I was able to figure out the Radj for question 5 which was 40 ohms but I didn\'t

Question

I was able to figure out the Radj for question 5 which was 40 ohms but I didn't get the rest correct. Help me, please and thank you.

VT= 180 V is applied to a shunt connected DC motor with Radj set so that IF = 3 A. For the motor, RA = 0.5 Ohm and RF = 20 Ohm . The motor needs to supply a torque of 50 Nm and has rotational losses equivalent to 5 Nm of torque. Determine the motor speed and value of Radj. Now you want to increase the torque from the motor described in so that the new torque supplied is 200 Nm instead of 80 Nm. What is the new speed? Now you want to decrease the speed of the motor described in (torque still at 50 Nm + rotational losses) by 3%. What should be the new value of Radj?

Explanation / Answer

speed = 1200 rpm

toque = 80 Nm

T1.W1 = T2.W2.

80 x 1200 = 200 x W2

new speed (W2) = 480 rpm

power = T.W = IR^2.

W = 1200 rpm

T = 50Nm + 15 = 65 Nm with 3% error

I =3A

R = Radj + Rf + Ra

65 x 1200 = IR^2

R = 20.82

Radj = 0.32 ohm

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.