Given that,

DC motor no-load current at rated speed = 1.2A

Armature voltage required to run no-load at rated speed = 450V

DC motor rated speed = 1200rpm

DC motor-rated armature current = 36A

DC motor rated field voltage = 300V

Armature winding resistance = 5 ohm

Field winding resistance = 330 ohm

Questions:

Calculate the following considering the no-load operating conditions:

1.1) Calculate the back-EMF at the rated speed;

1.2) Using the available information, determine the rotational losses at the rated speed.