Please Log in or Register for more.

If we change the excitation of synchronous machine will it affect on power factor?


123 views

1 Answer

Answer :

Yes, If we change the excitation of synchronous machine it will affect on power factor. If the synchronous motor is overexcited then it will have leading power factor and if the motor is underexcited then it will have lagging power factor.

Like 0 like

Please log in or register to answer this question.

Related Questions


If we change the excitation of synchronous machine will it affect on motor speed?
Last Answer : No, If we change the excitation of synchronous machine it will not affect on motor speed.

Show More

105 views 1 answer








Last Answer : Yes, we can make the power factor of synchronous motor leading by adjusting its excitation.

Show More

110 views 1 answer








Last Answer : Synchronsizing power of a synchronous machine is inversely proportional to the synchronous reactance.

Show More

95 views 1 answer








Last Answer : A synchronous motor running with normal excitation adjusts to load increases essentially by increase in armature current.

Show More

196 views 1 answer







what will happen when excitation of an unloaded salient pole synchronous motor suddenly gets disconnected?
Last Answer : When excitation of an unloaded salient pole synchronous motor suddenly gets disconnected the motor will stop.

Show More

367 views 1 answer







A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?
Last Answer : A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because stator supply is not required to produce magnetic field.

Show More

169 views 1 answer








Last Answer : The standard full-load power factor ratings for synchronous motors are unity or 0.8 leading.

Show More

98 views 1 answer








Last Answer : For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.

Show More

110 views 1 answer







If the load of the normally excited synchronous motor is increased the power factor will?
Last Answer : If the load of the normally excited synchronous motor is increased the power factor will become lagging.

Show More

150 views 1 answer







The synchronous motor which works on leading power factor and does not drive any mechanical load is called?
Last Answer : The synchronous motor which works on leading power factor and does not drive any mechanical load is called synchronous condenser.

Show More

163 views 1 answer







If the field of synchronous motor is under excited, power factor will be?
Last Answer : If the field of synchronous motor is under excited, power factor will be lagging.

Show More

483 views 1 answer







In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load  (A) The armature current increases and the power factor decreases  (B) The armature ... but is lagging  (D) The armature current decreases and the power factor increases and is leading
Last Answer : In a synchronous generator if the excitation increased from a low value to normal value, with a fixed load The armature current decreases and the power factor increases and is leading

Show More

130 views 1 answer







The effect of increasing load on a synchronous motor running with normal excitation is (A) Increase both its Ia and power factor. (B) Decrease Ia, but increase power factor. (C) Increase Ia, but decrease power factor (D) Decrease both Ia and power factor.
Last Answer : The effect of increasing load on a synchronous motor running with normal excitation is Increase Ia, but decrease power factor

Show More

550 views 1 answer







How can we improve power factor using synchronous motor?

Show More

78 views 0 answers







In a synchronous generator delivering lagging power factor load  (1) the excitation emf leads terminal voltage by the power angle (2) the excitation emf lags terminal voltage by the power angle (3) ... by the power factor angle (4) excitation emf lags the terminal voltage by the power factor angle
Last Answer : In a synchronous generator delivering lagging power factor load the excitation emf leads terminal voltage by the power angle

Show More

340 views 1 answer







The power factor angle and torque angle of a salient pole synchronous generator drawing a current of 1.0 pu from a lagging load are 45o and 15o, respectively. The direct axis and quadrature axis currents, respectively, are (A) 0.5 pu ... pu, 0.5 pu (C) 0.707 pu, 0.707 pu (D) 0.5 pu, 0.5 pu
Last Answer : The power factor angle and torque angle of a salient pole synchronous generator drawing a current of 1.0 pu from a lagging load are 45o and 15o, respectively. The direct axis and quadrature axis currents, respectively, are 0.866 pu, 0.5 pu

Show More

98 views 1 answer








Last Answer : In a distribution system, in order to improve power factor, the synchronous capacitors are installed at the receiving end.

Show More

185 views 1 answer







Can a synchronous condenser improve power factor?
Last Answer : Yes, synchronous condenser can improve power factor.

Show More

90 views 1 answer








Last Answer : A synchronous machine with low value of short-circuit ratio has lower stability limit.

