Design of a Microcontroller Based Automatic Voltage Stabilizer with Toroidal Transformer

Transcription

1 Design of a Microcontroller Based utoatic Voltage Stabilizer with Toroidal Transforer Thet Htun ung Departent of Electrical Power Engineering Mandalay Technological University Myanar bstract- Every electrical and electronic appliance is designed to work perfectly at a certain input voltage. In Myanar, household electrical and electronic appliances are designed to work properly at 220VC, 50Hz and ost of the ties the voltage supplied fro distribution copanies are as low as 130VC aking this appliances to work under threat of low voltage supply. This low supply voltage causes these appliances to alfunction and in ost cases daage the. Since the electric power supply/distribution copanies are unable to provide the consistent adequate voltage level (220VC) deanded by these sensitive appliances, therefore there is need for consuers to protect the appliances fro daage and ensure their safe operation, hence the use of autoatic voltage stabilizers to iprove the situation. In this research work, a PIC16F877 icrocontroller was prograed to onitor the input voltage fro distribution copanies and if voltage level is between 130 VC and 250VC, it gives a constant output voltage of nearly 220VC required by the appliance. The odel paraeter calculated fro the design inforation. Keywords Myanar, Household Electrical, Stabilizer, Input nd Output Voltage, Electric Power Supply, Distribution, Microcontroller. I. INTRODUCTION The developent of any country is largely hinged on the availability of undisturbed and regulated power supply. In Myanar, electricity is generated by turbine driven synchronous generators at 50Hz at a standard iniu voltage of 11kV. The generated voltage is then stepped up to the priary or secondary Grid voltage of 132kV to reduce power losses during transission. The generated power then travels fro the generating stations to the point of utilization via high voltage Transission lines, ost of which are suspended overhead. However due to the uneven power deand at the load end and the coplexity of the consuer network, a third party is required to ensure that the generated electricity is properly distributed according to the load deand, while taking into consideration the necessary geographic and econoic factors as they affect the overall socioeconoic growth of the nation. In Distribution, electrical power is stepped down at distribution sub-stations of various levels to a final voltage of 400 V (phase to phase) and 230V (phase to neutral) which is directly consued by ost electrical load. Voltage is the ost iportant paraeter in electrical power [1] syste and it is necessary to be aintained a constant output voltage because, it is the driving force that pushes current through the conductor. Voltage stability is vital for safety and optial perforance of electrical appliances. Most electrical appliances are designed for optial operation, axiu length of service and safety if the power rating of the appliance is aintained. The autoatic voltage stabilizer presented in this research ai at designing a suitable utoatic Voltage Stabilizer rated 15 kv with output 220 VC, when the input voltage is varying between 130 VC and 250 VC. II. MTHEMTICL EQUTIONS OF TOROIDL TRNSFORMER The rating of the servo otor autoatic voltage stabilizer is ainly depended on the transforer rating. The circuit diagra of the servo otor autoatic voltage stabilizer including variable autotransforer. The siplest device for regulating the voltage applied to a load is the variable auto-transforer. One of the best known types is the Variac. The core consists of a deep stack of ring-shaped lainations. The insulation is reoved fro a circular track around the upper horizontal face of the winding and a carbon brush carried on a rotating ar akes contact with any desired turn on the winding. For the input fluctuation 40%, +10% toroidal transforer ust be withstand the variation of the axiu input voltage is 242 V 250 V and the iniu input voltage is 132 V 130 V. The output voltage ust be nearly 220 V. Variable transforer type of this VS is toroidal transforer. The capacity of autoatic voltage stabilizer is 15 kv (single-phase). The output voltage regulation is ±5%.. Design Equation Equations such as e..f. equation, e..f. per turn in ters of output and output equation are needed to design 187

