TM 5-3810-307-24-1-2
PRODUCT INFORMATION AND SERVICE MANUAL
DELCOTRON GENERATOR
(21-SI SERIES)
CONTENTS
Introduction .................................................... D-3
Generator Bench Check............................................... D-9
Features......................................................... D-4
Generator Mounting ................................................... D-11
Operating Principles ...................................... D-5
Generator Specifications ............................................ D-13
Troubleshooting ............................................. D-6
A. All Charging Systems ......................... D-6
B. Systems without Indicator Light.......... D-6
C. No Output ........................................... D-7
D. Rated Output Check ........................... D-7
INTRODUCTION
The 21-SI series Delcotron Generator is a high-
output integral charging system with built-in diode
rectifier and voltage regulator, producing DC
current for battery electrical systems. The 21-SI
series is designed for use on large and mid-range
diesel and gasoline engines in over-the-road
service, as well as for off-road, agricultural, and
construction equipment.
The 21-SI generator may be operated in either
clockwise or counter-clockwise directions (external
fan may require changing to reverse rotation) at
continuous speeds of up to 10,000 generator rpm.
Intermittent speeds of up to 12,000 generator rpm
are also acceptable. The ambient temperature
range for proper operation is -34C to +93C (-
30F to +200F).
The solid state, integrated circuit voltage regulator
built into the 21-SI generator limits system voltage
by switching the ground circuit for the rotor field on
and off. When the ground circuit is on, field
current passes from a diode trio through the rotor
via brushes and slip rings on the rotor shaft.
Nominal regulated voltage is 27.5 volts for 24-volt
systems.
Figure 1. 21-SI Generator
Various output levels are available.
For 24-volt
systems, output rating 70 amperes. For output ratings
of specific 21-SI models refer to the Specifications
section of this manual.
