Recent questions tagged ac

asked Jan 6 by anonymous

List any four advantages and two disadvantages of 3 phase induction motor.

Last answer: Advantages of 3 phase induction motor: 1) Simple in construction. 2) Economical in cost. 3) Requires very less maintenance. 4) High efficiency. 5) Low maintenace cost. 6) Self starting. 7 ... operated below its full load capacity. 6) It takes a large current from line at instant of starting.

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asked Jan 6 by anonymous

Explain how in a 3 phase induction motor to a rotating magnetic field is developed.

Last answer: Production of Rotating Magnetic Field in Three-phase Induction Motor: In three-phase induction motor, the three-phase stator windings are displaced in space by 120° and their three-phase currents are displaced ... time by 120°. Such fluxes give rise to the resultant rotating magnetic field.

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3 views 1 answer

asked May 21, 2020 by anonymous

Explain working of static AC circuit breaker.

Last answer: Static AC Circuit breaker: The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

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asked May 19, 2020 by anonymous

Calculate the energy stored in the inductor and capacitor, respectively.

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asked May 19, 2020 by anonymous

State the frequency and amplitude for both the voltage waveforms.

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asked May 7, 2020 by anonymous

State the modification to be done in dc series motor to work satisfactorily as ac series motor. State applications of ac series motor.

Last answer: Modifications are necessary in a dc series motor so that it operates satisfactorily on ac supply. The modifications are as follows: 1) AC series motor is built with a few field turns as ... and grinders 5) High speed vacuum cleaners 6) Sewing machines 7) Food processors 8) Drilling machine

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77 views 1 answer

asked May 7, 2020 by anonymous

Explain construction and working of AC servomotor.

Last answer: Construction of AC Servo Motor: AC servo motor is mainly composed of a stator and a rotor. Laminated stator core is usually made of silicon steel. Two phase windings are placed in the stator slots at 90 degree ... on rotor. Due to the force or torque acting on the rotor, it is set in motion.

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87 views 1 answer

asked May 3, 2020 by anonymous

Compare the AC and DC Arc lamps.

Last answer: AC Arc Lamp DC Arc Lamp Cross section area of electrode is same Cross section area of electrode is positive rod is twice that of negative rod Series inductor is used for stability ... supply is used for DC arc lamp Luminous efficiency is less Luminous efficiency is high

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asked Apr 26, 2020 by anonymous

What is the advantage of AC over DC electrical transmission?

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asked Feb 21, 2020 by anonymous

15 kV AC railway electrification

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asked Nov 22, 2019 by anonymous

Alternating current (AC)

Last answer: AC stands for Alternating Current meaning voltage or current that changes polarity or direction respectively over time. An Alternating Current (AC) is an electric current whose magnitude ... energy are known as alternators and are simpler construction than DC electromechanical generators.

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148 views 2 answers

asked Oct 13, 2019 by anonymous

Explain working of AC circuit breaker using SCR with circuit diagram.

Last answer: AC Circuit Breaker: The circuit configuration of static AC circuit breaker using SCR is shown in the figure. When switch S' is closed, the SCRs T1 and T2 are fired in positive ... to non-availability of gate current. Thus the maximum time delay for breaking the circuit is one half-cycle.

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658 views 1 answer

asked Sep 4, 2019 by anonymous

operation of half wave rectifier type AC Voltmeter.

Last answer: Half-wave Rectifier Voltmeter The d'Arsonval meter movement only responds to the average or dc value of the current through the moving coil. In order to measure alternating ... ) input voltage signal alternating signal needs to be rectified first by using diode rectifier to produce

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197 views 1 answer

asked Sep 3, 2019 by anonymous

Why are DC motors used in trains and not AC motors ?

Last answer: The reason is torque. torque is inversely proportional to speed..i.e when th knowe train comes to rest position to motion.. initial speed is zero..so it requires high starting torque for ... current will flow through field and armature coils then maximum torque is available at the intial condition.

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138 views 1 answer

asked Aug 28, 2019 by anonymous

Why is AC considered more efficient than DC?

Last answer: Ac is more efficient than dc because it is easy to maintain and change the voltage of ac for transmission and distribution purpose. Plant cost of ac transmission is much lower compared to dc transmission. When fault occurs it is easy to interrupt ac supply.

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asked Aug 28, 2019 by anonymous

Which is more dangerous AC or DC and why ?

Last answer: Dc is more dangerous than Ac because in Ac the voltage will varies but in dc the constant voltage

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115 views 2 answers

asked Aug 25, 2019 by anonymous

Why is AC better for long distance power transmission than DC ?

Last answer: ac is more economical to transmit for long distances . wires can be made smaller by step up transformer .. since major cost are wires to transmit .. then at the end of distance step down transformer is used for commercial use.

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166 views 4 answers

asked Aug 19, 2019 by anonymous

Why can't we store AC in batteries instead of DC ?

