The reading of wattmeter in no load test of induction motor gives :

The reading of wattmeter in no load test of induction motor gives : (A) Friction and windage loss (B) Copper losses on no load in the stator (C) Core losses (D) Sum of all losses
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While measuring power in a three phase load by two wattmeter method, the reading of two wattmeter are

Description : 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 

Last Answer :  Option (d)  Load is purely inductive 

Consider the following statements with regard to induction type wattmeter : 1. Can be used on both ac and...

Description : Consider the following statements with regard to induction type wattmeter :  1. Can be used on both ac and dc systems.  2. Power consumption is relatively low.  3. It is accurate only at stated frequency and temperature.  Which ... /are correct ?  (a) 1 only (b) 2 only (c) 3 only (d) 1, 2 and 3

Last Answer : Consider the following statements with regard to induction type wattmeter :  1. Can be used on both ac and dc systems.  2. Power consumption is relatively low.  3. It is accurate only at stated frequency and temperature. ... correct ?  (a) 1 only (b) 2 only (c) 3 only (d) 1, 2 and 3

No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input

Description : No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. The intersection point ... ) Core loss (B) Stator copper loss (C) Stray load loss (D) Friction and windage loss

Last Answer : No-load test on a 3-phase induction motor was conducted at different supply voltage and a plot of input power versus voltage was drawn. This curve was extrapolated to intersect the y-axis. The intersection point yields Friction and windage loss

In two -wattmeter method of power measurement, if one wattmeter shows negative reading, then the...

Description : 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

Last Answer : Lagging   power   factor.

In a household single phase induction type wattmeter, the meter can be reversed by: -

Description :  In a household single phase induction type wattmeter, the meter can be reversed by: - a) reversing the supply terminals b) reversing the load terminal c) opening the meter connection ... opening the meter and reversing the connection of both the potential coil terminals and current coil terminals

Last Answer :  In a household single phase induction type wattmeter, the meter can be reversed by: - opening the meter connection and reversing either the potential coil terminals or current coil terminals 

An induction wattmeter can be used for?

Last Answer : An induction wattmeter can be used for A.C. 

The power delivered to a three-phase load can be measured by the use of 2 wattmeter only when the

Description : 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

Last Answer : The power delivered to a three-phase load can be measured by the use of 2 wattmeter only when the  Load is unbalanced

A three phase induction motor is driving full -load torque which is independent of speed. If the line voltage...

Description : A three phase induction motor is driving full -load torque which is independent of speed. If the line voltage drops to 90% of the rated value, % increase in motor copper losses  (a) 23% (b) -18% (c) 123% (d) None of these

Last Answer : A three phase induction motor is driving full -load torque which is independent of speed. If the line voltage drops to 90% of the rated value, % increase in motor copper losses (a) 23% (b) -18% (c) 123% (d) None of these

A 50 Hz, 3—phase induction motor has a full load speed of 1440 rpm. The number of poles of the motor is: ...

Description : A 50 Hz, 3—phase induction motor has a full load speed of 1440 rpm. The number of poles of the motor is:   (A)4 (8)6 (0)12  (D)8

Last Answer : Ans: A N= Ns (1-S) = NS –NS x S 1440 = Ns (1-S) Ns = 1440 / (1-S) Ns = (120 f/ p) = 120 x 50/p = 6000 p Ns will be closer to N i.e 1440 When P=2 ; Ns = 3000 rpm , not close to N When P=4 ; Ns = 1500 rpm , it is closer to N Therefore P =4 for N=1440

A ground on a particular phase of a three-phase low voltage distribution system would be indicated by a _____________. A. high switchboard wattmeter reading B. low switchboard wattmeter reading C. dark or dim switchboard ground detecting light D. bright switchboard ground detecting light

Description : A ground on a particular phase of a three-phase low voltage distribution system would be indicated by a _____________. A. high switchboard wattmeter reading B. low switchboard wattmeter reading C. dark or dim switchboard ground detecting light D. bright switchboard ground detecting light

Last Answer : Answer: C

A current-carrying conductor making electrical contact with a wiring conduit will be indicated by a _____________. A. high switchboard wattmeter reading B. totally dark switchboard ground detecting light C. low switchboard wattmeter reading D. all of the above

