Interview Questions.

Top 100+ Power Electronics Interview Questions And Answers

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Top 100+ Power Electronics Interview Questions And Answers

Question 1. What Is Holding Current In Scr?

Answer :

It is the minimum current required to maintain the SCR in forward conduction state. When the ahead modern-day turns into less than preserving current, SCR turns from ahead conduction country to forward blocking state.

Question 2. What Is Latching Current In Scr?

Answer :

It is the minimum cutting-edge required to latch(turn on) the SCR from ahead blocking kingdom to forward conduction country.

Electronic Circuits Interview Questions
Question 3. What Are The Different Turn On Methods Of Scr?

Answer :

Forward voltage triggering
Gate Triggering
dv/dt triggering
Temperature triggering
Light triggering

Question 4. What Is Snubber Circuit?

Answer :

The snubber circuit is used for the dv/dt protection of the SCR. It is a series combination of a resistor and a capacitor in parallel with the SCR.

Question five. What Is Hard Switching Of The Thyristor?

Answer :

When gate current is numerous times higher than the desired gate contemporary, the SCR is stated to be tough fired.It reduces the turn on time. And enhances the di/dt functionality.

Electrical Engineering Interview Questions
Question 6. What Is Firing Angle?

Answer :

The attitude between the 0 crossing of the enter voltage and the on the spot the SCR is fired is called as put off perspective or firing perspective.

Question 7. What Is Meant By Commutation?

Answer :

The process of converting the direction of current go with the flow in a particular path of the circuit. It is used to show off the SCR.

Printed Circuit Board Design (PCB) Interview Questions
Question 8. What Are The Advantages Of Free Wheeling Diode In Rectifier Circuit?

Answer :

The input power thing is progressed.It prevents the output voltage from becoming terrible.Load modern waveform is stepped forward.

Question nine. What Is Meant By Cyclo-converter?

Answer :

It is also referred to as frequency changer. It converts input power at one frequency to output electricity at any other frequency with one degree conversion.

Power Plant Project Interview Questions
Question 10. What Are The Types Of Cyclo-converters?

Answer :

Step up cyclo-converter
Step down cyclo-converter.

Question 11. What Is Step Up Cyclo-converter?

Answer :

It is the converter whose output frequency is much less than the enter frequency.

Power Transmission Interview Questions
Question 12. What Is Step Down Cyclo-converter ?

Answer :

It is the converter whose output frequency is greater than the input frequency.

Electronic Circuits Interview Questions
Question thirteen. What Is Ac Voltage Controller?

Answer :

It is the one which converts constant alternating voltage to a variable voltage without exchange in frequency.

Question 14. What Is Inverter?

Answer :

A device which converts dc power into ac strength at preferred output voltage and frequency is called as Inverter.

Question 15. What Are The Types Of Inverter?

Answer :

Voltage Source Inverter
Current Source Inverter
Circuit design Interview Questions
Question sixteen. What Is Duty Cycle?

Answer :

It is the ratio of the on time of the chopper to total term of the chopper.

D = Ton / [Ton + Toff]
Question 17. Can Fuses With An Ac Voltage Rating Be Used In A Dc Applications?

Answer :

Fuses must be rated for the voltage AC or DC wherein they will be used. Generally, fuses have a DC voltage rating that is half of of the maximum AC voltage rating.

Electrical Machines Interview Questions
Question 18. What Are The Different Operation Regions Of The Scr?

Answer :

SCR or thyristor may have 3 areas of operations based totally on the mode in which the tool is hooked up in the circuit.

Reverse blocking region: When the cathode of the thyristor is made fantastic with respect to the anode and no gate sign is carried out. In this area scr exhibits the opposite blocking off characteristics just like diode.

Forward blocking off area: In this location the anode of the thyristor is made advantageous with admire to the cathode and no gate signal is carried out to the thyristor. A small leakage contemporary float on this mode of operation of the thyristor.

Forward conduction area: when the ahead voltage carried out among the anode and cathode increases at unique spoil over voltage avalanche breakdown takes region and thyristor begins conducting modern in ahead route. By this form of triggering the tool damages the scr. Hence a gate signal is applied before the forward damage over voltage to trigger the scr.

Electrical Engineering Interview Questions
Question 19. What Is Latching Current?

Answer :

Gate signal is to be implemented to the thyristor to cause the thyristor ON in safe mode. When the thyristor starts offevolved accomplishing the ahead modern-day above the minimal value, referred to as Latching modern, the gate sign which is carried out to trigger the device in now not require to preserve the scr in ON role.

Question 20. What Is Holding Current ?

Answer :

When scr is engaging in modern in ahead conduction country, scr will go back to ahead blocking country while the anode contemporary or ahead modern falls below a low level known as Holding contemporary Note: Latching cutting-edge and Holding contemporary aren't equal. Latching cutting-edge is associated with the activate system of the scr while keeping cutting-edge is associated with the turn off procedure. In popular holding modern may be barely lesser than the latching modern-day.

DC motor Interview Questions
Question 21. Why Thyristor Is Considered As Charge Controlled Device?

