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In a low power factor wattmeter the compensating coil is connected in series with pressure coil.

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In a low power factor wattmeter the pressure coil is connected to the load side of the current coil.

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In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be?

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In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero. The power factor of the load must be 0.5.

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In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was?

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In a 3-phase power measurement by two wattmeter method, both the watt meters had identical readings. The power factor of the load was unity.

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The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is (A) 11% (B) 9% (C) 1.1% (D) 3%

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The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is 220 V. With the potential coil connected on the load side, the meter indicates 100 W. Approximate percentage error due to wattmeter connection is 11%

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Consider the following statements  1) The compensating coil of a low power factor wattmeter compensates the effect of the impedance of the current coil ii) The compensating coil of a low power factor wattmeter compensates the effect of the impedance of the voltage coil circuit  A) (i) is true but (ii) is false B) (i) is false but (ii) is true C) Both (i) and (ii) are true D) Both (i) and (ii) are false

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Consider the following statements  1) The compensating coil of a low power factor wattmeter compensates the effect of the impedance of the current coil ii) The compensating coil of a low power factor wattmeter compensates the ... C) Both (i) and (ii) are true D) Both (i) and (ii) are false

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When a D.C. series motor is connected to A.C. supply, the power factor will be low because of high inductance of field and armature circuits.

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The pressure coil of a wattmeter should be connected on the supply side of the current coil when load impedance is high.

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State any two disadvantages of one wattmeter method of measurement of 3 phase power.

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State any two disadvantages of one wattmeter method of measurement of 3 phase power. Disadvantages of one wattmeter method:- 1. Only used for balanced load 2. It can not be used for ... connection then neutral point must be available 4. Delta connection must be opened to connect current coil.

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State the effects of low power factor on efficiency and voltage regulation of short transmission lines. 

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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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The primary reason for low power factor is supply system is due to installation of induction motors.

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At which time power factor of the induction motor is low?

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The power factor of the inducction motor is low at the time of starting as compare to while the induction motor is running.

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The resistance in the circuit of the moving coil of a dynamometer wattmeter should be high.

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In a dynamometer 3-phase power factor meter, the planes of the two moving coils are at 120°.

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In a single phase power factor meter the phase difference between the currents in the two pressure coils is exactly 90°.

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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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The two pressure coils of a single phase power factor meter have the same dimensions and the same number of turns.

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A power factor meter has one current circuit and two pressure circuits.

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A moving-coil permanent-magnet instrument can be used as ammeter by using a low resistance shunt.

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In A.C. series motor compensating winding is employed to reduce sparking at the brushes.

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Compensating windings are used in D.C. generators to neutralise the cross-magnetising effect of the armature reaction.

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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) excitation emf leads the terminal voltage by the power factor angle (4) excitation emf lags the terminal voltage by the power factor angle

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In a synchronous generator delivering lagging power factor load the excitation emf leads terminal voltage by the power angle

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The benefit of power factor correction in a power system is (A) lower power consumption (B) increased demand charge (C) reduced load carrying capabilities in existing lines (D) reduced voltage profile

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The benefit of power factor correction in a power system is lower power consumption

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

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For high value of diversity factor, a power station of given installed capacity will be in a position to supply more number of consumers.

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The power factor at resonance in R-L- C parallel circuit is?

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since a rlc circuit at resonance behaves like a pure resistive circuit, i.e there is no phase difference between current and voltage, hence the power factor is unity.

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Power factor of an inductive circuit is usually improved by connecting capacitor to it in?

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Power factor of an inductive circuit is usually improved by connecting capacitor to it in parallel.

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Capacitors for power factor correction are rated in?

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Capacitors for power factor correction are rated in kVAR.

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In an alternator at lagging power factor the generated voltage per phase as compared to that at unity power factor?

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In an alternator, at lagging power factor the generated voltage per phase as compared to that at unity power factor must be more than terminal voltage.

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With a neat sketch explain working of 1 phase dynamometer type power factor meter.

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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. 

Description :

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

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Leading

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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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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

Description :

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, 0.866 pu (B) 0.866 pu, 0.5 pu (C) 0.707 pu, 0.707 pu (D) 0.5 pu, 0.5 pu

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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 0.866 pu, 0.5 pu

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The power factor of a D.C. circuit is always?

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The power factor of a D.C. circuit is always unity.

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The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is?

Answer :

The input of an A.C. circuit having power factor of 0.8 lagging is 40 kVA The power drawn by the circuit is 32 kW.

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The power factor of a single-phase induction motor is usually lagging.

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A synchronous motor has better power factor as compared to that of an equivalent induction motor. This is mainly because?

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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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For a consumer the most economical power factor is generally 0.95 lagging .

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Load factor of a power station is generally less than unity.

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Load factor of a power station is defined as average load/maximum demand.

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Can a synchronous condenser improve power factor?

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Yes, synchronous condenser can improve power factor.

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Can you have a power factor greater than 1?

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We cannot have power factor greater than 1. As it is a measure of cosine of angle between voltage and current. 

Description :

How does a capacitor improve power factor?

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Every circuit are usually more inductive than capacitive.it means that the current lags by voltage at small angle.hence we have to compensate this situation so we use Capacitor then this lag is compensate ... angle becomes low and the value of cos(phase angle) is increase and hence power also max.

Description :

Briefly explain how the power factor of an inductive circuit can be improved.

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. 

Description :

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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Why capacitors are used to improve power factor?

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.

Description :

Discuss how power factor tariff results into energy conservation.

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.

Description :

Draw and explain bulk correction method for power factor & control.

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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State the incentives and penalties related with power factor tariff.

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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State the significance of power factor.

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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 

Description :

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)

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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