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You Are On Multi Choice Question Bank SET 1288

64401. In a full wave converter (M - 2 connection) feeding an RLE load, the peak thyristor current is 15 A. For fully controlled bridge circuit and same load current, the peak thyristor current will be

64402. Induction heating systems require low frequency inverters.

64403. 1 like warm countries ......... Spain.?

64404. HVDC transmission systems generally use

64405. A single phase semiconverter is feeding a highly inductive load. The circuit has a freewheeling diode across the load and firing angle is a . During one cycle of input voltage, the total duration of conduction of freewheeling diode is

64406. During forward blocking state of SCR, the voltage and current respectively are

64407. In a 3 phase full converter the average load current is 150 A. The average thyristor current is

64408. The two modes of operation of three phase bridge inverters are known as

64409. In a dual converter both converters work as rectifiers.

64410. A single phase full wave regulator feeds R-L load. The best gating signal is

64411. A 3 phase induction motor is fed by a 3 phase ac regulator to change the stator voltage. The variation in speed will be more if

64412. A cycloconverter cannot give a frequency higher than input frequency.

64413. A thyristor has internal power dissipation of 40W and is operated at an ambient temperature of 20°C. If thermal resistance is 1.6° C/W, the junction temperature is

64414. In a single phase dual converter, a 1, and a 2 are firing angles of the two converters. Then

64415. The number of gates in an SCR is

64416. The waveshape of output voltage of half bridge inverter is

64417. A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the speed is 1440 rpm. At 25 Hz, the speed is likely to be

64418. The gate current required to turn on an SCR is

64419. A single phase half wave converter is used to charge a battery of 50 V. The thyristor is continuously fired by dc signal. Input voltage is v = Vm sin ωt. The thyristor will conduct

64420. The symbol in figure is for

64421. In a 3 phase semiconverter, the firing frequency is

64422. Present day HVDC converters are all

64423. A single phase full converter gives maximum and minimum output voltage at firing angles of

64424. A thyristor has its gate current zero. To start conduction the forward voltage must exceed

64425. Assertion (A): Snubber circuit has an RC series circuit in parallel with SCRReason (R): Voltage across a capacitor can not change instantaneously.

64426. In dielectric heating, the thyristor circuits consist of

64427. On load tap changer using thyristors can have a maximum of two taps.

64428. Assertion (A): A cycloconverter may be line commutated or forced commutatedReason (R): A step up cycloconverter requires forced commutation.

64429. In the below figure the rms voltage across each half of secondary is 200 V. The peak inverse voltage across each of thyristor is

64430. Assertion (A): A GTO circuit is more compact than SCR circuit Reason (R): A GTO can be turned off by negative gate pulse.

64431. In a single phase full wave ac regulator, the firing angles in the two half cycles

64432. ......... the suspected causes for earthquakes is the construction of dams.?

64433. As regards single phase dual converter

64434. To protect an SCR against high di/dt we connect

64435. In a parallel inverter

64436. A silicon controlled switch has :

64437. A dc chopper V = 500 V feeds an electric fraction dc series motor. The chopping frequency is 400 Hz. The series inductance required to limit the maximum current swing to 10 A is

64438. A single phase fully controlled bridge rectifier is fed by a source having inductance. The output voltage during overlap period is

64439. In a semi converter feeding a resistive load, the firing angle is a . Each thyristor conducts for

64440. Between which points does UJT exhibit negative resistance characteristics

64441. A thyristor has maximum allowable junction temperature of 110° C and the ambient temperature is 40°C, If the maximum internal power dissipation is 50 W, the thermal resistance is

64442. A single phase electric heater uses phase controlled thyristors. The firing angle is 90°. The degree of heating is

64443. Which of these commutation methods is used in AC-DC converters?

64444. When thyristors are connected in series and parallel, it may be necessary to have :

64445. A single phase half wave regulator uses

64446. A Shockley diode can be used

64447. An SCR has a turn on time of 4 μs. The gate pulse should have a duration of about

64448. In a multiphase chopper, the different choppers operate in

64449. In a 3 phase semiconverter, the dc output voltage for a certain firing angle is 50% of the maximum possible value. The firing angle is

64450. A high frequency series inverter consists of

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