EE 136- Electrical Machines 2
QUIZ 2- MIDTERM PERIOD
Instruction Solve the following problem in a clean sheet of paper and show your
solution, box your final answer only. Upload your output in PDF format.
1. A 3phase, Y connected alternator is rated at 1600kVA ,13500v. The armature
resistance and synchronous reactance are 1.5 ohm and 30 ohm respectively per
phase. Calculate the percentage regulation for a load of 1280 kw at 0.6 leading pf.
2. A 2000 kVa,11kV, 3phase and Y connected alternator has a resistance of 0.3 ohm
and reactance of 5 ohm/phase. It delivers a full load current of 0.6 lagging pf at
rated voltage. Compute the terminal voltage for the same excitation and load
current at 0.8 pf leading.
3. A given 5 MVA ,50 Hz, 11kV, 3 phase Y connected alternator when supplying 100 A
at 0 pf leading has a line to line voltage of 12,370v. When the load is removed, the
terminal voltage falls down to 11,000 v. Predict the regulation of the alternator when
supplying full load at 0.8pf lag. Assume an effective resistance of 0.4 ohm per phase.
4. A 25kVa alternator has a total loss of 2000Watts. When it delivers rated kVa to a load
of a pf of 0.76. Calculate its efficiency.
5. The dc armature winding resistance between terminals of a 750kVa ,4400 v, 3 phase
alternator is 0.9 ohm. Calculate the Cu loss in the winding at full load.