What is the power in 3-phase supply system?

What is the power in 3-phase supply system?
by

1 Answer

Answer :

In a single-phase system power ‘P’ = VPh * IPh * cosϕ watts.
 In 3-ϕ system power ‘P’ = 3 * VPh * IPh * cosϕ watts.
In Star connection, IL = IPh and VPh = VL/√3. Substituting the value of IPh and VPh
in the above 3-ϕ power equation,
 P = 3 * VPh * IPh * cosϕ watts.
 P = 3 * VL/√3 * IL * cosϕ watts.
 P = √3 * VL * IL * cosϕ watts.

In Delta connection, VL = VPh and IPh = IL/√3. Substituting the value of IPh and VPh
in the above 3-ϕ power equation,
 P = 3 * VPh * IPh * cosϕ watts.
 P = 3 * VL* IL/√3 * cosϕ watts.
 P = √3 * VL * IL * cosϕ watts.
So that the power in three phase supply system whether star connected or delta
connected is same and power P = √3 * VL * IL * cosϕ watts.
So cosϕ = P/ √3 * VL * IL .
by

Related questions

Which of the listed sections of an emergency switchboard is used to supply power for alarm signals under emergency conditions? A. The generator and bus transfer section B. The 450 volt, 60 cycle, 3 phase bus C. The 120 volt, 3 phase, 60 cycle bus D. The 24 volt DC bus

Description : Which of the listed sections of an emergency switchboard is used to supply power for alarm signals under emergency conditions? A. The generator and bus transfer section B. The 450 volt, 60 cycle, 3 phase bus C. The 120 volt, 3 phase, 60 cycle bus D. The 24 volt DC bus

Last Answer : Answer: D

AC and DC generators are similar in that they _____________. A. both generate alternating voltages B. both rectify the voltage before delivery C. are constructed at the same physical size for the same kilowatt rating D. both supply three-phase power

Description : AC and DC generators are similar in that they _____________. A. both generate alternating voltages B. both rectify the voltage before delivery C. are constructed at the same physical size for the same kilowatt rating D. both supply three-phase power

Last Answer : Answer: A

Why do we use 3 phase power supply for heavy loads?

Description : Why do we use 3 phase power supply for heavy loads?

Last Answer : With a single phase, the voltage drops to 0 every half-cycle. Therefore, the amount of power you can get out of the line is not constant over time; it has a very large 120-hz ripple. With ... this can be accomplished, but in every case there are drawbacks that are not present in the 3-phase system

In conversion of 3-phase to 2-phase supply with T connection, the transformation ratio of the teaser will be__ times to that of main transformer: a) 1.732 b) 1.15 c) 0.866 d) Unity

Description : In conversion of 3-phase to 2-phase supply with T connection, the transformation ratio of the teaser will be__ times to that of main transformer: a) 1.732 b) 1.15 c) 0.866 d) Unity

Last Answer : Ans: C

When testing for blown fuses in a three-phase supply circuit to a motor, you should first ___________________. A. apply the megger across the tops of the line fuses B. apply an ammeter diagonally across the top of the first line fuse and the bottom of the third line fuse C. apply the voltage tester across the bottoms of the line fuses D. ensure the circuit is de-energized, and then use a continuity tester

Description : When testing for blown fuses in a three-phase supply circuit to a motor, you should first ___________________. A. apply the megger across the tops of the line fuses B. apply an ammeter diagonally across ... of the line fuses D. ensure the circuit is de-energized, and then use a continuity tester

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

In a three-phase, squirrel-cage type, induction motor the rotating magnetic field is established by the _____________. A. current induced in the rotor windings B. application of a three-phase voltage supply to the stator windings C. laminated steel core and aluminum conductors in the rotor D. interaction of the magnetic field caused by the induced current in the squirrel-cage bars with the magnetic field of the stator

