PWM Speed Control of ACSingle Phase Induction Motor Using

Abstract—Single phase induction motor has been used

widely in discipline industry and household where a simple motor starter can't let vary speed in starting and also running with mechanical load. This paper introduces a method for controlling the speed of an AC single phase induction motor. Combination of micro controller unit & TRIAC has been used. A single phase induction motor adjustable speed control is implemented with hardware setup and software program. The main feature used in PIC17C756 microcontroller to control speed is pulse width modulation technique. Voltage drop across two terminals of TRIAC MT1 and MT2 is controlled with its gate voltage. Gate is controlled by DIAC and its input is controlled by an R-C triggering circuit. In triggering circuit variable resistor is used to vary TRIAC gate voltage through DIAC. DIAC gate voltage, TRIAC input voltage and output voltage are also simulated by “Electronic Workbench” software. One chip and re-programmable ROM avoids non-linearity and it can replace mechanical speed variation. Output voltage and capacity of the system can also be varied.

Index Terms—Pulse width modulation, micro controller unit, triode for alternating current, diode for alternating current, silicon controlled rectifier, metal oxide semiconductor field effect transistor.

I. INTRODUCTION An induction or asynchronous motor is a type of AC

motor where power is supplied to the rotor by means of electromagnetic induction, rather than by slip rings and commutators as in slip-ring AC motors [1]. Single phase induction motor is the most familiar of all electric motors & they are similar to a 3-phase squirrel cage induction motor. It has a squirrel-cage rotor identical to a 3-phase motor and a single phase winding on the stator [2].

There are several methods for controlling the speed of DC motors. One simple method is to varying frequency and voltage of the motor. Another method is controlling SCR for DC motors convert AC power to direct current, with adjustable voltage [3]. In PWM method, pulse width modulation is used to regulate the current sent to the motor. Unlike SCR method which switch at line frequency, PWM controls produce smoother current at higher switching frequencies, typically between 1 and 20 kHz [4].

At 20 kHz, the switching frequency is inaudible to humans, thereby eliminating the hum which switching at lower frequency produces. However, some motor controllers for radio controlled models make use of the motor to produce audible sound, most commonly simple beeps. A PWM controller typically contains a large reservoir capacitor and an H-bridge arrangement of

The authors are with with Islamic University of Technology,

Bangladesh (e-mail: [email protected]; e-mail: [email protected]).

switching elements e.g. thyristors, MOSFET, solid state relays, or transistors [5].

PWM is a commonly used technique for controlling power to inertial electrical devices, made practical by modern electronic power switches [6]. The average value of voltage and current fed to the load is controlled by turning the switch between supply and load on and off at a fast pace. The longer the switch is on compared to the off periods, the higher the power supplied to the load is. Duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time [7]. In this paper, the basic principles and operation of PWM inverters for ACMC applications using Induction Motor controller devices has been outlined [8]. PIC17C756 microcontroller, TRIAC and DIAC are used to control the speed of the DC motor. The performance of the proposed system in Electronic Workbench software has been evaluated in terms of duty cycle, PWM and output voltage.

II. INDUCTION MOTORS In an induction motor, power is supplied to the rotor by

means of electromagnetic induction. If a single phase voltage is applied to the stator, current will start flowing. This current produces a magnetic field BS, which will rotate in a counter clock wise direction. Speed of the magnetic field’s rotation is given by (1),

nsync = (1)

where f is the system frequency and P is the number of poles. This rotating magnetic field BS passes over the rotor bars and induces a voltage in them, which is given by (2)

eind = (v B). l (2)

where, vis the velocity of the rotor relative to the magnetic field and lis the length of conductor.There will be rotor current flow which would be lagging due to the fact that the rotor has an inductive element. The rotor current will produce a magnetic field at the rotor, BR. The interaction between both magnetic field would produce torque according to (3),

τind = kBR BS (3)

The resulting torque is counter clockwise. Since the rotor induced torque is counter clockwise, the rotor accelerates in that direction. In normal operation both the rotor and stator

