]OJ J International Conference 011 Electrical Energy and NeT11'orksr7CEEN ]OJ I!

Micro controller Based Control of Three Phase Induction Motor Using P\Vl\1Technique

S.M.Wank..hede, R.M.Holmukhe, Miss.A.M.Kadam, Miss.P.R shinde, *p.s.ChaudhariElectrical Engineering Department

Bharati Vidyapeeth Deemed University College of Engineering, Pune, India"Scientist, DRDO, Pune, India.

Email ID: rajeshmholmukhergjhotmail.com

Abstract-The speed of the induction motor can be controlledby various methods. The stator frequency control is one ofsimplest methods to control the speed of the Induction motor.The micro controller based speed controlling system can beused in various industries such as chemical, textile and cementto operate the motor according to the desired speed. This iscompletely dosed loop system and the speed of the motor willbe controlled automaucally by use. of feed back from motor interm of rpm ,The inductive magnetic sensor can be interfaced .with microcontroller easily and can sense rp m of the motor and giv'e it tomicro controller in digital form as a feed back from motor.

Keywords- microcontroller, induction motor, PHiM.cchnicue

1. INTRODUCT10N

1;-.;;]3!-;Y of the industrial applications, an electric motor istile most imporrant component. A complete production unitC,l;1SiSt5 primarily of three basic components; an electricmotor, an energy- transmining device and L'1eworking (ordriven) machine.An electric motor is the source of motivepower. An energy- transmitting device delivers power fromelectric motor to the driven machine (or the load); it usuallyconsists of shaft, belt, chain rope etc.The electric motor is widely classified asI. A.C Motor'1 D.CMotorSeveral industrial applications need adjustable speeds fortheir efficient operation. The various methods of speedControl semiconductor devices are as follows:I. Stator voltage control2. Stator frequency control, Stator voltage and frequency control4. Stator current control-. Static rotor- resistance control6. Slip-energy recovery control

Methods I to 4 are applicable to both (SelM and WRJM)whereas method 5 and 6 can be used for only WRl!\·1s. Outof above listed methods. Here stator frequency controlmethod to control the speed of the 3 phase induction motoris used.

In this research project paper a micro controller basedsystem to control the speed of the 3 phase LM.is developed

978-1-4244-9567-2/11/$26_00 ©2011 JEEE

using pulse width modulation technique. Here the speed ofthe motor is controlled by sensing the rprn and current valveof the rpm. The current value of rpm i5 sensed by inductivemagnetic switch and its output is fed :0 the micro controller.The micro controller compares the current value of the rprnwith set values and adjusts the rime period ef the pulsesapplied to the stator to control the frequency of the stator.

This system can be used effectively in the industrialapplications to control the speed of the 3 phase inductionmotor.

II. BLOCK DIAGRAM A~D WO~Ki:-\G

i,__ ._. i

l~;)[!~S:j~p~~!Fromh'1t,~0r ; i 1 Cor.:.r~·.i:::

----. ,i ~r .';vc:: )--1~ :,uP!'<" r-~i.------ -~~~,~~---! ,;(~~R::);-:.r..::i /--'

--- --'Fi~. c....oil:'r(Jlicr C:;ud

Fig.l.Block Diagram of Comrollcr card

Above figure shows the block diagram of the controllercard.The controller card consists of \1 icro controller andrelated circuitry to it such as oscillator circuit tIC. The rpmof the motor is sensed by inductive magnetic switch. Theoutput of the magnetic switch is fed to the micro controller.The micro controller performs the controlling action in thissystem. It monitors the status of .he magnetic i.\\litchcontinuously to measure the current :Vi11 of the motor. Thenit compares the read value (current value) of rprn with theset value. If the set value is less than the set value then itincreases the frequency of the pulses applied to the stator ofthe induction motor. It does so by decreasing the lime periodof these pulses. When the frequency of the pulses appl ied tothe stator increases the speed of the induction motorincreases. The exact reverse action will be taken if thecurrent rpm value of motor is greater than the set value.

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:;011 international Conference on Electrical Energy and NelWorks(lCEEN 20J 1)

Also the set value and the current value of the rprn isdisplayed by using LCD display.

