Electrical machines 2 lab manual

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This manual consists of some important experiments of ac electrical machines.This is prepared by satish babu and lokesh.They are working as staff in usha rama college,telaprolu.

Transcript of Electrical machines 2 lab manual

  • 1. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALPrepared byMr. J Satish Babu& Mr. A. LokeshDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 1

2. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUAL OC & SC TESTS ON SINGLE PHASE TRANSFORMERCircuit Diagram:(a) OC Test(b) SC Test Name Plate Details 1 T/F: KVA= LV Voltage = HV Voltage = Frequency =DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 2 3. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGYEM-II LAB MANUALOC& SC TESTS ON SINGLE PHASE TRANSFORMERExp. No. Date:AIM:To predetermine the efficiency, regulation at different operating conditions byconducting open circuit and short circuit tests on a single-phase transformerAPPARATUS:S. No. NameRangeTypeQuantity 1.Voltmeter 2.Voltmeter 3.Ammeter 4.Ammeter 5.Wattmeter 6.Wattmeter 7.Single-phase variac 8.Connecting wiresPROCEDURE:Open Circuit Test:It is usually done on the L.V. side, keeping the H.V. side open.1) Make the connections as shown in the circuit diagram.2) Apply the rated V0 voltage to L.V using variac3) Note down the no load current I0 and power W0 for rated voltage V0.Short Circuit Test:Short circuit test, is usually done on the H.V. side keeping the L.V. side short circuited.i. Make connections as shown in the circuit diagram.ii. Apply rated current (ISC) by varying variac.iii. Note the corresponding power input (WSC) and (ISC) for VSC. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING3 4. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALOBSERVATIONS:O.C. Test: CurrentPower VoltageI0 (amps)W0(Watts)V0 (Volts)S.C. Test:Current DrawnPower Input Voltage appliedIsc (amps) Wsc (Watts) VSC (Volts)FORMULAE:From O.C. Test:w0 No Load Power factor = Cos f0 ==f0 = V0 I 0Sin f 0 =I w = I 0 Cos f 0 = R0 = V0 / I w =Im = I 0 Sin f 0 =X 0 = V0 / I m =From S.C. Test:Total impedance referred to the H.V. sideV SCZ 02 = =I SCTotal resistance referred to the H.V. side W SCR 02 == 22 I 2 SCX 02 = Z 02 - R 02Therefore, total resistance and reactance referred to L.V. side (Primary side)R 02 X 02R 01 = 2X 01 =KK2Where k is transformation ratio% Efficiency at any load and given p.f :Let the load p.f. is Cos f andX = actual load / full loadThen, output power at actual load = X * full load = (X) (KVA) (p.f.) = _______ WattsIron losses Wi = WOC = DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING4 5. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGYEM-II LAB MANUAL Copper losses Wcu = (X2) (WSC) = Total losses (Wt) = Wi + Wcu % Efficiency = (output power)/(output + losses) = % Voltage regulation at full load of given p.f. : % Regulation at full load = (I2R02 Cos f + I2 X02 Sin f)/V2 % Regulation at any load = (xI2R02 Cos f + xI2 X02 Sin f)/V2 + for lagging power factor - for leading power factorCALCULATIONS:DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING5 6. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 6 7. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 7 8. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALTable - 1: Efficiency calculations: Fraction of PF = Cosfload (x)1.00.81/41/23/4 1Table - 2: % regulation:MODEL GRAPHS:1. Efficiency Vs. Output (For different power factors)2. Regulation Vs. Power FactorsUPF EFFICIENCY% Reg0.8 PF 0.2 0.61 0.6 0.2 XX X XXPf lead Pf lag OUTPUT (WATTS) DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING8 9. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALEFFICIENCY CURVEDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 9 10. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALREGULATION VS PF CURVEDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 10 11. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALPRECAUTIONS: 1. Loose connections are to be avoided. 2. Circuit connections should not be made while power is ON. 3. Ensure variac position is zero before starting the experiment. 3. Readings of meters must be taken without parallax error. 4. While doing the open circuit test, ensure that the H.V. side is open. 5. While doing the short circuit test ensure that the L.V. side is short circuited. 6. High voltage & low voltage sides of T/F should be properly connected. 8. Check the corresponding meters are connected as per the circuit diagram of thecorresponding testRESULT:Efficiency & Regulation of transformer are determined and equivalent circuit is drawn Signature of the FacultyVIVA-VOCE QUESTIONS: 1. Why iron losses are negligible in short circuit test? 2. The leakage flux in a transformer depends upon? 3. Why is it preferred to determine the efficiency of transformer indirectly rather than by loading it. 4. What will happen if DC supply is given to the transformer? 