Two 220V generators operate in parallel. One machine has a terminal voltage of 270V @ no load and 220V @ load current of 35A. the other has terminal voltage of 280 V@ no load and 220V @ load current of 50A. Calculate the power share of each machine and new bus voltage if the total load current is 60A.
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Ri1 = 50V/35A = 1.43 Ohm
Ri2 = 60V/50A = 1.2 Ohm
i1 + i2 must = 60A
i2 = 60A - i1
To operate in parallel both generator terminal Voltages must be equal under the 60 Amp total load current. Therefore;
270V - 1.43(i1) = 280V - 1.2(i2)
270 - 1.43(i1) = 280 - 1.2(60 - i1)
2.63(i1) = 62
i1 = 23.574 Amps
i2 = (60 - 23.574)A = 36.426 Amps
New bus Voltage = 270V - {(i1)*(Ri!)} = 280V - [(i2)*(Ri2)] = 236.29 Volts
Total load power = (236.29V)*(60A) = 14,177 Watts
Generator 1 output power = (236.29V)*(23.574A0 = 5,570 Watts
Generator 2 output power = (236.29V)*(36.426A) = 8,607 Watts
Ri2 = 60V/50A = 1.2 Ohm
i1 + i2 must = 60A
i2 = 60A - i1
To operate in parallel both generator terminal Voltages must be equal under the 60 Amp total load current. Therefore;
270V - 1.43(i1) = 280V - 1.2(i2)
270 - 1.43(i1) = 280 - 1.2(60 - i1)
2.63(i1) = 62
i1 = 23.574 Amps
i2 = (60 - 23.574)A = 36.426 Amps
New bus Voltage = 270V - {(i1)*(Ri!)} = 280V - [(i2)*(Ri2)] = 236.29 Volts
Total load power = (236.29V)*(60A) = 14,177 Watts
Generator 1 output power = (236.29V)*(23.574A0 = 5,570 Watts
Generator 2 output power = (236.29V)*(36.426A) = 8,607 Watts
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Assumptions: DC generators (since all other questions you have asked have been dc), separately excited generators (no info on field - but good chance actual generators are compound).
Generator 1
no-load voltage - 270V
full-load voltage - 220V
full-load current - 35A
Voltage drop for 35A = 270V - 220V = 50V
Voltage drop/Amp of output current 50V / 35A = 1.429V/A
Generator 2
no-load voltage - 280V
full-load voltage - 220V
full-load current - 50A
Voltage drop for 50A = 280V - 220V = 60V
Voltage drop/Amp of output current 60V / 50A = 1.2V/A
I_1 + I_2 = 60 A (1)
Generator 1 Terminal Voltage
V = 270 V - 1.429V/A I_1 (2)
Generator 2 Terminal Voltage
V = 280V - 1.2V/A I_2 (3)
3 equations, 3 unknowns. (2) and (3) eliminate V. Solve (1) for I_1 and substitute in and solve for I_2.
I_1 = 60 - I_2
270 - 1.429 I_1 = 280 - 1.2 I_2
270 - 1.429 ( 60 - I_2 ) = 280 - 1.2 I_2
-95.71 = -2.629 I_2
I_2 = 36.41A
I_1 = 23.59A
V = 280 - 1.2 * 36.41 = 236.3V
P2 = V I2 = 236.3V * 36.41A = 8605W
P1 = V I1 = 236.3V * 23.59A = 5574W
Generator 1
no-load voltage - 270V
full-load voltage - 220V
full-load current - 35A
Voltage drop for 35A = 270V - 220V = 50V
Voltage drop/Amp of output current 50V / 35A = 1.429V/A
Generator 2
no-load voltage - 280V
full-load voltage - 220V
full-load current - 50A
Voltage drop for 50A = 280V - 220V = 60V
Voltage drop/Amp of output current 60V / 50A = 1.2V/A
I_1 + I_2 = 60 A (1)
Generator 1 Terminal Voltage
V = 270 V - 1.429V/A I_1 (2)
Generator 2 Terminal Voltage
V = 280V - 1.2V/A I_2 (3)
3 equations, 3 unknowns. (2) and (3) eliminate V. Solve (1) for I_1 and substitute in and solve for I_2.
I_1 = 60 - I_2
270 - 1.429 I_1 = 280 - 1.2 I_2
270 - 1.429 ( 60 - I_2 ) = 280 - 1.2 I_2
-95.71 = -2.629 I_2
I_2 = 36.41A
I_1 = 23.59A
V = 280 - 1.2 * 36.41 = 236.3V
P2 = V I2 = 236.3V * 36.41A = 8605W
P1 = V I1 = 236.3V * 23.59A = 5574W
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The first generator has an OC voltage of 270 volts and an output resistance of (270-220)/35=1.428 ohms. The second one has an OC voltage of (280-220)/50=1.2 ohms. To finish the answer, put these 2 equivalent circuits in parallel with a 60 amp current source for a load and compute each current.