Answer :

During the triggering method of the thyristor from forward blockading country to forward conduction nation thru the gate sign, with the aid of making use of the gate sign (voltage between gate and cathode) increases the minority carrier density inside the p-layer and thereby facilitate the reverse spoil over of the junction J2 and thyristor starts engaging in. Higher the value of the gate present day pulse, lesser is the time required to inject the charge and turning at the scr. By controlling the amount of rate we will manipulate the turning on time of the scr.

Question 22. What Is The Relation Between The Gate Signal And Forward Break Over Voltage (vbo)?

Answer :

Thyristor may be brought about by means of increasing the forward voltage between anode and cathode, at forward wreck over voltage thyristor starts undertaking. However this procedure may additionally damage the thyristor, so thyristor is advices to cause on thru the gate pulse. When a gate signal is implemented thyristor turns on before attaining the damage over voltage. Forward voltage at which the thyristor triggers on relies upon at the value of the gate cutting-edge. Higher is the gate current decrease is the ahead break over voltage.

Question 23. What Are The Different Losses That Occur In Thyristor While Operating?

Answer :

Different losses that occur are:

Forward conduction losses in the course of conduction of the thyristor
Loss due to leakage contemporary all through forward and reverse blockading.
Power loss at gate or Gate triggering loss.
Switching losses at turn-on and flip-off.
Induction Motors Interview Questions
Question 24. What Are The Advantages Of Speed Control Using Thyristor?

Answer :

Advantages :

Fast Switching Characteristics than MOSFET, BJT, IGBT
Low value
Higher Accurate.
Printed Circuit Board Design (PCB) Interview Questions
Question 25. What Happens If I Connect A Capacitor To A Generator Load?

Answer :

Connecting a capacitor throughout a generator continually improves electricity factor, however it will help relies upon up at the engine potential of the alternator, other smart the alternator might be over loaded because of the extra watts consumed because of the improvement on pf. Secondly, do not join a capacitor throughout an alternator at the same time as it is selecting up or with none other load.

Question 26. Why The Capacitors Works On Ac Only?

Answer :

Generally capacitor offers limitless resistance to dc components (i.E., block the dc components). It allows the ac additives to bypass thru.

Electrical Power System Interview Questions
Question 27. Explain The Working Principal Of The Circuit Breaker?

Answer :

Circuit Breaker is one that makes or breaks the circuit. It has two contacts specifically constant contact & transferring touch under regular condition the transferring contact comes in contact with constant touch thereby forming the closed touch for the go with the flow of cutting-edge. During bizarre & faulty situations (whilst modern-day exceeds the rated fee) an arc is produced between the constant & shifting contacts & thereby it bureaucracy the open circuit Arc is extinguished by using the Arc Quenching media like air, oil, vacuum and many others.

Power Plant Project Interview Questions
Question 28. What Is The Difference Between Isolator And Circuit Breaker?

Answer :

Isolator is a off load device which is used for setting apart the downstream circuits from upstream circuits for the cause of any preservation on downstream circuits. It is operated by hand and does no longer comprise any solenoid unlike circuit breaker. It must now not be operated even as it's miles having load. First the weight on it ought to be made 0 and then it can effectively operated. Its specification simplest rated modern-day is given. But circuit breaker is onload automatic tool used for breaking the circuit in case of atypical conditions like short circuit, overload and so on., it is having 3 specification 1 is rated current and 2 is short circuit breaking potential and three is instantaneous tripping current.

Question 29. What Is The Difference Between Earth Resistance And Earth Electrode Resistance?

Answer :

Only one of the terminals is evident inside the earth resistance. In order to discover the second terminal we must recourse to its definition: Earth Resistance is the resistance present between the electrically accessible a part of a buried electrode and every other factor of the earth, which is far away.

The resistance of the electrode has the following additives:

the resistance of the metal and that of the relationship to it.
The touch resistance of the surrounding earth to the electrode.
Powerbuilder Interview Questions
Question 30. What Is Use Of Lockout Relay In Ht Voltage?

Answer :

A lock-out relay is usually located in line earlier than or after the e-prevent transfer so the power can be shut off at one valuable location. This relay is powered through the equal electric source as the manipulate electricity and is operated by means of a key lock switch. The relay itself can also have up to 24 contact points in the unit itself. This permits the control strength for a couple of machines to be locked out by using the turn of a single key switch.

Question 31. What Is The Power Factor Of An Alternator At No Load?

Answer :

At no load Synchronous Impedance of the alternator is accountable for developing angle difference. So it should be 0 lagging like inductor.

Question 32. How To Determine Capacitor Tolerance Codes?

Answer :

In digital circuits, the capacitor tolerance may be determined with the aid of a code that looks on the casing. The code is a letter that often follows a 3-digit variety (which include 130Z).The first two are the 1st and 2d giant digits and the 0.33 is a multiplier code. Most of the time the remaining digit tells you how many zeros to write after the primary two digits and these are read as Pico-Farads.

Electric Power Generation Interview Questions
Question 33. Why Most Of Analog O/p Devices Having O/p Range 4 To 20 Ma And Not zero To 20 Ma?

Answer :

4-20 mA is a widespread range used to signify measured values for any technique. The motive that 4ma is chosen rather than 0 mA is for fail safe operation .For example- a strain instrument gives output 4mA to suggest zero psi, up to 20 mA to suggest a hundred psi, or full scale. Due to any trouble in device (i.E) broken twine, its output reduces to 0 mA. So if variety is 0-20 mA then we will differentiate whether or not it's far because of damaged cord or because of 0 psi.

