# In a thyistorised converter a free wheeling diode is used to

7 views
In a thyistorised converter a free wheeling diode is used to

A) Add to the conduction current ofthe thyristor B) Oppose the thyristor conduction C) Conduct current during the off period of the thyristor D) Protect the thyristor by providing a shunt path

In a thyistorised converter a free wheeling diode is used to Conduct current during the off period of the thyristor

## Related questions

A 3-phase fully controlled bridge converter with free wheeling diode is fed from 400 V, 50 Hz AC source and is operating at a firing angle of 60o. The load current is assumed constant at 10 A due to high load inductance. The input displacement factor (IDF) and the input power factor (IPF) of the converter will be  (A) IDF IPF = = 0.867; 0.828 (B) IDF IPF = = 0.867; 0.552 (C) IDF IPF = = 0.5; 0.478 (D) IDF IPF = = 0.5; 0.318

A separately excited dc motor operating in first quadrant is fed from 3-phase semi -converter free -wheeling diode is open circuited, then the motor :  (A) can be operated in first quadrant (B) can be operated in first & second quadrants (C) can be operated in first & fourth quadrants (D) cannot be operated

A three phase fully controlled bridge converter is feeding a load drawing a constant and ripple free load current of 10 A at a firing angle of 30o. The approximate Total harmonic Distortion (%THD) and the rms value of fundamental component of input current will respectively be  (A) 31% and 6.8 A (B) 31% and 7.8 A (C) 66% and 6.8 A (D) 66% and 7.8 A

The no-load speed of a single-phase SCR bridge converter fed separately excited dc motor operating at a firing delay angle, α and flux, Φ (A) directly proportional to α and Φ (B) inversely proportional to α and Φ (C) directly proportional to α and inversely proportional to Φ (D) directly proportional to Φ and inversely proportional to α

A freewheeling diode in a phase controlled converter  A) Deceases the possibility of discontinuous conduction in the load B) Increases the possibility of discontinuous conduction in the load C) Reduces the power factor and causes over voltages D) Causes over voltages

A single-phase full-bridge diode rectifier delivers a load current of 10A, which is ripple free. Average and rms values of diode currents are respectively   (a) 10A, 7.07A (b) 5A, 10A (c) 5A, 7.07A (d) 7.07A, 5A

A three-phase, fully controlled thyristor bridge converter is used as line commutated inverter to feed 50 kW power 420 V dc to a three-phase, 415 V(line), 50 Hz ac mains. Consider dc link current to be constant. The rms current of the thyristor is  (A) 119.05 A (B) 79.37 A (C) 68.73 A (D) 39.68 A

IN TTL Ics the protective diode is used to limit the (a) positive excursion to 0.7V (b) negative excursion to -0.7V (c) positive excursion to 0.3 V (d) negative excursion to -0.3 V

A single phase fully controlled bridge converter supplies a load drawing constant and ripple free load current, if the triggering angle is 30o, the input power factor will be  (A) 0.65 (B) 0.78 (C) 0.85 (D) 0.866

A 6V zener diode is used to provide voltage regulation with a series resistance of 100 Ohms and supply voltage is 12V. When under no load the power dissipated in the zener diode is (a) 60mW (b) 36mW (c) 360mW (d) 3600mW

In an isolated output dc-to-dc fly back converter, the high frequency transformer used works as an inductor (a) during turn -on period of the switching device (b) during turn off period of the switching device (c) during both (d) none of these

A DC chopper is used for regenerative braking of a separately excited DC motor. The DC supply voltage is 400V. The armature current during regenerative braking is kept constant at 300 A with negligible ripple. For a duty cycle of 60% the power return to the DC supply is  (a) 78 kW (b) 58 kW (c) 38 kW (d) 48 kW

A DC reactor is connected in series with each pole of a converter station in order to: A) prevent commutation failures in the inverter B) supply reactive power to the converter C) improve system stability D) increase the power transfer capability

The number of comparators required in a 3-bit comparator type analog to digital converter is  A) 2 B) 3 C) 7 D) 8

In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in (A) voltage notching (B) harmonic distortion (C) voltage sag (D) voltage swell

A thyristor power converter is said to be in discontinuous when:  (A) The load current is zero even though the load voltage is present. (B) Both load voltage and load current are zero simultaneously. (C) The load current is present even though load voltage is zero. (D) When load current is ripple free.

