INTRODUCTION DC machine is a highly versatile and flexible machine. It can satisfy the demands of load requiring high starting, accelerating and retarding torques. If the conversion is from mechanical to electrical energy, the machine is called as Generator. If the conversion is from electrical to mechanical energy, the machine is called as Motor. Types of DC Machines: The types of DC machine depends upon the excitation of DC machine. The production of magnetic flux in the machine by circulating current in the field winding is called excitation. DC Machines can be classified according to the electrical connections of the armature winding and the field windings. There are two methods of excitation namely, separate excitation and self-excitation. In separate excitation, the field coils are energised by a separate DC source. The terminals of the winding can be connected across the input voltage terminals or fed from a separate voltage source. In self-excitation, the cur