77851. In a 3 phase bridge inverter with 180° mode of operation the numbers of thyristors conducting at one time are
77852. A single phase full converter can operate in
77853. In a 3 phase semiconverter, the freewheeling diode comes into operation only if firing angle
77854. In the circuit of figure, the load current when thyristor is off
77855. A full bridge inverter is fed by a battery of 30 V. The rms value of output voltage is
77856. In brushless excitation system of modern alternators, the main exciter is
77857. The two-transistor model of a thyristor consists of two transistors :
77858. In a thyristor, the forward breakover voltage
77859. The gate lead, in a thyristor is welded to :
77860. In a 3 phase full converter, the firing angle is less than 60°. The instantaneous output voltage
77861. In a stud mounted SCR, the stud is
77862. In pulse width modulation of chopper
77863. In a full bridge inverter, the waveshape of load current depends on
77864. The characteristics of which device has peak point and valley point
77865. In a thyristors are i = kva. The value of a is
77866. In an ordinary thyristor
77867. Thyristors connected in series need :
77868. Convert from CFC12 to HFC 134 appliance,the compressor displacement will be:
77869. If 4 quadrant operation is required we need
77870. A single phase half wave converter is feeding a resistive load. Output dc power is Pdc and total power delivered to load is Pac then
77871. Which of the following devices exhibit negative resistance characteristics?
77872. In integral cycle control of ac regulators, the period of integral cycle control, i.e., (m + n) T should be
77873. All other parameters remaining the same, a 3 phase bridge inverter with 180° mode of operation
77874. As compared to BJT, MOSFET has
77875. If a step down chopper is fed by a dc voltage V with Ton and Toff are on and off periods then is
77876. A voltage VBB is applied across the terminals of a UJT. The emitter voltage at peak point is
77877. A single phase bridge type cycloconverter uses eight thyristors.
77878. In the circuit of figure, the waveshape of load current when thyristor conducting is
77879. In the basic series inverter circuit, the source supplies load
77880. A current source inverter has simple commutation circuit.
77881. In load commutated chopper, the commutating element
77882. In a half bridge inverter each thyristor is gated at a frequency f. The output frequency is
77883. 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.
77884. 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.
77885. Multiphase choppers are used in
77886. 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
77887. Dry ice is:
77888. A step up chopper can give an output voltage
77889. The specified maximum junction temperature of thyristors is about
77890. A bridge type single phase cycloconverter changes the frequency f to f/3. Then one half wave of output contains
77891. A half bridge inverter
77892. A 3 phase series inverter has
77893. In figure, thyristor Th is in off state. When thyristor is turned on, the peak thyristor current can be
77894. HVDC systems are preferable for only long distances.
77895. Surge current rating of an SCR is
77896. Which of the following devices has metal-silicon junction?
77897. A dc chopper is feeding an RLE load. The condition for maximum ripple is
77898. In a series inverter
77899. When a power diode is conducting, the voltage drop across it is about
77900. A string of series connected thyristors needs equalising circuit to
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