Machine Parts

How do they differ from normal generator?    Draw their V-I characteristics and explain them? In short shunt connection the shunt field is connected directly across the armature terminals and the armature connection equals the sum of the shunt field current plus the load current . In this instance the load current flow s through the series field winding so that the load current and series field current are one and same.              In long shunt connection the voltage across the shunt field is the same as the terminal voltage of the generator and current in the armature will be the current in the series field. The armature current equals the shunt field current plus the load current.   A shunt generator has the field circuit connected directly across the armature. As more devices connected in parallel the load on the generator increases that the generator current increases which results decrease in terminal voltage of the generator.  

Assume that two generators and a load are connected parallely. Let us assume that generator 1 is operating and supplying current to the load. The polarity of the voltage at terminals of the generator is indicated in the diagram. The load of generator 1 now increases to the point where the rated current is exceeded. The second generator must be placed in operation to share the load. The prime mover of the second generator started and voltage builds up in generator 2. Before anything else is done after the voltage of generator 2 is build up. The polarity of generator 2 should be compared with the running generator 1. Since both of   these generators are to be connected in parallel. The positive terminal of each generator is to be connected together and the negative terminals of two generators are connected together. If the generators are not properly connected as just indicated, the improper connection will place both generators in series, with only the internal resistance of

The shunt generator is not satisfactory for supplying power to remotely located points because not only does the terminal voltage of the generator drop as load increases but there is also a volt drop in the line. The greater the load, the greater the volt drop in line. The combined effect of the reduction in generator voltage plus the line drop makes the shunt generator unsatisfactory for transmission of power over long distances. To overcome the reduction in generator voltage we can use cumulative compound generator. The cumulative compound generator is the same as a shunt generator with the addition of a series field winding which produces flux to aid the flux of the shunt field. We can use cumulative compound generator for the following characteristics. ·          The drop in the terminal voltage is small. ·          Maintaining the constant terminal voltage.           The terminal voltage rises as load as is applied to generator