1. Three 25.0KVA, 4801120VAC, single-phase, 60Hz transformers are connected delt-delta. The load on the bank is 50.0KVA, balanced load, with power factor of 1.0. A fault in one transformer required its removal, and the bank is operating open-delta. Determine the following:
a) What is the maximum load that could be placed on the bank before the failure?
b) What is the maximum line current allowed after the failure and removal?
c) What is the maximum capacity of the bank after the failure? Will it support the 50KVA load?
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2. Given a 480VDC separately excited generator operating at the rated speed of 1800rpm. The data on the machine is as follows: The saturation curve for this generator running at 1800rpm is attached. Assume the
Armature reaction = O.O VDC
The brush drop = O.O VDC
Ra = O.15 ohms
Rf= 24 ohms
Vf= 120 VDC
Using the saturation curve, solve for the following:
a) Eg, the induced voltage,
b) Ia, the armature current,
c) PL, the power delivered to the load, and
d) % Voltage Regulation
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