HPCL - Control system (Technical) Questions for Placement

HPCL – Control system (Technical) Questions for Placement

• In an automatic control system, from the below mentioned options, which of the following elements is not used?

a. Error detector
b. Final control element
c. Sensor
d. Oscillator

• What is a controller?

a. A summer
b. A amplifier
c. A clipper
d. A comparator

• What will you use from the below mentioned options to increase the bandwidth?

a. Phase lead network
b. Phase lag network
c. Both a & b in parallel
d. Both a & b in cascade
e. None of the above

• For Mp, which amongst the following will be considered a good factor?

a. Zero
b. More than 2.2
c. Less than 1
d. Infinity
e. Lying between 1.1 and 1.5

• What is included in a type – 0 systems?

a. No pole at the origin
b. Two poles at the origin
c. Net pole at the origin
d. Simple at one origin

• State the disadvantage of a feedback system?

a. Unreliability
b. Insensitivity
c. Instability
d. Inaccuracy
e. Inefficiency

• What does an open loop control system include off?

a. Internal system changes automatically taken care of
b. Controlling action, depending upon human judgement
c. Control action independent of the output or desired quantity
d. Both a & b
e. All of the above

• What will you use to achieve high power amplification?

a. Magnetic amplifier
b. Push pull amplifier
c. D.C. Generator
d. DC amplifier
e. Amplidyne

• If you have to determine the stability of a control system using the time domain method, which of the following option will you choose?

a. Nicholos chart
b. Bode plot
c. Root locus technique
d. Nyquist plot
e. Routh – Hurwitz array
f. Constant M and (fy) locus

• Why do we not use inductance in lag network?

a. Time delay and hysteresis losses
b. High reactance
c. Big size
d. None of the above

• How can you keep the noises low in a control system?

a. Attenuating such frequencies at which external signals get coupled into the system
b. Reducing the bandwidth
c. Both a & b
d. None of the above

• In which of the following will you use transfer function of a system is defined as the ratio of output to input?

a. Fourier transform
b. Z – transform
c. Simple algebraic form
d. Laplace transform

• In between 200 Hz and 800 Hz how many octaves are present?

a. 4 octave
b. 1 octave
c. 2 octave
d. None of the above

• The effect of which of the following is decreased by introduction of feedback?

a. Error signals
b. Disturbances
c. Noise signals
d. All of the above

• What is the breakaway point of root loci?

a. Open loop zeroes
b. Closed loop zeroes
c. Closed loop poles
d. Open loop poles

• Choose the correct option to describe the properties of a transfer function?

a. It depends on system elements and not input and output of the system
b. Coefficients of the powers of ‘S’ in denominator and numerator are all real constant. The order of denominator is usually greater than or equal to the order of numerator
c. It is ratio of two polynomials is S and assumes zero initial conditions
d. It is a function which transfer one physical system into another physical system
e. All of the above

• Choose the correct option for nonlinear system.

a. Speed control using SCR
b. Automatic voltage regulator
c. D.C servomotor with high field excitation
d. Temperature control of a furnace using thermistor
e. All of the above

• What are the disadvantages of magnetic amplifier?

a. Saturation of the core
b. Time lag, less flexible, non – sinusoidal waveform
c. Low power consumption and isolation of the active circuit
d. All of the above

• What action will you take to reduce the steady state error?

a. Decrease damping
b. Decrease natural frequency
c. Increase time constant
d. Increase gain constant of the system
e. Decrease damped frequency

• What is a signal flow graph?

a. Semi log graph
b. Polar graph
c. Log log graph
d. A topological representation of a set of differentials equations
e. A special type of graph for analysing modem control system

• Two blocks G1(s) and G2 (s) can be cascaded to get resultant transfer function as:

a. 1+G1(s) G2(s)
b. G1(s) + G2(s)
c. 1-G1(s)G2(s)
d. G1(s)/G2(s)
e. G1(s)G2(s)
f. Two blocks cannot be cascaded

• What should a servo system include compulsorily?

a. Capacity to control position or its derivative
b. Feedback system
c. Power amplifier to amplify error
d. All of the above
e. None of the above

• Where do you draw Nyquist plot?

a. Centimetre graph paper
b. Semi log graph paper
c. Log log graph paper
d. Polar graph paper

• What happens to the stability when a root moves further away from imaginary axis?

a. Decreases
b. Increases
c. Not affected
d. None of the above

• Choose the correct option that can be magnified by magnetic amplifier.

a. Power
b. Voltage
c. Current
d. None of the above