Power Transmission Interview Questions
Question 34. Two Bulbs Of 100w And 40w Respectively Connected In Series Across A 230v Supply Which Bulb Will Glow Bright And Why?

Answer :

Since two bulbs are in series they'll get identical amount of electrical modern but because the supply voltage is steady across the bulb(P=V^2/R).So the resistance of 40W bulb is more and voltage across 40W is extra (V=IR) so 40W bulb will glow brighter.

Question 35. What Is Meant By Knee Point Voltage?

Answer :

Knee factor voltage is calculated for electrical Current transformers and is very critical factor to select a CT. It is the voltage at which a CT receives saturated.(CT-modern transformer).

Question 36. What Is Reverse Power Relay?

Answer :

Reverse Power go with the flow relay are utilized in producing station's protection. A producing stations is supposed to fed electricity to the grid and in case generating gadgets are off,there's no technology inside the plant then plant may take power from grid. To stop the drift of energy from grid to generator we use reverse electricity relay.

Circuit layout Interview Questions
Question 37. What Are The Advantage Of Free Wheeling Diode In A Full Wave Rectifier?

Answer :

It reduces the harmonics and it also reduces sparking and arching across the mechanical switch in order that it reduces the voltage spike visible in a inductive load.

Question 38. What Is The Full Form Of Kvar?

Answer :

We understand there are three kinds of electricity in Electrical as Active, obvious & reactive. So KVAR is stand for ``Kilo Volt Amps with Reactive aspect.

Question 39. Definition Of Power Electronics?

Answer :

Power electronics refers to control and conversion of electrical electricity by electricity semiconductor devices wherein these gadgets perform as switches.

Question 40. What Is The Main Purpose Of Power Electronics?

Answer :

The fundamental mission of electricity electronics is to manipulate and convert electrical electricity from one shape to any other.

AC to DC conversion: Rectifier is used for converting an AC voltage to a DC voltage.

Rectifier programs: Variable pace dc drives, Battery chargers, DC energy components and Power deliver for a selected software like electroplating.

DC to AC conversion: Inverter circuit is used to transform DC voltage to an alternating voltage.

Inverter applications: Emergency lighting fixtures structures, AC variable speed drives, Un-interrupted strength elements and Frequency converters.

DC to DC conversion: A dc-to-dc converter circuit was known as a chopper.

Chopper packages: DC power, Battery charger and DC power supply.

AC to AC conversion: A cycloconverter converts an AC voltage to another AC voltage.

Cycloconverter packages: It is rarely used. Can be used for controlling the velocity of an AC traction motor

Electrical Machines Interview Questions
Question forty one. What Are The Different Operation Regions Of The Thyristor (scr)?

Answer :

SCR or thyristor can have three areas of operations based at the mode wherein the device is hooked up in the circuit.

Reverse blocking region: When the cathode of the thyristor is made high-quality with appreciate to the anode and no gate signal is implemented. In this region SCR reveals the reverse blocking characteristics similar to diode.

Forward blocking place: In this vicinity the anode of the thyristor is made fantastic with recognize to the cathode and no gate sign is carried out to the thyristor. A small leakage present day drift in this mode of operation of the thyristor.

Forward conduction vicinity: while the forward voltage applied between the anode and cathode increases at unique wreck over voltage avalanche breakdown takes location and thyristor starts carrying out cutting-edge in ahead direction. By this sort of triggering the tool damages the scr. Hence a gate sign is applied before the forward ruin over voltage to cause the scr.

Question 42. What Are The Losses That Occur In A Thyristor During Working Conditions?

Answer :

Forward conduction losses
Loss because of leakage present day throughout forward and opposite blockading
Switching losses at activate turn off
Gate triggering loss

DC motor Interview Questions
Question 43. What Are The Advantages Of Freewheeling Diode In Rectifier Circuit?

Answer :

The enter energy component is advanced. It prevents the output voltage from turning into poor. Load modern-day waveform is likewise stepped forward.

Question 44. Explain The Function Of Cyclo-converter?

Answer :

It is likewise known as frequency changer. It converts enter power at one frequency to output strength at every other frequency with one degree conversion.

Question 45. What Is An Inverter?

Answer :

A device which converts dc energy into ac power at preferred output voltage and frequency is called as Inverter.

Question forty six. Define Circuit Turn Off Time

Answer :

It is described as the time in the course of which a opposite voltage is applied across the thyristor throughout its commutation method.

Question 47. Why The Circuit Turn Off Time Should Be Greater Than Thyristor Turn Off Time?

Answer :

If the circuit turn off time is much less than the thyristor turn off time the tool may additionally switch on at an undesired immediately ensuing in commutation failure.

Question forty eight. What Is Chopper?

Answer :

A dc Chopper is equal to the transformer in ac circuit. It is a static switch used to get the variable dc voltage from a consistent dc voltage.

Question forty nine. What Are The Types Of Commutation? (or) Turn Off Methods?

Answer :

Natural commutation
Forced commutation

Question 50. What Is Natural Commutation?

