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You Are On Multi Choice Question Bank SET 1286

64301. For a series R-L-C circuit tuned at resonant frequency which of the following statements is correct?





64302. A network contains linear resistors and ideal voltage sources. If values of all the resistors are doubled, then the voltage across each resistor is





64303. If operator 'a' = 1 ∠120° then (1 + a + a2) =





64304. In a parallel resonant circuit, the circuit current at resonance is maximum.



64305. The rms value of wave in figure is





64306. An RLC series circuit is underdamped. To make it overdamped, the value of R





64307. Henry is equivalent to





64308. High side float valve is fitted on the condensing unit just after the:





64309. According to Ohm’s law I=





64310. 13When air is heated relative humidity





64311. Which chemical is used for condenser descaling?





64312. Which refrigerant charged in car C?





64313. The pipes which are used for absorption refrigeration system:





64314. A semiconverter feeding an RLE load operates in





64315. The phenomenon of overlap in converter operation due to





64316. A thyristor has a maximum allowable junction temperature of 120°C and the ambient temperature is 40°C. If thermal resistance is 1.6° C/W, the maximum allowable internal power dissipation is





64317. For a 12 pulse operation, the two 6 pulse units are fed by





64318. In a single phase full wave converter (M - 2 connection) feeding a highly inductive load, the firing angle for each thyristor is a in the respective half cycle. The period of conduction of each thyristor is





64319. An SCR is triggered at 40° in the positive half cycle only. The average anode current is 50 A. If the firing angle is changed to 80°, the average anode current is likely to be





64320. The characteristics of a non-linear resistance is i = kv4. If i becomes 100 times, v becomes





64321. In a step down chopper using pulse width modulation, Ton = 3 x 10-3 and Toff = 1 x 10-3 s. The chopping frequency is





64322. Thyristors are suitable for dc circuit breakers but not for ac circuit breakers.



64323. Assertion (A): Inverters and choppers use fast switching thyristors Reason (R): Fast switching SCR has low turn off time.





64324. The value of capacitor C for dynamic equalising circuit of series connected thyristors is determined by





64325. A chopper





64326. Assertion (A): If the duty cycle of chopper is low the current would not become discontinuousReason (R): If the time constant L/R of the load in chopper is low the current may become discontinuous.





64327. In a single phase full wave regulator, the firing angles in the positive and negative half cycles are generally





64328. An electric heater is controlled by thyristors through on-off control. If a = 0.4, the heating is





64329. A two winding transformer is feeding a single phase half wave rectifier circuit. The load is purely resistive. The rms value of transformer secondary current is Is and rms value of load current in Irms. Then





64330. The terminals of a power BJT are called





64331. In single phase half wave regulator, the average current over one full cycle





64332. The dynamic equalising circuit consists of a series combination of capacitor C and resistor RC across each thyristor. This resistance RC (along with parallel connected diode)





64333. A single phase semiconverter is feeding a highly inductive load and has freewheeling diode across the load. The waveshapes of output voltage and output current





64334. Current derating may be necessary when thyristors are operating in





64335. If duty cycle is a and the load is a resistance R, the rms value of output voltage is



64336. For a BJT a = 0.98, then β =





64337. Assertion (A): Power transistor has lower switching time than SCR Reason (R): Power transistor has greater switching time than SCR





64338. A 3 kV circuit uses SCR of 800 V rating. If derating is 25%, the number of SCRs in series is





64339. In a circuit using a full wave converter (M - 2 connection) the PIV of each thyristor is 400 V. For the same output voltage and fully controlled bridge converter, PIV will be





64340. A dc separately excited motor has constant field current. The armature is fed from a single phase supply through a full converter. When a = 0, speed is 500 rpm. If a = 45°, the speed is likely to be





64341. In a multiphase chopper, all choppers operate together.



64342. The terminals of a power MOSFET are called





64343. Assertion (A): The surge current which an SCR can withstand is much higher than rms on state current.Reason (R): The duration of surge current is very small.





64344. A single phase half wave controlled rectifier circuit has a free wheeling diode. The load is a combination of R and L. The firing angle is a . The period of conduction of SCR and free wheeling diode respectively are





64345. Assertion (A): A transistor requires a continuous base signal for conduction but a thyristor requires a gate pulse.Reason (R): Transistor find widespread application in power electronic circuits.





64346. In a thyristor the gate current is increased, then





64347. Thyristors are not suitable for logic circuits.



64348. A single phase half wave rectifier is feeding a resistive load. Input voltage v = Vm sin ωt. The output dc voltage is Vdc and output rms voltage is Vrms . If firing angle is 180°, Vdc and Vrms respectively are



64349. The number of leads in an SCR are :





64350. The person who led the Ezhava memorial of 1896?





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