Control Limits of Three-Phase AC Voltage Controller under Induction Motor Load A. I. Alolah Ali M. Eltamaly R. M. Hamouda

Size: px

Start display at page:

Download "Control Limits of Three-Phase AC Voltage Controller under Induction Motor Load A. I. Alolah Ali M. Eltamaly R. M. Hamouda"

Joella Bradford
6 years ago
Views:

1 Contol Liits of Thee-Phase AC Voltage Contolle unde Induction Moto Load A. I. Alolah Ali M. Eltaaly R. M. Haouda Abstact Thyistos ae now widely used in any powe electonics and otos dives applications. This is due to thei seveal advantages such as elatively sall size, low losses, aket availability, and low cost. In this pape, a stato voltage contol of thee-phase induction oto by using thyistos is analyzed and siulated in details. The stato voltage has been contolled by phase angle contol of thee-phase supply. The effect of haonic distotion in the line voltage and cuent have been studied and shown. The study eveals that, this ethod is suitable fo applications equiing a low toque and low speeds. The powe facto, efficiency and toque capability of the oto dop daatically fo lowe voltages. Fiing equieents and liits of contol have also been studied. Recent PSIM6. poga has been used to siulate the whole syste. The siulation esults fo PSIM6. have been found in coelation with thei countepat fo MATLAB 7. Index Tes Voltage contolle, induction oto, speed contol. I. INTRODUCTION: In the last decades, the poduction of powe electonics switches has been plentiful and divese. Soe of these switches ae thyistos, GTO's, bibopla powe tansistos, MOSFET's, IGBT's and MCT's [,]. Even with these devices, the basic thyisto still constitutes a obust, siple and econoical devices, that has any applications. Thyistos ae widely used fo contol of powe in both AC and DC systes. This is due to thei seveal advantages such as elatively sall size, low losses and fast switching. Apat fo any othe uses, such a contolle is used to contol the thee-phase AC powe in induction heating, light contol, eactive powe contol and stating as well as speed contol of AC otos. Thee phase AC voltage contolle has been used with R-L load [,] fo vaious cicuit configuations. This technique can be odified to be used with induction oto by educing the equivalent cicuit of induction oto to be just R and L [3]. Thee-phase AC voltage contolle used with thee-phase induction oto is shown in Fig.. The Authos ae with Electical Eng. Dept., College of Eng., King Saud Univesity, P.O.Box 8, Riyadh 4, Saudi Aabia. Using of Thee phase AC voltage contol in speed contol of induction oto has disadvantages such as low efficiency due to exta the oto coppe losses. Although it has these disadvantages, but geneally, this schee has soe advantages on othe aspects, including low cost in installation, ease to aintain and eliable which ake this schee popula option in industy. This schee has been used in any industial applications as in dive an ovehea taveling cane, an elevato speed contol syste [5], and stating and stopping eans fo induction oto [4-7]. In efeence [4] a signal fo the oto voltage and cuent ae used to contol the speed and toque espectively. But the ain disadvantage of this technique is not applicable fo squiel cage induction oto, oeove the contol of cuent without any efeence to the powe facto leads to a athe nonlinea toque/speed chaacteistic. In efeence [5] a tachoete geneato connected to thee-phase squiel-cage induction oto to geneate a speed signal epesenting the actual speed of the induction oto to copae it with coand speed signal to poduce a suitable fiing signal. In efeence [6] and [7] the thee phase AC contolle with cycle skipping ethod to contol, stat, and stop the thee-phase induction oto. II. SYSTEM MODELING Many eseaches analyzed the thee-phase AC contolle unde induction oto load to obtain atheatical and pogaable fo fo the vaiation of toque, speed and line cuents along with fiing angle. A detailed analysis fo induction achine by using efeence fae theoy has been caied out in [8,9] to obtain the vaiation of the toque and cuents with the vaiation of input voltage. This technique has been used fo single fequency balance thee-phase supply but it can be extended to deal with vaiable fequency, unbalanced thee-phase supply. This technique does not deal with the vaiation of the oto pefoance as the haonic distotion in phase voltages. In this eseach odeling of induction oto has been caied out by educing its equivalent cicuit to be R-L load. Then, MATLAB poga has been used to obtain all pefoance paaetes in tes of its fiing angle. A oden copute siulation poga (PSIM6.[]) has been used to validate the MATLAB siulation esults.