Answer :

The system of the contemporary flowing thru the thyristor goes thru a natural zero and allow the thyristor to show off is known as as herbal commutation.

Question fifty one. What Is Forced Commutation?

Answer :

The system of the cutting-edge flowing thru the thyristor is pressured to end up 0 with the aid of outside circuitry is known as as compelled commutation.

Question fifty two. What Is Step Down Chopper?

Answer :

In step down chopper, the average output voltage is less than the input supply voltage. It is also called Buck converter.

Question fifty three. What Is Step Up Chopper?

Answer :

In step up chopper, the common output voltage is extra than the enter supply voltage. It is also referred to as Boost converter.

Question 54. What Is Voltage Commutation?

Answer :

The method of a charged capacitor momentarily opposite biases the conducting SCR and turns it off is called as voltage commutation.

Question 55. What Is Current Commutation?

Answer :

The technique of a current pulse is made to glide in the opposite course via the engaging in SCR and as a result made the net SCR present day will become zero, therefore turn off the SCR is known as as modern commutation.

Question fifty six. What Are The Advantages Of Current Commuted Chopper?

Answer :

The blessings of cutting-edge commutated chopper is;

Commutation is reliable as load contemporary is much less than the height commutation contemporary
The auxiliary SCR is evidently commutated as its present day passes thru 0 fee.
The capacitor constantly stays charged with the perfect polarity.
Question fifty seven. What Is Load Commutation?

Answer :

In load commutation, the burden contemporary flowing through the thyristor both turns into zero or is transferred to any other tool from the accomplishing SCR.

Question fifty eight. Name Some Of The Current Controlled (modern Driven) Devices?

Answer :

SCR, GTO, GTR.

Question fifty nine. Name Some Of The Voltage Driven (voltage Controlled) Devices.

Answer :

IGBT, MCT, IGCT, SIT.

Question 60. What Is Meant By Pulse Triggered Devices?

Answer :

To switch on those form of gadgets single pulse of brief period is enough. Continuous gate voltage of entire on time isn't always required. It will avoid the hard triggering.

Example: Thyristor, GTO

Question sixty one. What Is Meant By Level-touchy Devices?

Answer :

In order to keep those type of gadgets in on-kingdom, we want to use non-stop gate present day /voltage.

Some of the extent sensitive gadgets are: MOSFET, IGBT, MCT, IGCT

Question 62. What Are The Advantages Of Igbt Over Bjt, Mosfet?

Answer :

IGBT has

Lower switch on and flip off instances than BJT
Lower on nation conduction losses than MOSFET
Excellent secure operating area
Question sixty three. Why Igbt Is Very Popular Nowadays?

Answer :

Lower hate requirements
Lower switching losses
Smaller snubber circuit necessities
Question sixty four. What Are The Different Methods To Turn On The Thyristor?

Answer :

Forward voltage triggering
Gate triggering
dv/dt triggering
Temperature triggering
Light triggering
Question sixty five. What Is The Difference Between Power Diode And Signal Diode?

Answer :

Power diode

Constructed with n-layer, called drift area between p+ layer and n+ layer.
The voltage, cutting-edge and energy rankings are higher.
Power diodes function at high speeds.
Signal diode

Drift region isn't gift.
The voltage, present day and energy rankings are Lower
Operates at better switching pace.
Question sixty six. Igbt Is A Voltage Controlled Device. Why?

Answer :

Because the controlling parameter is gate-emitter voltage.

Question sixty seven. Power Mosfet Is A Voltage Controlled Device. Why?

Answer :

Because the output (drain) current may be controlled by way of gate-source voltage.

Question 68. Power Bjt Is A Current Controlled Device. Why?

Answer :

Because the output (collector) cutting-edge can be managed by way of base current.

Question sixty nine. What Is The Relation Between α and β?

Answer :

 Submit

Question 70. What Are The Different Types Of Power Mosfet?

Answer :

N-channel MOSFET
P-channel MOSFET
Question 71. How Can A Thyristor Turned Off?

Answer :

A thyristor may be grew to become off via making the cutting-edge flowing thru it to 0.

Question 72. Define Latching Current?

Answer :

The latching modern-day is defined as the minimum price of anode modern which it need to reap in the course of activate method to keep conduction whilst gate sign is eliminated.

Question seventy three. Define Holding Current?

Answer :

The maintaining present day is described because the minimum value of anode modern-day below which it ought to fall to for turning off the thyristor.

Question 74. What Is A Snubber Circuit?

Answer :

It includes a sequence aggregate of a resistor and a capacitor in parallel with the thyristors. It is particularly used for dv / dt protection.

Question 75. What Losses Occur In A Thyristor During Working Conditions?

Answer :

Forward conduction losses
Loss due to leakage modern-day at some stage in forward and opposite blocking.
Switching losses at flip-on and flip-off.
Gate triggering loss.
Question seventy six. Define Hard-riding Or Over-driving?

Answer :

When gate cutting-edge is numerous times better than the minimal gate present day required, a thyristor is stated to be tough-fired or over-pushed. Hard-firing of a thyristor reduces its turn-on time and enhances its di/dt functionality.

Question 77. Define Circuit Turn Off Time?

Answer :

It is defined as the time at some stage in which a opposite voltage is applied across the thyristor all through its commutation system.