Description : In a three-phase, squirrel-cage type, induction motor the rotating magnetic field is established by the _____________. A. current induced in the rotor windings B. application of a three-phase voltage ... caused by the induced current in the squirrel-cage bars with the magnetic field of the stator

Last Answer : Answer: B

Erratic operation of the devices represented in the diagrams shown in the illustration could be traced to ____________. EL-0092 A. improper contact at 'R' slip rings or 'S' connections B. a low three-phase voltage supply C. improper contact at 'S' slip rings or 'R' connections D. a high three-phase voltage supply

Description : Erratic operation of the devices represented in the diagrams shown in the illustration could be traced to ____________. EL-0092 A. improper contact at 'R' slip rings or 'S' connections B. a low three- ... . improper contact at 'S' slip rings or 'R' connections D. a high three-phase voltage supply

Last Answer : Answer: A

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

Figure 'D' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Description : Figure 'D' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Last Answer : Answer: A

Figure 'C' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Description : Figure 'C' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Last Answer : Answer: C

Figure 'B' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Description : Figure 'B' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Last Answer : Answer: B

Figure 'A' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Description : Figure 'A' of the diagram shown in the illustration has a turns ratio of four to one. If a three-phase 440 volt supply is connected to terminals 'A-B-C', what voltage should develop across terminals 'a-b-c'? EL-0084 A. 64 volts B. 110 volts C. 190 volts D. 762 volts

Last Answer : Answer: B

Why we use 3-phase supply? Why are not 4 or something else?

Description : Why we use 3-phase supply? Why are not 4 or something else?

Last Answer : Three phase power has several advantages over single phase power, including smaller transformer size and weight, and simplified motor construction. Four phase power, which is actually two phase power ... of long transmission lines from the power source, three phase power is the best alternative.

What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?

Description : What is the supply rated o/p if two single phase transformer connect to give three phase o/p from a three phase I/p?

Last Answer : A. Each transformer is only capable of supplying 86.6%of its o/p rating

A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both eddy current and hysteresis losses increases. (C) Eddy current loss remains the same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Description : A 220/440 V, 50 Hz, 5 KVA, single phase transformer operates on 220V, 40Hz supply with secondary winding open circuited. Then (A) Both eddy current and hysteresis losses decreases. (B) Both ... same but hysteresis loss increases. (D) Eddy current loss increases but hysteresis loss remains the same.

Last Answer : (A) Both eddy current and hysteresis losses decreases.

The 24 volt DC bus on the emergency switchboard is used to supply power to the _____________. A. general alarm system B. gyrocompass power failure alarm system C. smoke detection system D. all of the above

Description : The 24 volt DC bus on the emergency switchboard is used to supply power to the _____________. A. general alarm system B. gyrocompass power failure alarm system C. smoke detection system D. all of the above

Last Answer : Answer: D

How much power is needed to supply the losses associated with the production of the magnetic field in a 3-phase motor?

Description : How much power is needed to supply the losses associated with the production of the magnetic field in a 3-phase motor?

Last Answer : You need to conduct No load and full load losses tests todetermine the losses.

A solar cell of 350 V is feeding power to an ac supply of 440 V, 50 Hz through a 3-phase fully controlled bridge

Description : A solar cell of 350 V is feeding power to an ac supply of 440 V, 50 Hz through a 3-phase fully controlled bridge converter. A large inductance is connected in the dc circuit to maintain the dc current at 20 A ... thyristor will be reverse biased for a period of  (A) 125o (B) 120o (C) 60o (D) 55o

Last Answer : A solar cell of 350 V is feeding power to an ac supply of 440 V, 50 Hz through a 3-phase fully controlled bridge converter. A large inductance is connected in the dc circuit to maintain the ... the solar cell resistance is 0.5 Ohm ,then each thyristor will be reverse biased for a period of 125o