Description : A current-carrying conductor making electrical contact with a wiring conduit will be indicated by a _____________. A. high switchboard wattmeter reading B. totally dark switchboard ground detecting light C. low switchboard wattmeter reading D. all of the above

Last Answer : Answer: B

A current-carrying conductor makes accidental contact with a wiring conduit. This will be indicated by a _____________. A. low switchboard wattmeter reading B. high switchboard wattmeter reading C. darkened switchboard ground detecting lamp D. darkened switchboard synchronizing lamps

Description : A current-carrying conductor makes accidental contact with a wiring conduit. This will be indicated by a _____________. A. low switchboard wattmeter reading B. high switchboard wattmeter reading C. darkened switchboard ground detecting lamp D. darkened switchboard synchronizing lamps

Last Answer : Answer: C

A current carrying conductor making an electrical contact with a wiring metal conduit is indicated by a _____________. A. low switchboard wattmeter reading B. reading of 1.0 on the power factor meter C. high switchboard voltmeter reading D. totally darkened switchboard ground-detecting light

Description : A current carrying conductor making an electrical contact with a wiring metal conduit is indicated by a _____________. A. low switchboard wattmeter reading B. reading of 1.0 on the power factor meter C. high switchboard voltmeter reading D. totally darkened switchboard ground-detecting light

Last Answer : Answer: D

Explain the effect of power factor on wattmeter reading in two wattmeter method for power measurement.

Description : Explain the effect of power factor on wattmeter reading in two wattmeter method for power measurement.

Last Answer : Effect of P.F. on Reading of Wattmeter in Two Wattmeter Method:

In a 3-phase power measurement by two wattmeter method the reading of one of the wattmeter was zero...

Description : 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?

Last Answer : 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.

A 3 phase 50 Hz induction motor has full load speed of 970 rpm. Calculate no of poles and slip frequency.

Description : A 3 phase 50 Hz induction motor has full load speed of 970 rpm. Calculate no of poles and slip frequency.

Last Answer : The number of poles in an induction motor can be calculated using the following formula: No. of poles = (120 * frequency) / speed In this case, the number of poles would be calculated as follows: No. of poles = ( ... ) - 50 Hz = 8.08 Hz So the motor has 6 poles and a slip frequency of 8.08 Hz.

Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under no load. C. A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.

Description : Which of the listed motors will operate at the highest RPM, assuming that each operates at the same frequency? A. A four-pole synchronous motor under normal load. B. A four-pole induction motor under ... A six-pole synchronous motor under normal load. D. A six-pole induction motor under full load.

Last Answer : Answer: A

The speed of a wound-rotor induction motor _____________. A. will be fixed by the number of field poles B. can be varied by a rheostat-type control C. can only be synchronous speed at full load D. can only attain synchronous speed at no load

Description : The speed of a wound-rotor induction motor _____________. A. will be fixed by the number of field poles B. can be varied by a rheostat-type control C. can only be synchronous speed at full load D. can only attain synchronous speed at no load

Last Answer : Answer: B

If a three-phase induction motor malfunctions and drops to a single-phase (one supply line open) ____________. A. the motor will continue to run if it is not heavily loaded B. more torque will be developed C. the motor will immediately stop and not be able to be restarted D. the motor will immediately stop and can only be restarted at no load

Description : If a three-phase induction motor malfunctions and drops to a single-phase (one supply line open) ____________. A. the motor will continue to run if it is not heavily loaded B. more torque will be ... be able to be restarted D. the motor will immediately stop and can only be restarted at no load

Last Answer : Answer: A

Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Description : Explain why the no load current of an induction motor is much higher than that of an equivalent transformer.

Last Answer : In induction motor, due to the presence of the air gap, the magnetizing current that is required to set up the flux is much higher. The working component of the current has to meet the ... eddy current loss, friction and windage losses. Hence the no load current of induction motor is higher.

