# Recent questions tagged phase

Explain following techniques related to energy conservation in transmission and distribution system. (i) By balancing phase currents (ii) Variable technical losses (I2R losses).

Split phase induction motor

What is Phase sequence? Draw waveforms of 3 phase emf.

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

State the use of:- (i) Clip-on-ammeter (ii) Phase sequence indicator

State the meaning of creeping error in 1 phase energy meter.

List any two methods of reactive power measurement in 3 phase circuit.

Define balanced and unbalanced load in three phase circuit.

Describe the following errors and their compensation: (i) Phase error (ii) Speed error

Describe with neat diagram phase sequence indicator.

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

State the application of phase sequence indicator; clip on ammeter, frequency meter & P.F. meter.

Draw and explain RC phase shift Oscillator.

State any four applications of three phase circuits.

For a balanced three phase star connected load for which line voltage is 230V and per phase resistance and reactance is 6 Ohm and 8 Ohm respectively. Calculate: 1) phase voltage 2) line current 3) power factor 4) total power absorbed

Write the relation between phase and line current, phase and line voltage for Star connection.

What is line voltage and phase voltage? Draw balanced three phase star connected system. Show all the voltages and currents.

Define phase sequence of three phase supply with waveforms. What is normal phase sequence? Which 3 standard colours are used to denote the phase sequence?

Draw the waveform of three phase AC supply voltage.

State any four advantages of three phase over single phase.

Write short notes on 3 phase AC system.

In an R-C phase shift oscillator, the minimum no. of R-C networks to be connected in cascade will be -

For 11kV line the inductance per km per phase will be of the order of:  (A) 1 H (B) 0.1 H (C) 1 mH (D) 0.1 mH

For 11 kV line the capacitance per km per phase will be of the order of:  (A) 1 Farad (B) 0.1 Farad (C) 0.01 Farad (D) 0.01 microF

A single phase transformer has resistance and reactance of 0.2 pu and 0.6 pu respectively. Its pu voltage regulation at 0.8 pf lagging would he

Oscillator independent of phase shift is  (1) Relaxation (2) Wein bridge (3) Clapp (4) All of these

Phase margin is the amount of angle to make the system  (1) Oscillatory (2) Stable (3) Unstable (4) Exponential

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

The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is

What is the slip (as a percentage) when a 6 pole single phase induction motor operating on 220 V and 60 Hz is rotating at speed of 1140 rpm? A) 60% B) 5% C) 10% D) None of these

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

When the phase difference between two sinusoidal quantities is 90° they are said to be ______ A) Phase right angle B) Phase quadrature C) Phase sinuright D) None of these

A 230 V, 50 Hz phase controlled single-phase full-controlled SCR bridge converter draws 15 A constant dc current. If the source inductance is 3 mH, the drop in dc output voltage is (A) 4.5 V (B) 6.75 V (C) 9 V (D) 13.5 V

In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in (A) voltage notching (B) harmonic distortion (C) voltage sag (D) voltage swell

A single core cable is designed to work for a single phase system with a peak voltage of 220 kV. The maximum permissible stress in the dielectric is not to exceed 20 kV/mm. For economical size, the overall core diameter of the cable is (A) 28.2 mm (B) 26.4 mm (C) 24.4 mm (D) 22.0 mm

When a V-V three phase transformer system is converted into a Δ-Δ system, increase in capacity of the system is (A) 86.6% (B) 50% (C) 57.7% (D) 73.2%

Phase modifier is normally installed

The disc of a single phase Induction-type energy meter makes 60 revolutions in 6 minutes. Meter Constant is 1200 rev/kWh. Power consumption in the load is (A) 1.2 kW (B) 1 kW (C) 600 W (D) 500 W

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%

The product of apparent power and cosine of the phase angle between circuit voltage and current is?

In a three-phase supply floating neutral is undesirable because it way give rise to?

What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value ?

The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that?