A series-connected dc motor is designed to operate with a variable load. The resistances RA and RF are negligible. To attain high efficiency, the motor has been designed to have very small rotational losses. For a load torque of 100 Nm, the machine runs at its maximum rated speed of 1200 rpm.
a. Find the speed for a load torque of 300 Nm.
b. What is the no-load speed? What are the potential consequences of having the load become disconnected from the motor without disconnecting the dc source?