Full load current of an Induction motor is 20 Ampere. The no-load current may be expected to be:

Description :  Full load current of an Induction motor is 20 Ampere. The no-load current may be expected to be: A) 25 Ampere to 28 Ampere B) 15 Ampere to 18 Ampere C) 11 Ampere to 14 Ampere D) 6 Ampere to 10 Ampere

Last Answer : D

The power factor of an induction motor under no load conditions will be close to

Description : The power factor of an induction motor under no load conditions will be close to (A) 0.2 lagging (B) 0.2 leading (C) 0.5 lagging (D) Unity

Last Answer : The power factor of an induction motor under no load conditions will be close to 0.2 lagging

A suspected 'open' in a motor field can be tested by using a/an ____________. A. potentiometer B. megger C. wattmeter D. ammeter

Description : A suspected 'open' in a motor field can be tested by using a/an ____________. A. potentiometer B. megger C. wattmeter D. ammeter

Last Answer : Answer: B

The true power indicated by a wattmeter depends on the current flow through the load, the magnitude of the potential across the load, and the _____________. A. power factor of the load B. angle of coil displacement C. inertia of the movable coil D. high resistance from the load

Description : The true power indicated by a wattmeter depends on the current flow through the load, the magnitude of the potential across the load, and the _____________. A. power factor of the load B. angle of coil displacement C. inertia of the movable coil D. high resistance from the load

Last Answer : Answer: A

Which of the following meters uses a shunt connected in series with the load, but parallel with the meter movement? A. voltmeter B. power factor meter C. wattmeter D. ammeter

Description : Which of the following meters uses a shunt connected in series with the load, but parallel with the meter movement? A. voltmeter B. power factor meter C. wattmeter D. ammeter

Last Answer : Answer: D

The true power indicated by the pointer movement of a wattmeter depends on the current flow through the load, the magnitude of the potential across the load, and the ____________. A. power factor of the load B. angle of coil displacement C. inertia of the movable coil D. high resistance from the load

Description : The true power indicated by the pointer movement of a wattmeter depends on the current flow through the load, the magnitude of the potential across the load, and the ____________. A. power factor of the ... B. angle of coil displacement C. inertia of the movable coil D. high resistance from the load

Last Answer : Answer: A

Which of the listed meters uses a shunt connected in series with the load, but parallel with the meter movement? A. Voltmeter B. Power factor meter C. Ammeter D. Wattmeter

Description : Which of the listed meters uses a shunt connected in series with the load, but parallel with the meter movement? A. Voltmeter B. Power factor meter C. Ammeter D. Wattmeter

Last Answer : Answer: C

Moving coil in dynamometer wattmeter connected a) In series with fixed coil b) Across supply c) In series with load d) Across load

Description : Moving coil in dynamometer wattmeter connected a) In series with fixed coil b) Across supply c) In series with load d) Across load

Last Answer : Ans: Across supply

Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.

Description : Draw the circuit diagram for:- i) Measurement of active power in 3-phase load circuit using two wattmeter. ii) Measurement of reactive power in 3-phase load circuit using one wattmeter.

Last Answer : (i) Measurement of active power in 3- phase load circuit using two- wattmeter: (ii) Measurement of reactive power in 3- phase load circuit using one wattmeter

In the measurement of power of balanced load by two wattmeter method in a 3-phase circuit, The readings

Description :  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 ... kVAR B) 0.2 & 6 √3 kVAR C) 0.32 & 2 kVAR D) 0.32 & 2 √3 kVAR

Last Answer :  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 ... of current coil. the power factor and reactive power of the load is 0.2 & 6 √3 kVAR

The power consumed by a balanced 3-ph load is measured by two-wattmeter method. The meter readings are

Description : 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

Last Answer : 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 between 0.5 and unity

The potential coil of a single phase dynamometer wattmeter has 4840 Ohm resistance. Voltage across the load is

Description : 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%

Last Answer : 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%

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

Last Answer : 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.

Why speed of the induction motor falls when load is increased?

Description : Why speed of the induction motor falls when load is increased?

Last Answer : As the load increases, the speed reduces to deliver theincreased torque required.

The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip increases, rotor reactance decreases. B. The pullout point on the torque curve is about seven times the normal full load torque value. C. At stand still, stator current is 150% of normal. D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Description : The torque and current curves for a three-phase induction motor with a cage rotor, are shown in the illustration. Which of the following statements is true concerning the depicted curves? EL-0056 A. As slip ... D. If the motor is loaded to the point where 40% slip has resulted, it will stall.