Question 78. Why Circuit Turn Off Time Should Be Greater Than The Thyristor Turn-off Time?

Answer :

Circuit turn off time should be extra than the thyristor flip-off time for dependable turn-off, otherwise the tool may additionally flip-on at an undesired immediately, a procedure known as commutation failure.

Question seventy nine. What Is The Turn-off Time For Converter Grade Scrs And Inverter Grade Scrs?

Answer :

Turn-off time for converter grade SCRs is 50 – a hundred ms flip-off time for converter grade SCRs and inverter grade SCRs and for inverter grade SCRs is three – 50 ms.

Question eighty. What Are The Advantages Of Gto Over Scr?

Answer :

Elimination of commutation of commutating components in compelled commutation, ensuing in discount in price, weight and quantity.
Reduction in acoustic noise and electromagnetic noise because of elimination of commutation chokes.
Faster turn-off, permitting excessive switching frequencies.
Improved performance of the converters.
Question 81. What Is Meant By Phase Controlled Rectifier?

Answer :

It converts fixed ac voltage into variable dc voltage.

Question 82. Mention Some Of The Applications Of Controlled Rectifier?

Answer :

Steel rolling generators, printing press, textile mills and paper turbines employing dc motor drives.
DC traction
Electro chemical and electro-metallurgical manner
Portable hand device drives
Magnet power materials
HVDC transmission system
Question 83. What Is The Function Of Freewheeling Diodes In Controlled Rectifier?

Answer :

It serves two process.

It prevents the output voltage from turning into negative.
The load modern-day is transferred from the principle thyristors to the freewheeling diode, thereby allowing all of its thyristors to regain their blocking states.
 

Question eighty four. What Are The Advantages Of Free Wheeling Diodes In A Controlled In A Controlled Rectifier?

Answer :

Input energy factor is progressed.
Load cutting-edge waveform is progressed and as a result the weight overall performance is higher.
Question eighty five. What Is Meant By Delay Angle?

Answer :

The put off attitude is described as the perspective among the 0 crossing of the enter voltage and the instant the thyristor is fired.

Question 86. What Are The Advantages Of Single Phase Bridge Converter Over Single Phase Mid-point Converter?

Answer :

SCRs are subjected to a height-inverse voltage of 2Vm in a completely managed bridge rectifier. Hence for equal voltage and modern-day ratings of SCrs, electricity dealt with through mid-point configuration is ready
In mid-factor converter, each secondary winding need to be capable of supply the burden strength. As such, the transformer rating in mid-point converter is double the burden score.
Question 87. What Is Commutation Angle Or Overlap Angle?

Answer :

The commutation period while outgoing and incoming thyristors are carrying out is called overlap period. The angular period, whilst both devices percentage conduction is referred to as the commutation perspective or overlap angle.

Question 88. What Are The Different Methods Of Firing Circuits For Line Commutated Converter?

Answer :

UJT firing circuit.
The cosine wave crossing pulse timing control.
Digital firing schemes.
Question 89. Give An Expression For Average Voltage Of Single Phase Semiconverters?

Answer :

Average output voltage Vdc = (Vm /Π) (1 + cosα).

Question ninety. What Is Meant By Input Power Factor In Controlled Rectifier?

Answer :

The input power issue is defined because the ratio of the total suggest enter electricity to the entire RMS enter volt-amperes.

PF = ( V1 I1 cos φ1 ) / ( Vrms Irms) in which V1 = phase voltage, I1 = fundamental

thing of the supply cutting-edge, φ1 = enter displacement attitude, Irms = deliver rms modern-day.

Question ninety one. What Are The Advantages Of Six Pulse Converter?

Answer :

Commutation is made easy.
Distortion at the ac aspect is reduced because of the discount in lower order harmonics.
Inductance reduced in collection is extensively reduced.
Question 92. What Is Meant By Natural Commutation?

Answer :

Here the current flowing thru the thyristor is going through a herbal zero and enable the thyristor to show off.

Question ninety three. What Is Meant By Forced Commutation?

Answer :

the thyristor is pressured to turn out to be 0 by means of outside circuitry.

Question 94. What Is Meant By Dc Chopper?

Answer :

A dc chopper is a excessive pace static transfer used to reap variable dc voltage from a regular dc voltage.

Question 95. What Are The Applications Of Dc Chopper?

Answer :

Battery operated automobiles
Traction motor manage in electric traction
Trolley motors
Marine hoists
Mine haulers
Electric braking.
Question 96. What Is Meant By Step-up And Step-down Chopper?

Answer :

In a step- down chopper or Buck converter, the average output voltage is much less than the input voltage. In a step- up chopper or Boost converter, the average output voltage is greater than the enter voltage.

Question 97. Write Down The Expression For Average Output Voltage For Step Down Chopper?

Answer :

Average output voltage for step down chopper V0 = α Vs, α is the responsibility cycle.

Question 98. Write Down The Expression For Average Output Voltage For Step Up Chopper?

Answer :

Average output voltage for step down chopper

          Vs     
  V0 =  ------  
        1 - α
α is the obligation cycle.

Question ninety nine. What Is Meant By Duty-cycle?

Answer :

Duty cycle is defined because the ratio of the on time of the chopper to the entire time period of the chopper. It is denoted by α.

