Last Answer : For power factor correction, synchronous motors operate at no-load and greatly over-excited fields.
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110 views
1 answer
asked
Mar 20, 2018
by
anonymous
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.
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150 views
1 answer
asked
Mar 18, 2018
by
anonymous
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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.
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163 views
1 answer
asked
Mar 18, 2018
by
anonymous
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.
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169 views
1 answer
asked
Mar 20, 2018
by
anonymous
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If we change the excitation of synchronous machine will it affect on power factor?
Last 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.
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123 views
1 answer
asked
Mar 18, 2018
by
anonymous
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.
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483 views
1 answer
asked
Mar 18, 2018
by
anonymous
Last Answer : Synchronous motors are generally not self-starting because the direction of instantaneous torque reverses after half cycle.
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93 views
1 answer
asked
Mar 20, 2018
by
anonymous
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
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340 views
1 answer
asked
Apr 29, 2018
by
anonymous
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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
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98 views
1 answer
asked
Apr 28, 2018
by
anonymous
Last Answer : In a distribution system, in order to improve power factor, the synchronous capacitors are installed at the receiving end.
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185 views
1 answer
asked
Mar 20, 2018
by
anonymous
Can a synchronous condenser improve power factor?
Last Answer : Yes, synchronous condenser can improve power factor.
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90 views
1 answer
asked
Mar 19, 2018
by
anonymous
How can we improve power factor using synchronous motor?
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78 views
0 answers
asked
Mar 15, 2018
by
anonymous
Last Answer : Yes, we can make the power factor of synchronous motor leading by adjusting its excitation.
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110 views
1 answer
asked
Mar 6, 2018
by
anonymous
SYNCHRONOUS MOTORS MCQ
Last Answer : 101. In a synchronous motor it the back e.m.f. generated in the armature at noload is approximately equal to the applied voltage, then (a) the motor is said to be fully loaded (b) the torque ... square of the applied voltage (c) inversely proportional to applied voltage (d) none of the above Ans: a
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20 views
3 answers
Damper winding is provided in 3 phase synchronous motors to :
Last Answer : Damper winding is provided in 3 phase synchronous motors to : provide starting torque and prevent hunting
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93 views
1 answer
asked
Apr 29, 2018
by
anonymous
What is the difference between synchronous and asynchronous motors?
Last Answer : The motor which rotates at constant speed is called synchronous motor. And that constant speed is called as synchronous speed. And the motor which does not rotates at constant speed are called asynchronous motor. Asynchronous motor is also called as Induction motor.
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143 views
1 answer
asked
Mar 15, 2018
by
anonymous
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.
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226 views
1 answer
asked
Mar 18, 2018
by
anonymous
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Last Answer : Synchronsizing power of a synchronous machine is inversely proportional to the synchronous reactance.
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95 views
1 answer
asked
Mar 20, 2018
by
anonymous
A 50 Hz, 3-phase induction motor delivers a full load speed of 1440 r.p.m. The number of poles of the motor will be
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34 views
0 answers
The efficiencies of transformers compared with that of electric motors of the same power are?
Last Answer : Transformers have high efficiency than the same ratted motors
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179 views
2 answers
asked
Mar 19, 2018
by
anonymous
Have you ever taken part in surveys about listening/watching ratings?
Last Answer : answer:Nielsen Ratings are widely used. They use different methods to see what a group of selected viewers are watching and use that as a sample group. ---------- Nielsen television ratings are ... identify it. That way they can tell more reliably if someone is watching a recorded program as well.
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0 views
1 answer
asked
Feb 27
by
anonymous
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Oil Filter Ratings
Last Answer : When grading oil filters, three main criteria must be considered: single-pass efficiency, multiple-pass efficiency, and the micron rating for particle pass-through. Single-Pass Efficiency Single- ... using an ISO approved particle counting is used to determine the real efficiency of oil filters.
