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ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 SAIT, JABALPUR DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGG. ELECTRICAL INSTRUMENTATION LAB SUB.CODE-EX-303 BRANCH-EX, SEM-III (GRADING) LIST OF EXPERIMENTS 1. Study of various types of Indicating Instruments. 2. To measure the low resistance using Kelvin’s Double Bridge. 3. To measure the medium resistance using Wheatstone Bridge. 4. To measure the insulation resistance using Megger. 5. To measure the earth resistance by fall of potential method and verification by using Earth Tester. 6. To measure the power in a single phase ac circuit by 3 voltmeter / 3 ammeter methods. 7. To measure the power in three phase circuit by two wattmeters. 8. To test the Current Transformer. 9. To test the Potential Transformer. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 1 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 INDEX S. NO. 1. NAME OF EXPERIMENT PAGE NO. DATE SIGN REMARK Study of various types of Indicating Instruments. 2. To measure the low resistance using Kelvin’s Double Bridge. 3. 4. 5. 6. 7. 8. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 2 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 EXPERIMENT NO.-01 AIM:- Measurement of low resistance using Kelvin’s Double bridge. APPARATUS REQUIRED:- Rx1=1Ω, Rx2=1Ω, Rx3=1Ω, Rx3=1Ω, Rx1=1Ω, Rx1=1Ω, Rx1=1Ω, CIRCUIT DIAGRAM THEORY:Bridges are divided into two categories: 1. AC Bridges – Inductance , Capacitance 2. DC Bridges – Resistance Some bridges are used for measuring inductance, capacitances, like that for measuring resistances Kelvin’s Bridge is used. Here we are using a circuit for measuring low resistances. Measurement of low resistances is not suitable for high resistance measurement, i.e., it will give more errors. In order to avoid this serious error measurement of low resistance technique is used. There are some methods for measurement of low resistance DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 3 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) Ammeter Voltmeter Method 1. Kelvin’s Double Bridge 2. Potentiometer method 3. Ducter Kelvin’s bridge is the modification of Wheatstone bridge and provides greatly increased accuracy in measurement of low value resistances. Consider the bridge circuit in fig. 1 shown below. Where r = resistance of the lead connected between R (unknown resistances) s = Standard Resistances When the G connected to point m, lead resistance is added to the standard resistances, resulting in very low value of R. When G connected to point n, lead resistance is added to the unknown resistance, resulting very high value for R. P/Q = r1/r2 Suppose that instead of using point m or n, we make G connection to any intermediate point c . So because of this point c at the potential between point m & n to eliminate the effect of connecting lead of resistance R and the standard S.It is shown in the above figure. The ratio P/Q is made equal to the p/q under balanced condition. There is no current through the galvanometer i.e, Ead=Eamc. Now Ead=p/(p+Eab) Eab=1(R+S+(P+Q)R/p+q+r) Eac=1(R+P/(p+q){(p+q)r/p+q+r}) For zero galvanometer deflection. Ead=Eamc If IF, = (P/Q).S This is the usual working equation of Kelvin’s Bridge. PROCEDURE:1. Switch ‘ON’ the power supply of the kit. 2. Connect unknown resistor ‘Rx’ in the circuit at proper place using patch chords. 3. Now measure the supply the voltage E using DC voltmeter. 4. Change the range selector switch for each of resistance from Rx1 to Rx2. 5. By varying the Pot S make bridge balanced i.e, galvanometer to shows zero deflection. 6. Disconnect the supply and measure the value of pot S. 7. Find thee value of unknown resistor Rx using formula Rx=SP/Q. 8. Repeat the same procedure for the other values of Rx. Calculation:The unknown resistor R can be found out by R=SP/Q OBSERVATION:Ratio Arm Resistor P Std. Arm Resistor S Calculated Rx Q DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 4 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 RESULT:Using Kelvin’s Double Bridge the value of unknown resistor is found and the measured value and calculated value is nearly same. EXPERIMENT NO.