power factor

The figure shows the single-line diagram of a synchronous generator delivering P = 50 MW of power at unity power factor to an infinite bus. I_s denotes the stator current phasor. I...

A single-phase voltage source v_s = 325 sin(2π50t) V delivers a current, i = 12 sin(2π50t) + 9 sin(2π150t) A to a load. The load power factor, correct up to two decimal places, is:

A device (single-phase, 50 Hz, AC) yields the following measurements at its terminals: voltage = 141.4 ∠ -10° V, current = 0.7 ∠ -55° A. The power factor of the device is ________...

The input voltage v(t) and current i(t) of a converter are given by, v(t) = 300 sin(ωt) V i(t) = 10 sin (ωt - π/6) + 2 sin (3ωt + π/6) + sin (5ωt + π/2) A where, ω = 2π × 50 rad/s....

Consider a distribution feeder, with R/X ratio of 5. At the receiving end, a 350 kVA load is connected. The maximum voltage drop will occur from the sending end to the receiving en...

Using shunt capacitors, the power factor of a 3-phase, 4 kV induction motor (drawing 390 kVA at 0.77 pf lag) is to be corrected to 0.85 pf lag. The line current of the capacitor ba...

The input voltage $v(t)$ and current $i(t)$ of a converter are given by, $v(t)=300 \sin (\omega t) \mathrm{V}$ $$ i(t)=10 \sin \left(\omega t-\frac{\pi}{6}\right)+2 \sin \left(3 \o...

Consider a distribution feeder, with $R / X$ ratio of 5 . At the receiving end, a 350 kVA load is connected. The maximum voltage drop will occur from the sending end to the receivi...

A 3-phase, 11 kV, 10 MVA synchronous generator is connected to an inductive load of power factor (√3/2) via a lossless line with a per-phase inductive reactance of 5 Ω. The per-pha...

A 3-phase, 11 kV, 10 MVA synchronous generator is connected to an inductive load of power factor $(\sqrt{3}/2)$ via a lossless line with a per-phase inductive reactance of 5 $\Omeg...

A 3-phase, star-connected, balanced load is supplied from a 3-phase, 400 V (rms), balanced voltage source with phase sequence R-Y-B, as shown in the figure. If the wattmeter readin...

The type of single-phase induction motor, expected to have the maximum power factor during steady state running condition, is

The voltage at the input of an AC-DC rectifier is given by $$v(t) = 230\sqrt 2 \sin \omega t$$ where $$\omega = 2\pi \times 50$$ rad/s. The input current drawn by the rectifier is...

A three-phase synchronous motor draws 200 A from the line at unity power factor at rated load. Considering the same line voltage and load, the line current at a power factor of 0.5...

A single-phase transformer of rating 25 kVA, supplies a 12 kW load at power factor of 0.6 lagging. The additional load at unity power factor in kW (round off to two decimal places)...

A single-phase fully-controlled thyristor converter is used to obtain an average voltage of 180 V with 10 A constant current to feed a DC load. It is fed from single-phase AC suppl...

A single-phase 100 kVA, 1000 V / 100 V, 50 Hz transformer has a voltage drop of 5% across its series impedance at full load. Of this, 3% is due to resistance. The percentage regula...

Two wattmeter method is used for measurement of power in a balanced three-phase load supplied from a balanced three-phase system. If one of the wattmeters reads half of the other (...

If a synchronous motor is running at a leading power factor, its excitation induced voltage (E_f) is

The following measurements are obtained on a single phase load: V = 220 V ±1%, I = 5.0 A ± 1% and W = 555 W ± 2%. If the power factor is calculated using these measurements, the wo...

For the balanced Y-Y connected 3-phase circuit shown in the figure below, the line-line voltage is 208 V rms and the total power absorbed by the load is 432 W at a power factor of...

A load is supplied by a 230 V, 50 Hz source. The active power P and the reactive power Q consumed by the load are such that 1 kW $\le P \le$ 2 kW and 1 kVAR $\le Q \le$ 2 kVAR. A c...

A 25 kVA, 400 V, Δ-connected, 3-phase, cylindrical rotor synchronous generator requires a field current of 5 A to maintain the rated armature current under short-circuit condition....

A three-phase, three winding Δ/Δ/Y (1.1 kV/6.6 kV/400 V) transformer is energized from AC mains at the 1.1 kV side. It supplies 900 kVA load at 0.8 power factor lag from the 6.6 kV...

In the circuit shown in the figure, the diode used is ideal. The input power factor is _________. (Give the answer up to two decimal places.)

A 3-phase, 50 Hz generator supplies power of 3MW at 17.32 kV to a balanced 3-phase inductive load through an overhead line. The per phase line resistance and reactance are 0.25$\Om...

The equivalent circuit of a single phase induction motor is shown in the figure, where the parameters are R₁ = R₂' = X₁₁ = X₁₂'=12 Ω, X_M=240 Ω and s is the slip. At no-load, the m...

Two wattmeter method is used for measurement of power in a balanced three-phase load supplied from a balanced three-phase system. If one of the wattmeters reads half of the other (...