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14 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
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98 views
1 answer
asked
Apr 28, 2018
by
anonymous
A transformer has negative voltage regulation when its load power factor is (1) Zero (2) Unity (3) Leading (4) Lagging
Last Answer : 0
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5.1k views
3 answers
asked
Apr 30, 2018
by
anonymous
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
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148 views
1 answer
asked
Apr 29, 2018
by
anonymous
Last Answer : The power factor of a single phase load can be calculated if the instruments available are three ammeters or three voltmeters.
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296 views
2 answers
asked
Mar 21, 2018
by
anonymous
Last Answer : Load factor of a power station is generally less than unity.
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107 views
1 answer
asked
Mar 20, 2018
by
anonymous
Last Answer : Load factor of a power station is defined as average load/maximum demand.
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321 views
1 answer
asked
Mar 20, 2018
by
anonymous
Minimum voltage regulation occurs when the power factor of the load is?
Last Answer : Minimum voltage regulation occurs when the power factor of the load is leading.
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224 views
1 answer
asked
Mar 19, 2018
by
anonymous
Last Answer : A synchronous motor running with normal excitation adjusts to load increases essentially by increase in armature current.
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196 views
1 answer
asked
Mar 20, 2018
by
anonymous
The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as?
Last Answer : The maximum constant load torque under which a synchronous motor will pull into synchronism at rated rotor supply voltage and frequency is known as pull-in torque.
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302 views
1 answer
asked
Mar 20, 2018
by
anonymous
Last Answer : The coupling angle or load angle of synchronous motor is defined as the angle between the rotor and the stator poles of opposite polarity.
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218 views
1 answer
asked
Mar 20, 2018
by
anonymous
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Last Answer : If the synchronous motor, properly synchronised to the supply is running on no load and is having negligible loss then the stator current will be zero.
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116 views
1 answer
asked
Mar 20, 2018
by
anonymous
In a synchronous motor which losses varies with load?
Last Answer : In a synchronous motor, copper losses varies with load.
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102 views
1 answer
asked
Mar 18, 2018
by
anonymous
Why the power factor of semiconverter is better than full converter?
Last Answer : Power factor of semiconverter is better than full converter
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2.9k views
1 answer
asked
Mar 8, 2018
by
anonymous
At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is : (A) 7000 W (B) 6000 W (C) 8000 W (D) 4000 W
Last Answer : At full -load of a transformer, the iron loss and copper loss are 3000 W and 4000 W respectively. Then total loss at maximum efficiency is : 6000 W
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305 views
1 answer
asked
Apr 30, 2018
by
anonymous
The ratio of full -load volt-amperes to short-circuit volt-amperes is equal to :
Last Answer : The ratio of full -load volt-amperes to short-circuit volt-amperes is equal to : Z (p.u)
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154 views
1 answer
asked
Apr 30, 2018
by
anonymous
Last Answer : The ratio of starting torque to full-load torque is least in case of shunt motors.
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878 views
1 answer
asked
Mar 20, 2018
by
anonymous
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.
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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)
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359 views
1 answer
asked
May 22, 2020
by
anonymous
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.
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183 views
1 answer
asked
May 17, 2020
by
anonymous
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
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197 views
0 answers
asked
May 17, 2020
by
anonymous
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.
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183 views
3 answers
asked
Aug 18, 2019
by
anonymous
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.
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2.6k views
1 answer
asked
Sep 29, 2018
by
anonymous
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).
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113 views
1 answer
asked
Sep 29, 2018
by
anonymous
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.
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142 views
1 answer
asked
Sep 22, 2018
by
anonymous
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.
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202 views
1 answer
asked
Sep 6, 2018
by
anonymous
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
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57 views
1 answer
asked
Sep 6, 2018
by
anonymous
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)
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167 views
1 answer
asked
Apr 30, 2018
by
anonymous
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
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209 views
1 answer
asked
Apr 29, 2018
by
anonymous
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