Charging Systems

AC 203 Alternator - Description

The AC 203 often had a colour band denoting its rating: yellow band for 60A and red band for 80A.

from a BR training booklet

This machine is similar in construction to the earlier AC8 and consists basically of a field coil assembly (rotor) which rotates inside a stationary set of generator windings (restator) but with the major difference that rectification of the generated alternating current is carried out by a built-in rectifier bank of 6 diodes (see fig. 1).

While again the field coil is fed via slip rings no separate provision is required for initial excitation as the d.c. supply for the field is supplied direct from the alternator and put via a seperate built-in auxiliary rectifier bridge of three diodes sharing the same heat sink as the six main diodes (see also fig.1).