Question a hundred. What Are The Two Types Of Control Strategies?

Answer :

Time Ratio Control (TRC)
Current Limit Control method (CLC)
Question a hundred and one. What Is Meant By Trc?

Answer :

In TRC, the price of Ton / T is various to be able to exchange the common output voltage.

Question 102. What Are The Two Types Of Trc?

Answer :

Constant frequency control
Variable frequency manage
Question 103. What Is Meant By Fm Control In A Dc Chopper?

Answer :

In frequency modulation control, the chopping frequency f (or the cutting period T) is various. Here two controls are possible.

On-time Ton is kept steady
Off duration Toff is saved consistent.
Question 104. What Is Meant By Pwm Control In Dc Chopper?

Answer :

In this control method, the on time Ton is various but chopping frequency is stored steady. The width of the heart beat is numerous and hence this sort of control is referred to as Pulse Width Modulation (PWM).

Question 105. Write Down The Expression For The Average Output Voltage For Step Down And Step Up Chopper?

Answer :

Average output voltage for step down chopper is VO = α VS.

Average output voltage for step up chopper is VO = α VS x [1/ ( 1- α)].

Question 106. What Are The Different Types Of Chopper With Respect To Commutation Process?

Answer :

Voltage commutated chopper.
Current commutated chopper.
Load commutated chopper.
Question 107. What Is Meant By Voltage Commutation?

Answer :

In this system, a charged capacitor momentarily reverse biases the engaging in thyristor and turn it off.

Question 108. What Is Meant By Current Commutation?

Answer :

In this method, a cutting-edge pulse is made to waft inside the opposite route through the carrying out thyristor and when the net thyristor current becomes zero, it's miles became off.

Question 109. What Is Meant By Load Commutation?

Answer :

In this manner, the load cutting-edge flowing thru the thyristor either will become 0 or is transferred to every other tool from the conducting thyristor.

Question one hundred ten. What Are The Advantages Of Current Commutated Chopper?

Answer :

The capacitor usually stays charged with an appropriate polarity.
Commutation is reliable as load present day is much less than the height commutation cutting-edge ICP.
The auxiliary thyristor TA is obviously commutated as its present day passes thru 0 price.
Question 111. What Are The Advantages Of Load Commutated Chopper?

Answer :

Commutating inductor is not required.
It is able to commutating any quantity of load present day.
It can work at excessive frequencies in the order of kHz.
Filtering necessities are minimal.
Question 112. What Are The Disadvantages Of Load Commutated Chopper?

Answer :

For high strength programs, efficiency becomes very low due to excessive switching losses at high operating frequencies.
Freewheeling diode is subjected to two times the deliver voltage.
Peak load voltage is equal to two times the supply voltage.
The commutating capacitor has to hold full load present day at a frequency of half chopping frequency.
One thyristor pair ought to be grew to become-on only whilst the other pair is commutated. This can be realized through sensing the capacitor current that is alternating.
Question 113. What Is Meant By Inverter?

Answer :

A device that converts dc strength into ac strength at favored output voltage and frequency is called an inverter.

Question 114. What Are The Applications Of An Inverter?

Answer :

Adjustable velocity drives
Induction heating
Stand-by using plane power elements
UPS
HVDC transmission
Question a hundred and fifteen. What Are The Main Classification Of Inverter?

Answer :

Voltage Source Inverter
Current Source Inverter
Question 116. Why Thyristors Are Not Preferred For Inverters?

Answer :

Thyristors require extra commutation circuits for turn off which leads to increased complexity of the circuit. For those motives thyristors are not favored for inverters.

Question 117. How Output Frequency Is Varied In Case Of A Thyristor?

Answer :

The output frequency is varied by using varying the flip off time of the thyristors in the inverter circuit, i.E. The postpone attitude of the thyristors is numerous.

Question 118. Give Two Advantages Of Csi?

Answer :

CSI does not require any comments diodes.
Commutation circuit is easy as it entails only thyristors.
Question 119. What Is The Main Drawback Of A Single Phase Half Bridge Inverter?

Answer :

It require a three-twine dc supply.

Question one hundred twenty. Why Diodes Should Be Connected In Antiparallel With Thethyristors In Inverter Circuits?

Answer :

For RL masses, load present day will not be in phase with load voltage and the diodes linked in anti parallel will allow the modern to drift whilst the primary thyristors are turned off. These diodes are referred to as feedback diodes.

Question 121. What Types Of Inverters Require Feedback Diodes?

Answer :

VSI with RL load.

Question 122. What Is Meant A Series Inverter?

Answer :

An inverter in which the commutating elements are connected in series with the load is referred to as a chain inverter.

Question 123. What Is The Condition To Be Satisfied In The Selection Of L And C In A Series Inverter?

Answer :

      4L 
R2 < ------
       C
Question 124. What Is Meant A Parallel Inverter?

Answer :

An inverter wherein the commutating factors are linked in parallel with the load is called a parallel inverter.

Question 125. What Are The Applications Of A Series Inverter?

Answer :

The thyristorised series inverter produces an about sinusoidal waveform at a high output frequency, starting from 2 hundred Hz to 100kHz. It is normally used for constant output applications along with

Ultrasonic generator.
Induction heating.
Sonar Transmitter
Fluorescent lighting fixtures.
 

