AC Voltage Controllers MCQs : This section focuses on the "AC Voltage Controllers". These Multiple Choice Questions (MCQs) should be practiced to improve the AC Voltage Controllers skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the average value of SCR current.
A. 21.68 A
B. 200 mA
C. 4.14 A
D. 2.07 A
Question 2
A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the input pf.
A. 0.6
B. 0.7746
C. 0.855
D. 0.236
Question 3
A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the power delivered to the load.
A. 2.1 W
B. 2.1 kW
C. 516 W
D. 5.16 kW
Question 4
A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the rms output voltage.
A. 189 V
B. 260 V
C. 156 V
D. 178 V
Question 5
A single-phase half wave voltage controller consists of
A. one SCR is parallel with one diode
B. one SCR is anti parallel with one diode
C. two SCRs in parallel
D. two SCRs in anti parallel
Question 6
A single-phase voltage controller, using one SCR in anti parallel with a diode, feeds a load R and Vs = 230 V. For a firing angel of 90° for the SCR, the PMMC voltage connected across R would read
A. 0
B. 51.8 V
C. –51.8 V
D. –36.82 V
Question 7
AC voltage controllers convert
A. fixed ac to fixed dc
B. variable ac to variable dc
C. fixed ac to variable ac
D. variable ac to fixed ac
Question 8
Earlier then the semiconductor technology, ___________ devices were used for voltage control applications.
A. cycloconverters
B. vacuum tubes
C. tap changing transformer
D. induction machine
Question 9
High frequency gating uses a
A. train of pulses
B. continuous gating block
C. carrier signal
D. none of the above
Question 10
In AC voltage controllers the
A. variable ac with fixed frequency is obtained
B. variable ac with variable frequency is obtained
C. variable dc with fixed frequency is obtained
D. variable dc with variable frequency is obtained
Question 11
In continues gating
A. overlap angle is very high
B. SCR is heated up
C. size of the pulse transformer is small
D. commutation cannot be achieved effectively
Question 12
In the integral cycle control method of ac voltage controller
A. the average power delivered to the load is controlled
B. the instantaneous power delivered to the load is controlled
C. the frequency of output voltage is controlled
D. none of the mentioned
Question 13
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.
A. m/2π(m+n)
B. n/2π(m+n)
C. m/π(m+n)
D. n/π(m+n)
Question 14
In the principle of phase control
A. the load is on for some cycles and off for some cycles
B. control is achieved by adjusting the firing angle of the devices
C. control is achieved by adjusting the number of on off cycles
D. control cannot be achieved
Question 15
Pulse gating is suitable for
A. R loads only
B. R and RL loads
C. RL loads only
D. all types of loads
Question 16
The AC voltage controllers are used in __________ applications.
A. power generation
B. electric heating
C. conveyor belt motion
D. power transmission