- 02 AIM: - Measurement of medium resistance using Wheatstone’s bridge THEORY:A very important device used in the measurement of resistances is the bridge. A Wheatstone Bridge has been is use longer than almost any electrical measuring instrument. It is still an accurate and reliable instrument and is extensively used in industry. The Bridge is an instrument for making caparison measurements and operates upon a null indication principle. This means the indication is independent of calibration of the null indicating instrument or any of its characteristics. For this reason, very high degrees of accuracy can be achieved using bridge. Accuracy of 0.1% is quite common with a Wheatstone bridge as opposed to accuracies of 3% to 5% with ordinary ohmmeter for measurement of medium resistances. Fig. (1) Shows the basic circuit of a Wheatstone bridge. It has four resistive arms , consisting of resistances P , Q , R & S together with a source of emf (A Battery) and a null detector , usually a Galvanometer (G) or other sensitive current meter. The current through the galvanometer depends on the potential difference between points ‘C’ & ‘D’ .The Bridge is said to be balanced when there is no current through the galvanometer or when the potential difference across the galvanometer is Zero. This occurs when the voltage from point ‘B’to point ‘A’ equals the voltage from point ‘D’ to point ‘B’: or, referring to the other battery terminal, when the voltage from point ‘D’ to point ‘C’ equals the voltage from point ‘B’ to point ‘C’. For bridge balance, we can write: I1P = I2P ------------------------------------- (1) For the galvanometer current to be zero, the following conditions also exist: I1 = I3 = E/P +Q ------------------------------------- (2) And Where ------------------------------------- (3) I2 = I4 = E/R +S E = emf of the battery Combining Eqns. (1), (2) & (3) and simplifying, we obtain: P/P+Q = R/R +S ----------------------------------- (4) DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 5 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) From which QR = PS ------------------------------------ (5) Eqn. (5) is the well known expression for the balance of Wheatstone bridge. If three of the resistances are known, the fourth may be determined from Eqn. (5) and thus obtaining: R = S (P/Q) -------------------------------------- (6) Where R is the unknown resistance S is called the ‘Standard Arm’ of the bridge and ‘P’ & ‘Q’ are called the ‘Ratio Arms’. PROCEDURE:1. Connect the unknown resistance across terminals marked X on the front panel. 2. Keep the function band switch at VR and toggle switch at R position. 3. Keep the Galvanometer switches at ‘Int’ position, battery switch at ‘Int’.Keep the ratio dial at ‘1’ & all other knobs at ‘0’.Simultanously press G & B switches. Note the deflection in the galvanometer. i. Generally galvanometer deflection should be in between.20 to 30 division (in maximum case). ii. If Galvanometer showing deflection out of scale then change ratio dial knob to higher range. 4. When the deflection comes into the scale then change the series arms knobs to take the null point. 5. Note down the readings i. Let the reading of Ratio arm (Multiply By) = P/Q ii. Let the reading of Series arm = SΩ iii. Then the resistance of sample = S (P/Q) Ω 6. For external Galvanometer and battery change the toggle switch on (EXT) external point. 7. Now repeat the experiment with different ratio arm readings and take the mean of all the readings. a. External Galvanometer like spot deflection Galvanometer can be connected to increase the sensitivity. PRECAUTIONS:_ 1. Galvanometer button should be just pressed to see wheather there is any deflection in galvanometer. The button should be immediately released if reading going over scale. 2. If dead null point is not obtained take the mean reading for each side deflection of the Galvanometer. FOR RESISTANCE MEASUREMENT Formula Used R = S (P/Q) Ω S.No. 1. Ratio Arm P/Q Series Arm S Calculated Value of unknown Resistance 1 100 Ω 100 Ω DEPARTMENT OF ELECTRICAL & ELECTRONICS Actual Value of unknown Resistance 100 Ω Page 6 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2. 1 1K Ω 1K Ω 1.02 KΩ 3. 10 1K Ω 10 KΩ 10.02 KΩ EXPERIMENT NO.-03 AIM: - Measurement of insulation resistance using megger. APPARATUS REQUIRED:S. NO. NAME OF EQUIPMENT RANGE QUANTITY 01. 01 02. 01 03. 01 THEORY:Megger is the portable insulation tester. It is used to remove very high resistance of the order of mega ohms. The megger is an indicating instrument, which is generally used to measure very high resistance such as insulation resistance. Construction of the megger has been shown in fig. As shown, it consists a hand driven d.c.generator, which can generate 500 V or 1000 V dc.It also consists two coils namely current coil (or deflecting coil) and pressure coil (or control coil).Both coils are fixed together at some angle in between the poles of permanent magnet and are free to rotate, about a common axis, along with the pointer, which moves from ∞ (extreme left) depending upon the resistance between the two terminals. The resistance under test is connected between L and E and the generator handle is then rotated at uniform speed of about 180 to 300 rpm. The generator will generate 500V/1000V (however a 500 V megger is used for testing the domestic installation).The current coil is connected in series with the test resistance and the combination in series with the current limiting resistance R1 connected across the generator terminal this produce reflecting Torque. The pressure coil (or control coil), P1 is connected across the generator terminal in series with the current limiting resistance R2 and compensating winding. The compensating coil, P2 is used to obtain better scale proportions. