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Electrical Machines-Ii ELECTRICAL MACHINES – II LAB ELECTRICAL MACHINES-II LABORATORY DEPT. OF EEE, PSCMRCET ELECTRICAL MACHINES – II LAB LIST OF EXPERIMENTS PAGE NO 1. Brake test on three phase Induction Motor 1 - 7 2. No-load & Blocked rotor tests on three phase Induction motor 8 - 15 3. Regulation of a three –phase alternator by synchronous 16 - 23 Impedance & M.M.F. Methods 4.V and Inverted V curves of a three- phase synchronous motor 24 - 30 5.Determination of Xd and Xq of a salient pole synchronous 31 - 36 Machine 6.Regulation of three–phase alternator by Potier triangle method 37 - 45 7.Equivalent Circuit of a single phase induction motor 46 - 54 8.Speed control of induction motor by V/f method. 55 - 63 9.Determination of efficiency of three phase alternator by 64 - 70 loading with three phase induction motor. 10.Power factor improvement of single phase induction motor 71 - 75 by using capacitors and load test on single phase induction motor DEPT. OF EEE, PSCMRCET ELECTRICAL MACHINES – II LAB INDEX EXPT PAGE STAFF S.NO DATE NAME OF THE EXPERIMENT MARKS NO. NO SIGN. 1 2 3 4 5 6 7 8 9 10 DEPT. OF EEE, PSCMRCET ELECTRICAL MACHINES – II LAB CYCLE OF EXPERIMENTS CYCLE - I 1.Brake test on three phase Induction Motor 2. No-load & Blocked rotor tests on three phase Induction motor 3. Regulation of a three –phase alternator by synchronous Impedance & M.M.F. Methods 4.V and Inverted V curves of a three- phase synchronous motor 5.Determination of Xd and Xq of a salient pole synchronous Machine CYCLE – II 6.Regulation of three–phase alternator by Potier triangle method 7.Equivalent Circuit of a single phase induction motor 8.Speed control of induction motor by V/f method. 9.Determination of efficiency of three phase alternator by loading with three phase induction motor. 10.Power factor improvement of single phase induction motor by using capacitors and load test on single phase induction motor DEPT. OF EEE, PSCMRCET ELECTRICAL MACHINES – II LAB (R13) EXPT.NO. : DATE : BRAKE TEST ON THREE PHASE INDUCTION MOTOR AIM: To obtain the performance curves of a three phase induction motor by conducting brake test. NAME PLATE DETAILS: 3Ø INDUCTION MOTOR APPARATUS: S.No. APPARATUS TYPE RANGE/RATING QUANTITY DEPT. OF EEE, PSCMRCET Page 51 1 ELECTRICAL MACHINES – II LAB (R13) CIRCUIT DIAGRAM : DEPT. OF EEE, PSCMRCET Page 52 2 ELECTRICAL MACHINES – II LAB (R13) PROCEDURE: 1. Connect the circuit as per the circuit diagram. 2. The supply is given and the stator button is pressed down, the motor stars from rest. 3. The readings as all meters and speed are noted in the table. The load on the motor is gradually increased up to its full load value by tightening the belt over the brake drum. 4. At each load the ratings of all meters, spring balances and speed of rotor are noted. 5. The load on the motor is removed, the supply is cut off. 6. Calculations are made as shown and draw the graphs for O/P versus speed, versus current, O/P -efficiency, O/P- slip, O/P- Torque, O/P-Power factor . Formulae Used : 1. Torque = ( S1~ S2 ) ( R ) x 9.81 N-m Where, S1, S2 - Spring Balance readings in Kg R - Radius of the brake drum in ‘m’ 2. Output Power = 2πNT/60 Watt N - Rotor Speed in RPM T - Torque in N-m 3. Input power = ( W1 + W2 ) Watts W1, W2 - Wattmeter Readings Output Power 4. Percentage efficiency = -------------------- X 100 Input Power Ns - Nr 5. Percentage Slip = --------- X 100 Ns Where, NS - Synchronous Speed Nr - Rotor Speed 6. Power Factor = Cos[Tan-1 {√3(W1 - W2)/( W1 + W2)] DEPT. OF EEE, PSCMRCET Page 53 3 ELECTRICAL MACHINES – II LAB (R13) OBSERVATIONS: Power Factor Slip Efficiency(%) Output Torque(N-M) Speed (RPM) 2 ~S (kg) 1 S 2 S (kg) Readings Spring Balance 1 S (kg) 2 + W 1 2 = W = (Watts) T + W + 1 W W W = 2 W (Watts) Input Power 1 W (Watts) Current(Amps) Voltage(Volts) S.No DEPT. OF EEE, PSCMRCET Page 54 4 ELECTRICAL MACHINES – II LAB (R13) PRECAUTIONS: 1. Connections should be tight, avoid loose connections. 2. Correct rated meters should be selected from the name plate details. 3. While during the experiment see that the meter readings should not be exceed its rated values. 4. Note down the readings without any parallax error. MODEL GRAPHS: S %S CosΦ N IL T %η %η T in N-m CosΦ N In rpm IL in Amps RESULT : DEPT. OF EEE, PSCMRCET Page 55 5 ELECTRICAL MACHINES – II LAB (R13) DEPT. OF EEE, PSCMRCET Page 56 6 ELECTRICAL MACHINES – II LAB VIVA-QUESTIONS: 1. Define Slip in Induction Machine? 2. Why Induction Machine always runs below synchronous speed ? 3. How direction of 3 phase Induction Motor can be changed ? 4. What are the different starting methods of 3 phase induction motor? 5. When we can get Maximum Torque in Induction Motor while starting? 