Reference no: EM131294765
Question 1:
A three-phase 225kV:24kV, 60 Hz, transformer with Δ-Δ connection is supplying a load of 24kV, 325MVA, with 0.93 PF (lagging). The transformer impedance is neglected but the feeder to the transformer has an impedance of 0.11+j2.2 Ω per each line connected to its high voltage terminal. Find the following:
a) The input current from the feeder
b) Line-to-line voltage applied to the feeder.
c) The load current on the secondary side of the transformer
d) The transformer winding currents (primary and secondary)
Question 2:
An elementary machine with a smooth air gap has the following flux linkages on its stator and rotor:
λs = Lss·is + Lsr·cos?(poles⁄2·θm )·ir
λr = Lrr·ir + Lsr·cos? (poles⁄2·θm )·is
Find expressions for the coenergy, W'fld and the torque, T in terms of
Lss, Lrr, Lsr, poles, θm, is and ir
Question 3:
An 8 pole, 400Hz, three-phase synchronous generator has rotor radius of 0.15m, a length of 0.3 m and an air-gap length of 1.5 mm. The field winding has 1000 turns and a winding factor of 0.95 If the stator winding factor is assumed to be 0.93 and the stator is wye-connected, what would be the turns per phase required to achieve 460V LL, keeping the peak air-gap flux density below 1 T (round to the nearest turn)?What is the field current?
Question 4:
A 60Hz, three-phase wye-connected synchronous generator has the following ratings:
V(LLRated) = 460 V rms
VARated = 150kVA
VBase = 266 V rms
IBase = 188 A rms
Open circuit and short circuit tests are performed and the Short Circuit Ratio, SCR, is found to be
SCR=1.1
Assume that the stator resistance is negligible.
What is the base impedance?
What is the synchronous reactance, Xs in ohms?
If the generator is feeding a load of 120kVA with a power factor of 0.9 lagging, what is the magnitude and phase of Ia and Eaf?
Draw the phasor diagram either using per unit values
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