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 7 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 The movement of the pointer on the scale depends upon the value of test resistance, which may be as follows: 1. When the test terminal is open, the resistance will be measured if infinite and pointer will be on the extreme left of the scale. As due to absence in current coil no reflecting torque is produced and due to torque is produce by the control circuit coil pointer will remain at ∞. 2. If the test terminal are joined together by a piece of wire, the resistance is zero ,so the pointer will move to extreme right under the influence of the torque produce on account of f s d current flowing in the current coil. 3. If the resistance will be measured is less then ∞ but more than zero(as megger is used to measure in mega ohm) then an appreciable amount of current flow in both the coils, producing torque in opposite direction and the pointer will indicate the value of the test resistance on the scale. PROCEDURE: 1. Connect the insulation resistance between the two terminals of megger. 2. Rotate the generator handle with the speed of 160 rpm and maintain it for a period of time. 3. Note down the reading of angle scale. This will be the value of insulation resistance. PREACUTIONS: 1. Do not touch the terminal during rotation of handle. 2. Connection should be made carefully. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 8 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) EXPERIMENT NO. – 04 AIM: - Measurement of Earth Resistance with Earth Tester. APPARATUS REQUIRED:S. NO. 01. 02. 03. NAME Earth Tester Steel Rod(Electrode) Wire RANGE 0-100 Ω 1 meter QUANTITY 01 02 THEORY: - The resistance of earth electrode or earth path is measured by a special Megger called Earth Tester. An earth tester essentially is a direct reading Ohmmeter which can read low value resistance. The tester essentially consists of two coils, one is current coil and another is pressure coil. The figure given below shows the internal construction of such tester. As shown in figure P1C1 are connected together and forming earth terminal, P2 and C2 are forming other two terminals. So an earth tester has three terminals instead of two terminals as in the megger. Some manufacturers of these instruments indicate these terminals as ‘E’ (Earth), ‘H’ (High) and ‘U’ (Under) . Here these terminals are E, P and C. Terminal E is connected to earth electrode / earth conductor or earthed metallic parts. C and P are connected to auxiliary electrode buried in soil at a suitable distance as per requirements. Three readings are generally taken by buying the electrode, a metal spike. Firstly ‘P’ electrode will be buried between E and C, secondly, 3 meters away from ‘E’ on left side of ‘C’. Thirdly, 3 meters away from ‘C’ on its right side. The man of the three readings is the earth resistance. CIRCUIT DIAGRAME:- DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 9 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 PROCEDURE :1. 2. 3. 4. Two terminals P1 and C1 are sorted to form a common point to be connected to the earth tester. The other two terminals P2 and c2 are to auxiliary electrode P and C respectively. Rotate the spindle with a minimum speed of 60 r.p.m. Note the meter reading (in Ω). RESULT: - The earth tester has been studied and the observed value of earth resistance is …………Ω. PRECAUTIONS:1. 2. 3. 4. Speed should be maintained at 60 r.p.m. Earth electrodes should be inserted properly under the ground. If the resistance observed is maximum, check the connection. All connections should be right and tight. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 10 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 EXPERIMENT NO. – 06 AIM:- To perform load test on a 3-ф SQCG IM and plot its performance characteristics. APPARATUS REQUIRED:S.NO . NAME TYPE RANGE 01. Squirrel Cage Induction Motor 3-ф RPM-1410 QUANTITY VOLTS-415 With Mechanical Loading AMPS-8.1 CONNECTION- Δ 01 PHASE-3 TEFC HZ-50 RATING-CONT. INSULATION-B CLASS KW/HP-3.7/5.0 Mechanical Loading 02. Wattmeter (a) UPF * 0-1500W/150-300-600V/10-20A DEPARTMENT OF ELECTRICAL & ELECTRONICS 02 Page 11 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 03. Voltmeter MI 300-600V 01 04. Ammeter MI 5-10A 01 05. (a) Auto- 3-ф 12.211KVA,0-415-470V,15A/Ph 01 (b) D.O.L. Starter 3-ф 3.7 KW/5.0 HP,415V,50Hz 01 06. Connecting Wires Multi-Strand 2.5 sq. mm. As Per Requirement 07. Tachometer (a)Digital Contact 60-50,000 RPM 01 60-1,00,000 RPM 01 Transformer (b)Digital Photo THEORY:By conducting the load test on three phase induction motor, the performance of the motor viz. slip, power factor, input, efficiency etc. at various loads can be studied. The induction motor is located by any of the following methods : 1. Brake test 2. By connecting a d.c. generator On induction motor side, ammeter reads line current and voltmeter reads line voltage VL. The two wattmeters are connected as per the two wattmeter method hence, Pin = Power input = W1 + W2 Pin of induction motor = W1 + W2 W cos Φ = Pin/(√3VL IL )= (W1 + W2)/(√3VL IL) = power factor DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 12 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) where 2015-2016 Ns = 120f / P for a given motor For various loads above parameters are obtained As the load on the induction motor increases, 1. The output of motor increases. 