Problem 528: A DC shunt motor has a full load rating of 15 hp, 230 volts, 57.1 amperes, 1400 rpm. The armature circuit resistance is 0.13 ohm and the field circuit resistance is 115 ohms. Neglecting the effect of armature reaction, determine the no-load line current.
A6.74 A
B5.62 A
C7.45 A
D8.64 A
#2📜 EE Board October 1998📘 1001 RojasEasy
Problem 544: The shaft power of a shunt motor is 7.8 hp. It draws 50 A from 120 V. The field winding draws 1.2 A. What is the efficiency of the motor?
A94.7%
B93%
C96.9%
D98.2%
#3📘 1001 RojasEasy
Problem 550: A 220 V series motor takes 15 A and runs at 700 rpm. The armature resistance including the resistance of the series winding is 0.8 ohm. At what speed will it run if a 2-ohm resistance is connected in series with supply voltage? Assume the motor is taking the same current.
A599 rpm
B601 rpm
C572 rpm
D583 rpm
#4📘 1001 RojasEasy
Problem 554: The field and armature resistances of a 220-V series motor are 0.2 \(\Omega\) and 0.1\(\Omega\), respectively. The motor takes 30 A of current while running at 700 rpm. If the total iron and friction losses are 350 W, determine the motor efficiency.
A90.6%
B91.5%
C89.4%
D92.2%
#5📘 1001 RojasEasy
Problem 557: The resistance of each of the two coils of a series motor is 0.04 ohm, armature resistance, 0.04 ohm. The motor takes 50 A at 100 V while running at 800 rpm and the coils are in series. What will it speed if the coils are re-connected in parallel while the load torque is doubled?
A800 rpm
B400 rpm
C200 rpm
D650 rpm
#6📘 1001 RojasEasy
Problem 569: A shunt motor was tested by means of a pony brake having a length arm of 3.5 feet and a tare weight of 5.7 lbs. The current drawn by the machine from a 240 V line was 50.9 A when the scale reading was 24 lbs and the speed of the motor was 1215 rpm. Calculate the rotational losses of the motor. The armature and shunt field resistances of the machine are 0.25 \(\Omega\) and 120 \(\Omega\), respectively.
A674 W
B692 W
C620 W
D705 W
#7📜 EE Pre-Board August 2013📘 PowerhouseEasy
The electromagnetic torque developed in a motor is 150 N-m. If the field flux is decreased by 20% and armature current is increased by 15%, find the new electromagnetic torque developed.
A138 N-m
B163 N-m
C159 N-m
D104 N-m
#8📜 EE Pre-Board August 2013📘 PowerhouseEasy
A dc motor takes an armature current of 100 A at 230 V. The armature resistance is 0.03 Ω. The total number of lap connected armature conductors is 500 and the number of poles is 4. The flux per pole is 0.03 Wb. What is the torque developed by the motor?
A242.86 N-m
B218.93 N-m
C238.73 N-m
D227.54 N-m
#9📜 EE Pre-Board March 2014📘 PowerhouseEasy
Find the horsepower rating of a motor running at 1,500 rpm and developing a torque of 105 lb-ft.
A22
B28
C30
D36
#10📜 EE Pre-Board March 2018📘 PowerhouseEasy
Find the horsepower rating of a motor running at 1,500 rpm and developing a torque of 105 lb-ft.