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

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

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

In accordance with Coast Guard Regulations (46 CFR), a steering gear feeder circuit from the emergency switchboard or alternate power supply must have the capacity for continuous operation of the rudder 15° side to side in not more than 60 seconds for a A. 1/4 hour B. 1/2 hour C. 1 hour D. 2 hours

Description : In accordance with Coast Guard Regulations (46 CFR), a steering gear feeder circuit from the emergency switchboard or alternate power supply must have the capacity for continuous operation of the rudder 15° side to side in not more than 60 seconds for a A. 1/4 hour B. 1/2 hour C. 1 hour D. 2 hours

Last Answer : Answer: B

The source of emergency lighting and power at loss of normal ship's power on a cargo vessel should be obtained from the ______________. A. emergency generator supply to the emergency switchboard B. emergency generator supply to the main switchboard C. battery supply to the main switchboard D. turbogenerator supply to the emergency switchboard

Description : The source of emergency lighting and power at loss of normal ship's power on a cargo vessel should be obtained from the ______________. A. emergency generator supply to the emergency ... switchboard C. battery supply to the main switchboard D. turbogenerator supply to the emergency switchboard

Last Answer : Answer: A

Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

Two 100 watt light bulbs are connected in parallel across a 100 volt power supply. The total power developed in the circuit is _______________. A. 200 watts B. 100 watts C. 50 watts D. equal to the product of the amperes times the voltage in each branch

Description : Two 100 watt light bulbs are connected in parallel across a 100 volt power supply. The total power developed in the circuit is _______________. A. 200 watts B. 100 watts C. 50 watts D. equal to the product of the amperes times the voltage in each branch

Last Answer : Answer: A

Which of the following statements is true if a 100 watt lamp and a 75 watt lamp are connected in parallel across a 100 volt power supply? A. The 75 watt lamp will draw as much current as the 100 watt lamp. B. The 100 watt lamp will have a greater resistance. C. Current flow will be the same across each lamp. D. The 75 watt lamp will have a higher resistance.

Description : Which of the following statements is true if a 100 watt lamp and a 75 watt lamp are connected in parallel across a 100 volt power supply? A. The 75 watt lamp will draw as much current as the 100 ... Current flow will be the same across each lamp. D. The 75 watt lamp will have a higher resistance.

Last Answer : Answer: D

A series wound DC motor has its armature and field connected in series with a resistor. When the motor is disconnected from its power supply, this motor will exemplify __________. A. the proper connections for across the line starting B. the proper connections for an automatic strip heater C. a reversing controller circuit D. dynamic braking

Description : A series wound DC motor has its armature and field connected in series with a resistor. When the motor is disconnected from its power supply, this motor will exemplify __________. A. the ... the proper connections for an automatic strip heater C. a reversing controller circuit D. dynamic braking

Last Answer : Answer: D

In the illustration, the component VR2 on the A1 AMPLIFIER MODULE is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply from common B. a variable resistor diode to control the output to terminal 1 that controls the input to terminal 10 C. a zener diode that regulates the voltage to terminal 2 at 9.1 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Description : In the illustration, the component VR2 on the A1 AMPLIFIER MODULE is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply from common B. a variable resistor diode to control the output to terminal ... 2 at 9.1 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Last Answer : Answer: C

In the illustration, the component VR1 on the A1 AMPLIFIER MODULE is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply from common B. a variable resistor diode to control the output to terminal 9 that controls the input to terminal 10 C. a zener diode that regulates the voltage to terminal 9 at 6.6 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Description : In the illustration, the component VR1 on the A1 AMPLIFIER MODULE is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply from common B. a variable resistor diode to control the output to ... terminal 9 at 6.6 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Last Answer : Answer: A

In the illustration, the component VR1 on the A1A1 PCB is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply B. a variable resistor diode to control the output to terminal 9 that controls the input to terminal 10 C. a zener diode that regulates the voltage to terminal 9 at 6.6 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Description : In the illustration, the component VR1 on the A1A1 PCB is _________. EL-0060 A. a zener diode to regulate the +9 volt power supply B. a variable resistor diode to control the output to terminal 9 that controls ... terminal 9 at 6.6 volts DC D. a tunnel diode with a breakdown voltage of 6.6 Volts DC