Last answer: Because the direction of the current changes in AC electricity, you cannot directly store the power. Placing a capacitor in an AC circuit has no effect on the alternating flow of the electricity. The only ... is indirectly, by storing DC and then using a power inverter to convert the DC to AC.

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94 views 3 answers

asked Aug 15, 2019 by anonymous

What is the conversion between. AC to AC ? DC to DC? AC to DC? DC to AC ?

Last answer: 1.ac to ac is regulation 2.dc to dc is chopper 3.ac to dc is rectifier 4.dc to ac is inverter

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63 views 1 answer

asked Aug 8, 2019 by anonymous

AC generator

Last answer: A.C power can be generated as a single phase or as a balanced poly-phase system. However, it was found that 3-phase power generation at 50 Hz will be economical and most suitable. Present day three phase generators ... has uniform air gap (figure 2.1(b)) and used when speed is high.

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2.3k views 1 answer

asked Aug 8, 2019 by anonymous

Changeover from D.C to A.C

Last answer: In later half of eighties, in nineteenth century, it was proposed to have a power system with 3- phase, 50 Hz A.C generation, transmission and distribution networks. Once a.c system was adopted, transmission of ... favor of A.C supply system own the debate on switching over from D.C to A.C system.

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2.4k views 1 answer

asked Jul 30, 2019 by anonymous

Define the terms related to a.c. supply with waveform : i) Instantaneous value ii) Time period iii) Amplitude iv) Phase difference.

Last answer: i) Instantaneous value: The instantaneous value is the value of an alternating quantity (it may ac voltage or ac current or ac power) at a particular instant of time in the cycle . OR ... difference: Phase difference is the difference in phase angle between two sinusoids or phasors.

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asked Jul 30, 2019 by anonymous

Define : i) Average value ii) RMS value of an AC Wave.

Last answer: i) Average value: The average value is defined as the average of all instantaneous values during one alternation . That is, the ratio of the sum of all considered instantaneous values to the ... as produced by the alternating current when flowing through the same resistance for the same time.

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78 views 1 answer

asked Jul 25, 2019 by anonymous

How to convert 12v dc to 12v ac

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asked Jul 6, 2019 by anonymous

AC power plugs and sockets

Last answer: .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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2.5k views 1 answer

asked Jul 6, 2019 by anonymous

AC adapter

Last answer: .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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asked Jul 6, 2019 by anonymous

AC power

Last answer: Ac power is in sinusoidal wave form .Alternating current pulsating sinusoidally that is positive half cycle and negative half cycle.

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89 views 2 answers

asked Jun 29, 2019 by anonymous

Describe the difference between direct and alternating current.

Last answer: Direct current is the flow of electricity or charge in one direction.. Alternative current is the flow of charge that doesn't flow in one direction.

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5.0k views 4 answers

asked Jun 29, 2019 by anonymous

Is the power line voltage available in our homes a dc or an ac voltage?

Last answer: The power line voltage available in our homes is AC. Mobile dwellings are the most commonly DC-supplied homes and even then they tend to include AC supply for heavier loads.

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5.0k views 1 answer

asked May 26, 2019 by anonymous

AC Circuits with Resistance but No Reactance

Last answer: AC Circuits with Resistance but No Reactance AC Circuits with Resistance but No Reactance Series resistances let two resistances R 1 and R 2 are connected in series as shows in figure and there ... voltage. Voltage V A is common to both the branch hence voltage V A is common reference.

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68 views 1 answer

asked Sep 7, 2018 by anonymous

What is the need of polarity marking in polyphase AC circuits?

Last answer: Need of Polarity Marking in Polyphase AC Circuits: i) Polarity marking of terminals provides reference polarity for better understanding of system, even if the polarity of ac voltage changes ... of current transformers in relay protection circuit and getting desired performance is very difficult.

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74 views 1 answer

asked Sep 7, 2018 by anonymous

Explain how sinusoidal AC voltage is generated by using simple one loop generator.

Last answer: An electric current produced by means of electrical machine is known as generator which converts mechanical energy into electrical energy. When conductor cuts the magnetic flux, emf induced in it. (Faraday' ... upon position of armature. The nature of emf is alternating as shown by the waveform.

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1.2k views 1 answer

asked Sep 6, 2018 by anonymous

‘PMMC instrument is not suitable to measure AC quantity’. State the reason.

Last answer: The direction of force exerted on moving coil depends on the direction of current flowing through moving coil. If the direction of magnetic field is kept constant, it produces unidirectional torque if the current is ... on the coil in one cycle to zero. Hence the meter cannot read A.C. quantities.

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asked Sep 5, 2018 by anonymous

How range of A.C. ammeter & A.C. voltmeter is extended? Draw suitable diagram.

Last answer: Extension of A.C. Ammeter Range: The range of a.c. ammeter can be extended by using CT, the arrangement is shown in figure. The CT is current transformer having less number of primary turns carrying high ... high magnitude of source voltage. In this way range of a.c. voltmeter can be extended.