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from·Micro

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i /'--...........,~/ '-I !I i Inductionf-+\ Motor ,

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Fig.:!. Block Diagram of Dr inn Circuit

The driver circuit consists of MOSFET driver IC lR2110 and other additional components as diodes, capacitorsetc. The driver circuit is used to drive the induction 1110tor,which is connected as load to the VFD. The Speed of theinduction motor, is controlled by varying the frequency ofthe pulses applied to the stator of the motor .These pulsescoming from the microconrroller are fed to the MOSFETdriver IC IR 211a.TIle IlUII 0 is high voltage. high- speedpower MOSFET and [GBT driver with independent highand low side referenced output channels. The output of theIR 2110 is given to tile \10SFET JRF 540.lt is used forswitching purpose because of tile its high current rating .Thepulses coming from the frequency of the stator and in tUi11tocontrol the speed of the induction motor.

ur. HA~DWARE OVERVIEW

1I) DESIGN CO.NSIDERA TIOSS:-The most important and basic aspect of the any system is

to design the circuit (t.c. hardware design) for the specificapplication. This inv ohes deciding which component to use.specifications of different components. mathematicalcalculations, components selection and other related issues.The detailed information of the hardware desizn of the oursystem is an follows. -b) IC FEATCRES AM) BRItJS:-

In our system we hav e used micro controller AT89C51and other external peripherals such as the magnetic switch,Opto isolators. 1\10SFETs. 1\10SFET driver IC etc. Thissection focuses on the: features and brief introduction ofthese IC's peripherals, their significance etc.

1) Micro Controller AT .\'9C51Microprocessors and micro controllers stem from the

same basic idea. are made b). the same people, and are soldto the same types of sysr m designers and programmers.What is the difference between the \\\-0"

MicroprocessorsA microprocess, r. ~" iItc term has come w be known. is

a general purpose digital computer central processing unit(CPU). Although ;->opula;ly know n 2, <I "Computer on achip", the microprocesso: is in no S=Il'~ a complete digitalcomputer. Figure h:I()\'. sho« S 2 block diagram ;r a

microprocessor CPU, which contains ap' Arithmetic andLogic (ALU) a program Counter (PC), a Stack Pointer (SP),some working registers, clock timing circuit and interruptcircuits. To make a complete microcomputer, one must datamemory (RAM), memory decoders, an oscillator and anumber of input / output (I/O) devices, such as parallel andserial data ports. In addition, special purpose devices, suchas interrupt handlers and counters. may be added to relievethe CPU from time consuming counting or timing chores.Equipping the microcomputer with mass storage devices.commonly a floppy and hard dist drives, and I/O peripherals,such as a keyboard and a CRT display. yields a smallcomputer that can be applied to a range of general purposesoftware application.

,------I,----.J ,A.:i(t;metic a'ldLogic U!'li~

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---'---'--~._______ .L . _

. C!():k (;i~o:ui';

Fig.3.Block Diagram of Microprocessor CPU

The key term in describing the design of themicroprocessor is general purpose. The hardware design O!'

a microprocessor CPU is arranged so that a small or \'ei\large system can be configured around the CPLJ 2S theapplication demands. The internal CPU architecture as \\ -:1ias the resultant machine level code that operates rnearchitecture is comprehensive but as flexible as possible.

The prime use of a microprocessor is to read dn~.perform extensive calculations on that data, and store thosecalculations in a mass storage device or display the resi.ltsfor human use. The programs used by the microprocessorare stored in the mass storage device and loaded into R.'\ \ jas the user directs. A few microprocessor prclg'l!'11' ,.'2

srored in ROM. The ROM based programs are prirnarilvsmall fixed programs that operate peripherals and otherfixed devices that are connected to the system. The designof the microprocessor is driven by the desire to make it asexpandable and flexible as possible, in the expectation ofcommercial success in the marketplace.

Micro ControllersFigure shows the block diagram of a typical micro

controller which is a true computer on a chip. The designincorporates all of the features found in a micro processorCPU: ALU, PC, SP. and registers. It ;,150 has added theother features needed to make a complete computer: RO. 1.RA1\1, parallel 10, serial I '0. counters. and a clock circuitLike the microprocessor. :1 microcontroller is a aeneralpurpose device, but one that is meant ro read data, pe-rformslimited calculated on the data. and control its e: \ ironmentbased on the those calculations. The prime use of amicrocontrollcr is to cor-trot the operation of a machin;

2011lnternafional Conference on Electrical Energy and J.:erl1'vrks(1CEE\"201 J)

using a fixed program that is stored in ROM and that doesnot change over the lifetime of the system,

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\nternal ROt.."Aceumutetor

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Ctcc«Circuits

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Fig_4, Block Diagram ofT) pical Microcontroller

The design approach of the micro controller mirrors thatof the microprocessor. The microcontroller design uses asimilar. much more limited set of single and do~ble byteinstructions that are used in microprocessors to move codead data from internal memory to the ALU. Manyinstructions are coupled with pins on the integrated packagethe pins are "Programmable" that is capable of havingseveral di fferern functions depending on the wishes of ther;'()grammer,

The microconrroller is concerned with ceninz data fromand to it" own pins: the archite ture and I~struc~ion .et areopurmzed to handle data in bit and byte size,

Comparison between Microprocessors and-',f icrocontrollers

The ontrast between a microcontrolier and aI~';:croprocessor is best explained by the fact that mostrr.icroprocessors have many operational codes Cop codes) formoving data from external memory to the CPU;microcontrollers mav have one or two, Microprocessorsmay hav e one or rwo types of bit handling instructions;mici ocomrollers will have many,

surnmarize: the microprocessor is concerned withrapid mov ernent of code and data from external addresses tothe chip; the microcontrcller is concerned with rapidmovement of bits within the chip, The microcontroller canfunction as a computer with the addition of no externaldigital parts; the microprocessor must have many additionalpans to be operational.

