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You Are On Multi Choice Question Bank SET 1291

64551. In a single phase full wave ac regulator the firing angles during both half cycles are equal.



64552. In a 3 phase full wave regulator feeding a star connected resistance load, firing angle is 75°. Then the number of thyristors conducting at one time is





64553. Weak insulation can be checked by:





64554. The turn on characteristics of a power transistor can be assumed to be linear, as shown in the below figure . During turn on time T, voltage reduces linearly from V to 0 and current rises linearly from 0 to I. The energy loss during time T is


64555. In window type air-conditioners the following expansion device used:





64556. A single phase half bridge inverter required to feed R-L loads needs





64557. Typical values of for an SCR are in the range of





64558. When a dc chopper feeds an RLE load, the load current, during steady state operation





64559. In a single phase full wave ac regulator feeding R-L load, the gate pulses





64560. In a semi converter feeding a resistive load,





64561. In a single phase semi-converter the number of thyristors is





64562. A dc chopper is feeding an RLE load. The current can become discontinuous if





64563. Which of these commutation methods uses two leads?





64564. A single phase half wave rectifier is feeding a resistive load. As firing angle is increased





64565. A cycloconverter for single phase operation has





64566. A chopper is a high efficiency circuit.



64567. The difference between resonant commutation and self commutation is





64568. Freon 12 ideal pressure is:





64569. A NAND gate has 3 inputs and one output. The number of thyristors required for this gate are





64570. Which of these devices is used in relaxation oscillator?





64571. In a single phase semiconverter feeding a highly inductive load, the load current is





64572. Two thyristors of the same rating and specifications




64573. A 3 phase induction motor is controlled by voltage and frequency control such that the ratio V/f is constant. At 50 Hz, the starting torque is 100 N-m. At 25 Hz, the starting torque





64574. In a three phase to single phase full wave bridge cycloconverter, the number of thyristors is





64575. In a cycloconverter it is possible to vary





64576. A single phase full bridge inverter for R-L loads needs





64577. In the basic series inverter circuit, the source current has





64578. Thyristors connected in series need static and dynamic stabilizing circuits.



64579. In a controlled rectifier a freewheeling diode is necessary if the load is





64580. For an illumination control circuit it is advisable to use a matched TRIAC-DIAC pair.



64581. Assertion (A): An ac regulator uses natural commutationReason (R): An ac regulator can be used for static on load tap changing of transformer.





64582. When a UJT is used as a relaxation oscillator the current should be





64583. In auxiliary commutated chopper, the charging and discharging time of capacitor





64584. Which chopper circuit uses saturable reactor?





64585. A thyristor circuit is feeding an R-L load. The turn on time can be reduced by





64586. A single phase semiconverter is supplying RLE load and has a freewheeling diode across the load. The firing angle is a . The freewheeling diode conducts for





64587. In a single phase full wave regulator feeding a resistive load, the average current over one full cycle





64588. Two single phase semi-converters are connected in series to form a series converter. The input is v = Vm sin ωt and a 1, a 2 are the firing angles. If a 1 = 0, the dc output voltage is





64589. The total number of leads in MOS controlled thyristor is





64590. Assertion (A): Chopper always requires forced commutationReason (R): Morgan chopper uses a saturable reactor.





64591. In a power diode the reverse recovery time is the time from the instant the forward current is zero to the instant when reverse recovery current has decayed to





64592. Assertion (A): McMurray Bredford half bridge inverter uses complementary commutationReason (R): Three phase inverter can have two modes of operation.





64593. A capacitor C farads is charged to a voltage V. It discharges through a thyristor, a diode and an inductance L. The peak current in the circuit is


64594. Which of these devices have four layers?





64595. When UJT is used for thyristor gate signal, the output of UJT is





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