HW3. A DC motor is driven by a voltage source Vs through a resistor of R = 5 N. The rotor of the motor comprises ten wire turns, all of which are rectangles with the length of 45 cm and the width of...

Extracted text: HW3. A DC motor is driven by a voltage source Vs through a resistor of R = 5 N. The rotor of the motor comprises ten wire turns, all of which are rectangles with the length of 45 cm and the width of 20 cm. The magnetic flux density B exerted on the rotor is assumed to be a constant of 50 mT. Although the torque that B imposes on the rotor varies with the angle 0 between the rotor and B, for simplicity, a constant equivalent torque is considered which is assumed to be 80% of the peak torque value. This equivalent torque balances the mechanical load torque, giving a constant speed n of the rotor. In the beginning, I = 6 A, n = 2000 rpm and 00=30°. The energy-conversion efficiency of the motor is 90%. After running for some time, the mechanical load torque Tm is first increased by 40%, i.e., TMnewl = 1.4TM- After reaching the new steady state operation (i.e., the equivalent torque balances the mechanical load torque), the mechanical load torque is then decreased by 40%, i.e., TMnew2 = 0.67Mnewl - What would the value of n be after the two changes of the load torque? Assume that the voltage across the motor is VM = kv@, where kv is a constant. Choose the value that is closest to the answer. N S + VM Vs А. 850 гpm В. 2000 гpm С. 3146 грm D. 4528 грm E. None of the above.