2. The power factor increases. 3. The efficiency increase up to certain load and then decreases. 4. The speed decreases marginally. 5. The slip increases. 6. The input current increases. The various performance characteristics can be obtained as shown in the Fig.2. Fig. 2 The graphs indicate the behaviour of various performance parameters against output of the induction motor and not shown to the scale. CIRCUIT DIAGRAM FOR LOAD TEST ON 3-ф SQUIRREL CAGE INDUCTION MOTOR DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 13 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 PROCEDURE:1. Connect ckt. as shown in diagram. 2. Adjust ‘Zero set’ for Balances. 3. Switch on Mains supply. 4. Start AC Motor Pressing START Push button of DOL Starter. 5. Note down readings of voltmeter, Ammeter, Wattmeters & load on balances W1 & W2 Kg. 6. Using hand wheel of Brake drum arrangement load the motor in steps from no load to rated torque. 7 Rated torque T = (W1-W2)*A A = Break drum Constant = Radius of Pulley (Meter) * 9.81 8 At each step repeat step 5. 9. Calculate power output P = 2ЛNT. 10. Calculate efficiency = output / input. OBSERVATION TABLE:- DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 14 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) S.No. Line Line Wattmeters I/P Load Load Volts Amps. watts W1 W2 VL IL Power P1 + P2 Kg. Kg. P1 P2 W1-W2 Speed RPM 1 2 3 4 CALCULATIONS:- RESULTS:- PRECAUTIONS:1. All connections should be right and tight and as per the circuit diagram . 2. Ammeter should always be connected in series and Voltmeter should always be connected in parallel with the circuit . 3. The Current Coil of Wattmeter should always be connected in series and the Potential Coil of Wattmeter should always be connected in parallel with the circuit . 4. Uninsulated parts should never be touched. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 15 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 5. Before switching ON the circuit, check whether the pointer of the auto-transformer and the pointers of all the meters is at zero mark or not, if not bring them to zero. 6. Check for parallax, remove if it exists. 7. Depending upon the circuit, proper range of meters should be selected. EXPERIMENT NO. :-07 AIM: - Study of testing of Current Transformer. APPARATUS REQUIRED:S. NO. NAMEOF EQUIPMENT RANGE 01. Current Transformer Primary C - 10/30/50/100 01 Secondary C - 5A 02. Single Phase Transformer 03. 04. QUANTITY Auto- 0-270 V , 10 A 01 Voltmeter 0-300 V 01 Ammeter 0-10/20 A 02 THEORY:The current transformer is used with its primary winding connected in series with line carrying the current to be measured and, therefore the primary current is dependent upon the load connected to the system and is not determined by the load(burden)connected to the secondary winding of the current transformer. The primary winding consists of few turns only and therefore there is no appreciable voltage drop across it. The secondary winding of current transformer has more number of turns, the exact number being determined by the Turns Ratio. The ammeter is connected directly across the secondary winding terminals. Thus a current transformer operates its secondary winding nearly under short circuit conditions. One of the terminals of the secondary DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 16 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 winding is earthed so as to protect the equipments and personnel in the vicinity in the event of a breakdown in the current transformer. The above fig shows current being measured by act. The primary winding is so connected that the current being measured passes through it and the secondary winding is connected to an ammeter. The C.T. steps down the current to the level of ammeter. CIRCUIT DIAGRAM FOR CURRENT TRANSFORMER PROCEDURE: – 1. Connect auto-transformer, ammeters, current transformer and resistive load in series as shown in the fig. 2. Gently increase the Auto-Transformer upto 220 V. 3. Switch “ON” the Resistive Load circuit. Now switch “ON” The knob of 1 A (installed at RL) in steps so that eventually 10A current flows through the circuit. 4. Note the readings of two Ammeters (i.e. one on the primary side of C.T. that reads 10A and the other on secondary side of C.T. that reads 5 A, confirming the C.T. Action). 