With given power rating for lower current and higher voltage rating of a d.c. machine, one should prefer_________.

Related MCQs

• If the applied voltage to a DC machine is 230V, then back emf for maximum power developed is ___.
• A shunt motor runs at 500rpm on a 200V circuit. Its armature resistance is 0.5Ω and the current taken is 30A in addition to field current. What resistance must be placed in series with armature circuit to reduce to speed to 300 rpm; the current in armature remains same.
• A sinusoidal voltage of frequency 1 Hz is applied to the field of a d.c generator. The armature voltage will be
• A 220V DC series motor is taking a current of 40A. Resistance of armature is 0.5Ω and series field is 0.25Ω. What is the voltage at the brushes?
• If the applied voltage of dc motor is reduced to half with load torque doubled the armature current will be____
• The mechanical power developed in a dc motor is maximum when back emf (Eb) is equal to ------the applied voltage (V)
• If the voltage equation of a dc motor is multiplied by ----- on both sides, we get power equation of dc motor
• A 250V DC shunt motor takes a total current of 20A. Resistance of shunt field winding is 200Ω and that of armature is 0.3Ω . What is the current in the armature?
• A 200V DC series motor runs at 500rpm when taking a line current of 25A.The resistance of the armature is 0.3Ω and that of the series field is 0.5Ω. If current taken remains constant, calculate the resistance necessary to reduce the speed to 350rpm.
• A 440V, 20HP, 3phase motor operates at full load, 88% efficiency and 0.65 power factor lagging, the current drawn by motor is