The device which allows reverse power flow and withstands highest switch frequency is (A) GTO (B) MOSFET (C) IGBT (D) Inverter grade SCR
Last Answer : The device which allows reverse power flow and withstands highest switch frequency is MOSFET
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1 answer
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Apr 28, 2018
by
anonymous

Last Answer : Burden of a protective relay is the power absorbed by the circuit of relay.
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811 views
1 answer
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Mar 19, 2018
by
anonymous

What happens when you reverse the direction of the current in an electromagnet?
Last Answer : When you reverse current direction in an electromagnet, the magnetic poles will also change.
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174 views
1 answer
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Mar 14, 2018
by
anonymous
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A diode in which the change in reverse bias voltage varies the capacitance is called as A) Varactor diode B) Switching diode C) Tunnel diode D) Zener-diode
Last Answer : A diode in which the change in reverse bias voltage varies the capacitance is called as Varactor diode
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157 views
1 answer
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Jun 18, 2018
by
anonymous

What is a reverse conducting thyristor?
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85 views
0 answers
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Mar 19, 2018
by
anonymous

How can we reverse the direction of rotation of synchronous motor?
Last Answer : By reversing supply phase sequence we can reverse the direction of rotation of synchronous motor.
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306 views
1 answer
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Mar 18, 2018
by
anonymous
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What is the difference between forward and reverse bias?
Last Answer : Forward bias is a PN junction bias which allows current to flow through the junction. Forward bias decreases the resistance of the depletion layer. Reverse bias is a PN junction bias that allows only ... Positive polarity on the n-type material and negative polarity to the p-type material.
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280 views
3 answers
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Dec 9, 2017
by
anonymous

Last Answer : In cut-off region of BJT both the emitter-base junction and collector-base junction are reverse biased.
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94 views
2 answers
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Sep 27, 2017
by
anonymous

main parts of Relay
Last Answer : Coil, plunger, contacts, springs, connecting terminals and enclosure.
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71 views
1 answer
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Aug 28, 2019
by
anonymous

What is phase failure relay and how it's work?
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60 views
0 answers
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Aug 12, 2019
by
anonymous

Buchholz relay is used as a safety device with respect to which of the following? A) Audio transformers B) Oil filled power transformers C) Air core transformer D) None of these
Last Answer : Buchholz relay is used as a safety device with respect to which of the following? A) Audio transformers B) Oil filled power transformers C) Air core transformer D) None of these
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108 views
1 answer
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Apr 29, 2018
by
anonymous

Fuel Pump Relay
Last Answer : Some car owners immediately suspect a fuel pump failure when their cars stall. However, there are many other engine problems that may resemble a fuel pump failure, such as restricted fuel filters, smashed ... advisable to bring your car to the repair shop so that the whole engine can be checked.
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10 views
1 answer
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May 5, 2021
by
anonymous

The purpose of the restraining coil in a biased differential relay is (A) To reduce CT saturation during fault. (B) To increase the sensitivity of the relay. (C) To match the transformation ratio. (D) To limit the spill current through the relay during heavy external fault.
Last Answer : d
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711 views
2 answers
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May 8, 2018
by
anonymous

A relay used for protection of motors against overload is : (A) Impedance relay (B) Electromagnetic attraction type (C) Thermal relay (D) Buchholz's relay
Last Answer : D
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549 views
2 answers
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May 8, 2018
by
anonymous

A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is
Last Answer : A relay has a rating of 5 A, 2.2 sec IDMT and a relay setting of 125% TMS = 0.6. It is connected to a supply circuit through a C.T. 400/5 ratio. The fault current is 4000 A. The operating current of the relay is 6.25A
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733 views
1 answer
asked
May 3, 2018
by
anonymous

The operating time of instantaneous relay is
Last Answer : The operating time of instantaneous relay is 0.1 sec
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118 views
1 answer
asked
May 3, 2018
by
anonymous

