WorksheetsModule 3
Total questions: 25
Worksheet time: 13mins
A fully controlled converter uses
Diodes only
Thyristors only
both diodes and thyristors
none of the mentioned
A single phase full-converter using R load is a _________ quadrant converter and that using an RL load without FD is a __________ quadrant converter
one, one
two, one
one, two
two, two
The average output voltage is maximum when SCR is triggered at ωt =
π
0
π/2
π/4
In the method of phase control, the phase relationship between ___ & ___ is controlled by varying the firing angle
supply current, supply voltage
end of the load current, end of the load voltage
start of the load current, start of the load voltage
load current, load voltage
In a single phase half-wave thyristor circuit with R load & Vs=Vm sinωt, the maximum value of the load current can be given by
2Vm/R
Vs/R
Vm/2
Vs/2
In a semi-converter with RLE load during the freewheeling period, the energy is
fed back to the source
fed to the inductor(L) and absorbed by E
absorbed by the L & E and dissipated at R
fed to the L & E and dissipated at R
The expression for the average output voltage with Vs = Vm sinωt and firing angle α
(Vm/π) cosα
(Vm/π) (1+cosα)
(2Vm/π) cosα
(2Vm/π) (1+cosα)
A single-phase symmetrical semi-converter employs
one SCR and one diode in each leg
two SCRs and two diodes in each leg
two SCRs in each leg
two diodes in each leg
Dual converters provide
two quadrant operation
three quadrant operation
four quadrant operation
none of the mentioned
A dual converters has
two full converters in series
two half converters in series
two full converters in anti-parallel
two half converters in anti-parallel
For a single-phase dual converter, with converters C1 and C2 connected in anti-parallel, which relation among the following is true to keep the average voltages from C1 and C2 equal? C1 and C2 have firing angles α1 and α2 respectively.
α1 = α2
α1 + α2 = 360°
α1 + α2 = 180°
none of the mentioned
In non-circulating current mode dual converters, the circulating current is avoided by
connecting a series reactor
maintaining α1 + α2 = 180°
operating only one converter
adding an extra SCR
AC voltage controllers convert
fixed ac to fixed dc
variable ac to variable dc
fixed ac to variable ac
variable ac to fixed ac
In AC voltage controllers the
variable ac with fixed frequency is obtained
variable ac with variable frequency is obtained
variable dc with fixed frequency is obtained
variable dc with variable frequency is obtained
The AC voltage controllers are used in __________ applications.
power generation
electric heating
conveyor belt motion
power transmission
In the principle of phase control
the load is on for some cycles and off for some cycles
control is achieved by adjusting the firing angle of the devices
control is achieved by adjusting the number of on off cycles
control cannot be achieved
A single-phase half wave voltage controller consists of
one SCR is parallel with one diode
one SCR is anti parallel with one diode
two SCRs in parallel
two SCRs in anti parallel
The below given controller circuit is a
half wave controller
full wave controller
none of the mentioned
will depend upon the firing angle
The SCR T1 is fired at an angle of α, and the supply Vs = Vm sinωt. Find the average value of the output voltage.
(Vm/2π) (cosα + )
(Vm/2π) (cosα)
(Vm/2π) (cosα – 1)
Vm
In the integral cycle control of ac voltage controller, is the load is on for n cycles and off for m cycles, then the periodicity is given by? Consider the output is sinusoidal.
m/2π(m+n)
n/2π(m+n)
m/π(m+n)
n/π(m+n)
Ripple factor is the ratio of
Rms value of the ac component of load voltage to the dc voltage
Average value of the ac component of load voltage to the peak value of voltage
Average value of the dc component of load voltage to the ac voltage
Peak value of the dc component of load voltage to the ac voltage
In rectifiers, load current flow is
Unidirectional
Bidirectional
Either (a) or (b)
Non directional
Pulse gating is suitable for
R loads only
R and RL loads
RL loads only
all types of loads
In circulating current mode dual converters, the circulating current is avoided by
connecting a series reactor
maintaining α1 + α2 = 180°
operating only one converter
adding an extra SCR
Choose the correct statement
Circulating current exists only in circulating current mode
Circulating current exists only in non-circulating current mode
Circulating current exists in both the circulating and non-circulating current mode
none of the mentioned