5. Now bring the jockey of Auto-Transformer to zero position and switch “OFF” the AC supply. 6. Now reduce the 10A Resistive Load to 5 A by switching “OFF” the 5 knobs out of 10. 7. Now interchange the connection of the two Ammeters so that the Ammeter which is connected to the primary of C.T. and is in series is ready to read 10 A (which is the incremented value). 8. Note the readings of the two Ammeters i.e. one on the primary side of C.T. that reads 5 A and the other on the secondary side of C.T. that reads 10 A , again confirming C.T. action either ways. OBSERVATION TABLE:Case I: S. NO. C.T. as Step Down Transformer Input supply Applied Resistive Load Current voltage(AC) in volts to in parallel i.e. 10 primary the primary winding of Resistances of 220 Ω winding DEPARTMENT OF ELECTRICAL & ELECTRONICS in Current in C.T.Ratio secondary winding side i.e. PW/SW Page 17 2015-2016 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) each in parallel and side of C.T. of C.T. in A controlled by ON-OFF in A knob in Ω C.T. 1. 2. Case II: S. No. C.T. as Step UP Transformer Input supply voltage(AC) in volts to the primary winding of C.T. Applied Resistive Load in parallel i.e. 5 Resistance of 220 Ω each in parallel and controlled by ON-OFF knob in Ω Current in primary winding side of C.T. in A Current in C.T.Ratio secondary winding side i.e. PW/SW of C.T. in A 1. 2. RESULT:The result obtained from the above experimental setup confirms the C.T. action either ways. PRECAUTIONS:1. All connections should be tight and right and as per the circuit diagram. 2. Proper range of meters should be selected. 3. Uninsulated parts should never be touched. 4. Ammeter should always be connected in series and Voltmeter in parallel with the circuit. 5. Gently vary the jockey of the Auto-Transformer to bring the pointer to the desired value of voltage (input). 6. Before switching “ON” the circuit. Check whether the position of pointer in the meters is at zero or not, if not bring it to zero. 7. Check the parallax, and remove if it exists. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 18 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 EXPERIMENT NO.- 08 AIM: - Study of testing of Potential Transformer. APPARATUS REQUIRED:S. NO. 01. NAME OF EQUIPMENT Potential Transformer RANGE Primary C - 250 V QUANTITY 01 SecondaryC-75/150/300/600V 02. Single Phase Auto- 0-270 V , 10 A Transformer 01 03. Voltmeter 01 0-300 V THEORY:Potential Transformers are used to operate Voltmeters, the potential coils of Wattmeters and relays from high voltage lines. The primary winding of the transformer is connected across the line carrying the voltage to be measured and the volt circuit is connected across the secondary winding. The design of the potential transformer is quite similar to that of a power transformer but the load of a potential transformer is always small, sometimes only a few volt amperes. The secondary winding is designed so that a voltage of 100-120 volt is delivered to the instrument load. The normal secondary voltage rating is 110 volt. The adjoin fig. shows voltage measurement with a P.T. The primary winding is connected to the voltage being measured and the secondary winding to the voltmeter. The P.T. steps down the voltage to the level of voltmeter. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 19 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 CIRCUIT DIAGRAM PROCEDURE: 1. Connect Auto -Transformer, Voltmeters and Potential Transformer in parallel to each other as shown in the fig. 2. Now switch “ON” the power supply. 3. Gently increase the Auto-Transformer up to 220V. 4. Note the readings of the two Voltmeters i.e. one on the primary side of P.T. that reads 220V. 5. Now gently bring the jockey of Auto-Transformer at zero position and switch “OFF” the AC supply. 6. Now reverse the position of supply so that the previous primary now becomes secondary and viceversa. This implies that AC supply is now given between C and 75/150/300V and the secondary reads 250V, confirming P.T. action. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 20 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 RESULT: The result obtained from the above experimental setup confirms the P.T. action either ways. OBSERVATION TABLE: Case I: P.T. as step Down Transformer S.No. Applied Input Voltage to Measured Output Voltage Ratio of P.T. Primary Winding of P.T. in at Secondary Winding of i.e.PW/SW volts P.T. in Volts 1. 2. 3. 4. 5. Case II: P.T. as step Down Transformer S.No. Applied Input Voltage to Measured Output Voltage Ratio of P.T. Primary Winding of P.T. in at Secondary Winding of i.e.PW/SW volts P.T. in Volts 1. 2. 3. 4. 5. DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 21 ST.ALOYSIUS INSTITUTE OF TECHNOLOGY, JABALPUR (M.P) 2015-2016 DEPARTMENT OF ELECTRICAL & ELECTRONICS Page 22