2 Table() Modes of opeations of the contol systes. Mode Liits / α Φ π / 3 / Φ π / 3 α Φ Φ α Φ + π / 3 /3/ Φ + π / 3 α π / 3 / π / 3 α 7π / 6 Fig. Thee-phase AC voltage contolle unde induction oto load. V R s X s I s I X E X I R /s Whee: α : is the fiing angle. Φ : The oto powe facto angle o, the phase angle of the ipedance (i.e. is the phase-angle diffeence between the phase voltage and the phase cuent). Φ : Angle of the input cuent of the oto unde sinusoidal supply cuent (i.e. it is coesponding to the tie between a voltage zeo cossing and the instant at which the cuent fundaental coponent fist eaches zeo following voltage zeo cossing.). Fig. Equivalent cicuit of thee-phase induction oto. A. R-L Modeling The siplified equivalent cicuit of an induction oto is as shown in Fig.. The total ipedance can be expess as shown in (). This equation can be educed to be just R and L eleents in tes of slip as shown in () and (3) espectively. Z = Z s Z + Z * Z + Z ( X * R ) R / () Rs + R = * () s X + X X / R ( ) R * X L = X s + + X X X + X (3) s X + X Once the total ipedance of the syste is found, it could be epesented by a thee-phase contol cicuit as shown in Fig.3. Afte that the analysis shown in [,3] has been used to deteine the supply cuent and all othe pefoance paaetes in the induction oto by using MATLAB copute poga. The analysis and opeations of the thee phase voltage contolle unde induction oto load depends on the elative values of fiing and phase angles. These diffeent values will ake the syste woks in diffeent odes of opeations, naely, ode, ode / o ode / []. Fig.4 shows the theephase supply cuent fo diffeent odes of opeations. Fo intensive siulation esults, the fiing angle anges fo the thee odes of opeation have been obtained and suaized as shown in Table(). It is clea that the ode has nea sinusoidal cuent wavefo. Fig.3 Induction oto epesented as R-L load. Fig.4 Thee-phase cuents fo diffeent odes of opeations. B. PSIM Copute Siulation The siulation of thee-phase phase angle contolle unde thee-phase induction oto load has been caied out by using PSIM6. copute poga. Intensive siulation has been caied out fo diffeent odes of opeations to deteine the opeating liits of this syste. The naeplate oto data used in this siulation is shown below: kw, /38 V, sta connection, 3.A, 4 poles, 8p, 6 Hz, Rs =. 583 pu, R =. 47 pu, X =.5 pu, X =. 8 pu, and X =. 5 pu. s

3 III. SIMULATION RESULTS The siulation has been caied out unde two cases of opeations. The fist case is constant toque vaiable fiing angle (see Fig.5 to Fig.) while the second case is constant fiing angle vaiable speed (see Fig. to Fig.6). ) Case : The vaiation of peak value of phase voltage with fiing angle fo diffeent values of toque is shown in Fig.5. It is clea that the phase voltage is appoxiately linea only in the egion of ode whee the phase voltage invesely popotional to the fiing angle fo all values of toque. The vaiation of speed with fiing angle fo diffeent values of toque is shown in Fig.6. This cuve eveals that the speed invesely popotional to the fiing angle fo ode and diectly popotional in any othe ode of opeations. So, the speed contol syste has to identify the ode of opeation to send a coect value of fiing angle to switches othewise the syste will get out of contol. The vaiation of powe facto with fiing angle fo diffeent values of toque is shown in Fig.7. It is clea that the powe facto invesely popotional to fiing angle in no load fo all odes of opeations. But, at high loads the powe facto invesely popotional to the fiing angle only in ode and diectly popotional in any othe ode of opeations. The vaiation of powe facto angle ( Φ ) with fiing angle fo diffeent values of toque is shown in Fig.8. It is clea that the liits shown in Table() agee with the cuves shown in this figue. The vaiation of THD with fiing angle fo diffeent values of toque is shown in Fig.9. It is clea that the THD is low and diect popotional to fiing angle only in ode. In any othe ode of opeation except the egions nea to ode the THD is vey high due to the distotion in line cuents. The high THD in line cuents educes the efficiency of the oto due to ion and coppe losses associated with the cuent haonics coponents as shown in Fig.. Phase Voltage in (PU) T=no-load T=.5 PU T= PU T= / / T=.5PU / T=. PU / Fig.5 Phase voltage vaiation fo diffeent values of toque. Speed in (PU) T=.5 PU T=. PU T= / / T=.5PU / T=. PU / Fig.6 Speed vaiation fo diffeent values of toque. Powe Facto T=.5 PU T=. PU T= / / T=.5N. / T=5N. / Fig.7 Powe facto vaiation fo diffeent values of toque. fai Φ in (Degees) No-Load T=.5N. T=.5 PU T=5N. T=. PU α, (Degees) T= / / T=.5N. / T=5N. / Fig.8 Powe facto angle, Φ fo diffeent values of toque.

