EE301 HW37 Name_________________ Section______________ Instructor____________ Date__________________
1a.) For a 4 pole, 60 Hz generator, determine the speed in rpm of the rotor:
b.) For a 2 pole rotor operating at 7200 rpm, determine the frequency of the electrical signal.
c.) How many poles would a generator need if it operated at half the rotor speed of problem
(1b), but produced the same frequency?
2) Given: At a hydroelectric plant on the great Columbia River, a 3-phase, Y-connected
synchronous generator is rated at 300 MVA, 60Hz and a line voltage of 25KV. It operates with
a lagging power factor of 0.75 and negligible armature resistance and reactance. Use Van as the
voltage reference.
Req’d:
a) Find the line current phasor Ia. (This would include the angle!).
b) Draw the power conversion diagram.
c) If there are no mechanical losses, find PIN. What is the efficiency of this generator?
Soln:
3) Given: A Y-connected, 4-pole, 3-phase, 2.2 KV, 60Hz synchronous generator with 0.06Ω per
phase resistance supplies rated line voltage/current to a Y connected load with a 0.85 lagging
power factor. The power out is 1.492 MW. The mechanical losses are 92KW. Use Van as the
voltage reference
Req’d:
a) Find Ia (phasor).
b) What is the efficiency of the generator?
c) Draw the power conversion diagram.
d) At what speed does the shaft rotate (rpm)?
e) What is the prime mover torque?
Soln: