72. Fora given torque, increasing diverter- resistance of a de series motor :
(A) Decreases its speed, but armature current remains the same
(B) Decreases its speed, reducing armature current
(C) Increases its speed, reducing armature current
(D) Increases its speed, but armature current remains the same
78. Triac can be used in:
(൨) ae voltage regulator (B) inverter
(൮ cyeloconverter (D) solid state type of devices
74, A boost regulator has an input voltage of 5V and average output voltage of 15V. The duty
eycle 15 :
(A) 3 (B) 1/8
(C) 5/2 @) 15/2
75. Stepper motors are mostly used for :
(A) high power requirements (B) control system applications
(C) very high speed of operation ൩) very low speed of operation
76. The most suitable device for high frequency inversion in SMPS is :
(A) BIT ®) IGBT
(€) MOSFET 2 0
77, Ina self-controlled synchronous motor fed from a variable frequency converter :
(ಹಿ) The rotor poles invariably have damper winding
(B) The frequency of stator decides the rotor speed ‏۔‎
‎(C) There are starting problems
(D) The speed of rotor decides rotor frequency
78. An ideal chopper operating at a frequency of 500 Hz supplies a load having a resistance of
3 Q and an inductance of 9mH from a 50 V battery. The mean value of load voltage for on/off
ratio of 4/1 is :
(A) 200 ४ (8) 28%
(0) 4४ (0) 40%
79. The most suitable solid state converter for controlling the speed of three- phase cage motor at
25 Hzis:
(A) Cycloconverter (B) Current source inverter
(C) Voltage source inverter (D) Load commutated inverter
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