ATli9CS2 It1/CROCO_!\'TROLLER HARDWAREThe AT8,-,C52 is a low power, high performance (MO

8-bit microcomputer with 8K bytes of Flash programmableand erasable read only memory (PEROM), The dev ice ismanufactured using Armel's high density nonvolatilememory technology and is compatible \\ ith the industry';cdHL;-J :--'OC.'i I and 80C52 instruction ".'t an i i~::llll1. The(':1 UHf rla~h allow s the pru~raI" mcm. r, l ~reprogr mined 111 5) stem or b) a COI1\ enuonal 11)i1\ -Lulemcmor. programmer. B~ cornl-imng a \ cr s.nile \; bit L'PLJ\Ilth Hash on a monolithic chip. the .vtmel AT. -IL:,2 I' a

powerful microcomputer which provides a highly flexibleand cost effective solution to many embedded controlapplications,

C) INTERFACING DETAILSIn this chapter the interfacing of the micro

controller with other iC's is discussed. Tha: is it explainsconnection of the each pin of micro- vnuoller ":ith the otherlC's and external peripherals used in '1-' -vsrern.The Controller Card

The controller card .s the .: .- :'IC:, the Microcontroller AT 89(51 is placed.

The other objects 011 the C llj(, .iner card are powersupply and the connectors for display. tvlOSFET driverCircuit etc. The interfacing of the master micro conrrollerwith all these components is listed in .he following table,

$'",,, (,), "".0"',. •.'C on , t""C'; I I•..•,.

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.;J'" i\,i:' ••:-,. ,- .•... :-.,:.l ..-,,.-;,'-,--.

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D) PULSE WIDTH, TODl'LI:"Figure shows a bl.vck ',,1:;1" ," .he power

onversion unit in a P\\ \\' dr:v <: I ;, i~ "l of dnve. adiode bndge recutier PI'" 11..1.:, t,;~ Iku; .,.: Ul c irc n:the DC voltage is filtered in a LC 1,'\\ pass filter. Outputfrequency and voltage is controlled electronically bycontrolling the width of the pulses ,1' voltage to the motor.Essentially, there techniques reqi.u , ,', ilchi:ig the inverterpower devices (Transistor or ICBT<oj t':l and air many timesin order to generate the proper R;"1S .•l,;t;Jg:: levels,

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::C11 International Conference 011 Electrical Energy and Networks(ICEEN 2011)

This switching scheme requires a more complexregulator than the VVI. With the use of a microprocessor,these complex, regulator functions are effectively handled.Combining a triangle \\ ave and a sine wave produces theoutput voltage waveform.

~----'~'~--~'-------,

Irlan;;l:Sens:at:1

P\Nr.~

ii 1Med.-al c,'i ':'~nC'5t:1 r-------~L ~I

Fig.7.PWM Generator

.The triangular _izual is the carrier or switchingfrequency of the in;;:'rter. The modulation generatorproduces a sinewave signal the determines the width of tilepulses, and therefore the RMS voltage output of the inverter.

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'J I I '-' \' "1-· 'I , I I "f I I I

_ ---- 1------4' ~_

<II ;t;.~.\\ aveforrns

AC drives that use :1 PWM type schemes have varyinglevels of performance based on control algorithms. Thereare 4 basis rypes of con n I for AC drives t~day. There are'olts per Hertz. Sensor e s Vector Control. Flux VectorControl and field Oriented Control. V/Hz control is a basiccontrol method. providing a variable frequency drive forapplications like fan <InJ "lump. It provides fair speed andtorque control. at a re:i~ vnable cost. Sensor less VectorControl provides better s;,,'eo regulation. and the ability toproduce high starring W'·_'.i,~. Flux Vector control providesmore precise speed Cl':c- torque control, with dynamicresponse. Field Orieme.t ~'ornrol drives provide the bestspeed and torque CO!J1r,; available for AC motors, Itprovides DC performance tor AC motors. and is well suitedfor typical DC applications.

