IJSER. =η (3) = 1 INTRODUCTION DESCRIPTION OF THE DRIVE

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1 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April Low Cost Speed Sensor less PWM Inverter Fed Intion Motor Drive C.Saravanan 1, Dr.M.A.Panneerselvam Sr.Assistant Professor 1, Professor Research Scholar 1, JNTUH 1, Hyderabad, Tagore Engineering College 1,, Chennai Abstract An analysis of the PWM inverter intion motor drive with speed sensor less control is controlled by DC link crrent is presented in the paper. The first part of the paper is devoted to the verification of dynamic possibilities of the proposed concept of the control by means of simlation. The second part of the paper is devoted to the optimization of steady state performance. At the end the ret achieved on the prototype model for 1.5Kw were presented. INTRODUCTION The application of microprocessors is easy to control in intion motor drives. However, in practice simple, cheap and reliable drives are often needed, where it is possible to control the speed, with more modest reqests regarding dynamic featres. A significant step in the direction of realization of sch a drive is the acceptance of the control concept with as small nmber of sensors, as possible, and primarily withot speed sensor. The main goal of this paper is to describe the implementation of low cost speed-sensor less intion motor drive, based on the simple idea, the speed drop compensation in fnction of load, i.e. the dq axis link motor crrent. In order to increase speed of calclation of speed corrections, the lookp table stored in EPROM was sed. This drive was made and tested in Tagore Engineering College, Department of Electrical and Electronics Engineering, Chennai. DESCRIPTION OF THE DRIVE (Wref'=Wr) and the ip freqency (W). The necessary ip freqency vale is obtained from the ip freqency table, according to the reference speed and motor crrent. The information on the motor crrent vale is obtained by means of link crrent vale. In this way only one (previoy mentioned) crrent sensor was sed in the presented drive. In deriving the necessary analytical relations we mst start from the v/f characteristics which is defined in advance and bilt in the "table of voltage", and which is sed in the calclation procedre of the transistor leading time in the inverter. Sch an approach enables a simple adjstment of mechanical motor characteristics to the nee of loading, for example, the increase of the initial moment in the traction application. There from it follows: s ( ω r, ω ) = f ( ωe ) = f ( ωr + ω ) (1) where s is the effective vale of the stator voltage. In or case relation (1) is: s ω e = 1 ωe 1 ωe 1 () Figre.11 presents the block diagram of the drive, where from we can see the basic idea of the applied manner of speed reglation. The system displayed consists of two basic parts, power part - freqency converter and control circit system. Freqency converter consists of diode rectifier, DC link with LC filter, and three phase bridge connected IGBT inverter. The over crrent protection of transistors in the inverter reqires fast and precise measrement of DC crrent. In the DC circit there is a block for dynamic brake, consisting of the resistor and the braking transistor. The algorithm applied in the control circit system is based on the simple idea that in the fnction of motor load the increase of stator freqency for ip freqencies is made. As shown in Figre 1, the spply freqency (We) is calclated as a sm of the reference speed freqency On the basis of known relations [6] in per nit, it can be written (. i + i ). i c qs qs. 3 =η (3) Where iqs, i and qs are the crrent and the voltage of the motor in q and d-axes, of synchronos reference frame, and h c is inverter efficiency. From (3) we get 3 η ( i. i ) c i = qs. qs + If at time t=0 q axis and phase A aligned, the (4)

