QUESTIONS CARRY TWO MARKS EACH.
In the chopper circuit shown,the main thyristor (TM) is operated at a duty ratio of 0.8 which is much larger the commutation interval. If the maximum allow able reapplied dε/dt on TM is 50 V/ms, what should be the theoretical minimum value of C1? Assume current ripple through L0 to be negligible.
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Solution
QUESTIONS CARRY TWO MARKS EACH.
The figure shows a three-phase delta connected load supplied from a 400 V, 50 Hz, 3-phage balanced source.The pressure coil (PC) and current coil (CC) of a wattmeter are connected to the load as shown, with the coil polarities suitably selected to ensure a positive deflection.The wattmeter reading will be
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A transducer measures a range of 0–200 N force with are solution of 0.15 percent of full scale. What is the smallest change which can be measured by this transducer?
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Solution
Smallest change which can be mesured
\(=\frac{0.15}{100}\times 200=0.3\: N\)
QUESTIONS CARRY TWO MARKS EACH.
The closed loop system shown below become marginally stable if the constant K is chosen to be ______
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Solution
QUESTIONS CARRY TWO MARKS EACH.
The characteristic equation of a control system is given by
s6+ 2s5+ 8s4+ 12s3+ 20s2 + 16s + 16 =0
The number of the roots of the equation which lie on the imaginary axis of s-plane is ________
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Solution
The Routh array is
s6 1 8 20 16
s5 2 12 16
s5 1 6 8
s4 2 12 16
s4 1 6 8
s3 0 0 0
As the term in the s3- row are all zero, the Routh’s test break down. Now the auxillary polynomial.
A(s) = s4 + 6s2 + 8
Its derivative is
A(s) = 4s3+ 12s
Now the Routh array is
s3 4 12 0
s3 1 3 0
s2 3 8
s1 1/3 0
s0 8Now solving the auxillary polynomial s4+ 6s2 + 8 = 0,the roots on the jw-axis is
s =±j√2 and s=±j2
QUESTIONS CARRY TWO MARKS EACH.
Given K.kt= 99; S = j 1 rad/s. The sensitivity of close loop system (shown in figure) to variation a parameter ‘K’ is approximately
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Solution
QUESTIONS CARRY TWO MARKS EACH.
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Solution
QUESTIONS CARRY TWO MARKS EACH.
In a dual slope integrating type digital voltmeter the first integration is carried out for 10 periods of the supply frequency of 50 Hz. If the reference voltage used is 2 V, the total conversion time for an input of 1 V is.
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Solution
In a dual slope integrating type digital voltmeter,
Vin = Vref(t2/t1)
Where, t1 is the first integration time.
t1= 10 × 1/50 =0.2 s
Vm = 1 V
Vref= 2
t2= Vin T11/ Vref= 1× 0.2/ 2= 0.1 sec
QUESTIONS CARRY TWO MARKS EACH.
An average-reading digital multi-meter reads 10 V when fed with a triangular wave, sysmmetric about the time-axis. For the same input an rms-reading meter will read
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Solution
QUESTIONS CARRY TWO MARKS EACH.
An ideal meter movement has a full scale deflection of 1mA. This meter is to be used in series with a very-non-ideal voltage source of 10 V to produce an ohm meter. It is noted that the ohm-meter shows a full scale deflection when the terminals are shorted (zero resistance). When the terminals are open circuited, the meter movement deflection is zero(infinite resistance). If 5 k ohm is placed across the terminals,the meter movement will have a deflection of
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Solution
All the three errors may occur in bridge method of measurement.