Last Answer : Answer: C

Before using an all-purpose electric measuring instrument (multimeter) utilizing internal batteries to supply power for resistance measurements, you should FIRST ____________. A. remove one of the batteries B. remove all the batteries C. calibrate using a known external resistance D. select the proper resistance range

Description : Before using an all-purpose electric measuring instrument (multimeter) utilizing internal batteries to supply power for resistance measurements, you should FIRST ____________. A. remove one of the ... batteries C. calibrate using a known external resistance D. select the proper resistance range

Last Answer : Answer: D

You are calibrating a multimeter using internal batteries to supply power for resistance measurements. However, you are unable to adjust the pointer to 'zero' using the adjustment knob. Therefore, you should _____________. A. replace the batteries in the instrument B. measure resistance by dividing the voltmeter indication by the ammeter indication C. set the pointer using a bridge D. change scales to the R X 100 scale and adjust using the 'zero ohms' adjusting knob

Description : You are calibrating a multimeter using internal batteries to supply power for resistance measurements. However, you are unable to adjust the pointer to 'zero' using the adjustment knob. Therefore, you should ... change scales to the R X 100 scale and adjust using the 'zero ohms' adjusting knob

Last Answer : Answer: A

In the illustration, if one of the devices labeled 'TURB' should fail the ___________. EL-0003 A. device labeled 'EXC' will drive the alternator B. device labeled 'BKR' for that alternator should automatically open because of the reverse power relay C. operator must open all the devices labeled 'BKRS' to reduce the load on the remaining turbo-alternator D. emergency generator should automatically start and be placed on line to supply emergency load centers

Description : In the illustration, if one of the devices labeled 'TURB' should fail the ___________. EL-0003 A. device labeled 'EXC' will drive the alternator B. device labeled 'BKR' for that ... -alternator D. emergency generator should automatically start and be placed on line to supply emergency load centers

Last Answer : Answer: B

The device labeled 'REG SW' in the illustration is used to ___________. EL-0003 A. shift from the automatic voltage regulator to the manual voltage regulator B. shift the governor control from manual to automatic/zero droop C. enable the operator to read the field voltage on device 'REG ADJ' or device 'MAN ADJ' D. supply regulated control power to the switchboard

Description : The device labeled 'REG SW' in the illustration is used to ___________. EL-0003 A. shift from the automatic voltage regulator to the manual voltage regulator B. shift the governor control from manual to ... device 'REG ADJ' or device 'MAN ADJ' D. supply regulated control power to the switchboard

Last Answer : Answer: A

Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Description : Upon failure of the normal power supply, the emergency generator is placed on the line by the _____________. A. main bus tie feeder B. automatic bus transfer device C. line connection feeder D. power failure alarm bus

Last Answer : Answer: B

What is the power consumed by 'R3' in the circuit illustrated if the supply is 24 volts and resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 12 watts B. 20 watts C. 24 watts D. 48 watts

Description : What is the power consumed by 'R3' in the circuit illustrated if the supply is 24 volts and resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 12 watts B. 20 watts C. 24 watts D. 48 watts

Last Answer : Answer: B

What is the power consumed by 'R2' in the circuit illustrated, if the supply is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 16 watts B. 20 watts C. 24 watts D. 28 watts

Description : What is the power consumed by 'R2' in the circuit illustrated, if the supply is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 16 watts B. 20 watts C. 24 watts D. 28 watts

Last Answer : Answer: A

The +5 volt regulated power supply shown in the illustration is fed directly from the _______________. EL-0094 A. 115 volt AC bus B. Annunciator Module C. +24 volt supply D. Annunciator Controller

