Figure 13-15. Thermostatic Control of Third-Brush Generator.

Custom Search

Back
Step-Voltage Control.

Up
TM-9-8000 Principles of Automotive Vehicles Manual

Next
Figure 13-16. Thermostatic Control of Third-Brush Generator.

TM 9-8000

Figure 13-15. Thermostatic Control of Third-Brush Generator.

d. Thermostatic Control.

long enough for the high charging rate to heat the

generator, the thermostat contacts open (due to the

bending of the thermostat blade), causing a resistance

(1) Another type of control for the third-brush generator

unit across the contacts to be connected in series with

uses a thermostat blade to control the field strength. If

the third-brush field and thereby reducing the current

the generator is set to give the greatest possible current

output. The charging rate is reduced approximately 30

to take care of demands during the winter, the battery

percent when the thermostat contacts are opened.

would be in a constant state of overcharge in warm

weather and soon be ruined. The thermostat blade

(4) The chief advantages of thermostatic control are

automatically takes care of the changing current

that it gives a large battery-charging rate in cold weather

demands under different conditions.

when the efficiency of the battery is lower than in warm

weather, and also a larger charging rate when the

(2) The control consists of a bimetal thermostat blade

vehicle is being driven intermittently and the demands on

made of a strip of spring brass welded to a strip of nickel

the battery are greater because of frequent use of the

steel. The blade warps or bends when heated, due to

starter. This control also prevents the generator and

the greater expansion of the brass side. The blade is set

battery from overheating in summer by reducing the

so that a contact on its end is held firmly against a fixed

charging rate when the temperature rises.

contact at low temperatures. When the temperature

rises to approximately 1600 to 1650F, the blade bends

and separates the contacts.

13-17. Split-Series Field Generators (Fig. 13-17

a. Generator regulation sometimes is accomplished by

(3) The thermostat is connected in the third-brush field

means of a split-series field. A generator with this

circuit (fig. 13-16) so that the full field current passes

method of regulation combines third-brush, reversed-

through the thermostat contacts when closed, permitting

series

(differential),

and

cumulative-compound

full current from the generator. After the engine has

principles.

been run

TA233554

13-16