# In the case of power measurement by two wattmeter method in a balanced 3Φ system with a pure inductive load

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In the case of power measurement by two wattmeter method in a balanced 3Φ system with a pure inductive load both the Wattmeter will indicate the same but of opposite sign.

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In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings of the wattmeters are 4 kW and 2 kW respectively, the later is being taken after reversing the connections of current coil. the power factor and reactive power of the load is A) 0.2 & 6 kVAR B) 0.2 & 6 √3 kVAR C) 0.32 & 2 kVAR D) 0.32 & 2 √3 kVAR

Measurement of power and power factor of a 3-phase system by two wattmeter method can be obtained in case of  1. Balanced load and balanced source  2. Balanced source with 3-phase 3-wire unbalanced load  3. Unbalanced source with 3-phase 3-wire balanced load  4. Balanced source with 3-phase 4-wire unbalanced load  5. unbalanced and unbalanced source    (a) 1 only (b) 2, 3 and 5 (c) 1, 2, 3, 4 and 5 (d) 1, 2, 3 and 5

Two wattmeter method is employed to measure power in a 3 -phase balanced system with the current coil connected in the A and C lines. The phase sequence is ABC. If the wattmeter with its current coil in A -phase line reads zero, then the power factor of the 3 -phase load will be

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?

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

In the measurement of power by two wattmeter method, when the readings of the two wattmeters are equal, the power factor is (A) Zero (B) Leading (C) Lagging (D) Unity

The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are 8 kW and 4 kW. The power factor of the load is (A) zero (B) 0.5 (C) between zero and 0.5 (D) between 0.5 and unity

While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are equal and opposite, when (a) load is balanced (b) power factor is unity (c) phase angle is between 60° to 90° (d) the load is purely inductive

For power measurement of three phase circuit by two wattmeter method, when the value of power factor is less than 0.5 lagging:

Two wattmeter method can be used in a three phase system excited with balanced three phase supply  A) To measure real power and power factor in a balanced load B) To measure reactive power in a balanced load C) To measure real power in an unbalanced load D) All of the above

In the measurement of three phase power by two wattmeter method, if the two wattmeter readings are equal then power factor of the circuit is  (A) 0.8 lag (B) Unity (C) 0.8 lead (D) Zero

In two -wattmeter method of power measurement, if one wattmeter shows negative reading, then the power factor of the circuit is treated as (A) Unity (B) Lagging (C) Leading (D) Zero

Measurement of power by voltmeter and ammeter method in a circuit resulted in calculated maximum errors of ±1 % and ± 2 %, respectively. The likely error in calculated power is (A) ± 3 % (B) ± 0.022 % (C) ± 1.5 % (D) ± 0.22 %

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

Two wattmeters are used to measure the power in a 3 -phase balanced system. What is the power factor of the load when one wattmeter reads twice the other ?  (a) 0 (b) 0.5 (c) 0.866 (d) 1

Describe with neat circuit diagram the method of measurement of power in a High voltage, high current a.c circuit.

The power in a 3-phase load is measured by two watt meters. If one watt meter reads zero, then the load power factor is (A) Zero (B) 0.5 (C ) 0.866 (D) unity

The minimum number of wattmeter(s) required to measure 3-phase, 3-wire balanced or unbalanced power is  A) 1 B) 2 C) 3 D) 4

The power delivered to a 3-phase load can be measured by the use of two wattmeters only when the  (a) load is unbalanced (b) load is balanced (c) three phase load is connected to the source through three wires (d) three phase load is connected to the source through four wires

In a balanced 3 -phase 200 V circuit, the line current is 115.5 A. When the power is measured by two wattmeter method, one of the wattmeters reads 20 kW and the other one reads zero. What is the power factor of the load ?

If the reference bus is changed in two load flow runs with same system data and power obtained for reference bus taken as specified P and Q in the latter run, the system losses  A) Will be unchanged but complex bus voltages will change B) Will change but complex bus voltage remain unchanged C) As well as complex bus voltage will changed D) As well as complex bus voltage will be unchanged

A single-phase voltage source square -wave inverter feeds pure inductive load. The waveform of the load current will be

If a dynamometer wattmeter is connected in an ac circuit, the power indicated by the wattmeter will be (a) volt-ampere product (b) average power (c) peak power (d) instantaneous power

A balanced Delta connected load supplied with 440 V 50 Hz three phase AC supply has R=10 Ohm and L=0.6 mH in is each arm. Calculate line and phase current, active power.

The power delivered to a three-phase load can be measured by the use of 2 wattmeter only when the A. Load is balanced B. 3 -phase load is connected to the source through 3 wires C. Load is unbalanced D. 3 -phase load is connected to the source through 4 wires

Pure inductive circuit takes power from the A.C. line when?

A single phase full-wave half-controlled bridge converter feeds an inductive load. The two SCRs in the converter are connected to a common DC bus. The converter has to have a freewheeling diode.  (A) because the converter inherently does not provide for free-wheeling (B) because the converter does not provide for free-wheeling for high ... the AC supply (D) or else if a gate pulse to one of the SCRs is missed, it will subsequently cause a high load current in the other SCR.

Total instantaneous power supplied by a 3-phase ac supply to a balanced R-L load is

The best method for measurement of temperatures of hot bodies radiating energy in the visible spectrum is (a) bolometer (b) optical pyrometer (c) thermocouple (d) thermopile

The line current in a balanced delta system is 30 A. The load current is (A) 30√3 A (B) 30/√3 A (C) 10 A (D) 30/√2 A

Which of the following is not a method of resistance measurement ? (a) Ammeter – Voltmeter method (b) Post – Office box method (c) Ohm – Meter method (d) Two wattmeter method

In the case of an instrument reading of 8.3 V with a 0 to 150 voltmeter having a guaranteed accuracy of 1% full scale reading, the percentage limiting error is   (A) 1.810% (B) 0.181% (C)12.45% (D) 0.0018%

In case of a power transformer, the no load current in terms of rated current is (1) 10-20% (2) 15-30% (3) 2-6% (4) 30-50%

In case of a 3-phase short-circuit fault in a system, the power fed into the system is   (a) Mostly reactive (b) Reactive only (c) Mostly active (d) Active and Reactive both equal

In dynamometer type of wattmeter, which of the coil is split up into two parts?

In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will?

In case of load flow analysis one of the system buses is taken as swing bus (a) as reference bus (b) to compensate the system losses (c) both (a) and (b) (d) to reduce the system losses

The usual value of slip of a 3Φ induction motor at full load is about:  (A) 0.05 (B) 0.1 (C) 0.3 (D) 0.8

A dynamometer type wattmeter with its voltage coil connected across the load side of instrument reads 250 W. If the load voltage be 200 V, what power is being taken by load? The voltage coil has resistance of 2000 Ω. (1) 200 W (2) 215W (3) 230 W /(4) 245 W