Characteristics of DC Generators

Characteristics of DC Generators Points : Characteristics of DC Generators The curves or graphs giving the relationship between various quantities such as excitation (or field current), generated emf, terminal voltage and the load current etc are known as generator characteristics. There are three most important characteristics of a dc generator, which are generally studied. 1. Magnetic or Open-circuit Characteristic This characteristic, also known as no-load saturation characteristic, gives the relation between the generated emf in armature on no load, E₀ and field current, I_f at a given speed. The shape of this characteristic curve is practically the same for all types of generators whether they are separately excited or self-excited. 2. Internal or Total Characteristic It is a curve which gives the relation between the emf actually generated in the armature, E (less than E due to the demagnetizing effect of armature reaction) and the armature current. This curve, therefore, lies below the 0CC. 3 External Characteristic This curve gives the relation between terminal voltage V and the load current I under the given conditions of speed and excitation. The terminal voltage V is always less than E on account of voltage drop in armature. This curve, therefore, lies below the internal characteristic. This characteristic is of utmost, importance for determining the suitability of a generator for a particular service.