3525A PWM generator circuit frequency control waveform

(a) minimum fiequency

(b) maximum frequency

SG3525A PWM generator circuit Duty cycle control waveform

(a) minimum duty cycle

(b) maximum duty cycle

Gate drive PWM output waveform

5.24 Power factor vs mechanical load torque curve

5.25 Output voltage at different frequency chart

5.26 Torque and Speed chart at different frequency

LIST OF TABLES

Table Title Page

Project planning chart

Three-phase standard capacitor ratings

Software package

Variable Voltage Fixed Frequency (VVFF)

Fixed Voltage Variable Frequency (FVVF)

Variable Voltage Variable Frequency (VVVF)

Motor operating value at different load conditions

Power factor at different load conditions

Motor operating value at different load conditions

Power factor at different load conditions

Frequency control results

Mechanical load torque, motor active, reactive, apparent power

and power factor

Output voltage at different frequency

Torque and speed at different frequency

LIST OF APPENDIX

No Title Page

A VARIABLE FREQUENCY DRIVE AND POWER FACTOR A1

B DSP APPROACH B1

CHAPTER 1

INTRODUCTION

Energy saving is important for efficient power consumption and cost savings

especially for big industrial company that uses lots of electrical equipment that tends to

waste energy in their business. It is their goal to reduce power usage while increasing

their production.

Power electrical engineers today have used lots of equipment, devices and

methods to control power consumption. The main goal is to reduce power consumption

thus reducing electrical bill cost and production cost. Actually, the thing they are doing

is to increase their power factor.

In industry, AC induction motor is the workhorse. It is used for many

applications. It is also the machine that tends to reduce the plant power factor. Using this

kind of machine without any energy saving device will waste power usage and increase

electrical bill.

Adjustable speed operations for induction motor are being used in numerous

applications such as centrihgal pumps and fans to realize substantial energy savings.

The applications are implemented in the basis of kilowatts (kW) savings with long term

period payback. The power factor characteristic of a variable frequency drive (VFD)

differs from the fixed speed induction motor. It is one of the energy saving method to

use the VFD to improve the induction motor power factor.

This thesis report will be discussing about induction motor characteristic and the

energy saving power factor correction method through the used of VFD. The main

component in preparing this thesis is the analysis of the induction motor and VFD

characteristic including the related parameters. These consist of induction motor

operations and how it can be operate to reduce power consumption as much as possible.

Brief history on induction motor and VFD are also included.

As for conclusion, deep understanding about induction motor construction and its

operation can hrther helps to well save the energy. All the important data obtained in

this research analysis is expected to hrther helps in improving the energy saving method

of induction motor.

1.1 Problem Statement

Induction motors are the kind of electrical equipment that tends to reduce a

plant's power factor. The efficiency of an induction motor will fall at a reduced load. An

induction motor takes both active and reactive power from the supply. The rotating

torque of the motor is created as an interaction between the active current component

and the magnetic field.

The field is produced by the reactive current component. Light load take less

active current but, the magnetic field as well as the reactive current stay constant. This

means that the power factor of the motor decreases as the load decreases. The current is

mainly active at the full load but mainly reactive at the light load. By using the variable

speed drive, the benefit of power factor improvement can be realize thus increasing

energy saving through speed control. The process control involving the use of induction

motor can also be improved.

Traditionally, the induction motor was operated directly from the grid with

almost constant shaft speed. With the development of power electronic converter,

induction motor could now be controlled by variable frequency or variable speed drives

(VFD). This means that by inserting a converter between the motor and the electrical

grid, it is possible to obtain variable speed motor operation. Since the motor applications

accounts for a large proportion of electrical energy consumption, VFD would contribute

considerably in reducing the energy consumption.

1.2 Project Objectives

The objectives of this project are as follows

a) To study & analyze the energy saver power factor controller for induction motor

using variable frequency drive (VFD)

b) To understand the characteristics of an induction motor

c) To understand the operation of VFD

d) To perform simulation on VFD using simulation software packages

e) To analyze the characteristic of Induction motor with VFD

f) To compare the result with the motor without VFD

1.3 Project Scopes

This project covers the knowledge management of the previously studied

Electrical Machine course which has been taken in the previous semester. The operation

of induction motor and information on how it can save energy via speed control are

studied. The main things to be done are to learn the VFD which consists of a rectifier,

filter, inverter and controller.

The information of energy saving VFD is obtained through readings of books

and journals and also internet resources. The electronic circuit of the drive (controller) is

analyzed and simulates to obtained performance characteristics before proceeding to the

hardware construction part.