2 of the agnetic circuit (ain diensions of core, yoke and window). B. E.M.F. Equation When the alternating voltage is applied across the priary of the transforer, it takes a agnetizing current and a flux; φ is established in the transforer core. The flux, φ is uniforly distributed over the transforer core section and is linked with all the turns of priary and secondary windings. The ain flux, φ established in the core is alternating in nature. Hence an e..f. is induced in the priary winding, due to the change of ain flux, which is given by, e 1 = N 1 (1) φ φ cosω t (2) N d (φ cosω t) 1 e 1 = = N 1 ω φ sin ω t dt E 1 = 4.44 f N 1 φ volts (3) E 1 = 4.44 f N 1 B i (where φ = B i ) (4) Induced e..f. in secondary winding, E 2 = 4.44 f N 2 B i volts (5) e..f. per turn, = 4.44 f B i (6) For E.M.F per Turn, = 4.44 f φ (7) K.V. rating per phase, V = V I 10-3 = IN 10-3 N = IN 10-3 (8) The ratio of cross-sectional area of the core and the copper area of the windings will be constant for a particular transforer i.e. i = constant (9) c Cross sectional area of core, i = φ or (10) B P i = sq in (11) 5.58 Copper area of the windings, c = a N = δ I i = c IN N δ B s current density, δ and flux density, B is nearly constant, IN = constant = r (12) Substituting for IN fro Equation 12 into Equation 8, kv = Et 10-3 (or) phase r φ = kv ( ) r phase 10 3 (13) Substituting for φ fro Equation 13 into Equation 7, = 4.44 f 2 kv ( ) r phase = (4.44 f r 10 3 ) e..f. per turn, 4.44 B Nef = 8 10 = K (kv/phase) i kv phase 10 3 volt (14) 3 Where K = 4.44 f r 10 (15) In order to utilize equation 12, for finding out the e..f. per turn, the value of the factor, K is needed. nd then, the turns per volt will be got. Turns per volt, N e = B f i (16) C. Factor K Factor, K which basically depends upon the ratio of cross sectional area of core to the copper section of the windings, will be different for two types of transforers i.e. core and shell. The value of factor K with respect to transforer type is shown in Table I. TBLE I. CONSTNT K WITH RESPECT TO TRNSFORMER TYPE Type K ( Factor) (1) Single phase core (2) Single phase shell (3) Three phase core (power) (4) Three phase core (distribution) (5) Three phase shell D. Stacking Factor To get the required core section, the transforer core is prepared by stacking together thin sheets of lainations. These lainations are insulated on both sides usually by spray of varnish. That, the assebled core includes the area of insulation as well. The gross core section gi, is related with the net core section, i, by a factor K s called stacking factor. Thus, i = K s gi (17) K s = stacking factor, usually value is 0.85 ~

