Lecture
This lecture covers the principles and applications of direct current (DC) machines. It begins with an introduction to the basic concepts of magnetic circuits and transformers, followed by a detailed explanation of the functioning of DC machines. The instructor discusses the construction of the rotor and stator, emphasizing the role of excitation and the importance of the magnetic field. Various types of DC motors, including shunt, series, and compound motors, are introduced, along with their operational characteristics. The lecture also addresses the electromagnetic torque generated in these machines and the relationship between voltage, current, and power. The instructor explains the significance of the commutator in maintaining the direction of rotation and the challenges associated with arcing at the brushes. Practical examples illustrate the use of DC machines in real-world applications, including their role in electric traction and as generators. The session concludes with a discussion on the advantages and limitations of different excitation methods in DC machines.