R.Khan and M.M.S. Riyadh

PWM Speed Control of ACSingle Phase Induction Motor Using MCUSeries Combined With TRIACTechnology

International Journal of Computer and Electrical Engineering, Vol. 3, No. 6, December 2011

865

Manuscript received October 3, 2011; revised December 12, 2011.

mw

deSlsp

wregi

roso

mmprmmimHsm

msmshERcuthroThanmro

to

magnetic field while the rotor

The voltage epends on the lip speed,nslippeed and rotor

nslip =nsync

where, nm is elative speed iven by (5)

s = (

If the rotor tuotor is stationomewhere betw

IIIA net ma

magnetization magnetization

roportional to magnetic field,motor, E1 varimpedances cau

However, thesemall, so E1 is a

At no load, tmotion betweemall, and rotohown in Fig.1R induced in urrent IRis smahe reactance ootor current IRhe rotor curren angle just

magnetic field,otor running is

τind = kBR B

Fig. 1. M

Since the rotorque is also q

τind = kBRB

BR and BS itself turns at induced in speed of roto

p is as the dir speed.

nm

mechanical sexpressed on

%

=

urns at synchrnary, s = 1. ween those tw

I. TORQUE-SP

gnetic field,current, IMcurrent andthe voltage E

, Bnet in the mies as the loause varying ve drops in theapproximatelythe rotor slip ien the rotor aor frequency i. Since the ro

the rotor isall. Because thof the rotor is R is almost in pent thus produ

slightly grea, Bnet. The ins given by (6)

Bnet

Magnetic field in

tor magnetic quite small. Its

Bnet sin δ

rotates at sya slower speea rotor of an

or relative to thifference betw

shaft speed on a percentag

( %

ronous speed,All normal

wo limits.

PEED CHARAC

, Bnet is pM. The mad hence of E1. If E1 is conmotor is consad changes, b

voltage drops e stator windy constant withis very small, and the magnis very small.

otor motion is s very small he rotor frequnearly zero,

phase with thces a small mater than 90

nduces torque

an induction und

field is very s magnitude is

ynchronous sped. n induction mhe magnetic fiween synchro

of motor. Slge basis, whi

s = 0, while motor speeds

CTERISTICS produced by agnitude of

Bnet is dirnstant, then thstant. In an abecause the swith varying

dings are relath changes in land so the rel

netic field is . This conditismall, the voand the resu

ency is very sand the maxie rotor voltag

magnetic field 00 behind the, which keep

der light loads

small, the inds given by (7)

peed,

motor fields. onous

(4)

lip is ch is

(5)

if the s fall

the the

rectly he net actual stator load.

tively load. lative very

ion is oltage ulting small, imum ge ER. BR at e net ps the

(6)

duced

(7)

If the rno mmagrotorcurreBR aand frequcurremagoperincredecrsupp

Thshowsyncbetwtorqubreaof thlargecarry

Thsquamotodirecthe mmagrapidrevemattswit

f the load in anrotor speed falmore relative gnetic fields. Gr voltage ERent IR. With aalso increasesBR changes auency rises, ent lags furth

gnetic field shirating at a fairease the torqrease the torquply the motor’

Fig. 2. Magn

he induction mwn is Fig.3. Tchronous speeween no load aue that canno

akdown torquehe motor. Ther than its fuying any load

Fig. 3. Inductio

he torque on are of the appor is driven ction of the inmotor is turnin

gnetic fields, thdly and will t

ersing the direter of switchching two pha

n induction inclls. Since the motion betw

Greater relativR which in tua larger rotor s. However thas well. Since and rotor rea

her behind theifts the currenrly high load.