I"'. 5-0r-; \Softw arc ,'.: "":';:1-: .

interfacing of tile' ~k'keyboard. \DC \(;,('interface lhe c ,~: ,

,\RC 0 ':ER\'lE\\'~ '!I~_j~~ ~ :-o~;-:.·~.. ·,\T:~i..?n f();- thecontroller \\'Ilil LCD display,liJ:!; ci"cui','1d the mobile. i' , ',j, _ 'ltr,)ller arc best

explained with the help of the flow charts includes in thischapter. .

1_ The next step is to understand the softwareprogramming incorporated in the microcontroller to achievethe given task.While performing its calculations and control,the rnicrocontroller need to be human friendly both in termsof data input and display, .

2. The software has been written instructured mannerin which all the subroutines are linked to a single mainprogram, Each subroutine is further divided ir .o sub subroutine as per the requiremen_t. _

Flo'W Ch~rt> ( 51 ;.1{1 'J'--_/

.....,....···-jr-.n"j1 ALSoL -,:: ,.11.: '-I.TI'~'r 1'0,: .••••.• ••n •...,....•

------r---- - .--.'!..--:---- ------I \\ '\1: FuR Si Tn {J

. (\1- R "IV· FR~ v"", J ••.£ Y H(.l/d~ I)

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Fig. 9.FJo\\ chart

2011 International Conference on Electrical Energy and Networks (JCEE.'" ]011)

V. PULSE WIDTH MODULA TION TECHNIQUES

PWM l-ridges the. gap between the digital and analogregimes allowing one to exchange tone for voltage. Mostpeople use hardware to generate PWW waveforms. Thereart! few different techniques for generating pulse widthModulated square waves using software. It 'turns out thatmany of techniques described here mav also beimplemented in VijDL.

VI. COMPONE IT LIST

m:f,' UI,IT::JESCRfPTION PRICE-:----, -fiansform-&----~·-·----l-- ---1~{j --

- --- II/lIem ccntrcllep -- --;r,- '"-AT 89C52 --

- .--- ~~Fs~E;-----;r-1-------.- ..-- so"'-Mos=n - ..- -- ----.---- -

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--~--l

'L _~""2 ':~~;r.I=(,2 \!~'(~I::'

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VIi. TESTTI G AND TROUBLE SHOOTING

Following testing are carried out in the three phasevariable frequency drive model.

I) Low voltage with lamp load2) High voltage (230V) testing with lamp load.3) High voltage (230V) testing with motor load.

J) L(lW voltage testing lamp load:To observe the proper functioning of drive circuit, low

voltage testing is carried out. A 12V DC supply coming outfrom the transformer and bridge rectifier circuit is given toinput of drive circuit and following observation are made

• Square waves across the s\\ itching transistors6 Square waves acres load i.e. in bridge inverter

circuit.• Similarly desired waveforms across the

rnicrocontroller circuit.2) High voltage (230 V) Testing will! Lamp Load:

\\1 ile Joing this 230 V testing with sing!.: phaseVariable fr quency drive problem faced was: heaung andl-urning of \10SFET bridge circuit.The reason IS that. thebridge circuit it is required thr.t two \IU F[T should be

'ON' at a time and at that instant other MOSFET should beturned 'OFF' but while testing it is observed that turning'ON' and turning 'OFF' both these two pair were overlapping.Following may be the reason behind this:• Mismatching of actual delay time of MOSFET bridge

ckt. with programmed delay time.• Due to failure oflR21 10 IeFollowing are the remedies Taken TO overcome the problems:I) Modification of the program in the microcontroller2) Application of heat sink for the ;,10SFET bridge circuit3) Addition ofTC MCT 2E for isolation purpose.3) High Voltage Testing 011 Moto>.

By providing the above modif.cauon. we proceeded for230 volt motor testing. In this no volt testing we observedthe proper functioning of micro controller circuit as well asof the drive circuit. Also by varying the load the variation inFrequency according to load current Ie observed.

vm. FUTURE E, 'H.'\.J 'CEI'vIE1\T

There are certain features thai can be added in thissystem. Some of the fearures ar ii. ed below.

• Incorporate RTC chip DS I '(j- which can be usedto how the time. and w e can soft differentreadings ofrpm in timely manner.

• Use serial memory hip. T 2·kO.:l and can storethe e records il the system.

• Upload this data to the PC by serial communicationusing MAX 232 IC

• Efficiency of motor can b controlled using thissystem.

• Instead of a \liLw-:Oilti', I,: .v e can use? CPLDchip since the CPLD I"','q~,)]'aie~ mall) morefeatures than a Microcor.rroiler. \'LSI VHDL canbe used for CPLD programming.

COI\'CLUSIU:"Micro controller based system cun be effectively used

for speed control of the 3phase induction motor along withPWM techniques,

ACKNOWLL"GHE\:TBharati Vidyapeeth Deemer' '.': '<::<lY, Pune.

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