A forward potential of 10V is applied to a Si diode. A resistance of 1 KΩ is in series with the diode. The current through the diode is

In electric traction for a trapezoidal speed-time curve, the time period is (A) free running speed period = constant speed period (B) free running period = coasting period (C) free running period + coasting period = constant speed period (D) average speed period = scheduled speed period

The diode oftenly used for voltage regulation in electronic circuits is (a) Zener (b) Varactor (c) Silicon (d) Germanium

Zener diode is used in _______. A. Regulated power supplies B. Power generators C. Sensor D. All of these

In a weighted-resistor digital-to-analog converter with 8-bit input, if the resistance corresponding to the MSB is 2K, what will be the resistance corresponding to the LSB?  (a) 250 Ω (d) 512 KΩ (c) 256 KΩ (d) 25.5 Ω

To get minimum harmonic distortion in the output, a 3-Ф to 3-Ф cyclo-converter requires :  (A) 12 SCRs (B) 18 SCRs (C) 36 SCRs (D) 72 SCRs

A circuit is said to be free from phase distortion if its phase response shows: (1) Quadrature variation with frequency (2) Independent of frequency (3) Linear variation with frequency (4) Proportional to frequency

In successive approximation converter input to the comparator is through (A) DAC (B) Latch (C) Flip-flop (D) Sample and hold circuit

In which type of AC to DC converter efficiency is higher :

A moving coil meter has a resistance of 3 Ω and gives full scale deflection with 30 mA. To measure voltage up to 300 V, the external resistance to be connected in series with the instrument is (A) 9997 Ω (B) 10000 Ω (C) 997 Ω (D) 10003 Ω

How much time a diode takes to switch ON in forward bias condition.

In a metal conductor, what is a free electron?

In a loss-free R-L-C circuit the transient current is?

A 4-bit R/2R digital-to-analog (DAC) converter has a reference of 5 volts. What is the analog output for the input code 1010:  (1) 0.3125 V (2) 3.125 V (3) 0.78125 V (4) –3.125 V

In IC, transistors are utilised as diodes.To get highest breakdown voltage for such diode, it is adjusted to have  A) Ie=0 B) Ic=0 C) Vcb=0 D) Vce=0

In a three phase controlled bridge rectifier with an increase of overlap angles the output dc voltage

When reverse bias is applied to a junction diode, it  1.increases the potential barrier 2.decreases the potential barrier 3.greatly increases the minority carrier current 4.greatly increases the majority carrier current

what is the minimum voltage required to turn on a diode ?

In static Kramer drive, motor turns ratio is 0.6, the firing angle is 120o. The motor slip is   (a) 0.633 (b) 0.533 (c) 0.833 (d) 0.733

When The dc converter in figure shown has a resistance load of R = 10 Ω and the input voltage is Vs 220 V the converter switch remains on, its voltage drop is Vo -2 V. The chopping frequency is fI K sW Vs If the duty cycle is 50%, determine: (a) the average output voltage V (b) the RMS output voltage Vo (c) the converter efficiency (d) the effective input resistance of the converter

In D/A converter, the resolution required is 50mv and the total maximum input is 10v. The number of bits required is   (A) 7 (B) 8 (C) 9 (D) 200

A converter which can operate in both 3 pulse and 6 pulse mode is a  (A) 1 phase full converter (B) 3 phase half wave converter (C) 3 phase semi converter (D) 3 phase full converter.

In an R-2R ladder D/A converter, the input resistance is  1. Not same for all digital inputs 2. R for each input 3. 2R for each input 4. 3R for each input

In a single-phase full converter, the number of SCRs conducting during overlap is   (a) 1 (b) 2 (c) 3 (d) 4

In a clock mechanism, the gear train used to connect minute hand to hour hand, is : (A) Epicyclic gear train (B) Reverted gear train (C) Compound gear train (D) Simple gear train

To find current in a resistance connected in a network, Thevenin's theorem is used VTH = 20 V and RTH = 5 Ω. The current through the resistance: (1) is 4 A (2) is 4 A or less (3) is less than 4 A (4) May be 4 A or less or more than 4 A

A typical Solder composition used in component assembly to PCB is