que, while inue. The overals increased lo

netic field in an in

IV. TORQUE

motor torque-The induced toed. The torqueand full load. ot be exceedee, is 2 to 3 tim

he starting torull load torquthat it can sup

on Motor Torque

the motor foplied voltage. faster than snduced torqueng backward rhe induced totry to rotate itction of magn

hing any twoases in order t

creases, its slirotor speed is

ween the rotorve motion produrn producescurrent, rotor

he angle of throtor slip is

actance incree rotor voltagnt. Fig. 2 show. The increasencrease in anll induced tor

oad.

nduction under he

E-SPEED CURV

-speed charactorque of the me-speed curveThere is a ma

ed. This torqumes the rated rque of the mue, so this mpply at full po

e-Speed Character

or a given sliIf the rotor o

synchronous e in the machrelative to therque will stopt in the other netic field rotao stator phasto stop the mo

ip increases, as slower, therer and the staduces a strong a larger ror magnetic fiehe rotor currelarger, the ro

eases. The roge, and the rows the inductie in BR tends ngle δ tends rque increases

eavy loads

VE teristics curvemotor is zero

e is nearly lineaximum possibue is pull-out

full load torqmotor is slighmotor will stower.

ristics Curve

ip varies as tof the inductispeed, then thine reverses.e direction of tp the motor vedirection. Sin

ation is simplyses. The act otor very rapid

and e is tor ger tor eld ent tor tor tor ion to to

s to

e is o at ear ble or

que htly tart

the ion the If the ery nce y a of

dly


866

is in

w

hapugecococlceanThcr

30LCLi

called pluggin an induction

Pconv = τindω

where,ωm is the

PWM MotorPWM is a m

as two signal pulse varies beenerated by uontroller consomparator. If leared and theertain value. Ind reset for thhis cycle wrossing[10].

PIC17C756 011 TRIAC DCD DisplayightResistor, C

ing. The powemotor is give

ωm

e angular velo

r Control method for biperiods (high

etween 0 and using the timestantly checks

the conditione timer will sIf it reaches ahe next cycle

will repeat by

V. CIR

MicrocontrolDriver, DIAC,y, RewritableCapacitor.

VI. CIR

VII. FL

er converted toen by (8)

city of the mo

inary signals and low).Thethe period,T.

er and the cos for zero cron is true the ostart. The tima predefined ve. The outputy waiting fo

RCUIT ELEMEN

ller, MAC223, Transformere Cartridge

RCUIT DIAGRA

LOW CHART

o mechanical

otor.

generation, we width, W of .A PWM sign

omparator [9].ssings througoutput pin wi

mer counts upvalue it is stot pin will alsoor the next

NTS 3A TRIAC, Mr, Rectifier Br

Fuse, Indi

AM

form

(8)

which f each nal is . The h the ill be

p to a opped o set.

zero

MOC ridge, icator

TA

F

T

VIII. HAR

IX. RESU

ABLE I:RESULT

Fig.4. Voltage vs s

TABLE II: RESUL

RDWARE VIEW

ULT

T AT NO-LOAD

speed at no-load

LT AT ON-LOAD

W


867

foditrarepeTo[8hamItscobycivacoM

X

In this paperor PWM adjuivided in thansformer and

ectified AC weak-peak. Theo test this mo

8]. The designave a pulse a

modules.TRIACs voltage dropontrolling its gy DIAC. DIAircuit [9]. In trary TRIAC gonnected in s

MT2 across dr

Fig. 5. Voltage

X. INPUT-

XI. r, microcontroustable speedhree modulesd rectifier. At

wave at 120 He next moduleodule MCU isnated output pat 120 Hz. MC has three tep across MT1gate voltage.

