77951. Thyristors connected in series need static and dynamic stabilizing circuits.
77952. In a controlled rectifier a freewheeling diode is necessary if the load is
77953. For an illumination control circuit it is advisable to use a matched TRIAC-DIAC pair.
77954. Assertion (A): An ac regulator uses natural commutationReason (R): An ac regulator can be used for static on load tap changing of transformer.
77955. When a UJT is used as a relaxation oscillator the current should be
77956. In auxiliary commutated chopper, the charging and discharging time of capacitor
77957. Which chopper circuit uses saturable reactor?
77958. A thyristor circuit is feeding an R-L load. The turn on time can be reduced by
77959. 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
77960. In a single phase full wave regulator feeding a resistive load, the average current over one full cycle
77961. 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
77962. The total number of leads in MOS controlled thyristor is
77963. Assertion (A): Chopper always requires forced commutationReason (R): Morgan chopper uses a saturable reactor.
77964. 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
77965. Assertion (A): McMurray Bredford half bridge inverter uses complementary commutationReason (R): Three phase inverter can have two modes of operation.
77966. 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
77967. Which of these devices have four layers?
77968. When UJT is used for thyristor gate signal, the output of UJT is
77969. The stud in a stud mounted SCR acts as
77970. In a single phase full wave regulator feeding R-L load, short gate pulse are not suitable.
77971. Half bridge and full bridge inverters of one type use different commutation methods.
77972. In rectifier circuits, the rms value of ac component of output voltage is equal to
77973. A UJT exhibits negative resistance characteristics when
77974. A dc chopper feeds an RLE load and has a duty cycle of 1. The load current will be such that
77975. In rectifier circuits, ripple factor RF and form factor FF are related as
77976. If we connect two silicon unilateral switches in anti- parallel we get
77977. Assertion (A): SUS is a PUT and avalanche diode connected between gate and cathodeReason (R): SBS has two SUS inbuilt together and connected in anti-parallel
77978. In a single phase full wave controlled rectifier using centre tap transformer, the voltage across each half of secondary is Vm sin ωt. The peak inverse voltage is
77979. Which statement is correct?
77980. In a three phase series inverter, the firing frequency is
77981. A 3 phase fully controlled converter is a
77982. In a half bridge inverter the gate pulses of the two thyristors have a phase displacement of
77983. A fully controlled bridge converter can operate in quadrants
77984. A class E chopper
77985. A cycloconverter uses
77986. Assertion (A): A fully controlled bridge converter can operate in first and fourth quadrant.Reason (R): A semi converter is cheaper than a full converter.
77987. The commutation method in an inverter, is
77988. Inverters find applications in
77989. When a thyristor is conducting, the voltage drop across it is about
77990. The use of free wheeling diode in controlled rectifier improves the waveshape of load current.
77991. As the firing of a thyristor is delayed, the output voltage of a controlled rectifier decreases.
77992. Assertion (A): A GTO can be turned on and turned off by gate pulses Reason (R): A GTO can be turned off by negative gate pulse.
77993. In a half bridge inverter circuit fed by a battery of voltage V, the rms value of fundamental component of output voltage is
77994. In a full bridge single phase inverter feeding RLC load
77995. It is possible to use a freewheeling diode in
77996. Assertion (A): When the anode current of an SCR starts increasing during turn on process, the anode cathode voltage drop starts decreasing. Reason (R): During turn on the reverse biased junction in SCR breaksdown.
77997. In a certain inverter circuit each thyristor carries 26.67 A for 60°, 13.33 A for 120° and zero A for 180° of the cycle. The rms current of thyristor is
77998. The factor η for a UJT is about
77999. The storage capacity of a oxygen cylinder is:
78000. In a single phase full converter fed by a source having inductance, the number of thyristors conducting during overlap is
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