A DC machine is a device which converts electrical energy in the form of direct current into mechanical energy or mechanical energy into electrical energy in the form of direct current. Therefore, a DC machine is basically an electromechanical energy conversion device.

Based on the energy conversion, DC machines can be classified into the following two types −

• DC Motor

• DC Generator

The basic construction of both DC motor and DC generator is almost similar. However, the fundamental principles involved in the operation of DC motor and DC generator are different.

Every DC machine essentially consists of a system of conductors and system of magnets or electromagnets. The system of conductor is called armature, and in case of DC machines it is mounted on a movable shaft. The system of magnets or electromagnets is known as the field system, and it produces the required working magnetic flux.

DC Motor

The block diagram of a DC motor is shown in Figure-1.

When the DC machine is designed to convert DC electrical energy into rotational mechanical energy, it is called a DC motor. Therefore, in case of a DC motor, the electrical energy is supplied to the machine through input terminals and mechanical energy output is taken from the shaft in the form of rotation of the shaft.

DC Generator

The block diagram of a DC generator is shown in Figure-2.

A DC machine which can convert mechanical energy input into electrical energy output is known as a DC generator. Thus, in a DC generator, the mechanical energy from a source like engine, turbine, etc. is supplied to the DC machine in the form of rotational energy of the shaft and the DC electrical energy is received as output from the armature terminals.