6. What are the different losses in 3 phase induction motor? 7.What is the relation between torque and supply voltage in 3 phase induction motor? 8. Why skewing is done in squirrel cage Induction motor? DEPT. OF EEE, PSCMRCT 7 ELECTRICAL MACHINES – II LAB (R13) EXPT.NO. : DATE : NO-LOAD & BLOCKED ROTOR TESTS ON THREE PHASE INDUCTION MOTOR AIM : To conduct the no load test and Blocked rotor test on three phase squirrel cage induction motor and to draw the equivalent circuit. NAME PLATE DETAILS : 3-Ø INDUCTION MOTOR AUTOTRANSFORMER APPARATUS REQUIRED:- S.No. APPARATUS TYPE RANGE/RATING QUANTITY DEPT. OF EEE, PSCMRCET Page 19 8 ELECTRICAL MACHINES – II LAB (R13) CIRCUIT DIAGRAM FOR NO LOAD TEST : DEPT. OF EEE, PSCMRCET Page 20 9 ELECTRICAL MACHINES – II LAB (R13) CIRCUIT DIAGRAM FOR BLOCKED ROTOR TEST : DEPT. OF EEE, PSCMRCET Page 21 10 ELECTRICAL MACHINES – II LAB (R13) PROCEDURE: NO LOAD TEST: 1. Make the connections as per the circuit diagram. 2. The 3- autotransformer is kept in zero voltage position and see that the brakedrum rotates freely. 3. TPST switch is closed. By adjusting the 3- auto transformer variable knob, increase the applied voltage gradually until the voltmeter reads the rated voltage of the motor. 4. Note the voltmeter (V0), Ammeter (I0) & Wattmeter (W1, W2) readings. 5. Bring the 3- autotransformer to zero output voltage position and open the supply TPST switch. BLOCKED ROTOR TEST: 1. Tight the belt around the brake drum to block the rotor of induction motor. 2. The applied voltage is increased slowly by varying 3- autotransformer variable knob until the ammeter reads rated current. 3. Note down Voltmeter (Vsc), ammeter (Isc) & wattmeter (Wsc) reading. 4. Bring the 3- autotransformer to zero output voltage position and open the supply TPST switch. PRECAUTIONS:- 1. The auto transformer should be kept at minimum voltage position 2. Initially all switches are in open position 3. Note down the readings without parallax error. DEPT. OF EEE, PSCMRCET Page 22 11 ELECTRICAL MACHINES – II LAB (R13) MODEL GRAPH OBSERVATIONS: TABLE 1: FOR NO LOAD TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR No load No load Wattmeter readings 1 Po P = W – W = Cos voltage Current 0 1 2 (W) 3V0I0 V (V) I (A) W1(W) W2 (W) 0 0 Degree DEPT. OF EEE, PSCMRCET Page 23 12 ELECTRICAL MACHINES – II LAB (R13) TABLE 2: FOR BLOCKED ROTOR TEST ON THREE PHASE SQUIRREL CAGE INDUCTION MOTOR P = Cos1 o VSC (V) ISC (A) Wsc (Watt) SC 3VSCISC RESULTS: DEPT. OF EEE, PSCMRCET Page 24 13 ELECTRICAL MACHINES – II LAB (R13) DEPT. OF EEE, PSCMRCET Page 25 14 ELECTRICAL MACHINES – II LAB VIVA-QUESTIONS: 1. Name the tests to be conducted for predetermining the performance of 3-phase induction machine. 2. What are the information’s obtained from no-load test in a 3-phase I M? 3. What are the information’s obtained from blocked rotor test in a 3-phase I M? 4. What is circle diagram of an I M? 5. What are the advantages of 3-phase induction motor? 6. What are the methods adopted to reduce harmonic torques? DEPT. OF EEE, PSCMRCT 15 ELECTRICAL MACHINES – II LAB (R13) EXPT.NO. : DATE : REGULATION OF A 3- ALTERNATOR BY SYNCHRONOUS IMPEDANCE AND M.M.F METHODS AIM: To predetermine the regulation of an alternator by i) Synchronous Impedance & ii) M.M.F method. NAME PLATE DETAILS: 3Ø Alternator DC Shunt motor APPARATUS REQUIRED:- S.No. APPARATUS TYPE RANGE/RATING QUANTITY DEPT. OF EEE, PSCMRCET Page 26 16 ELECTRICAL MACHINES – II LAB (R13) CIRCUIT DIAGRAM : DEPT. OF EEE, PSCMRCET Page 27 17 ELECTRICAL MACHINES – II LAB (R13) PROCEDURE: 1. Connect the circuit as per the circuit diagram. 2. Start the motor with the help of 3-point starter and adjust the field regulator of a Motor till rated speed obtained. 3. Keep the TPST knife switch open position and by varying the excitation of the Alternator, note down the ammeter and voltmeter readings in (table-1) till rated field Current of the alternator. 4. Now, close the TPST knife switch and by varying the excitation of the alternator note down field current short circuit current (in table-2) till rated field current of the Alternator. 5. Draw the graphs and calculate the regulation. PRECAUTIONS:- 1. Avoid loose connections. 2. Correct rated meters should be used from the nameplate details. 3. While doing the experiment see that meter readings should not exceed its rated value. 4. Note down the readings without any parallax error. DEPT. OF EEE, PSCMRCET Page 28 18 ELECTRICAL MACHINES – II LAB (R13) OBSERVATIONS:- OPEN CIRCUIT TEST: Terminal voltage V = V / 3 in S.No Field current ph 1 VL in volts Volts SHORT CIRCUIT TEST: S.No Field current in A Short Circuit current in A DEPT.
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