1. If the handle of a three point starter goes back to OFF position, it may be due to (a) zero or very low supply voltage. (b) overload. (c) high field circuit resistance. (d) all of the above. 2. A 3 point starter is considered suitable for ………… dc motors. (a) series (b) shunt (c) […]
1. Consider the following statements regarding speed control of dc motors: Ward Leonard method is suitable for constant torque drive. Field control method facilitates speed control below the base speed. Armature resistance control method is more efficient when compared to Ward Leonard method. Field control method is suitable for constant power drives. Of these statements
1. For the same power output rating and full-load speed, the motor that will have poorest starting torque, is (a) cumulative compound. (b) differential compound. (c) series. (d) shunt. 2. A motor used for punching machine is usually subjected to (a) full load continuously. (b) part of full load continuously. (c) no load. (d) intermittent
1. In a dc motor; if armature current is increased, keeping field current constant, the torque developed will (a) remain unchanged. (b) decrease in inverse proportion. (c) increase proportionately. (d) increase in proportion to the square of the armature current. 2. If the supply voltage to a dc shunt motor is increased by 15%, which
1. In an electric motor, the electromagnetic torque developed is (a) in opposite direction to both load torque and frictional torque. (b) in the same direction as the load torque but in opposite direction to frictional torque. (c) in the same direction as the load torque and frictional torque. (d) in the same direction as
1. In the block diagram of a separately excited dc motor, how does the armature induced emf appear as? (a) Positive feedback. (b) Negative feedback. (c) Disturbance input. (d) Output. 2. The current drawn by a 220 V dc motor of armature resistance 0.5 Ω and back emf 200 V is (a) 40 A (b)
1. Which of the following are true in respect of interpoles in dc machines? Reduce armature reaction effects in interpolar region. Windings are connected in series with armature. Have the same dimensions as main poles. Select the correct answer using the code given below: (a) 1 and 2 only. (b) 2 and 3 only. (c)
1. Consider the following statements In a dc series generator, full-load voltage is more than the no-load voltage. In a separately excited de generator full-load voltage is more than the no-load voltage. In a dc shunt generator, full-load voltage is less than the no-load voltage. Of these statements. (a) 1, 2 and 3 are correct.
1. In a DC generator, the ripples in the generated DC are reduced by employing (a) commutator with large number of segments. (b) equalizer rings. (c) carbon brushes. (d) graphite brushes. 2. In order to ascertain whether a DC machine is lap wound or wave wound on the basis of visual observations of the armature,
1. In an electromechanical energy conversion devices (e.g. generators and motors) a small air gap is left between the stator and the rotor in order to (a) reduce the reluctance of the magnetic path. (b) increase flux density in the air gap. (c) permit mechanical clearance. (d) avoid saturation of field. 2. The EMF induced