5. Why is the core of transformer laminated. 6. What is the role of power transformers in power systems? 7. What are the assumptions made in drawing the equivalent circuit? 9. What is the condition for maximum efficiency of a 1- transformer? 10. Why copper losses are negligible in OC test. 11. Why low power factor wattmeter are used in OC test. 12. Why unity power factor wattmeter is used in SC test. 13. Why no load current and no load power factor is low. 14. Why transformer oil is used in the transformer. 15. Why half of LV & half of HV are placed on the same limb in Core type Practical Transformer. 16. Why HV Winding is placed over the LV winding. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING11 12. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGYEM-II LAB MANUALPARALLEL OPERATION OF TWO 1- TRANSFORMERSSC TEST Name Plate Details 1 T/F: KVA= LV Voltage = HV Voltage = Frequency =DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING12 13. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALPARALLEL OPERATION OF TWO 1- TRANSFORMERSExp. No.Date:AIM:To conduct parallel operation on given single phase transformers.APPRATUS:S. No. ItemTypeRangeQuantity 1 Transformers of same voltage ratio 2 Ammeters 3 Voltmeters 4 Watt meters 5 Variac 6 Single pole Knife switchPROCEDURE:Polarity Test: 1. Connections are made as per the circuit diagram. 2. Apply voltage of say 100 V. 3. Measure voltage across terminals A-a 4. If VA-a is equal to V1+V2 then it is Additive polarity. 5. If VA-a is equal to V1-V2 then it is Subtractive polarity. 6. Mark the terminals (Dot convention) after the polarity test.Parallel operation: 1. Connections are made as per the circuit diagram. 2. Switch on the power supply. 3. Slowly increase the voltage upto its rated value of transformer primaries. 4. Verify the voltage across the switch is one of the secondary of transformer, if it is zero, then close the switch, otherwise switch off the supply and change for correct polarity and repeat the steps 3 and 4. 5. After closing the switch, gradually increase the load in steps and note the values of all meters at each step till full load is reached. 6. Decrease the load and switch off the mains supply. 7. Tabulate the readings as shown. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING13 14. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALOBSERVATIONS: S. NO. VPI VP2IP1 IP2IS1IS2VL ILFORMULAE:Draw the vector diagram for full load value and verify IS1+IS2 = IL.For all values verifyZ1 I S1 =ILZ1 + Z 2Z2IS2 =ILZ1 + Z 2VECTOR DIAGRAME = E1 = E2Z I 1Z 1= I 2 20 V2 I 1X 1 2I2 XI 1R1 I2I2 R12I1ILPRECAUTIONS:1. Ensure the correct connections of the transformers.2. Check the KVA ratings of the transformers.3. Avoid loose connections are to be made. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING14 15. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALCALCULATIONS:DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 15 16. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALDEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 16 17. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGYEM-II LAB MANUALRESULTS:The two transformers have been operated in parallel and checked for the equal load sharing.Signature of the FacultyVIVA-VOCE QUESTIONS: 1. Define voltage regulation of a transformer? 2. What are the conditions for parallel operation? 3. Why do the transformer operated in parallel? 4. Why transformer is operated at constant frequency? 5. How to calculate power transform conductivley and inductively in auto transformer? 6. What is auto transformer? 7. How eddy current losses are reduced? 8. What is the importance of Buchloz relay? 9. Draw the phasor diagram of transformer at inductive load conditions? 10. Why transformer in KVA? 11. Define all-day efficiency of transformer. 12. Draw the phasor diagram of an auto transformer? 13. Explain the losses of transformer. 14. Why, we are calculate the all-day efficiency of a distribution transformer 15. Why, the efficiency of transformer is high a half load compared to full-load? DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 17 18. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGY EM-II LAB MANUALSUMPNERS TEST Name Plate Details 1st T/F: Name Plate Details 2nd T/F: KVA=KVA= LV Voltage =LV Voltage = HV Voltage =HV Voltage = Frequency = Frequency =DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING 18 19. USHA RAMA COLLEGE OF ENGINEERING & TECHNOLOGYEM-II LAB MANUALSUMPNERS TESTExp. No. Date:AIM:To conduct Sumpners test on two similar 1-f transformers and to find the efficiency andregulation of each transformer at different load conditions.APPARATUS:S. No.Name RangeTypeQuantity 1.Voltmeter 2.Voltmeter 3.Voltmeter 4.Ammeter 5.Ammeter 6.Wattmeter 7.Wattmeter 8.Variac (230/270V),15A 9.Variac (230/270V),15A 10. DPST Switch 11. Connecting wiresPROCEDURE: 1. Give connections as per circuit diagram. 2. Apply a small voltage to the L.V. windings of the transformers. The voltme