Important control systems questions helpful for TsGenco , Transco, NPDCL,SPDCL

1. What is the characteristic of good control system ?

a) sensitive to parameter variation

b) Insensitive to parameter variation but sensitive to input commands

c) Insensitive to input commands

d) neither sensitive to parameter variation nor sensitive to input commands

ans: b

2. In control system, the use of negative feedback

a) eliminatea the chances of instability

b) increases the reliability

c) reduces the effect of disturbances & noise signals in the forward path

d) increases the noise signals 

 

ans: c

3. The Nyquist plot of loop transfer fiction G(s)H(s) of a closed loop control system passes through the point (-1,j0) in the G(s)H(s) plane. The phase margin of the system is 

a) 0°   b) 45° c) 90°. d) 180 ° 

ans: 0° 

Explanation:

phase margin of a system is the amount of additional phase lag required to bring the system to the point of instability or (-1,j0) 

Here system passes through (-1j0)  so no required additional phase lag

Hence phase margin 

PM = 180° + <G(jw)

= 180° -180°= 0°

4.The Nyquist plot of a open loop transfer fiction G(jw) H(jw) of a system encloses the (-1,j0) point. The gain margin of the system is 

a) less than zero 

b) zero 

c)greater than zero

d) infinity

 

ans: a

5.  while designing controller, the advantage of pole zero cancellation is

a) the system order is increased

b) the system order is reduced

c) the cost of controller becomes low

d) type of the system increases

ans:b

Explanation:

Due to pole zero cancellation , no. Of poles and zeros are reduced 

as order of the system depends on no. of poles , hence order of the system reduced