A 240V series motor has a total resistance of 0.2 . At the speed of 1800 r.p.m. absorbs 40 A. Brush-brush voltage drop, iron and

A 240V series motor has a total resistance of 0.2 Ω. At the speed of 1800 r.p.m. absorbs 40 A.  Brush-brush voltage drop, iron and mechanical losses are neglected.


a) Find the resistance that must be added in series with the motor to limit the speed to 3600 r.p.m. when the current is 10 A, assuming that the flow is proportional to the current when it is between 10 and 40 A.
b) Obtain the resistance to connect in series with this machine so that the speed is 900 r.p.m. for a current of 60 A, knowing that the flow at 60 A is 18% greater than the flow at 40 A.
c) At what speed will the motor rotate when it is connected directly to the line and draws 60 A?
d) What will be the torque that this motor will give when the current is 40A?