What is the difference between relay and contactor?
Last Answer : Relay have smaller ratings. Contactor is a high rating relay.
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5.1k views
1 answer
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May 2, 2018
by
anonymous

A negative sequence relay is used for protection of (1) Generator (3) Motor (2) Transformer (4) Long Transmission lines
Last Answer : A negative sequence relay is used for protection of Generator
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627 views
1 answer
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May 1, 2018
by
anonymous

Buchholz relay is (1) located in the conservator tank (2) located in the transformer tank itself (3) connected in the pipe connecting main tank of transformer and conservator (4) installed in the circuit breaker
Last Answer : Buchholz relay is connected in the pipe connecting main tank of transformer and conservator
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119 views
1 answer
asked
Apr 30, 2018
by
anonymous
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To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with (1) second harmonic current (2) third harmonic current (3) fifth harmonic current (4) seventh harmonic current
Last Answer : To prevent mal-operation of differentially connected relay while energizing a transformer, the relay restraining coil is based with second harmonic current
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498 views
1 answer
asked
Apr 29, 2018
by
anonymous

Reactance relay is normally preferred for protection against
Last Answer : Reactance relay is normally preferred for protection against earth faults
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120 views
1 answer
asked
Apr 29, 2018
by
anonymous

In the induction type directional over current relay, when a short-circuit occurs in the circuit (A) power flows in reverse direction (B) power flows in normal direction (C) directional power element does not operate (D) over current element is not energized
Last Answer : In the induction type directional over current relay, when a short-circuit occurs in the circuit power flows in reverse direction
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124 views
1 answer
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Apr 28, 2018
by
anonymous

A solid state relay (A) withstands voltage transients (B) does not require auxiliary dc supply (C) provide low burden on CT and P (D) does not provide earth fault protection
Last Answer : A solid state relay provide low burden on CT and P
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69 views
1 answer
asked
Apr 28, 2018
by
anonymous
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A reactance relay is (A) Voltage restrained directional relay (B) Directional restrained over-current relay (C) Voltage restrained over current relay (D) Directional restrained over voltage relay
Last Answer : A reactance relay is Directional restrained over-current relay
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147 views
1 answer
asked
Apr 28, 2018
by
anonymous

Last Answer : The torque produced in induction type relay (shaded pole structure) is inversely proportional to the square of the current.
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831 views
1 answer
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Mar 20, 2018
by
anonymous

Last Answer : Admittance relay is directional relay.
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154 views
1 answer
asked
Mar 20, 2018
by
anonymous
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Last Answer : The relay with inverse time characteristic will operate within 5 to 10 sec.
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115 views
1 answer
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Mar 20, 2018
by
anonymous

Last Answer : The under voltage relay can be used for generators, busbars, transformers, motors.
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68 views
1 answer
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Mar 20, 2018
by
anonymous

Last Answer : Reactance relay is preferred for phase fault on short transmission line.
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110 views
1 answer
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Mar 20, 2018
by
anonymous

Last Answer : Induction cup relay is operated due to changes in current, voltage, impedance.
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352 views
1 answer
asked
Mar 20, 2018
by
anonymous

Last Answer : Interruption of large currents by relay requires arc suppressing blow out coils, wide separation of the opened contacts, high speed opening of contacts.
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96 views
1 answer
asked
Mar 20, 2018
by
anonymous

Last Answer : Overheating of relay contacts or contact born out is due to slow making and breaking of load circuit contacts, foreign matter on the contact surface, too low contact pressure.
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152 views
1 answer
asked
Mar 20, 2018
by
anonymous

Last Answer : A differential relay measures the vector difference between two or more similar electrical quantities.
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160 views
1 answer
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Mar 19, 2018
by
anonymous

Last Answer : In order that current should flow without causing excessive heating or voltage drop, the relay contacts should have low contact resistance, be clean and smooth, be of sufficient size and proper shape.
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154 views
1 answer
asked
Mar 19, 2018
by
anonymous