Last Answer : Answer: D

A four-pole 60-hertz induction motor has a synchronous speed of 1800 RPM and a slip of 4 percent at full load. What will be its full load speed? A. 1728.0 RPM B. 1730.7 RPM C. 1800.0 RPM D. 1872.0 RPM

Description : A four-pole 60-hertz induction motor has a synchronous speed of 1800 RPM and a slip of 4 percent at full load. What will be its full load speed? A. 1728.0 RPM B. 1730.7 RPM C. 1800.0 RPM D. 1872.0 RPM

Last Answer : Answer: A

What is the rotor speed of a four pole, 60 cycle, induction motor operating at full load with 3% slip? A. 270 RPM B. 540 RPM C. 873 RPM D. 1746 RPM

Description : What is the rotor speed of a four pole, 60 cycle, induction motor operating at full load with 3% slip? A. 270 RPM B. 540 RPM C. 873 RPM D. 1746 RPM

Last Answer : Answer: D

If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced torque B. speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

Description : If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced ... speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

Last Answer : Answer: A

A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Description : A split-phase induction squirrel-cage motor will not come up to speed, even though the rated voltage, rated frequency, and rated load are applied. The suspected trouble could be due to _____________. A. a faulty centrifugal switch B. broken rotor bars C. worn bearings D. all of the above

Last Answer : Answer: D

If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B. starting winding will burn out C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Description : If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B ... C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Last Answer : Answer: B

Regarding an induction motor, the power developed by the rotor automatically adjusts itself to the _____________. A. power required to drive the load B. speed required to drive the load C. current flow in the motor stator D. torque developed by the rotating field

Description : Regarding an induction motor, the power developed by the rotor automatically adjusts itself to the _____________. A. power required to drive the load B. speed required to drive the load C. current flow in the motor stator D. torque developed by the rotating field

Last Answer : Answer: A

In a 15 HP induction-type motor with a cage rotor, the current required at standstill to produce starting torque is approximately ____________. A. half the full load current B. equal to the full load current C. five times the full load current D. ten to twenty times the full load current

Description : In a 15 HP induction-type motor with a cage rotor, the current required at standstill to produce starting torque is approximately ____________. A. half the full load current B. equal to the full load current C. five times the full load current D. ten to twenty times the full load current

Last Answer : Answer: C

What is the effect of increased load on power factor of induction motor?

Description : What is the effect of increased load on power factor of induction motor?

Last Answer : Power factor of an induction motor increases with loading.

The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only. (C) low at light and heavy load both. (D) low at rated load only.

Description : The power factor of a squirrel cage induction motor is (A) low at light load only. (B) low at heavy load only. (C) low at light and heavy load both. (D) low at rated load only.

Last Answer : (A) low at light load only.

The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero.

Description : The frequency of the rotor current in a 3 phase 50 Hz, 4 pole induction motor at full load speed is about (A) 50 Hz. (B) 20 Hz. (C) 2 Hz. (D) Zero.

Last Answer : (C) 2 Hz.

An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load

Description :  An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: A) 1000 rpm B) 920 rpm C) 950 rpm D) 970 rpm

Last Answer : An 8-pole alternator runs at 750 rpm and supplies power to a 6-pole induction motor which has a full load slip of 3 percent. The full load speed of the induction motor will be: 970 rpm

A 3-phase induction motor is driving a constant torque load at rated voltage and frequency. If both voltage

Description : A 3-phase induction motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactance and core loss are ... (A) All (B) 1, 2 and 3 (C) 2, 3 and 4 (D) 1 and 4

Last Answer : A 3-phase induction motor is driving a constant torque load at rated voltage and frequency. If both voltage and frequency are halved, following statements relate to the new condition if stator resistance, leakage reactance and core loss are ... A) All (B) 1, 2 and 3 (C) 2, 3 and 4 (D) 1 and 4

A 400 V, 15 kW, 4-pole, 50 Hz, Y-connected induction motor has full load slip of 4%. The output torque of the

Description : A 400 V, 15 kW, 4-pole, 50 Hz, Y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is  (A) 1.66 Nm (B) 95.50 Nm (C) 99.47 Nm (D) 624.73 Nm

Last Answer : A 400 V, 15 kW, 4-pole, 50 Hz, Y-connected induction motor has full load slip of 4%. The output torque of the machine at full load is 99.47 Nm

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

Description : The type of single-phase induction motor having the highest power factor at full load is (A) shaded pole type (B) split-phase type (C) capacitor-start type (D) capacitor-run type

Last Answer : The type of single-phase induction motor having the highest power factor at full load is capacitor-run type