This report will discuss about all the research that has been done including the

basic theoretical part of the project in study. The basic theory of power factor, the basic

characteristics of induction motor and introduction to VFD are included in the literature

review. The expected hture results of the project and comparisons of power factor

performance of induction motor with and without VFD are also studied.

1.4 Project Planning

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This literature review is done by using references from books and online journal

from IEEE and numerous author using web resources to hrther understand the research

being performed. There are also references taken from the previously studied subject

lecture note used in the preparation of this report.

2.2 Introduction to Power Factor

Power factor is the ratio of true power or watts (kW) to the apparent power or

volt amperes (kVA). They are identical only when the current and voltage are in phase.

Then the power factor will be 1 .O. Power factor is a measure of how effective the current

is converted into useful work output.

All current will cause loss in the supply and distribution system. A poor power

factor can be the result of phase different between current and voltage at the load

terminals or it can be due to harmonic distorted current waveform. The power in an

alternating current (AC) circuit is seldom equal to the direct product of volts and

amperes.

In direct current (DC) electrical circuit, power is a measure of the delivery rate of

energy and expressed as the product of volts and amps. But in AC power system, AC

currents may flow into and back out of the load without delivering energy. This current

which is called the reactive current gives rise to apparent power (Volt x Amp) which is

larger than the actual power consumed. The difference between the apparent power and

the true power gives rise to the power factor. Therefore the actual power in an AC

system is the VA rating multiplied by the power factor.

The higher the percentage of reactive power (kVAR) results in the lower ratio of

kW to kVA thus resulting in lower power factor. The relationship of kW, kVAR, and

kVA is illustrated by the power triangle shown in figure 2.1.

KIT-

Figure 2.1 : Power triangle

From the figure 2.1, the mathematical equations for the power factor is as followed

kW power factor = - = cosB

kVA

Since power factor is defined as the ratio of true power to the apparent power, we

see that low power factor results when the true power is small in relation to apparent

power. Low power factor causes an increase in required apparent power. So, a facility

with low power factor causes the utility to have to increase its generation and

transmission capability in order to handle this extra demand. This would occur when the

reactive power is large and the main cause of large reactive power is the inductive load.

Inductive load which are the source of reactive power includes the transformer,

induction motor, and others.

Power factor improvement (unity power factor) is the goal of power electrical

engineer. The benefits of improving power factor include:

a) Lower utility fees by reducing peak kW billing demand and eliminating the

power factor penalty

b) Increased system capacity and reduces system losses in power system

c) Increased voltage level in electrical power system

2.3 Induction Motor

Induction motor is widely used in the industrial. It is the workhorse of the

industrial. This fact is proved when 70% of industrial power consumption came from

this kind of motor.

Brief history of induction motor can be understood by knowing the history of

Nikola Tesla. He is one of the pioneers that invent the usage of field forces toward the

operation of electrical motor. In 1882, he discovered the principle of magnetic field

rotation. He later performs hrther research on the principle and manages to design a

unique two-phase induction motor on the year of 1883. His invention has attracted many

of intellectual at that time to fbrther the researches which contribute a lot in today

electric motor technology.

Tesla discovery of rotational magnetic field principle has opened a new sheet of

motoring design when the new era of industrial revolution started in the year of 1888.

This is proved through the ability and power of industry to improve the efficiency of

electrical generation, transmission and distribution in a more far distance. Before Tesla

contributed his thinking, motor operation are simply based on linear movement across

conductors on static magnetic field. In his research, he proposed that commutator which

is normally used as conductors can be removed and replaced with other device that

operates toward rotational magnetic field.

Later in 1889, Tesla's invention has been recognize and patented by the United

State. His invention had become famous where the induction motor at that time being

called electromagnetic alternating current motor.

Induction motor is one of the alternating current types of motors and has an

endearing characteristic that it can be run by direct connection to a three phase power

source. This type of motor is called induction because the rotor voltage which produced

rotor current and rotor magnetic field is induced in the rotor windings. It is a singly fed

motor which does not require commutator or brushes. An induction motor is like a

rotating transformer where the source is only connected to the primary winding and the

secondary winding receives energy through induction while it rotates. This means that

there is no mechanical contact between the stator and the rotor.

Because of this induced rotor voltage, no DC field current is required to run the

motor. The behavior of the motor depends on rotor voltage and current which relates to

speed.

There are many advantages of induction motor compared to other types of

motors. The advantages include:

i) High efficiency

Induction motor can operate with high efficiency level. However, the motor

ability to run efficiently depends on motor's rated parameters. Ratio of work

must be suitable with the motor's rated power ratings.