Measurement of Energy and Power · Electrical and Electronics Measurement · GATE EE

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 (both positive), then the power factor of the load is

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 method. The readings of the two wattmeters are

An $$LPF$$ wattmeter of power factor $$0.2$$ is having three voltage settings $$300V,$$ $$150V$$ and $$75V,$$ and two current settings $$5 A$$ and $$10A.$$ The full scale reading is $$150.$$ If the wattmeter is used with $$150V$$ voltage setting and $$10A$$ current setting, the multiplying factor of the wattmeter is __________.

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 ___________.

Power consumed by a balanced $$3$$-phase, $$3$$-wire load is measured by the two wattmeter method. The first wattmeter reads twice that of the second. Then the load impedance angle in radians is

For the circuit shown in the figure, the voltage and current expressions are
$$v\left( t \right) = {E_1}\sin \left( {\omega t} \right) + {E_3}\sin \left( {3\omega t} \right)$$ and
$$i\left( t \right) = {{\rm I}_1}\sin \left( {\omega t - {\varphi _1}} \right) + {{\rm I}_3}\sin \left( {3\omega t - {\varphi _3}} \right) + {{\rm I}_5}\sin \left( {5\omega t} \right)$$

The average power measured by the Wattmeter is

Consider the following statement:
(i) 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 wattmeter is connected as shown in the fig. the wattmeter reads

A sampling wattmeter (that computes power from simultaneously sampled values of voltage and current) is used to measure the average power of a load. The peak to peak voltage of the square wave is $$10V$$ and the current is triangular wave of $$5A$$ $$p$$-$$p$$ as shown in the figure. The period is $$20$$$$ms$$. The reading in $$W$$ will be

The circuit in fig is used to measure the power consumed by the load. The current coil and the voltage coil of the watt meter have $$0.02$$ $$\Omega $$ and $$1000$$ $$\Omega $$ resistance respectively. The measured power compared to the load power will be

The line to line input voltage to the $$3$$ phase, $$50$$ Hz, ac circuit shown in fig is $$100$$ $$V$$ $$r.m.s$$ Assuming that the phase sequence is $$RYB$$ the wattmeter would read.

The minimum number of wattmeter(s) required to measure 3 $$-$$ phase, 3 $$-$$ wire balanced or unbalanced power is

Electro dynamic type watt meters have large errors while measuring power in a.c circuits at low power factor conditions, since the voltage across and the current though the

A dynamometer type wattmeter responds to the

The moving coil in a dynamometer wattmeter is connected

A water boiler at home is switched on to the $$A.C$$ mains supplying power at $$230$$ $$V/50$$ $$Hz.$$ The frequency of instantaneous power consumed by the boiler is

V_RN, V_YN and V_BN are the instantaneous line to neutral voltages and i_R, i_Y and i_B are instantaneous line currents in a balanced three-phase circuit, the computation, V_RN (i_y $$-$$ i_B) $$-$$ (V_YN $$-$$ V_BN) i_R will yield a quantity proportional to

The load shown in the figure is supplied by a $$400$$ $$V$$ (line-to-line) $$3$$-phase source ($$RYB$$ sequence). The load is balanced and inductive, drawing $$3464$$ $$VA.$$ When the switch $$S$$ is in position $$N$$, the three watt-meters $${W_1},\,{W_2}$$ and $${W_3}$$ read $$577.35$$ $$W$$ each. If the switch is moved to position $$Y,$$ the readings of the watt-meters in watts will be:

The coils of a wattmeter have resistances $$0.01$$ $$\Omega $$ and $$1000$$ $$\Omega $$; their inductances may be neglected. The wattmeter is connected as shown in the figure, to measure the power consumed by a load, which draws $$25$$ $$A$$ at power factor $$0.8$$. The voltage across the load terminals is $$30$$ $$V$$. The percentage error on the wattmeter reading is______________.

The figure shows a three phase delta connected load supplied from a $$400V,$$ $$50Hz,$$ $$3\phi $$ balanced source. The pressure coil and current coil of a wattmeter are connected to the load as shown. With the coil polarities suitably selected to ensure a positive deflection. The wattmeter reading will be.

A $$3$$ $$V$$ $$dc$$ supply with an internal resistance of $$2\,\,\Omega $$ supplies a passive non-linear resistance characterized by the relation $${V_{NL}} = {\rm I}_{NL}^2.$$ The power dissipated in the non-linear resistance is

An energy meter connected to an immersion heater (resistive) operating on an $$AC$$ $$230V,$$ $$50$$ $$Hz,$$ $$AC$$ single phase source reads $$2.3$$ units ($$kWh$$) in $$1$$ hour. The heater is removed from the supply and now connected to a $$4000$$ $$V$$ peak to peak square wave source of $$150$$ $$Hz.$$ The power in $$kW$$ dessipated by the heater will be

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 power and the power factor respectively are

A dc A-h meter is rated for 15 A, 250V. The meter constant is 14.4 A-sec/rev. The meter constant at rated voltage may be expressed as

A single-phase load is connected between $$R$$ and $$Y$$ terminals of a $$415$$ $$V,$$ symmetrical, $$3$$-phase, $$4$$-wire system with phase sequence $$RYB$$. A wattmeter is connected in the system as shown in figure. The power factor of the load is $$0.8 $$ lagging. The wattmeter will read

A wattmeter reads $$400$$ $$W$$ when its current coil is connected in the $$R$$ phase and its pressure coil is connected between this phase and the neutral of a symmetrical $$3$$-phase system supplying a balanced star connected $$0.8$$ $$p.f.$$ inductive load. The phase sequence is $$RYB.$$ What will be the reading of this wattmeter if its pressure coil alone is reconnected between the $$B$$ and $$Y$$ phases, all other connections remaining as before?

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 $${85^0}$$ (instead of $${90^0}$$). The errors introduced in the reading of this meter when the current is $$5$$ $$A$$ at power factors of unity and $$0.5$$ lagging are respectively

The two wattmeter method is used to measure active power on a three phase, three wire system. If the phase voltage is unbalanced, then the power reading is

The voltage phasor of a circuit is $$10\angle {15^ \circ }V$$ and the current phasor is $$2\angle - {45^ \circ }A.$$ The active and the reactive powers in the circuit are

For the circuit shown in Fig, the wattmeter reading will be .... W and the power dissipted in the load is ......W

A $$3$$ - $$\phi $$ load operates with balanced voltages applied to its terminals, and draws balanced currents. The potential coil of a moving coil wattmeter is connected from $$R$$ to $$Y$$ terminals of the load. The current coil of the meter is connected in series with phase $$B.$$ by appropriate derivation, show that the quantity indicated by this wattmeter is proportional to the reactive power drawn by the load

A symmetrical $$400V,$$ $$3$$-$$\phi $$ supply is connected to the network shown in fig. The phase sequence is $$RYB.$$ Find the reading on the wattmeter

$${R_1} = 30\Omega ,\,\,{X_1} = 50\Omega ,\,\,$$ and $${X_2} = 40\Omega $$