DC Motors

A 220 V series motor takes 10 A and runs at 600 rpm. The total resistance is 0.8 Ω. At what speed will it run when a 5 Ω resistance is connected in series, the motor taking the same current at the same supply voltage?

A shunt motor runs at 500 rpm on a 200 V circuit. Its armature resistance is 0.5 Ω and the current taken is 30 A in addition to the field current. What resistance must be placed in series in order that the speed may be reduced to 300 rpm, the current in the armature remaining the same?

The resistance of the field coil of a motor is 200 Ω at 15 °C. After the motor worked for a few hours on full load, the resistance increases to 240 Ω. Calculate the temperature rise of the coil, assuming the temperature coefficient of resistance is 0.0042 per °C at 0 °C.

A 20-HP, 110 v dc shunt motor has an efficiency of 88% and an exciting current of 4 amperes and an armature resistance of 0.04 ohm. What is the starting resistance required for full-load torque?

A 220-volt dc shunt motor runs at 500 rpm with an armature current of 50 amperes and an armature resistance of 0.1 Ω. Calculate the speed if the torque is halved.

A 110-volt shunt motor has an armature resistance of 0.8 Ω and a field resistance of 220 Ω. At full load the motor takes 10 amperes, and the speed is 1,200 rpm. At what speed must this motor run as a generator to deliver 10 amperes to an external circuit at 110 V?

A 440-V, 70-HP shunt motor has an armature resistance of 0.185 Ω and field resistance of 350 Ω. The current drawn by this machine is 135 A at full load. If this machine is to deliver torque equal to 175 percent of that at full load, what would be the best resistance of its starter?

A 4 pole lap winding motor with 16 slots, 42 conductors per slot, 480 v runs at 1800 rpm. Find the flux produced per pole.

A 15-hp motor operates at an efficiency of 87.5 percent at full load. If the stray power loss is approximately one-fourth of the total loss, calculate the copper loss.

A 4-pole shunt motor develops 20 lb-ft of torque when the flux per pole is 700,000 maxwells. If the armature winding has 264 conductors and is wave wound, calculate the total armature current.

A dc shunt motor has a nameplate rating of 15 HP, 230 V, 57.1 amperes and 1,400 rpm. The field circuit has a resistance of 115 Ω and the armature circuit resistance is 0.13 Ω. Neglecting the effect of armature reaction, find the no-load line current.

A shunt motor with an armature resistance of 0.15 ohm is running at 1,200 rpm for a load which requires an armature current of 50 A from a 230 V source. At no load, the armature current is 5 A. If armature reaction has reduced the air-gap flux by 2% from no load to full load, what is the no-load speed?

A 9.6 kW, 240 V shunt generator having an armature resistance of 0.10 ohm and a shunt field resistance of 240 ohms delivers full load at rated voltage and 800 rpm. The machine is now run as a motor taking its full-load line current of 40 A at 250 V. Neglecting brush drop and assuming flux proportional to field current, what is the speed of the motor?

Find the horsepower rating of a motor running at 1,500 rpm and developing a torque of 105 lb-ft.

A 240 V DC series motor develops a shaft torque of 200 N-m at 92% efficiency while running at 600rpm. Calculate the motor current.

Calculate the torque in N·m developed by a 440 V dc motor having an armature resistance of 0.25 Ω and running at 750 rpm when taking a current of 60 A.

A dc shunt motor develops 15 hp at 120 v . If the effective armature resistance is 0.061 ohm and the field winding draws 2 amperes, what is the overall efficiency?