4 8 T=.5 PU T=. PU The vaiation of powe facto with speed fo diffeent values of fiing angle is shown in Fig.3. The powe facto diectly popotional to speed at low speed and invesely popotional to speed nea to synchonous speed. THD T= / / T=.5N. / T=5N. / Fig.9 The THD vaiation fo diffeent values of toque. Moto Effeciency (%) T=.5 pu T=. pu The vaiation of powe facto angle ( Φ ) with speed fo diffeent values of fiing angle is shown in Fig.4. The powe facto angle invesely popotional to speed at low speed and diectly popotional to speed nea to synchonous speed. The vaiation of THD with speed fo diffeent values of fiing angle is shown in Fig.5. The THD diectly popotional to speed at low speed and invesely popotional to speed nea to synchonous speed. The vaiation of efficiency with speed fo diffeent values of fiing angle is shown in Fig.6. It is clea that the efficiency is appoxiately sae in each oto speed fo diffeent fiing angle. Phase Voltage in (PU) α=9 α=7 α= T=.5N. / T=5N. / Fig. The oto efficiency fo diffeent values of toque. ) Case : In this case, thee diffeent values of fiing angle have been used. These values ae 9 o, 7 o o and 5 espectively. The speed has been used as independent vaiable and changed fo.5 pu to pu. The vaiation of peak value of phase voltage with speed fo diffeent values of fiing angle is shown in Fig.. It is clea that the oto woks ainly in the ode fo any fiing angle except nea to synchonous speed it goes to ode /. Phase voltage is invesely popotional to speed at low speed and is diectly popotional to speed nea to synchonous speed. The vaiation of toque with speed fo diffeent values of fiing angle is shown in Fig.. The oto toque diectly popotional to speed at low speed and invesely popotional to speed nea to synchonous speed. α=5 o α=7 o α=9 o Toque in (PU) α=5 o α=7 o α=9 o Fig. Phase voltage fo diffeent values of fiing angle / α=9 α=7 α=5 Fig. The oto toque fo diffeent values of fiing angle. /

5 Powe Facto α=5 o α=7 o α=9 o α=9 α=7 α=5 Fig.3 Powe facto vaiation fo diffeent values of fiing angle. F in (Degees) Φ α=5 o α=7 o α=9 o α=9 α=7 α=5 Fig.4 The powe facto angle ( Φ ) vaiation fo diffeent values of fiing angle. THD α=5 o α=7 o α=9 o α=9 α=7 α= Speed, (p) PU Fig.5 The THD vaiation fo diffeent values of fiing angle. / / / Moto Effeciency (%) α=5 o α=7 o α=9 o α=9 α=7 α=5 Fig.6 The oto efficiency fo diffeent values of fiing angle. IV. CONCLUSIONS This pape pesents a odeling and siulation of theephase AC voltage contolle unde thee-phase induction oto load. The siulation esults fo PSIM6. have been found in coelation with thei countepat fo MATLAB 7. The speed contol of the induction oto is achieved by contolling the fiing angle. The elation between the speed of the oto and the fiing angle depends on the ode of opeation. So, the speed contol syste has to identify the ode of opeation to send a coect value of fiing angle to switches othewise the syste will get out of contol. Efficiency and THD of the syste depends on the ode of opeation of the syste whee thei values ae good aound ode. So, it is ecoended to foce the oto to wok in this ode of opeation and avoid othes. The contol liits of this syste exist ove a wide ange of delay angle in light loads and visa vesa. Siulation esults pesented in this pape deonstate the siplicity of this technique. REFERENCES [] Shephed, W. "Thyisto Contol of AC Cicuits", Book, Lockwood staples Ltd, st ed. England, 975. [] Dubey, G. K., Doadla, S. R., Hoshi, A. and Sinha, R. M., "Thyistoized Powe Contolles", Book, John Wiley & Sons, India, 986. [3] Haed, S. and Chales, B., " Analysis of vaiable-voltage thyisto contolled induction otos" IEE Poc., Vol. 37(3), Pt. B, pp , May 99. [4] Motes et. al. "Contol syste fo egulating the speed of an electic oto" U.S. Patent , June 978. [5] Kaaike, H. "Elevato speed contol syste" U.S. Patent 4565, Oct [6] Rowan, T. M., Meison, J. C. "Electic oto speed contol appaatus and Method" U.S. Patent , Feb. 99. [7] Delange, R. J. " Electic oto contol appaatus and Method" U.S. Patent 58749, Feb [8] Lipo, T. A., Multiple efeence faes applied to ipedance unbalances of induction achiney-the open cicuited stato phase, IEEE Conf. on Systes, Netwoks and Coputes, Ocztepec, Mexico, 97, pp [9] Lipo, T.A., The Analysis of Induction Motos with Voltage Contol by Syetically Tiggeed Thyistos, IEEE Tans. Powe Appaatus and Systes, vol. PAS-9, no., 97, pp [] PSIM6., available: /

Analyze Power Supply Rejection Ratio of LDO Regulator Based on Accurate Small Signal Model

Analyze Power Supply Rejection Ratio of LDO Regulator Based on Accurate Small Signal Model Poceedings of the Intenational Confeence on Electonics and Softwae Science, Takaatsu, Japan, 05 Analyze Powe Supply ejection atio of LDO egulato Based on Accuate Sall Signal Model Po-Yu Kuo*, Gang-Zhi