# Characteristics of DC Compound Generator

- Link: https://studyelectrical.com/2014/08/characteristics-of-dc-compound-generator.html
- Published: 2014-08-19T09:42:00+00:00
- Author: 

In a compound generator, both series and shunt excitation are combined as shown 
in the figure. The characteristics of [DC compound generator](https://studyelectrical.com/2014/08/types-of-dc-generators.html)
is different for series and shunt generator characteristics.

[⌊DC Compound Generator⌉⌊DC Compound Generator⌉[

DC Compound Generator

The shunt winding can be connected either across the armature only (short-shunt 
connection S) or across armature plus series field (long-shunt connection G).

The compound generator can be cumulatively compounded or differentially compounded
generator. More about them is explained in the [Types of DC Generator.](https://studyelectrical.com/2014/08/types-of-dc-generators.html)

The differentially compounded generator is rarely used in practice. Therefore, we
shall discuss the characteristics of a cumulatively compounded generator in this
article.

It may be noted that the external characteristics of long and short shunt compound
generators are almost identical.

## External characteristic of DC Compound Generator

The external characteristics of a cumulatively compounded generator are shown in
the figure.

![External characteristic](http://4.bp.blogspot.com/-CrRCxeYkAoA/U_MP0i6pEdI/AAAAAAAABHQ/
8w8LBOOdyaU/s400/preview_file%2B(1).png "External characteristic")

External characteristic

The series excitation aids the shunt excitation. The degree of compounding depends
upon the increase in series excitation with the increase in load current.[

### Over Compounded Generator

If series winding turns are so adjusted that with the increase in load current the
terminal voltage increases, it is called over-compounded generator.

In such a case, as the load current increases, the series field m.m.f. increases
and tends to increase the flux and hence the generated voltage.

The increase in generated voltage is greater than the IaRa drop so that instead 
of decreasing, the terminal voltage increases as shown by curve A.

### Flat Compounded Generator

If series winding turns are so adjusted that with the increase in load current, 
the terminal voltage substantially remains constant, it is called **flat-compounded
generator**.

The series winding of such a machine has a lesser number of turns than the one in
an over-compounded machine. Therefore, does not increase the flux as much for given
load current. Consequently, the full-load voltage is nearly equal to the no-load
voltage as indicated by curve B.

### Under Compounded Generator

If the series field winding has a lesser number of turns than for a flat compounded
machine, the **terminal voltage falls with an increase in load current** as indicated
by curve C.

Such a machine is called under-compounded generator.

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