Differential Compound Wound Generator Characteristics

Differential Compound Wound Generator Characteristics Points : Differential Compound Wound Generator Characteristics If the series field of the compound wound dc generator (may be either short-shunt or long-shunt) is connected so that the flux produced by the series field opposes the flux produced by shunt field. This is accomplished by interchanging the connections of series field winding. In such a generator, the induced voltage on no-load would be the same as for the shunt generator because series field does not create any flux. When the generator is loaded, load current (or armature current) flows through the series field windings creating magnetic flux that opposes the flux created by shunt field. This results in decrease of induced emf and, therefore, in terminal voltage. In such generators the terminal voltage drops very rapidly with the increase in load current and, therefore it is interesting to note that a short- circuit cannot cause any damage to it. Critical Load Resistance If a line from the origin 0 is drawn tangential to internal characteristic curve, the gradient of this line will give the minimum value of the external load resistance for which the generator will excite on load. This resistance is known as critical load resistance. If the resistance of the external load circuit is less than this value, the generator will fail to build up its voltage.