Question

please answer 13.16

at rated load of unity power factor and rated terminal voltage, determine efficienc including field rheostat loss. Ans. 93.139 13.11 A generator under test is rated at 100 KVA, 3-phase, 60-Hz; 2,400 volts. (a) If driven b a de motor unexcited, the motor output is 1.26 KW. (b) If driven by a de motor, generato on open circuit and excited to generate rated potential, the motor output is 2.5 KW. ( Ifdriven by a de motor, generator on short-circuit with full load current flowing through its armature, the motoroutput is 6.88 KW. Determine the core loss, friction and windage loss, and armature copper loss of the generator. Ans. 1.24 KW; 1.26 KW; 5.62 KW 13.12 Given: A 6,000 KVA; 6,600-volt Y connected 2-pole 60 Hz turbine driven alternator rated load with unity power factor, the armature loss is 1.5% of output. The field excitation voltage is 240 volts; the field currentat unity power factorand 0.8 power factor are 120 and 140 amps. respectively; resistance of field winding at 75°C is 1.5 oh friction and windage loss is 75 KW. Excluding field rheostat loss, determine the efficiency of the alternator at rated load and (a) unity power factor and, (b) 0.8 power factor if core loss at unity and 0.8 power factor are 60 and 65 KW respectively ms; Ans, 96%,94.8% 13.13 Using the data in Prob. 13.04, calculate the angle between the equal voltages of230 volts if the circulating current is 1,000 amperes when the alternntors are paralleled Ans. 32.8 degrees total 13.14 Solve Prob. 13.05 with a load of 2,200 KW, 0.8 power factor lagging eurrent Ans. 1,786 KW; 1,000 Amp., 0.777 KVA 25 C 13.15 Two three-phase alternators are operating in parallel to supply a load of 6,000 KW, 0.9 power factor lagging at 6,900 volts. The current of alternator 1 is-200 amperes at 0.85 power factor, leading current. Determine for alternator 2, (a) power, (b) current, and 59 KW (c) power factor. per Load e 15 Ans. 3,970 KW; 481 amperes, 0.691 ffi 13.16 Two synchronous generators A and B are operating in parallel. Measurements show that generator A is delivering 100 amperes at 0.866 lagging power factor and that generator B is delivering 142 amperes at 0.707 lagging power factor. (a) What is the r factor of the load? (b) What percentago of the load is each supplying? (c) In order that both generators may operate at the power factor of the load, in which direction does 38% cted per tion KW. the field current of each have to be varied? Ans. 0.779; 46.5%: 53.6%