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365 views 1 answer

asked Sep 4, 2018 by anonymous

State any four advantages of A. C. over D. C .

Last answer: .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }

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asked Aug 25, 2018 by Notes

UNIT 1 fundamentals of AC rotating machine

UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor (Coil pitch and distributed winding) 1.7 Distribution factor 1.8 EMF equation of alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

Last answer: 1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

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181 views 2 answers

asked Aug 11, 2018 by anonymous

Draw the waveform of three phase AC supply voltage.

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asked Aug 11, 2018 by nbattack

is it DC better than AC to transmit? explain it.

Do you think is DC better than AC to transmit energy?

Last answer: In Long distance DC transmission will be better in cost. It requires more equipments for flexiblity In short distance AC transmission is better in cost. It is more Flexible

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447 views 2 answers

asked Aug 11, 2018 by anonymous

Write short notes on 3 phase AC system.

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asked Aug 8, 2018 by anonymous

Distinguish between AC and DC.

Last answer: Particulars Direct Current Alternating Current Definition It is the current whose magnitude and direction do not change with respect to time. It is the current whose ... system, electroplating, Battery charging, Traction. AC machines, Domestic and industrial supply.

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414 views 2 answers

asked Jun 18, 2018 by anonymous

The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of

The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of A) 10 kHz B) 10 Hz C) 5 kHz D) 5 Hz

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asked Jun 18, 2018 by anonymous

An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to

An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V

Last answer: An AC supply of 230 V is applied to a half-wave rectifier circuit through a transformer having primary to secondary turn’s ratio 12:1. The peak inverse voltage is A) 8.62 V B) 12 V C) 19.17 V D) 27.11 V

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118 views 1 answer

asked May 8, 2018 by anonymous

The main advantage of AC over DC is:

The main advantage of AC over DC is: (A) Conversion flexibility from one voltage level to other (B) AC can be easily converted into DC by using a rectifier (C) AC is easy to maintain & can be easily distributed at long distances (D) All of the above

Last answer: Ac is easy to maintain and ac can be easily converted to dc by rectifier .There is no commutator for conversion in ac that's why ac machines are weight less and more efficiency.ac machines occupy less space than dc .

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111 views 2 answers

asked Apr 30, 2018 by anonymous

An ac voltmeter using full -wave rectification and having a sinusoidal input has an ac sensitivity equal to

An ac voltmeter using full -wave rectification and having a sinusoidal input has an ac sensitivity equal to (1) 1.414 times dc sensitivity (2) dc sensitivity (3) 0.9 times dc sensitivity (4) 0.707 times dc sensitivity

Last answer: An ac voltmeter using full -wave rectification and having a sinusoidal input has an ac sensitivity equal to 0.9 times dc sensitivity

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427 views 1 answer

asked Apr 30, 2018 by anonymous

The ac bypassing of RF by CF in a common emitter configuration :

The ac bypassing of RF by CF in a common emitter configuration : (A) increases ac signal across emitter -base junction (B) decreases ac signal across emitter -base junction (C) decreases voltage amplification (D) stabilizes the Q -point

Last answer: The ac bypassing of RF by CF in a common emitter configuration : increases ac signal across emitter -base junction

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asked Apr 30, 2018 by anonymous

For measurement of radio frequency ac signals __________ type meter is used

Last answer: For measurement of radio frequency ac signals thermo-couple type meter is used

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asked Apr 29, 2018 by anonymous

An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic

An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be (1) unaffected (2) decreased (3) increased (4) either decreased or increased depending on the direction of the DC field

Last answer: An unshielded moving iron voltmeter is used to measure the voltage in an AC circuit. The stray DC magnetic field having a component along the axis will be either decreased or increased depending on the direction of the DC field

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258 views 1 answer

asked Apr 29, 2018 by anonymous

A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals

A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance to remain constant immediately after the fault, acceleration of the generator rotor is

Last answer: A large AC generator, supplying power to an infinite bus, has a sudden short-circuit occurring at its terminals. Assuming the prime mover input and the voltage behind the transient reactance ... , acceleration of the generator rotor is inversely proportional to the moment of inertia of the machine

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asked Apr 29, 2018 by anonymous

Which of the following motors can run on both AC and DC?

Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

Last answer: Which of the following motors can run on both AC and DC? A) Universal motor B) Dual wattage motor C) Flexible motor D) All the above

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113 views 1 answer

asked Apr 28, 2018 by anonymous

The direction of rotation of an inverter fed 3-phase ac motor is reversed by

The direction of rotation of an inverter fed 3-phase ac motor is reversed by (A) a mechanical reversing switch (B) reversing the input dc link voltage (C) operating the inverter as a rectifier (D) changing the sequence of switching

Last answer: The direction of rotation of an inverter fed 3-phase ac motor is reversed by changing the sequence of switching

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116 views 1 answer