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You Are On Multi Choice Question Bank SET 1290

64501. A single phase bridge type cycloconverter uses eight thyristors.

64502. In the circuit of figure, the waveshape of load current when thyristor conducting is

64503. In the basic series inverter circuit, the source supplies load

64504. A current source inverter has simple commutation circuit.

64505. In load commutated chopper, the commutating element

64506. In a half bridge inverter each thyristor is gated at a frequency f. The output frequency is

64507. Assertion (A): A transistor has lower voltage drop during conduction as compared to thyristorReason (R): Transistors are manufactured in very high voltage and current ratings.

64508. Assertion (A): Typical value of thermal resistance from source to sink of an SCR is about 0.3° C/WReason (R): Heat sinks of thyristors are generally made of aluminium.

64509. Multiphase choppers are used in

64510. In a single phase converter using a centre tapped transformer and with a highly inductive load, the firing angles is a . Each thyristor conducts for a period

64511. Dry ice is:

64512. A step up chopper can give an output voltage

64513. The specified maximum junction temperature of thyristors is about

64514. A bridge type single phase cycloconverter changes the frequency f to f/3. Then one half wave of output contains

64515. A half bridge inverter

64516. A 3 phase series inverter has

64517. In figure, thyristor Th is in off state. When thyristor is turned on, the peak thyristor current can be

64518. HVDC systems are preferable for only long distances.

64519. Surge current rating of an SCR is

64520. Which of the following devices has metal-silicon junction?

64521. A dc chopper is feeding an RLE load. The condition for maximum ripple is

64522. In a series inverter

64523. When a power diode is conducting, the voltage drop across it is about

64524. A string of series connected thyristors needs equalising circuit to

64525. A surge voltage

64526. The minimum gate current which can turn on SCR is called :

64527. The total number of leads in SUS, SBS and SCS respectively are

64528. Which of these devices can conduct in both directions?

64529. Assertion (A): A half wave controlled rectifier has poorer efficiency and higher ripple factor than a full wave controlled rectifier.Reason (R): The use of a freewheeling diode in half wave controlled rectifier circuit improves the waveform of load current and circuit power factor.

64530. A 3 phase dual converter consists of

64531. Which inverter circuit uses coupled inductors?

64532. When an SCR is in forward blocking mode, the applied voltage

64533. In sinusoidal PWM for inverters the width of different pulses are not the same.

64534. A class D chopper

64535. Relay is protection device used in:

64536. The efficiency of a chopper circuit is about

64537. If the frequency is less than the damped frequency in a series- inverter

64538. The output frequency of a cycloconverter can be changed by changing the firing angle.

64539. Mc Murray full bridge inverter uses

64540. Assertion (A): A DIAC has four layers but only two terminals. Reason (R): A DIAC can conduct in both directions.

64541. In a 3 phase full converter, the instantaneous output voltage can have negative part if

64542. In a single phase full wave ac regulator using two thyristors only, the gate circuits of the two thyristors

64543. The circuit in figure is for

64544. A fully controlled bridge converter is feeding an RLE load. For some circuit conditions firing angle is 47°. If connections of battery are reversed, the firing angle is likely to be

64545. In a single phase half wave converter feeding resistive load and full wave converter (M - 2 connection) feeding a resistive load the circuit conditions are similar. The firing angle is a . Then the waveshapes of voltages across thyristors

64546. In a 3 phase full converter feeding a highly inductive load, the average load current is 150 A. The peak current through thyristor is

64547. The main utility of SCR is due to

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