3 E. Flux Density (B ) The voltage equation as well as output equation indicates that the higher value of flux density B is chosen, the core area i reduces. This will reduce the diaeter of circucircle thereby reducing the length of ean turn. The choice of B will also depends upon the type, service conditions of the transforer. It has already been pointed out that a distribution transforer should be designed for lower iron losses giving good all-day efficiency. Therefore, for distribution transforer coparatively lower flux density is assued. Using hot rolled silicon steel Power transforers to 1.4 Tesla Distribution transforers to 1.3 Tesla Using cold rolled grain oriented silicon steel Power transforers to 1.7 Tesla Distribution transforers to 1.5 Tesla Lower values should be used for sall rating transforers. III. CLCULTION OF TOROIDL TRNSFORMER ccording to Equation 1 to Equation 17, 15 kv rating of the variable transforer is designed in this research. Core Design of Toroidal Transforer Cross section area of iron core, = = in 2 = c 2 ssue stacking factor (k s ) = Net-cross sectional area of iron core, = 0.9 = c 2 For cold rolled grained oriented silicon steel, Flux density, B = 1.4~1.5 Wb/ 2 ssue flux density, B = 1.4 Wb/ 2 Turns per volt, t K = 0.8, = = Turns per volt, N e = = 0.5 turns/volt Since the for of the toroidal type transforer is a circular ring, the circuference condition, the inner diaeter, the outer diaeter, height of the core and the width place take by the winding will be considered first. Width of the ring face, = = c The ratio of the B/ ust have 1.5~2 ties. In 15 kv autotransforer design, if = 9 c, the height of the core, B, ust be c. ssue inner diaeter (d i ) = 12 c 3 Inner radius (r i ) = 6 c Outer radius (r 0 ) = r i + = 15 c So, outer diaeter (d o ) = 2r 0 = 30 c Section view of toroidal autotransforer is shown in Fig. 1. r0 ri B Figure 1. Section View of Toroidal utotransforer Winding Design of Toroidal Transforer In winding design, S = 15 kv V = 250 V f = 50 Hz ssue Efficiency, η = 0.9 (90%) Maxiu current rating of the transforer, I = = So, S.W.G (6) will be chosen. Fro standard wire gauge table, Net cross-section area = Diaeter of bare conductor = Length for a turn = 2 ( + B) = 2 ( ) = c 53 c Total length for a winding = ean length for a turn nuber of turns = = 6625 c Fro standard wire gauge table, For S.W.G (6), 1000 ft 111.6lbs c lbs 6625 c? = lbs 25 lbs Therefore, 25 lbs of the winding will be needed for the SWG (6) of the toroidal transforer. Wiring diagra of toroidal autotransforer is shown in Fig. 2. Nuber of winding turns fro P to N = = 125 turns Nuber of winding turns fro to N = = 110 Nuber of winding turns fro to P = 15 turns Figure 2. Wiring Diagra of Toroidal utotransforer 189

4 Current rating of each winding, I each = Current density, δ = 2.00 to 2.5 / 2 ssue, current density, δ = 2 / 2 Cross sectional area of each winding, = = = π r 2 = r = Diaeter of each winding, d = 2 r = Diaeter of all winding, d 1 = = Circuference of all winding = π d 1 = 225 Diaeter of core, d 2 = 9 c = 90 Circuference of core = π d 2 = Spacing of winding = = Spacing of each winding = = Spacing of each winding = = 0.15 The calculated values of toroidal autotransforer are shown in Table II. IV. ROTTIONL TESTS During the fluctuation of 40%, +10% servootor autoatic voltage stabilizer will give the following tables. In this region, this stabilizer will produce the stable output voltage 220 V. The variable autotransforer is arranged 0.5 turns per voltage and 180 circular is taken due to the liit switch position. Variable autotransforer with forward condition and reverse condition are shown in Fig. 3 and Fig. 4. L Ɵ Forward condition Liit switch Figure 3. Variable utotransforer with Forward When the supply voltage is lower than the output voltage, the variable autotransforer of brush will rotate the clockwise condition. Ɵ Reverse condition TBLE II. DETILED DESIGN SHEET FOR TOROIDL UTOTRNSFORMER Description Sybol Unit Designed values kv Rating P (or) S kv 15 Cross sectional area i c Net cross sectional area gi c Turn per volt N e T/V 0.5 Width of ring face of core c 9 Height of core B c Inner diaeter d i c 12 Inner radius r i c 6 Outer diaeter d o c 30 Outer radius r o c 15 Current I Nuber of turns N Conductor area a Bare diaeter b Length for a turn - c/turn 53 Total length for a winding - c 6625 Pounds of the winding - lbs 25 Current of each winding I each Cross sectional area of each winding Diaeter of each winding d Diaeter of all winding d Circuference of all winding Circuference of core Spacing of winding Spacing of each winding L Liit switch Figure 4. Variable utotransforer with Reverse Where; Ɵ = rotational angle L = linear displaceent When the supply voltage is higher than the output voltage, the variable autotransforer of brush will rotate the anticlockwise condition. V. MODE OF OPERTION During the fluctuation of -40%, +10% servootor autoatic voltage stabilizer will give the following result. The VS will produce the stable output voltage 220 V. If the supply voltage is equal the output voltage of autoatic voltage stabilizer, the servo otor does not run in this condition. Figure 5 shows the output result of servo otor when the input voltage is stable by using Proteus Software. In this figure, the input voltage of icrocontroller is 4.34 V for phase R, Y and B. During the under voltage condition, the input voltage of the stabilizer is lower than output voltage. In this condition, the otor drives in forward direction as to increase the stabilizer output voltage to the 220 V. Figure 6 shows the siulation result of under voltage condition. In this figure, the input voltage of icrocontroller is 190