Question 126. How Is The Inverter Circuit Classified Based On Commutation Circuitry?

Answer :

Line commutated inverters.
Load commutated inverters.
Self commutated inverters.
Forced commutated inverters.
Question 127. What Is Meant By Mcmurray Inverter?

Answer :

It is an impulse commutated inverter which is predicated on LC circuit and an auxiliary thyristor for commutation within the load circuit.

Question 128. What Are The Applications Of A Csi?

Answer :

Induction heating
Lagging VAR compensation
Speed control of ac vehicles
Synchronous motor beginning.
Question 129. What Is Meant By Pwm Control?

Answer :

In this technique, a fixed dc enter voltage is given to the inverter and a controlled ac output voltage is received by using adjusting the on and stale intervals of the inverter additives. This is the most popular method of controlling the output voltage and this technique is called as PWM control.

Question 130. What Are The Advantages Of Pwm Control?

Answer :

The output voltage can be obtained without any additional components.
Lower order harmonics may be removed or minimized together with its output voltage manipulate. As the better order harmonics may be filtered effortlessly, the filtering necessities are minimized.
Question 131. What Are The Disadvantages Of The Harmonics Present In The Inverter System?

Answer :

Harmonic currents will cause excessive heating within the induction automobiles. This will lessen the weight wearing ability of the motor.
If the manipulate and the regulating circuits are not nicely shielded, harmonics from power ride can have an effect on their operation and malfunctioning can result.
Harmonic currents cause losses within the ac gadget and might even a while produce resonance within the gadget. Under resonant conditions, the instrumentation and metering can be affected.
On vital loads, torque pulsation produced by way of the harmonic modern can be useful.
Question 132. What Are The Methods Of Reduction Of Harmonic Content?

Answer :

Transformer connections
Sinusoidal PWM
Multiple commutation in each cycle
Stepped wave inverters
Question 133. Compare Csi And Vsi?

Answer :

VSI:

Input voltage is maintained constant
The output voltage does not rely upon the load  
The significance of the output modern-day and its waveform relies upon on the character of the load impedance
It requires remarks diodes 
Commutation circuit is complicated i.E. It carries capacitors and inductors.
CSI:

Input present day is consistent but adjustable
The output modern-day does now not depend on the load
The significance of the output voltage and its waveform relies upon on the character of the weight impedance
It does not calls for remarks diodes
Commutation circuit is simple i.E. It consists of most effective capacitors.
Question 134. What Are The Disadvantages Of Pwm Control?

Answer :

SCRs are high-priced as they have to own low turn-on and turn-off instances.

Question a hundred thirty five. What Does Ac Voltage Controller Mean?

Answer :

It is device which converts constant alternating voltage right into a variable voltage with out trade in frequency.

Question 136. What Are The Applications Of Ac Voltage Controllers?

Answer :

Domestic and industrial heating
Lighting manipulate
Speed manage of unmarried phase and 3 segment ac motors
Transformer tap converting
Question 137. What Are The Advantages Of Ac Voltage Controllers?

Answer :

High performance
Flexibility in control
Less upkeep
Question 138. What Are The Disadvantages Of Ac Voltage Controllers?

Answer :

The essential pull away is the creation of harmonics within the deliver modern and the burden voltage waveforms mainly at low output voltages.

Question 139. What Are The Two Methods Of Control In Ac Voltage Controllers?

Answer :

ON-OFF manage
Phase control
Question 140. What Is The Difference Between On-off Control And Phase Control?

Answer :

ON-OFF manipulate: In this technique, the thyristors are hired as switches to attach the weight circuit to the source for a few cycles of the burden voltage and disconnect it for any other few cycles. Phase control: In this approach, thyristor switches join the weight to the ac supply for a component of every half cycle of enter voltage.

Question 141. What Is The Advantage Of On-off Control?

Answer :

Due to 0-voltage and zero current switching of thyristors, the harmonics generated via the switching movement are reduced.

Question 142. What Is The Disadvantage Of On-off Control?

Answer :

This kind of control is applicable in systems which have excessive mechanical inertia and excessive thermal time steady.

Question 143. What Is The Duty Cycle In On-off Control Method?

Answer :

Duty cycle K = n/ (n + m),
in which n = range of ON cycles,
m = quantity of OFF cycles.

Question 144. What Is Meant By Unidirectional Or Half-wave Ac Voltage Controller?

Answer :

Here the electricity glide is managed most effective all through the wonderful half of-cycle of the input voltage.

Question one hundred forty five. What Are The Disadvantages Of Unidirectional Or Half-wave Ac Voltage Controller?

Answer :

Due to the presence of diode on the circuit, the control variety is limited and the effective RMS output voltage can be various among 70.7% and 100%.
The enter contemporary and output voltage are asymmetrical and include a dc thing.If there is an input transformer, saturation trouble will occur
It is handiest used for low energy resistive load.
Question 146. What Is Meant By Bidirectional Or Half-wave Ac Voltage Controller?

Answer :

Here the electricity waft is controlled in the course of both cycles of the enter voltage.

Question 147. What Is The Control Range Of Firing Angle In Ac Voltage Controller With Rl Load?