2 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April ( )(. Bf ) qs = K m e 1+ ω (5) ( ωe ) Bf d K m. = (6) Where Km (ῳe) is the modlation index of PWM inverter which is the fnction of basic freqency, i.e. ῳe in or case defined on the basis of (), Bf q and Bfq corresponding to qd transformation of the harmonic terms. Upon the sbstittion of (5) and (6) into (4) it becomes i ( )( i ( 1+ Bf ) i Bf ) 3 = K ω. 4 η (7) c m e qs q + Expression (7) shows that the mean vale of link crrent fnction is the q component of the machine crrent, i.e. the active Components of this crrent. From the machine theory it is known that ( ω ) ω = ω (8) r,i qs Spposing the sccessflly realized speed reglation we have ῳref =ῳr that sbstitting (7) into (8) we get q d (,i ωref ) ω = ω (9) Figre 1 Block diagram of whole system On the basis of fnction (9) it is clear that depending on the mean vale of link crrent, for a desired speed, we can determine the needed ip freqency, i.e. the basic freqency of the inverter. Relations derived (7, 8, 9) are very complex and depend on varios magnitdes and parameters, losses in inverter, carrier-freqency, dead time, motor losses and satration, change of motor parameters with freqency [7].Therefore, dependence (9) cannot be directly implemented into the control algorithm, bt on the basis of it the table can be formed which wold be written in into the EPROM, and Where from the processor wold read ot the Necessary vales the control sbsystem, presented in Figre 1, is realized by means of ATMAL'S 16-th bit processor 89C5. Apart from ip freqency table, there are two soft starts, limiting the dynamics of the change of the desired speed, i.e. freqency, by their adjstment dynamical processes can be optimized. The overload protection block has higher priority and in the case when the crrent excee the permitted vale it decreases the freqency, and thereby the speed ntil the load is reed. This is particlarly sitable for drive with the load torqe directly depending on of the speed with inverters, in order to get the corresponding voltage and the freqency at the otpt, a sinsoidal PWM method is applied with the impressed third harmonic into the phase voltage. Since the inverter works at high freqencies of Commtation, for faster calclation three more lookp tables, voltage table, sin table and phase table are sed: all of them are calclated and introed into EPROM The remaining indispensable hardware consists of the interface ensring the division of the signal for positive and negative bridge branch and the ato protective drivers realizing a reglar and reliable switching in and switching ot of transistors. This part of the system nites the protection from excessive instant over crrent vale. Also, the dead time is generated on drivers, which considerably simplified the control algorithm. Low pass filter in the. Crrent feedback has two significant fnctions. Primarily, it eliminates higher harmonics - the conseqence of the inverter operation, thereby enabling the measrement of the mean vale only of this crrent. Second, it enables stable operation of the drive even at higher resoltion of crrent vales for ip freqency table, which will be dealt with later The presented algorithm in this paper has some shortcomings. The static control speed error is depending on three factors, the nmbers of rows and colmns in the ip freqency table, and the based inverter freqency resoltion. Those parameters are of great significance for the drive dynamic behavior, too. In this case the nmber of rows in the ip freqency table is depending on the desired reference speed resoltion. In practice this nmber of rows is final. Bt the nmber of colmns in the ip freqency table, and the based inverter freqency resoltion is a very important parameter of the drive. These two resoltions affect the dynamical properties of

3 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April the drive. In order to research this qestion the mathematical model of the system was made, where the respective tests were made, which will be the topic of the next part of the paper. Also, the isse of the filling in of ip freqency table is to be stressed, becase for obtaining these data with indispensable accracy, it is necessary to know the vales of all parameters of the motor, inclding their change in the regimes nder consideration. This isse will be dealt with in detail. MATHEMATICAL MODEL The analysis of the system behavior dring dynamic regimes was made by means of compter simlation. The synchronoy rotating frame motor model with constant parameters was sed. The inverter model was a simplified nit power factor (qc=l) and only the based harmonics of the voltage were taken into consideration. Upon these simplifications from eqations (5, 6 and 7) it follows ( ω ) qs = Km e = 0 (10) = 3 m( e ). i qs 4 η K ω c (11) i The block diagram of mathematical model is shown in figre Figre Mathematical model of drive The vales for ip freqency table are calclated for the range of the desired speed and crrent i from 0.1 to p.. with the increment of 0.1 p.. The vales for ip freqencies are calclated by sing the system of eqations, obtained when (10 and 11) are sbstitted in the model of intion motor. Then, in accordance with (9), independent variables were Wref and i. link crrent has the minimal vale dring d e no load operation. The maximal link crrent vales nder which the stable operations are possible are the vales in the regime when the desired speed is eqal to the breakdown speed. In the table for the given vales of the crrent smaller than the mentioned minimal vales, the zeros were written, while for the vales greater than the maximal, the vale of the breakdown ip freqency is written. The basic freqency of the inverter in the model is changed in the range from 0.1 to p.. with the increase of 0.1 p.. which is correspon to the readjstment of the laboratory model. The simlation rets obtained show that the drive has satisfactory dynamic possibilities with a modest resoltion in the ip freqency table, and based inverter freqency, when the low pass filter (LPF) in crrent feedback is sed. To come to this conclsion it is possible by compare Figres 3 and 4.

