Electrical Engineering is a free introductory textbook to the basics of electrical engineering. See the editorial for more information....  # Parallel Operation of Compound Generators

Author: E.E. Kimberly Fig. 10-23. Cumulative Compound Generators in Parallel With Equalizer Bus

In order that two over-compounded generators may share a common load in proportion to their respective capacities, their characteristics must be identical and the resistances of their series fields, including the equalizer conductor, must be inversely proportional to their respective capacities.

Calculation of Series-Field Turns for Compounding a Shunt Generator. If space permits, a shunt generator may be converted into a compound generator by the addition of a series-field winding. In order to calculate the correct number of turns to produce flat compounding, it is necessary to know the number of shunt-field turns per pole and to make a simple test. With the generator loaded to full-load current, the field rheostat should be adjusted until the required terminal voltage is obtained, and the field current should be recorded. The difference between this field current and the field current required for no-load voltage will be the necessary increase in the field current. This current increase multiplied by the number of shunt-field turns per pole gives the increase in the number of ampere-turns per pole required to accomplish compounding. The ampere-turn increase divided by the full-load current gives the required number of series turns per pole.

Example 10-4. - A 230-volt shunt generator requires 1 ampere of field current at no load. At full load of 100 amperes the field current required for 230 volts is 1.4 amperes. The shunt-field winding has 3000 turns per pole. How many series-field turns per pole must be added to flat-compound this generator?

Solution. - The required increase in the field current for a change from no load to full load is and the increase in the number of ampere-turns in the shunt field is The series field should contain Last Update: 2011-02-23