pwm speed control of acsingle phase induction motor using
TRANSCRIPT
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
International Journal of Computer and Electrical Engineering, Vol. 3, No. 6, December 2011
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
International Journal of Computer and Electrical Engineering, Vol. 3, No. 6, December 2011
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,
International Journal of Computer and Electrical Engineering, Vol. 3, No. 6, December 2011
868