91. The full-load armature current of a 440 𝑉 shunt motor is 120 𝐴. The armature resistance is 0.2 Ω and the speed is 800 rpm . If torque on the motor is reduced to 60 % of its full-load value and a resistor of 1.5 Ω is included in the armature circuit with field strength remaining same, the speed will be:

(a) 700 rpm
(b) 610 rpm
(c) 520 rpm
(d) 430 rpm

Answer: (b)

92. Corona loss is less when the shape of the conductor is:
(a) Circular
(b) Flat
(c) Oval
(d) Square

Answer: (a)

93. 
(a) 0.48
(b) 0.56
(c) 0.64
(d) 0.72

Answer: (b)

94. Which power semiconductor switching device is having the property of uncontrolled turn on and off?
(a) SCR
(b) BJT
(c) MOSFET
(d) Diode

Answer: (d)

95. In a GTO the n layer forms the:
(a) Anode and Gate
(b) Cathode and Gate
(c) Cathode
(d) Gate

Answer: (c)

96. The GTO can be turned off by:
(a) Positive gate signal
(b) Negative gate signal
(c) Negative anode and cathode voltage
(d) Removing gate signal

Answer: (b)

97. The TRIAC can be represented by two:
(a) SCRs in anti parallel
(b) SCRs in parallel
(c) Diodes in anti parallel
(d) Diodes in parallel

Answer: (a)

98. Which terminal does not belong to thyristors?
(a) Anode
(b) Cathode
(c) Gate
(d) Base

Answer: (d)

99. A closed-loop control is normally required to satisfy the steady-state and transient performance specifications of ac drives. The control strategy can be implemented by:
1. Scalar control: where the control variables are dc quantities and only their magnitudes are controlled
2. Vector control: where both the magnitude and phase of the control variables are controlled

Which of the above statements is/ are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1nor 2

Answer: (c)

100. Consider the following statements regarding advantages of power electronics converters:
1. Increase efficiency of power converter due to less loss in power semiconductor devices
2. Low reliability of power converter based system
3. Life period of power converter circuit is long
4. The size and weight of power electronics is less. Hence the installation cost is low

Which of the above statements are correct?
(a) 1, 2 and 3 only
(b) 1, 3 and 4 only
(c) 1, 2 and 4 only
(d) 2, 3 and 4 only

Answer: (b)