ENGLISH ORIGINAL TEX
DC GENENRATORS
1. INTRODUCTION
For all practical purposes, the direct-current generator is only used for special applications
and local dc power generation. This limitation is due to the commutator required to rectify the
internal generated ac voltage, thereby making largescale dc power generators not feasible.
Consequently, all electrical energy produced commercially is generated and distributed in
the form of three-phase ac power. The use of solid state converters nowadays makes
conversion to dc economical. However, the operating characteristics of dc generators are still
important, because most concepts can be applied to all other machines.
2. FIELD WINDING CONNECTIONS
The general arrangement of brushes and field winding for a four-pole machine is as shown
in Fig.1. The four brushes ride on the commutator. The positive brusher are connected to
terminal A1 while the negative brushes are connected to terminal A2 of the machine. As
indicated in the sketch, the brushes are positioned approximately midway under the poles.
They make contact with coils that have little or no EMF induced in them, since their sides are
situated between poles.
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