Show More

103 views 1 answer







V - curve of synchronous machine shows the relation between?
Last Answer : V - curve of synchronous machine shows the relation between AC armature current and DC field current.

Show More

80 views 1 answer







Why synchronous machine is called doubly excited machine?
Last Answer : Armature windings of synchronous machines either deliver 3 phase AC or absorb 3 phase AC source,  whereas field windings are energized from DC source. Thus due to presence of AC on armature and DC on field windings, synchronous machines are often referred as doubly excited machines.

Show More

3.3k views 2 answers







Which machine is the exciter of synchronous machine?
Last Answer : DC shunt machine is the exciter of synchronous machine.

Show More

70 views 1 answer








Last Answer : In two part tariff, variation in load factor will affect operating or running charges.

Show More

79 views 1 answer







For a 500 Hz frequency excitation, a 50 km long power line will be modeled as
Last Answer : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as long line

Show More

2.8k views 1 answer







In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as  (1) synchronous motor (2) synchronous generator (3) asynchronous motor (4) asynchronous generator
Last Answer : In a synchronous machine, if the field flux axis ahead of the armature field axis in the direction of rotation, the machine is operating as synchronous generator 

Show More

603 views 1 answer







The 'Equal area criterion' for the determination of transient stability of a synchronous machine connected to an infinite bus  (1) ignores line as well as synchronous machine resistance ... consideration the possibility of machine losing synchronism after it has survived during the first swing.
Last Answer : 1

Show More

690 views 2 answers







The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole)  (A) has q -axis current only (B) has d -axis current only (C) has both d and q axis currents (D) cannot be divided between q and d axis currents
Last Answer : The armature current on symmetrical 3 phase short circuit of a synchronous machine (salient pole) has d -axis current only

Show More

193 views 1 answer







During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s)
Last Answer : During a disturbance on a synchronous machine, the rotor swings form A to B before finally setting down to steady state at point C on the power angle curve. The speed of the machine during oscillation is synchronous at point(s) only at C

Show More

249 views 1 answer







Torque angle for the synchronous machine is the angle between (A) stator magnetic field and rotor magnetic field (B) stator magnetic field and net magnetic field in the air gap (C) rotor magnetic field and net magnetic field in the air gap (D) excitation voltage and impedance voltage drop
Last Answer : Torque angle for the synchronous machine is the angle between rotor magnetic field and net magnetic field in the air gap

Show More

129 views 1 answer







The synchronous motor will develop maximum power when the load angle is?
Last Answer : The synchronous motor will develop maximum power when the load angle is 900.

Show More

226 views 1 answer







The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is (A) 0.25 pu (B) 0.5 pu (C) 1.0 pu (D) 1.5 pu
Last Answer : The maximum reluctance power of a salient-pole synchronous motor having direct-axis reactance, 1.0 pu and quadrature-axis reactance, 0.5 pu, and input voltage, 1.0 pu is 0.5 pu

Show More

98 views 1 answer







While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then (A) It would over-run the other alternator (B) Its rotor ... (C) Its portion of share in load will increase (D) Its power factor would be decreased.
Last Answer : While keeping the excitation constant, if the steam supply of an alternator running in parallel with another identical alternator is increased, then Its portion of share in load will increase

Show More

430 views 1 answer








Last Answer : For a D.C. shunt motor if the excitation is changed torque will change but power will remain constant.

Show More

168 views 1 answer







Why do we need to correct power factor?

Show More

62 views 0 answers







How can we reverse the direction of rotation of synchronous motor?
Last Answer : By reversing supply phase sequence we can reverse the direction of rotation of synchronous motor.

Show More

305 views 1 answer







Can we use the synchronous motor as the synchronous capacitor?
Last Answer : Yes, we can use the synchronous motor as the synchronous capacitor when the synchrnous motor is overexcited.

Show More

91 views 1 answer







What is meant by Power factor?
Last Answer : Ans. Power factor means ratio of true power to apparent power. It is cosine of phase angle between voltage and current. Its value is 1 for Unity P.F. Loads, 0 to 1 lagging for inductive loads and o to 1 leading for capacitive loads.

