Question

THESE ARE QUESTION FROM THE TOPIC POWER FACTOR IMPROVEMENT FROM THE SUBJECT POWER SYSTEM FUNDAMENTALS PLEASE DO THE QUESTIONS STEP BY STEP AND IN NEAT HAND WRITTING THE ANSWERS ARE GIVEN WITH THE QUESTIONS

1) A 3-phase synchronous motor having a mechanical load (including losses) of 122 kW is connected in parallel with a load of 510 kW at 0·8 p.f. lagging. The excitation of the motor is adjusted so that the kVA input to the motor becomes 140 kVA. Determine the new power factor of the whole system.

ANS [0·8956 lagging]

2) A 3-phase synchronous motor is connected in parallel with a load of 700 kW at 0·7 power factor lagging and its excitation is adjusted till it raises the total p.f. to 0.9 lagging. Mechanical load on the motor including losses is 150 kW. Find the power factor of the synchronous motor.

ANS [0·444 leading]

Answer #1

THESE ARE QUESTION FROM THE TOPIC POWER FACTOR IMPROVEMENT FROM
THE SUBJECT POWER SYSTEM FUNDAMENTALS PLEASE DO THE QUESTIONS STEP
BY STEP AND IN NEAT HAND WRITTING THE ANSWERS ARE GIVEN WITH THE
QUESTIONS
1) . A station supplies 250 kVA at a lagging power factor of
0·8. A synchronous motor is connected in parallel with the load. If
the combined load is 250 kW with a lagging p.f. of 0.9, determine
:
(i) the leading kVAR taken by the...

THESE ARE QUESTION FROM THE TOPIC POWER FACTOR IMPROVEMENT FROM
THE SUBJECT POWER SYSTEM FUNDAMENTALS PLEASE DO THE QUESTIONS STEP
BY STEP AND IN NEAT HAND WRITTING THE ANSWERS ARE GIVEN WITH THE
QUESTIONS
1) 1. What should be the kVA rating of a capacitor which would
raise the power factor of load of 100 kW from 0·5 lagging to 0·9
lagging
ANS (125 KVA)
2) A 3-phase, 50 Hz, 3300 V star connected
induction motor develops 250 H.P....

The 400 V, 50 kVA, 0.8 power factor leading delta connected
synchronous motor has synchronous reactance of 3-ohm, resistance
neglected. It is supplying a 12-kW load with initial power factor
of 0.86 lagging. The windage and friction losses are 2.0 kW and the
core losses are 1.5 kW. Determine
(a) the motor efficiency; the line current; armature current;
and excitation voltage.
(b) If the flux of the motor is increased by 20 percent
determine the excitation voltage; armature current; and...

A 3 phase, 3.3 kV industrial plant has an overall power factor
of 0.88 lagging. A 200 kVA synchronous motor is added to the system
and is run at zero power
factor and slightly reduced rating to provide power factor
correction only. The total load is then 350 kVA at unity power
factor. It was then decided to run the synchronous machine at its
rated kVA and use it as a source of mechanical power, what gross
mechanical power would...

1.
A single phase circuit has a load of 500kVa at a power factor of
0.707 lagging. Calculate the kVA of the capacitors needed to
improve the power factor to unity
3. When connected to a 120-v(rms), 60Hz power line, a load
absorbes 4 kw at a lagging power factor of 0.8. Find the
capacitance necessary to raise the pf to 0.9
4. A three phase motor draws 20kva at 0.707 power factor
lagging from a 208V source. Determine the...

Q1. A 3-phase, 400 V synchronous motor having a power
consumption of 50 kW is connected in parallel with an induction
motor which takes 200 kW at a power factor of 0·8 lagging.
(i) Calculate the current drawn from the mains when the power
factor of the synchronous motor is unity.
(ii) At what power factor should the synchronous motor
operate so that the current drawn from the mains is
minimum.

THESE ARE QUESTION FROM THE SUBJECT POWER SYSTEM FUNDAMENTALS
AND THE TOPIC IS TRANSMISSION LINES
1) A 200 km, 3-phase transmission line has its
conductors placed at the corners of an equilateral triangle of 2·5
m side. The radius of each conductor is 1 cm. Calculate
: (i) line to neutral capacitance of the line,
(ii) charging current per phase if the line is maintained at 66
kV, 50 Hz.
ANS IS [(i) 2·02 µF (ii) 24·2 A]
2) A single...

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...

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...

Q4)
A three-phase, 104 kW, 3300 V, 50 Hz, Y-connected induction
motor delivers full output power to a
load connected to its shaft. The full-load slip is 0.02 and
full-load power factor is 0.85 lagging. If the stator
copper loss is 2400 W, the stator core loss is 3500 W, and the
friction and windage loss is 1200 W. Calculate:
(i) The developed mechanical power.
(ii) The air gap power.
(iii) The rotor copper loss.
(iv) The efficiency of the...

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