Question

A 3- phase, 2 pole Y-connected synchronous machines has a line-line voltage of 6,000V in 60Hz power line, has an armature reactance of 2ohms/ phase and negligible armature resistance. Compute the following

A) In case of generating action if the line current is 385 A at a leading power factor of 0.8, the armature voltage per phase is 3464V, Compute the voltage per phase and power angle.

B) Draw the phasor diagram.

C) If the losses in the machine is 1000W Calculate the efficiency and the voltage regulation for the above case

D) compute the torque applied to generate the rated voltage

E) In case of the motoring action if the line current is 385A at a lagging power factor of 0.8, calculate the voltage per phase if armature voltage =3464V and power angle.

F) Draw the phasor diagram

G) If the losses in the machine is 1500W compute the output torque generated for the rated voltage.

H) Calculate the efficiency of the machine and speed regulation

Answer #1

A submarine has a 3-phase, Y-connected, 2- pole, 60Hz
synchronous generator rated to deliver 1687.5 kVA at a FP = 0.8
lagging with a line voltage of 450-V. The machine stator resistance
RS = 0.004 ?. The synchronous reactance is Xs=0.08 ?. The actual
system load on the machine draws 900 kW at FP = 0.6 lagging. Assume
that a voltage regulator has automatically adjusted the field
current so that the terminal voltage is its rated value. Mechanical
losses are...

A three-phase, 9,375 kVA, 13.8 kV, 4-pole, 60 Hz, Y-connected
synchronous generator has a synchronous reactance, Xs = 17.9, and
is connected to an infinite bus at rated voltage. If the rotational
and electrical losses are negligivle, what is Ia, Ef, delta, theta,
Tdrive, Phasor diagram, and power flow diagram (label completely
with numerical values for,
A) the machine as a generator; the prime-throttle is opened and
If is adjusted so that the machine delivers rated kVA, 0.8 pf
lagging,...

Please be clear in concept and handwriting.
A 20HP, three-phase, Wye-connected synchronous motor is
connected to a 277VAC, 60Hz
power supply. At rated conditions, the motor runs at 3600 rpm and
presents a 0.85 lagging
power factor to the power supply. The per-phase armature reactance
is 350m?. Armature
resistance is negligible, as are all other sources of power
loss.
Considering rated conditions,
a. draw a single-phase equivalent circuit showing V?, Ea and IA,
with values.
b. draw a phasor diagram...

A three phase Y connected synchronous motor has negligible
armature resistance and a synchronous reactance of 12 ohm/phase.
The motor takes 12,000kW at a line voltage of 13,200V. If the line
current is adjusted so that the excitation voltage is
9000V/phase:
a. What is the torque angle?
b. At what power factor is the motor operating?
c. What is its armature current?

A 20kW. 3-phase, +40 V. 4 pole, delta-connected permanent magnet
synchronous motor has following parameters Xs=5 ohm, Rs
negligible rated power factor = 1.0. Machine is
controlled by variable frequency control at a constant (V/f) ratio.
Calculate
(i) Armature current. torque angle and power factor at half full
load torque and 750 rpm.
(ii) armature current, torque angle and power factor at half
full load torque and 1000 rpm.
(iii) The braking torque, torque angle and power factor when
working under...

A 42 kVA three-phase synchronous generator with line voltage
4.16 kV at a frequency of 60 Hz, is connected in star
configuration. The generator has a winding whose armature
resistance is 0.8 Ω and a synchronous reactance of 7.4 Ω, both per
phase. Determine the voltage regulation when the power factor is
0.600 lagging.

A 3-phase, 5 MVA, kV, 60 Hz synchronous machine has a
synchronous reactance of 10 ohms per phase. The machine is
connected to kV, 60 Hz bus and is operated as synchronous condenser
(synchronous motor at no-load condition)
a. For normal excitation (excitation voltage terminal voltage),
find the line current. Draw the phasor diagram
b. If the excitation is increased to 150% of the normal excitation,
find the line current and reactive power delivered or absorbed by
the bus. Draw...

4) A three-phase synchronous motor of 4000 hp nominal, 13,200 V,
60 Hz, 2 poles, connected in star, operating at 0.84 of power
factor in advance, has an efficiency of 96.5%.
The synchronous reactance per phase is 49.33 Ω:
• Draw the phasor diagram on the grid sheet
• Determine the loading angle
• Determine the load torque

A three phase, 200 kW, 2300 V, 50 Hz star (wye) connected
non-salient rotor synchronous
motor has a synchronous reactance of 11 Ohms per phase. When it
draws 175 kW the power
angle is 10 electrical degrees. Neglect the ohmic losses.
a. Determine the excitation voltage per phase.
b. Calculate the supply line current.
c. Determine the supply power factor.
d. Draw the phasor diagram.
e. By what percentage should the field current be changed to
minimize the line current.

Please be clear in conceot and handwriting, thank
you.
A 20 kVA three-phase synchronous machine is connected to a 480
V, 60 Hz electrical service.
The per-phase armature reactance is 80%. Armature resistance is
negligible, as are all other sources of power loss.
Part A: Motor Configuration
The machine is configured to run as a motor. Its rated mechanical
power is 20 HP and it is 94% efficient.
The motor provides rated output mechanical power.
The excitation is set such...

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