Show More

17 views 1 answer







State the effects of low power factor on efficiency and voltage regulation of short transmission lines. 
Last Answer : i) Effect of Low power factor on efficiency:- When power factor of load reduces current drawn by transmission line increases so copper losses in transmission line increases, hence transmission ... increases, so voltage drop in transmission line increases so regulation increases. (Become Poor) 

Show More

359 views 1 answer







Briefly explain how the power factor of an inductive circuit can be improved.
Last Answer : As we know that power factor should be corrected to ensure that the current supplied is cost friendly. Meaning the power factor should be around one but not greater than one(0.8-0.9) in a ... an inductive circuit due to the inductive reactance which oppose the change of current in the ac circuit. 

Show More

183 views 1 answer







What is the value of capacitance required to improve power factor from 0.7 to 0.9. Given that: Real power = 50 W Vrms of the source = 120 Frequency = 50 Hz   #powerfactor

Show More

197 views 0 answers







Why capacitors are used to improve power factor?
Last Answer :  Capacitors generate reactive power instead of that drawn from source which is required by inductive loads.so it reduce the reactive current which is drawn from source to be drawn from capacitor.This control in Electric bills cost.

Show More

183 views 3 answers







Discuss how power factor tariff results into energy conservation.
Last Answer : Power factor tariff results into energy conservation: i) Applying incentives and penalties according to power factor is an effective way, which enables consumer to improve power factor so that he can ... finally leads to reduction in the current drawn by the load and helps for energy conservation.

Show More

2.6k views 1 answer







Draw and explain bulk correction method for power factor & control.
Last Answer : Bulk correction method for power factor & control: i) Here individual starter controls the capacitors located at distribution panel. ii) Centralized compensation is employed in large industrial plants where many ... capacitor units in steps to maintain P.F. more than preset limit (0.95). 

Show More

113 views 1 answer







State the incentives and penalties related with power factor tariff.
Last Answer : Incentives and penalties related with power factor tariff: In addition to basic tariff (Maximum Demand Tariff / KVA Maximum Demand Tariff / Load factor tariff) the tariff in which P.F. of ... industrial consumer/H.T/ commercial consumers with contract demand above 80 kw/ 100Kva/107 hp consumer.

Show More

142 views 1 answer







With a neat sketch explain working of 1 phase dynamometer type power factor meter.
Last Answer : Working of 1 phase dynamometer type power factor meter : The current coil is connected in series with load. Two pressure coils marked as A and B are connected across the supply terminals ... becomes stationary and the pointer shows steady deflection corresponding to the power factor of the load. 

Show More

202 views 1 answer







State the significance of power factor.
Last Answer : Significance of power factor:-  1. Cosine of angle between voltage & current in a circuit is called power factor. 2. It is a measure of the real power in a circuit. 3. Inductive & ... KVA rating equipment 5. Greater conductor size 6. CosØ = R/Z  CosØ= Active Power/ Apparent Power 

Show More

57 views 1 answer







A transformer has negative voltage regulation when its load power factor is   (1) Zero (2) Unity (3) Leading (4) Lagging
Last Answer : 0

Show More

5.1k views 3 answers







The power factor of dielectric :  (A) is a function of temperature of the dielectric only (B) depends only on voltage stress to which the dielectric is stressed (C) always constant (D) both (A) and (B)
Last Answer : The power factor of dielectric :  (A) is a function of temperature of the dielectric only (B) depends only on voltage stress to which the dielectric is stressed (C) always constant (D) both (A) and (B)

Show More

167 views 1 answer







Power station having Load factor = 70%, capacity factor = 50%, used factor = 60%, maximum demand = 20MW then annual energy production is  (1) 122.8 GWh (2) 198.55 GWh (3) 128.2 GWh (4) 188.82 GWh
Last Answer : Power station having Load factor = 70%, capacity factor = 50%, used factor = 60%, maximum demand = 20MW then annual energy production is 122.8 GWh

Show More

148 views 1 answer







What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these
Last Answer : What is the power factor when a single phase watt meter operating on 200 V and 5 A for 5 hours makes 2016 revolutions and the meter constant in revolution is 420? A) 0.04 B) 1.04 C) 0.96 D) None of these

Show More

209 views 1 answer






Show More⇦ PreviousNext ⇨