4 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April As mentioned, the ip freqency table mst be formed with great attention, the qality of system operation is depending on these vales, and therefore a special procedre for it was developed. The table can be filled in by simple measring bt thogh we have shown that the nmber of necessary data can be partially reed, the nmber of measrements is high. In practice the carrying of these measrements is often impossible. In the previos part of the paper, the manner of calclating the data for the table was explained, for the case of constant parameters, however, if we wish to take into accont the variation of some important parameters the definite additional dependences mst be known. The paper analyses and applies the method of calclation based on the minimal nmber of measrements namely, it is necessary to carry ot two measrements each in characteristic freqencies, at the drive in the steady state operation, with as big as possible difference in loading. Figre 3 Dynamic responses withot LPF This difference affects essentially the accracy of the rets obtained. In the mentioned measrements the speed, freqency, phase and crrent shold be measred, and the ratio of the voltage and the freqency mst be according to the adopted relation (1). On the basis of these measrements the parameters of eqivalent circit cold be determined, where the stator resistance (it mst be separately measred) and the leakage intances were constant, and the resistance (R r), mtal intance (M) and core-loss resistance (Rp),are fnctions of the stator freqency. These fnctions are interpolated between the vales obtained by measrements. The data obtained are athentic becase they are measred in the drive, bt they are valid for v/f dependence where the measrements are made. On the basis of the data obtained, and mentioned parameter fnctions vs freqency, the arbitrary nmber of the vales necessary for filling in ip freqency table cold be calclated. EXPERIMENTAL RESULTS Figre 4 Dynamic response of LPF In Figre 6 the inflence of speed control dring load change is shown. Figre 7 represents the motor speed change when the reference speed is changed. SLIP FREQUENCY TABLE The experimental rets of the proposed speed controller are shown in following figres. The tested drive model has the spply freqency range between 10% and 00%, with 1% resoltion, there are 11 colmns, i.e. 11 crrent vales in range between no load and limited crrent (15% rated crrent) in the ip freqency table. The overload protection is activated on 15% rated load. The dynamic performance of the drive after reference speed change is illstrated by the waveforms

5 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April shown in Figres 5 and 6. In Figres 7 and 8 the inflence of speed control dring load change is shown. In figre 9 the hardware photo shown. Figre 8 Load Changes with w ref = 0.6p CONCLUSION Figre 5 Dynamic Performance of drive with speed reference A low cost speed sensor less drive is easily controlled general prpose intion motor drive with PWM inverter is developed. The rets of the performed theoretical and the experimental investigations have confirmed the expected effectiveness of the proposed algorithm for speed control, based on a single measrement of dq axis link crrent. The Presented control concept is convenient for complicated drives, bt with modest dynamic performances. In frther work we will verify the control algorithm on drives of different Figre 6 Speed change at No Load powers with forward and reverse operation. We will Endeavor to extend the range of reglation to the braking systems, in the case nder consideration the brakes were of short dration, only at the retion of speed, dring the speed which was not nder a direct control, bt only pon the end of this systems. Figre 7 Speed Change nder Load DRIVE DATA Motor: 1.5 kw; Speed : 1440RPM; Load Crrent: 3. A. Inverter: V=510 V; Inpt/otpt: 3phase 400V; 50 Hz

6 International Jornal of Scientific & Engineering Research, Volme 5, Isse 4, April REFERENCES Figre 9 Hardware Photo [1] W.Leonhard, "Adjstable-Speed AC Drives", Proc. Of the IEEE, Vo1.76,no.4, pp , April [] Electric motor drives modeling, analysis and control by R.Krishnan [3] U.Baader,M.Depenbrock,G.Gierse "Direct Self Control of Inverter- Fed Intion Machine, a Basis for Speed Control withot Speed- Measrement", IEEE IA Annal meeting, Annal Meeting, S.Diego, pp , October 1989 [4] M.A.Chodhry, M.A.Rahman, "Determination of Operating Conditions of Sbmersible Intion Motors"' IEEE Trans. on IA, Vo1.8, No.3, pp , May/Jne 199. [5] B.K.Bose, "Power Electronics and AC Drives" Prentice-Hall, New Jersey1986, pp [6] D.S. Coming and O.G. Staadt, "Velocity-Aligned Discrete Oriented Polytopes for Dynamic Collision Detection," IEEE Trans. Visalization and Compter Graphics, vol. 14, no. 1, pp. 1-1, Jan/Feb 008, doi: /tvcg (IEEE Transactions ) [7] D. W.Novotny,S. A.Nasar, B.I. JefieniC, D.Maly, "Freqency Dependence of Time Harmonic Losses in Intion Machines", Proc. ICEM 90, Boston, Jly 1990.