the generated e.m.f.

The O.C.C. of a shunt generator when separately-excited and running at 1000 r.p.m. is given by :O.C.C. volt : 56 112 150 180 200 216 230Field amp. : 0.5 1.0 1.5 2.0 2.5 3.0 3.5If the generator is shunt-connected and runs at 1100 r.p.m. with a total field resistance of 80 Ω, determine(a) no-load e.m.f.(b) the output when the terminal voltage is 200 V if the armature resistance is 0.1 Ω.(c) the terminal voltage of the generator when giving the maximum output current.Neglect the effect of armature reaction and of brush contact drop.

Two d.c. generators are connected in parallel to supply a load of 1500 A. One generator has an armature resistance of 0.5 Ω and an e.m.f. of 400 V while the other has an armature resistance of 0.04 Ω and an e.m.f. of 440 V. The resistances of shunt fields are 100 Ω and 80 Ω respectively. Calculate the currents I1 and I2 supplied by individual generator and terminal voltage V of the combination. [381.2 V, 12.88 kW, 558.9 kW]

Sketch the load characteristic of a d.c. generator with (i) shunt (ii) series excitation. Give reasonsfor the particular shape in each case.The O.C.C. at 700 r.p.m. of a series generator with separately-excited field is as follows :Field current (A) : 20 40 50 60 75Armature e.m.f. (V) : 190 360 410 450 480Determine the current and terminal voltage as a self-excited series machine when running at 600 r.p.m.with a load of 6 Ω connected to the terminal. Resistance of armature and series winding is 0.3Ω. Ignore effectof armature reaction.

A generator supplying a load is shown in the figure. A second load is to be connected in parallel with the first one. The generator has a no-load frequency of 61.0 Hz and a slope S, of 1 MW/Hz. Load I consumed a real power of 1000 kW at 0.8 PF lagging while load 2 consumes a real power of 800 kW at 0.707 PF lagging. a) Before the switch is closed, what is the operating frequency of the system? b) After load 2 is connected, what is the operating frequency of the system? c) After load 2 is connected, what action could an operator take to restore the system frequency to 60 Hz? Load 1 Turbine generator Load 2

H. W.: A 35 kW induction motor has power factor 0.9 and effliciency 0.9 at full-load, power factor 0.6 and efficiency 0.7 at half full-load. At no load the current is 25% of full-load current and power factor is 0.I. Capacitors are supplied to make the line power factor 0.8 at half full- load. With these capacitors in circuit, find the line power factor at: (i) full load, and (ii) no load.

When Line Voltage (Vey) = 29.8 V, Stator CurrentClph) -4.94A and Totel Cáph) inpot feal powere 214.7We Eddy Current breke Torque s0. 4& Nm. statorphase resistance e 1.92. Equivalent circuit, when slip I Cie et stat) the rotor circuit has lower impedane iph (Foll-load) RI Vph, credoced) X1+X2´equals Xeg can be obbained from the input reactive power and curent. R1+R2'CRI= Stator Resistance R2'= Rotor Resistance) czn be obtzined from input power and Current. Total real power PLz 3CI Line)R, tR2') W reachve Total absorbed inductor far power QL=3(lkine) Xeq VAc 2 What Xeq, R1+R2,RI,RZ'?

Suppose two generators supplying a load. Generator-1 has a no-load frequency of 61.5 Hz and a slopesp1 of 1 MW/Hz. Generator-2 has a no-load frequency of 62 Hz and a slope sp2 of 1MW/Hz. The twogenerators are supplying a real load totaling 2.5 MW at 0.8 PF lagging. Draw the resulting systempower-frequency or house-diagrams. Determine (a) at what frequency is the system operating, andhow much power is supplied by each of the generators? (b) if an additional 0.75-MW load wereattached to this power system. What would the new system frequency be, and how much powerwould the each generator supply now? (c) with the system in the configuration described in part (b),what will the system frequency and generators power be if the governor set points on generator-1 areincreased by 0.5 Hz?

32. The incremental cost characteristics of two generators delivering a load of 200 MW are as follows: dF = 2.0 + 0.01 P, dP, dP dF, -= 1.6 + 0.02 P, For economic operation the generators P, and P, should be (a) 120 MW and 80 MW (b) 81 MW and 120 MW (c) 120 MW and 120 MW (d) 80 MW and 80 MW

A single-phase, 120V(rms),60Hz source supplies power to a series R-L circuit consisting of R=10 and L=40mH. (a) Determine the power factor of the circuit and state whether it is lagging or leading. (b) Determine the real and reactive power absorbed by the load. (c) Calculate the peak magnetic energy Wint stored in the inductor by using the expression Wint=L(Irms)2 and check whether the reactive power Q=Wint is satisfied. (Note: The instantaneous magnetic energy storage fluctuates between zero and the peak energy. This energy must be sent twice each cycle to the load from the source by means of reactive power flows.)