The following measurements are obtained on a single phase load: $$V = 220 V$$ $$ \pm $$$$1$$%. $${\rm I}$$$$= 5.0$$ $$A$$ $$ \pm \,1$$% and $$W=555$$ $$W$$ $$ \pm \,2$$%. If the po...

A 3-phase 50 Hz generator supplies power of 3 MW at 17.32 kV to a balanced 3-phase inductive load through an overhead line. The per phase line resistance and reactance are 0.25 $$\...

A load is supplied by a $$230$$ $$V,$$ $$50$$ $$Hz$$ source. The active power $$P$$ and the reactive power $$Q$$ consumed by the load are such that $$1$$ $$kW$$ $$ \le P \le 2\,kW\...

A 3-phase balanced load which has a power factor of 0.707 is connected to a balanced supply. The power consumed by the load is 5 kW. The power is measured by the two-wattmeter meth...

A single phase induction motor draws $$12MW$$ power at $$0.6$$ lagging power. A capacitor is connected in parallel to the motor to improve the power factor of the combination of mo...

While measuring power of a three-phase balanced load by the two-wattmeter method, the readings are $$100$$ $$W$$ and $$250$$ $$W$$. The power factor of the load is ___________.

The input voltage given to a converter is $${V_i} = 100\sqrt 2 \,\,\,\sin \,\,\,\left( {100\pi t} \right)\,\,V$$ The current drawn by the converter is $${i_i} = 10\sqrt 2 \,\,\,\si...

Match the items List-$${\rm I}$$ (To) with the items in List-$${\rm II}$$ (Use) and select the correct answer using the codes given below the lists. List-$${\rm I}$$ $$A.$$ improve...

A single phase full bridge converter supplies a load drawing constant and ripple free load current. If the triggering angle is $${30^ \circ },$$ the input power factor will be

A synchronous motor is connected to an infinite bus at $$1.0p.u$$ voltage and draws $$0.6$$ $$pu$$ at unity power factor. Its synchronous reactance is $$1.0$$ $$pu$$ and resistance...

A single $$-$$ phase fully controlled thyristor bridge $$ac$$ $$-$$ $$dc$$ converter is operating at a firing angle of $${25^ \circ }$$ and an overlap angle of $${10^ \circ }$$ con...

A three phase synchronous motor connected to ac mains is running at full load and unity power factor. If its shaft load is reduced by half, with field current held constant, its ne...

A $$3$$-phase $$4000$$ $$V,$$ $$5$$ $$kW,$$ star connected synchronous motor having an internal reactance of $$10$$ $$ohms$$ is operating at $$50\% $$ load, unity power factor. Now...

In transformers, which of the following statements is valid?

At an industrial sub-station with a $$4$$ $$MW$$ load, a capacitor of $$2$$ MVAR is installed to maintain the load power factor at $$0.97$$ lagging. If the capacitor goes out of se...

Two wattmeter's, which are connected to measure the total power on a three-phase system supplying a balanced load, read $$10.5$$ $$kW$$ and $$–2.5$$ $$kW$$ respectively. The total...

The type of single-phase induction motor having the highest power factor at full load is

A $$500$$ $$MW$$ $$3$$-phase $$Y$$-connected synchronous generator has a rated voltage of $$21.5kV$$ at $$0.85$$ $$pf.$$ The line current when operating at full load rated conditio...

The voltage-flux adjustment of a certain $$1$$-phase $$220$$ $$V$$ induction watt-hour meter is altered so that the phase angle between the applied voltage and the flux due to it $...

A stand-alone engine driven Synchronous generator is feeding a partly inductive load. A capacitor is now connected across the load to completely nullify the inductive current. For...

In a single phase $$3$$ winding transformer the turns ratio for primary: secondary: tertiary windings is $$20:4:1.$$ With the lagging currents of $$50A$$ at a power factor of $$0.6...

A $$415$$ $$V,$$ $$2$$ pole, $$3$$ phase, $$50$$ $$Hz,$$ star connected, non-salient pole synchronous motor has synchronous reactance of $$2\,\Omega $$ per phase and negligible sta...

The flux per pole in a synchronous motor with the field circuit ON and the stator disconnected from the supply is found to be $$25$$ $$mWb.$$ When the stator is connected to the ra...

A $$2300$$ $$V,$$ $$3$$-phase synchronous motor driving a pump is provided with a line ammeter and a field rheostat. When the rheostat is adjusted such that the $$ac$$ line current...

A $$5MVA$$, $$11kV$$, $$3$$-phase star connected alternator is synchronized to the bus bars and is operating with an induced $$EMF$$ of $$125\% $$ of the rated voltage. If the load...

In an induction motor, if the air gap is increased

The per unit voltage of two synchronous machines connected through a lossless line are $$0.95\,\,\angle \,{10^0}\,\,$$ and $$1.0\,\,\angle \,{0^0}\,\,$$. Match the two sides in the...

Two $$550$$ $$kVA$$ alternators operate in parallel to supply the following loads $$(i)$$ $$250$$ $$kW$$ at $$0.95$$ power factor lag $$(ii)$$ $$100$$ $$kW$$ at $$0.8$$ power facto...

A synchronous motor operates at $$0.8$$ $$p.f.$$ lagging. If the field current of the motor is continuously increased $$(1)$$ the power factor decreases upto a certain value of fie...