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Answers must be accurate to within 3 significant figures!
Problem 1: Consider the linear machine shown below.
Find the initial starting force magnitude and final speed if the length of the bar (l) is 0.01 m, VT
is 24 V, RA is 3 , and the magnetic field is 3.7 T. (10 points)
Problem 2: A shunt-connected dc motor has the magnetization curve shown with VT = 20 V, RA
= 3 , and RF+Radj = 40 .
a) Find the no-load speed. (5 points)
b) Find the torque once a load is added that drops the speed to 20% less than the no-load
speed. (10 points)
Problem 3: A shunt connected DC motor has the following magnetization curve.
If RF = 30 , RA = 5 , Radj = 0 , and VT = 285 V. Find the speed and torque developed when
the power delivered by the motor is 3000 W and there are no rotational losses given the motor is
operating in its normal operating range. (40 points)
Problem 4: VT = 100 V is applied to a shunt connected DC motor with Radj set so that IF = 2 A.
For the motor, RA = 1 and RF = 45 . The motor needs to supply a torque of 4.5 Nm and has
negligible rotational losses. Determine the motor speed and value of Radj. (20 points)
Problem 5: Now you want to increase the speed of the motor described in Problem 5 (torque
still at 4 Nm) by 3.5%. What should be the new value of Radj? (15 points)
Problem 6: VT = 100 V is applied to a shunt connected DC motor with Radj = 5 . For the
motor, RA = 0.5 and RF = 20 . The motor has negligible rotational losses. Plot the
efficiency vs torque curve assuming no rotational losses (YOU MUST UPLOAD YOUR PLOT
WITH YOUR HW). What is the most efficient torque? What is the efficiency at this torque?
(25 points)