5 2.55 V for phase R, 3.73 V for phase Y and 2.96 V for phase B. Table II shows the direction of servo otor depending on the variable input voltage to get nearly the stable output voltage 220 V. Figure 5. Siulation Result of VS Controller in Stable During the over voltage condition, the input voltage of the stabilizer is higher than output voltage. In this condition, the otor drive in reverse direction as to decrease the stabilizer output voltage to the 220 V. Figure 7 shows over voltage condition of servo control syste by using Proteus Software. In this figure, the input voltage of icrocontroller is 4.52 V for phase R, 4.69 V for phase Y and 4.89 V for phase B. TBLE II. FOR LOW VOLTGE UP TO 40 % ND HIGH VOLTGE UP TO +10%, NGLE DISPLCEMENT WITH RESPECT TO VOLTGE FLUCTUTION Input voltage Different voltage Nuber of turns Clockwise direction Output voltage º º º º º º º º º º º º º In this research, when the voltage fluctuation is lower than 130 V and higher than 250 V, the servo control autoatic voltage stabilizer is autoatically shut down and does not operate in this situation. The servo otor autoatic voltage stabilizer will nearly produce the stable output voltage 220 V. Figure 6. Siulation Result of VS Controller in Under Voltage CONCLUSIONS Test outcoe shows that the output voltage reains virtually constant at varying input voltage. However, at extreely low voltages below 130V there was no output voltage because the switching device is not even activated. On the other hand, at voltages beyond 250V the syste protection is activated and no output voltage. Therefore the research has ade it possible for the device to operate fro as low as 130 V. The priary objective of this work which was to iprove the perforance of conventional C voltage stabilizer was achieved. The work was designed in consideration with soe factors such as econoy, availability of coponents, efficiency, copatibility, portability and durability. CKNOWLEDGMENT The author greatly expresses to his thanks to all persons who will concern to support in preparing this research. Figure 7. Siulation Result of VS Controller in Over Voltage VI. TEST RESULTS OF STBILIZER OUTPUT T DIFFERENT INPUT VOLTGES REFERENCES [1] BartloiejBelko, M. C.: The Conception and Ipleentation of Control Syste for Servo Motor with pplication of Local rea Network, Cracow, (2010). [2] Metrel: Single-phase Built-in Variable Transforer, Three-phase Built-in Variable Transforer, Motor 191

6 Driven Variable Transforer, Desk top Variable Transforer, (2009). [3] Hans Beijher: Output Transforers and Magnetic Forulas, Prentice-Hall, Noord-Holland, Netherlands, (2004). [4] Matt Ruff: Servootor Control pplication, Freescal Seiconductor Inc., Japan, (2004). [5] Biswanath Paul: Industrial Electronics and Control, Prentice-Hall of Private Liited, India, (2001). [6] Chuck McManis: Servo Basic, Oron sia Pacific Pte, Ltd., Korea, (2000). [7] Mark Readan: Motors, Seiens Copany, London, (1997). [8] Bhopal: Design of Electrical Machines, Standard Publisher Distributors, 4th Ed., 1705-E, NalSarak, DELHI , (1996). [9] Patchett, G.N.: utoatic Voltage Regulators and Stabilizers, Sir Isaac Pitan and Sons Ltd., 2nd Ed., Canada, (1954)