77751. Which of these triggering methods for series connected SCRs use LASCR in the gate circuit?
77752. A 3 phase ac regulator uses
77753. The average load current supplied by a thyristor depends on
77754. In a 3 phase full wave regulator feeding a star connected resistance load the input voltage is 400 V line to line. The firing angle is 160°. The line to line output voltage would be
77755. A thyristor is reverse biased. A positive gate pulse is applied. The thyristor
77756. A single phase series converter is used for
77757. A single phase half wave controlled rectifier circuit has an R-L load. A freewheeling diode is also in the circuit. When freewheeling diode is conducting the SCR
77758. An SBS can conduct is one direction only.
77759. A 750 A circuit uses thyristor of current rating 175 A. If derating is 25%, the number of thyristors in parallel is
77760. Assertion (A): An inverter does not require forced commutation Reason (R): A series inverter is a forced commutation inverter.
77761. In a single phase full wave converter (M - 2 connection), the rms transformer voltage is 300 V across each half of secondary. The PIV for each thyristor is
77762. The number of doped regions in a SCR is
77763. All inverters use forced commutation.
77764. In 180° mode of operation of a 3 phase bridge inverter, two thyristors conduct at one time.
77765. In a single phase full wave ac regulator the rms value of load current is 20 A load is purely resistive. Then
77766. A reactor is used in a dual converter operating in non-circulating current mode.
77767. Which of these commutation methods uses an auxiliary SCR?
77768. A thyristor needs protection against
77769. In integral cycle control the period of on-off control should be more than mechanical time constant of load.
77770. A single phase half wave converter is feeding a resistive load. Just before triggering, the voltage across thyristor is
77771. In a 3 phase full wave regulator feeding resistance load connected in star, the possible range of firing angle a is
77772. Assertion (A): A dual converter may be circulating current type or non circulating current type.Reason (R): In circulating current dual converter only one converter can be operated at one time.
77773. Current chopping leads to
77774. A 3 phase bridge inverter is fed by 400 V battery. The load is star connected and has a resistance of 10 Ω per phase. The peak value of load current is
77775. In an SCR, the anode current is controlled by
77776. The rated current of a thyristor is 40 A. The holding current will be about :
77777. A cycloconverter is
77778. The number of leads in a power semiconductor diode are
77779. If ton and toff are the turn on and turn off times of a thyristor, then
77780. Assertion (A): The gate current of an SCR is always in the form of pulses. Reason (R): The gate losses, in pulse triggering, are low.
77781. UJT can be used for
77782. 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
77783. Induction heating systems require low frequency inverters.
77784. HVDC transmission systems generally use
77785. 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
77786. During forward blocking state of SCR, the voltage and current respectively are
77787. In a 3 phase full converter the average load current is 150 A. The average thyristor current is
77788. The two modes of operation of three phase bridge inverters are known as
77789. In a dual converter both converters work as rectifiers.
77790. A single phase full wave regulator feeds R-L load. The best gating signal is
77791. 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
77792. A cycloconverter cannot give a frequency higher than input frequency.
77793. 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
77794. In a single phase dual converter, a 1, and a 2 are firing angles of the two converters. Then
77795. The number of gates in an SCR is
77796. The waveshape of output voltage of half bridge inverter is
77797. 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
77798. The gate current required to turn on an SCR is
77799. 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
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