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Dc machine
| 1-Dont try to cram or spend more time here just read it fast and cover syllabus then practice MCQ's cheptor of same topic to check your progress. . |
| 2-Wrong options are also given but dont concentrate there, Right answer is in bold format. |
| Q1 ⇒ DC series motor is best suited for electric traction as it develops high starting torque. [other wrong options] [Discuss in forum] |
| Q2 ⇒ For continuously running rolling mills with intermittent loading,
the most suitable dc drive is dc cumulatively compounded motor. [other wrong options] [Discuss in forum] |
| Q3 ⇒ If the supply voltage to a dc shunt motor is increased by 15%,
which of the following will reduce ? Full-load current [other wrong options] [Discuss in forum] |
| Q4 ⇒ The speed of a dc shunt motor can be raised above its rated value
by inserting an additional resistance in the field circuit. [other wrong options] [Discuss in forum] |
| Q5 ⇒ Flywheel is employed with a dc compound motor to reduce peak
demand, The compound motor should be cumulative compound. [other wrong options] [Discuss in forum] |
| Q6 ⇒ A 220 V. DC shunt motor is operating at a speed of 1,440 rpm.
The armature resistance is 1.0 Ω and armature current is 10 A. If
the excitation of the machine is reduced by 10%, the extra resistance
to be put in the armature circuit to maintain the same speed and
torque will be 1.79Ω [other wrong options] [Discuss in forum] |
| Q7 ⇒ Which of the following dc motors has least drop in speed from noload
to rated full load? Shunt motors with interpoles. [other wrong options] [Discuss in forum] |
| Q8 ⇒ In Ward-Leonard system, the lower limit of speed is imposed by residual magnetism of the generator. [other wrong options] [Discuss in forum] |
| Q9 ⇒ Consider the following statements: The speed of a dc motor can be controlled by the variation of 1. armature voltage. 2. field current. 3. armature circuit resistance. 4. angle of brush shift. Which of the statements given above are correct? 1, 2, 3. [other wrong options] [Discuss in forum] |
| Q10 ⇒ If a resistance is connected across the armature of a dc series
motor, its speed for a constant load torque will decrease. [other wrong options] [Discuss in forum] |
| Q11 ⇒ The most inefficient method for speed control of dc motors is armature control. [other wrong options] [Discuss in forum] |
| Q12 ⇒ In series-parallel control of dc series motor, the torque produced in
series arrangement will be ____ of that in parallel arrangement. four times [other wrong options] [Discuss in forum] |
| Q13 ⇒ Ward-Leonard system for controlling the speed of a de motor is
used where all of the above. [other wrong options] [Discuss in forum] |
| Q14 ⇒ For efficient operation of a dc motor, the additional resistance
inserted in the armature circuit should be cut-out in steps [other wrong options] [Discuss in forum] |
| Q15 ⇒ Consider the following statements regarding speed control of dc
motors: 1. Ward Leonard method is suitable for constant torque drive. 2. Field control method faciiitacs speed control below the base speed. 3 . A rmature resistance control method is more efficient when compared to Ward Leonard method. 4. Field control method is suitable for constant power drives. Of these statements 1 and 4 are correct. [other wrong options] [Discuss in forum] |
| Q16 ⇒ A DOL starter is employed for starting motors of ratings up to 3.75 kW [other wrong options] [Discuss in forum] |
| Q17 ⇒ As compared to the use of a single series dc motor for electric
traction for a given starting time t, the series parallel control using
two similar motors with time t/2 for each series and parallel
operation would give a saving in starting energy of 0.25 [other wrong options] [Discuss in forum] |
| Q18 ⇒ In a dc compound motor, 4-point starter is employed not to affect the current flowing through 'Hold On' coil even when the field current changes [other wrong options] [Discuss in forum] |
| Q19 ⇒ In dc shunt motors, at start, the field excitation is kept at maximum
value in order to reduce armature heating [other wrong options] [Discuss in forum] |
| Q20 ⇒ The plugging provides ____ braking torque in comparison to
rheostatic and regenerative braking systems. highest [other wrong options] [Discuss in forum] |
| Or |