Answer :

The manage range is Φ < α <180°,

where Φ = load strength thing angle.

Question 148. What Type Of Gating Signal Is Used In Single Phase Ac Voltage Controller With Rl Load?

Answer :

High frequency service gating sign is used for single section ac voltage controller with RL load.

Question 149. What Are The Disadvantages Of Continuous Gating Signal?

Answer :

More heating of the SCR gate.
Increases the dimensions of pulse transformer.
Question a hundred and fifty. What Is Meant By High Frequency Carrier Gating?

Answer :

Thyristor is turned on through using a train of pulses from a to p. This form of sign is called as high frequency service gating.

Question 151. What Is Meant By Sequence Control Of Ac Voltage Regulators?

Answer :

It method that the stages of voltage controllers in parallel prompted in a right collection one after the alternative for you to gain a variable output with low harmonic content.

Question 152. What Are The Advantages Of Sequence Control Of Ac Voltage Regulators?

Answer :

System energy factor is improved.
Harmonics are reduced in the source modern and the burden voltage.
Question 153. What Are The Two Types Of Cyclo-converters?

Answer :

Step-up cyclo-converters
Step-down cyclo-converters
Question 154. What Is Meant By Step-up Cyclo-converters?

Answer :

In those converters, the output frequency is much less than the deliver frequency.

Question one hundred fifty five. What Is Meant By Step-down Cyclo-converters?

Answer :

In those converters, the output frequency is extra than the supply frequency.

Question 156. What Are The Applications Of Cycloconverter?

Answer :

Induction heating
Speed control of high electricity ac drives
Static VAR generator
Power supply in plane or deliver forums
Question 157. What Is Meant By Positive Converter Group In A Cyclo-converter?

Answer :

The part of the cyclo-converter circuit that allows the glide of cutting-edge all through superb half cycle of output current is known as wonderful converter group.

Question 158. What Is Meant By Negative Converter Group In A Cyclo-converter?

Answer :

The a part of the cyclo-converter circuit that allows the float of cutting-edge all through poor half of cycle of output cutting-edge is referred to as terrible converter institution.

Question 159. Draw The Two Transistor Model Of Scr And Derive An Expression For Anode Current?

Answer :

Schematic diagram (2M)
Two transistor version diagram (2M)
Operation (4M)
Question a hundred and sixty. What Are The Characteristics Of Scr?

Answer :

Equivalent circuit
V-I characteristics
Switching traits
Question 161. Describe The Various Methods Of Thyristor Turn On?

Answer :

Forward voltage triggering
The dv/dt triggering
Gate triggering
Temperature triggering
Light triggering
Question 162. What Are The Operation Of Mosfet?

Answer :

Basic shape, image
Operation
V-I characteristics, Switching characteristics
Question 163. What Are The Operation Of Igbt?

Answer :

Basic shape, image
Operation
V-I traits, Switching characteristics
Question 164. Derive The Expressions For Average Output Voltage And Rms Output Voltage Of 1Φ Semi Converter?

Answer :

1Φ semiconverter bridge circuit
waveforms of vo , io , ifd, is, VT1, VT2
Operation
Average output voltage, rms fee of output voltage expression
Question a hundred sixty five. Describe The Working Of 1Φ Fully Controlled Bridge Converter In The Rectifying Mode And Inversion Mode. And Derive The Expressions For Average Output Voltage And Rms Output Voltage?

Answer :

1Φ full converter bridge circuit
waveforms of vo , io , ifd, is, VT1, VT2
Operation for α < 900, α > 900
Average output voltage, rms cost of output voltage expression.
Question 166. Describe The Working Of threeΦ Fully Controlled Bridge Converter In The Rectifying Mode And Inversion Mode. And Derive The Expressions For Average Output Voltage And Rms Output Voltage?

Answer :

3Φ full converter bridge circuit
waveforms of vo , io , iA, vs
Operation
Average output voltage expression.
Question 167. Describe The Working Of threeΦ Semi Converter. And Derive The Expressions For Average Output Voltage And Rms Output Voltage?

Answer :

threeΦ semi converter bridge circuit
waveforms of vo , io , iA, vs
Operation
Average output voltage expression.
Question 168. Describe The Working Of Dual Converter?

Answer :

3Φ dual converter bridge circuit
waveforms of vo , io , vo1 , vo2 , i1, i2 , vs , ic
Operation for with circulating present day and without circulating present day
load voltage expression, top price icp
Question 169. For A Type A Chopper (first Quadrant), Express The Following Variables As A Function Of Vs, R And Duty Cycle In Case The Load Is Resistive Average Output Voltage And Current?

Answer :

chopper circuit
output voltage & modern-day waveforms
Average load voltage expression
Question 170. Describe The Principle Of Step-up Chopper. Derive An Expression For The Average Output Voltage In Terms Of Input Dc Voltage & Duty Cycle?

Answer :

chopper circuit
output voltage & cutting-edge waveforms
Average load voltage expression
Question 171. Describe The Working Of Four Quadrant Chopper?

Answer :

chopper circuit
operation
Question 172. Explain The Working Of Current Commutated Chopper With Aid Of Circuit Diagram And Necessary Wave Forms. Derive An Expression For It




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