Description : The +5 volt regulated power supply shown in the illustration is fed directly from the _______________. EL-0094 A. 115 volt AC bus B. Annunciator Module C. +24 volt supply D. Annunciator Controller

Last Answer : Answer: C

What is the power consumed by 'R1' in the circuit illustrated if the supply is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 2 watts B. 3 watts C. 6 watts D. 12 watts

Description : What is the power consumed by 'R1' in the circuit illustrated if the supply is 24 volts and the resistance of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 2 watts B. 3 watts C. 6 watts D. 12 watts

Last Answer : Answer: D

A resistor placed in parallel to the output of a power supply _____________. A. is a temperature compensator B. corrects power factor C. prevents excessive currents D. aids in output voltage regulation

Description : A resistor placed in parallel to the output of a power supply _____________. A. is a temperature compensator B. corrects power factor C. prevents excessive currents D. aids in output voltage regulation

Last Answer : Answer: D

What is the total power consumed by the illustrated circuit if the supply is 24 volts and the resistances of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 2 watts B. 12 watts C. 48 watts D. 288 watts

Description : What is the total power consumed by the illustrated circuit if the supply is 24 volts and the resistances of R1 is 3 ohms, R2 is 4 ohms, and R3 is 5 ohms? EL-0020 A. 2 watts B. 12 watts C. 48 watts D. 288 watts

Last Answer : Answer: C

When troubleshooting electronic equipment, the FIRST step to be taken before testing the circuit voltage is to _________. A. set the meter to the lowest range B. check the voltage supply from the power source C. remove the suspected component D. check the current flow through the circuit

Description : When troubleshooting electronic equipment, the FIRST step to be taken before testing the circuit voltage is to _________. A. set the meter to the lowest range B. check the voltage supply from the power source C. remove the suspected component D. check the current flow through the circuit

Last Answer : Answer: B

Before working on an electric cargo winch master switch or controller, you should _____________. A. spray the gasket surface with a solvent B. drain condensate from the box C. open the circuit breaker in the power supply and tag D. heat the switch box to remove any moisture

Description : Before working on an electric cargo winch master switch or controller, you should _____________. A. spray the gasket surface with a solvent B. drain condensate from the box C. open the circuit breaker in the power supply and tag D. heat the switch box to remove any moisture

Last Answer : Answer: C

Basic operating characteristics of the operational amplifier such as gain and stability are the function of its _____________. A. differential input stage B. power output stage C. feedback circuit D. supply voltages

Description : Basic operating characteristics of the operational amplifier such as gain and stability are the function of its _____________. A. differential input stage B. power output stage C. feedback circuit D. supply voltages

Last Answer : Answer: C

To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Description : To carry out an insulation resistance test, one terminal of the megohmmeter should be connected to the winding, with the other terminal being connected to the ____________________. A. power supply B. variable resistor C. frame of the machine D. armature

Last Answer : Answer: C

The circuit shown in the illustration represents a/an ____________. EL-0085 A. operational amplifier B. Wheatstone bridge C. magnetic amplifier D. power supply

Description : The circuit shown in the illustration represents a/an ____________. EL-0085 A. operational amplifier B. Wheatstone bridge C. magnetic amplifier D. power supply

Last Answer : Answer: D

In which section of the 24 VDC power supply circuit illustrated, does the greatest change in voltage level take place when fed from ships power. EL-0085 A. I B. II C. III D. IV

Description : In which section of the 24 VDC power supply circuit illustrated, does the greatest change in voltage level take place when fed from ships power. EL-0085 A. I B. II C. III D. IV

Last Answer : Answer: A

Capacitors are used on the output of the power supply in today's consoles to _____________. A. filter out 'ripple' B. prevent overloads C. act as a permanent load D. decrease the average value of the output voltage

Description : Capacitors are used on the output of the power supply in today's consoles to _____________. A. filter out 'ripple' B. prevent overloads C. act as a permanent load D. decrease the average value of the output voltage

Last Answer : Answer: A