AC input is criggering circugate voltage eries with Mrop increases

vs speed at no-lo

OUTPUT WAV

CONCLUSIONS

oller PIC17C7d control. Ths. The firstt the end of thz at half of the is zero crosss needed withpin of the MCMOC and TRerminals (MT and MT2 caIn the circuitontrolled by uit there is a v

trough DIACotor input soMotor input

oad

VEFORM

S 756 has been he circuit cat module ishis stage therehe original vos detection cih program runCU is expectRIAC are the1, MT2 and G

an be controllet gate is contran R-C trigg

variable ResistC. As TRIA, if TRIAC Mvoltage decr

used an be the e is a oltage ircuit. nning ted to e last Gate). ed by rolled gering tor to

AC is MT1- reases

and voltaRPMRPMsoftwimplresuprob

Mthe musinusincontobtacont

[1]

[2]

[3]

[4]

[5]

[6]

[7][8]

[9]

[10]

if TRIAC MTage increases

M reaches at M reaches at raware has beenlementation alt. The prop

blems on speed

Mathematical mmotor speed g MATLAB g controller troller, etc. Hained by usingtroller also can

S. J. Chapman,2005, pp. 381-38V. K. Mehta and2007, pp. 637-63I. M. Gottlieb, EHill, February 1,I. M. Gottlieb, P8, 1997. F. B. Crocker anand application,NB. P. Lathi,ModOxford Universihttp://en.wikipedJ. A. HouldswoControl System fand ications, VolD.A.Grant, J.A.HAC drive,” IEEEJ.E.Gilliam, J.AMotor with InteAPEC,pp. 92-96

T1-MT2 acros. When the m65V only. Wated value gran used to evaland program tposed systemd control and

XII. FUT

model can beresponse. Froimproved mopackage e.g. Higher voltagg IGBT. Fullyn be designed

REFERE

, Electric Machi85. d R. Mehta, Objec38. Electric Motors , 1994.

Practical Electric

nd M. Arendt, ENew York, D. Vadern Digital andty Press, 2007, pp

dia.org/wiki/Dutyorth and W.B. Rfor Three Phase l.2, No.2, FebruarHouldsworth, K.NE Transactions, V.Houldsworth, Legral Ultrasonic ,1988.

R. Khan receivEngineering fro(IUT) in 2010.institute of ReDhaka. CurrenElectrical and EGreen Universinterests includand renewable e

M. M. S. RiyElectronic EngTechnology (ITechnologies he is servingElectronic Enof InformationHis research biomedical im

ss drop decreamotor runs a

When the motoadually.Electrouate the resulthe two appro

m can avoidmechanical sp

TURE WORKS e obtained froom the mathe

otor speed canPID controll

ge and powey automatic Pfor better reli

ENCES inery Fundamen

ctive Electrical T

and Control Tec

c Motor Handboo

Electric motors, tan Nostrand Comd Analog Commp. 260-263.

y_cycle. Rosink, Introduct

AC motors, Elecry 1980. N.Lower, “A new

Vol. IA-19, No 2, L.Hadley, “Variab

PWM Inverter,”

ved B.Sc in Electom Islamic Unive He is student oenewable Energytly, He is worki

Electronic Enginesity of Banglad

de power systemsenergy.

yadhreceived B.Sgineering from IsIUT) in 2010. He(BD) Ltd. as a B

g as a Lecturerngineering departn Technology aninterests include

maging, LTE techn

ases motor inpt no-load, rator runs at loaonic Workbenlts. By hardwaoaches the samd non linearpeed variation

om the graph ematical mod

n be obtained ler, fuzzy loger can also LC based speiability.

ntals, McGraw-H

Technology, S.Cha

chniques, McGra

ok, Newnes, Octo

their action, contmpany. munication Syste

ion to PWM Spctronic Compone

w high-quality PW1983.

ble Speed Induct” IEEE Conferen

trical and Electroersity of Technoloof M.Sc Eng. In y of University ing as a lecturereering departmendesh. His reseas, power electron

Sc in Electrical aslamic Universitye worked at HuawBSS Engineer. Nor in Electrical atment of Universnd Sciences (UITe power electronnology.

put ted ad,

nch are me rity n.

of del, by gic be

eed

Hill,

and,

aw-

ober

trol

ems,

eed ents

WM

tion nce,

onic ogy the of

r in t of

arch nics

and y of wei ow, and sity

TS). nics,


868

Documents

PWM Speed Control of ACSingle Phase Induction Motor Using