Last Answer : The relay operating speed depends upon the spring tension, the rate of flux built up, armature core air gap.
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271 views
1 answer
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Mar 19, 2018
by
anonymous

Last Answer : A Buchholz relay can be installed on oil cooled transformers.
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71 views
1 answer
asked
Mar 19, 2018
by
anonymous
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Last Answer : Buchholz's relay gives warning and protection against electrical fault inside the transformer itself.
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108 views
1 answer
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Mar 19, 2018
by
anonymous

How do relay works ?
Last Answer : Relay working like contact it is noise less
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134 views
1 answer
asked
Dec 30, 2017
by
anonymous

What is the use of Buchholz relay in transformer?
Last Answer : This is a transformer that is used to step up and down current.
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153 views
1 answer
asked
Dec 17, 2017
by
anonymous
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What is the difference between a switch and a relay?
Last Answer : Switch is simply a mechanical contact mechanism and relay is a electromagnetic switch . Switch can be direct mechanically turn on and off but relay can be operated by energising coil .
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110 views
1 answer
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Dec 17, 2017
by
anonymous

About trnsformer
Last Answer : Acc to Ohms law V=IR but it is only applicable when our resistance R is constant, as in case of transformer we take impedence which is equivalent to resistance is not constant it varies with system parameters that why Ohms law not applicable in case of transformer
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120 views
1 answer

Briefly explain how the power factor of an inductive circuit can be improved.
Last Answer : As we know that power factor should be corrected to ensure that the current supplied is cost friendly. Meaning the power factor should be around one but not greater than one(0.8-0.9) in a ... an inductive circuit due to the inductive reactance which oppose the change of current in the ac circuit.
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183 views
1 answer
asked
May 17, 2020
by
anonymous

What is the value of capacitance required to improve power factor from 0.7 to 0.9. Given that: Real power = 50 W Vrms of the source = 120 Frequency = 50 Hz #powerfactor
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197 views
0 answers
asked
May 17, 2020
by
anonymous

Why engine power is measured in horsepower (HP) ?
Last Answer : James Watt compared engine output with that of work done by a horse. WD by horse = 746W.
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199 views
2 answers
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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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211 views
4 answers
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Aug 25, 2019
by
anonymous

Why don't we burry power lines underground ?
Last Answer : Because conductor used for power transmission are not insulated and if we do so it create phase to ground fault causing interruptions to supply.
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107 views
5 answers
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Aug 18, 2019
by
anonymous

Why capacitors are used to improve power factor?
Last Answer : Capacitors generate reactive power instead of that drawn from source which is required by inductive loads.so it reduce the reactive current which is drawn from source to be drawn from capacitor.This control in Electric bills cost.
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185 views
3 answers
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Aug 18, 2019
by
anonymous

Draw the block diagram of satellite sub-system and explain power subsystem.
Last Answer : POWER SUBSYSTEM- This system provides the necessary DC power to the satellite. All communication satellites derive their electrical power from solar cells. There is also a battery backup facility used during ... . to d.c. converter is used to raise the level of low voltages to high voltage.
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3.1k views
1 answer
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Aug 8, 2019
by
anonymous

Compare the Nuclear power station with Hydro power station.
Last Answer : SR. No. Points Nuclear Power plant Hydro Power station 1 Site/ Location Where there is ample supply of water is available, away from thickly populated areas to avoid radioactive ... Field Application As base load Used as base load during as well as peak load
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75 views
1 answer
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Aug 2, 2019
by
anonymous

What are the basic requirements of locating wind power plant ?
Last Answer : The basic requirements of locating wind power plant: 1) The site should be selected where winds are strong i.e. where pressure of wind is high and there is continuity. 2) Wind pressure ... the turbine which can affect the system's overall performance. 10)Possibility to connect to power grid.
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137 views
1 answer
asked
Aug 2, 2019
by
anonymous
