HW3. A DC motor is driven by a voltage source Vs through a resistor ofR=5 Q. 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...

Extracted text: HW3. A DC motor is driven by a voltage source Vs through a resistor ofR=5 Q. 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 O0=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 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 = 1.4TM. After reaching the = 0.6TMnewl. What would the value of n be after the two changes of the load torque? Assume that the voltage across the motor is VM = ky@, where ky is a constant. Choose the value that is closest to the answer. В -20 сm- 45 cm- N + Vm R Vs