Parallel operation of synchronous generators free essay sample

The alternators are conneted as shown in FIG. 1 using two single-phase wattmeters The d. c shunt motors are started and the alternators are brought up to speed. By varying the alternator fields, the terminal voltages are brought up to the rated values(110V). The speeds of the sets are adjusted by means of the motor field rheostat control until thealternators run at rated frequency The synchronising switch is closed in the middle of a dark period of the lamps. ( The alterantors should now be working in parallel, but they should not be delivering any load. Also , if the voltage and speed have been properly adjusted, there should be no interchange odf current between the alternators and the ammeters should read zero. For a particular load output at consatnt frequency and voltage, input ot the d. c machine is varied and the outputs shared by each alternator are noted from the wattmeter readings. We will write a custom essay sample on Parallel operation of synchronous generators or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Inputs to the d. c side are also noted. A graph is plotted between the input power and the load shared by each machine, as shown in FIG. 2 Keeping the input power , outputload , terminal voltage an dfrequency constant, the current outut of each alternator is noted for different excitaitons. A graph of output (in VA) versus excitation as shown in FIG. 3 is plotted. Observations: Wattmeter constants = Frequency= Voltage = Load Current= No. W1 (watts) A1 (amps) LOAD SHARING Iac1 Vdc1 W2 (amps) (Volts) (watts) Voltage = Load current = A2 (amps) Iac2 (amps) Vdc2 (volts) Frequency = W1 = W2 = No. Machine I If1(amp) Iac1(amp) Machine II 1. 73VIac1(VA) If2(amp) Iac2(amp) 1. 73Viac2(VA) Results: S. No. Machine I A. C Output,Watts D. C Input ,Watts Machine II A. C Output,Watts D. C Input ,Watts Remark: Variation of load angle with cahnge in the output load can be observed with a stroboflash arrangement FIG. 1 Two D. C motor -alternator sets as follows are used. Ifpm A Rf1=0-185 ohm S1 Ra Ia A 0-60A Starter A1 110 V D. C Supply F1 R Y B N M Vt 0-150V D. C F1 A2 F2 F2 Rf2 =0-35 ohm Star-connected alternator 130 V,13. 9 A, 3 kVA,50Hz 1000 rpm A 0-6 A D. C L1 R1 From Alternator 1 A W W 110V 10A N1 Vg 0-150 V 46-54 Hz 0-20A R2 A N2 From Alternator 2 Vb F F 46-54 Hz Y1 Y2 B1 B2 A L2 L3 0-60A To 3-phase load FIG. 2 Output Power/Machine (Watts) 1000 800 Machine I 600 Machine II 400 200 30 0 500 700 900 1100 Input Power/Machine (Watts) FIG. 3 Field Current (Amps) 1300 1500 1700 Load Current I1 Load Current I2 MachineII MachineI MachineI Machine II Volt- amperes