Table of Contents
Advertisement
FOBART
e
QD
;MOTOR
GENERATOR
DIVISION
::
:
z
HOBART
BROTHERS
COMPANY
%
4s
Q. ,,+*
OPERATION,
MAINTENANCE,
AND
OVERHAUL
MANUAL,
TM-240A
SELF-PROPELLED
GENERATOR
SET,
SPEC.
NO.
5381A
The system consists
of four principal
components
which are illustrated
schematically
in Figure
1 and identified
as:
"electric
governor
control
box 'I, "magnetic
pickup",
"actuator",
and a speed setting
potentiometer
"2RH " .
The electronic
circuitry
of the control
box will
not,
and need not,
be
discussed
in the theory
of operation.
Operators
and maintenance
per-
sonnel should concern themselves
only with signals
which enter and leave
the control
box.
Servicewise
the control
box should
be considered
as an
adjustable
and replaceable
module and should be serviced
as such.
(b)
Theory
of operaticn
Operating
power is supplied
to the control
box from the 12-V
DC engine
through
the engine control
switch
(6s) and one set of the two sets of con-
tacts in the excitation-deenergization
relay
(EDR).
Input power is connected
to terminal
No.
1 on the control
box.
The control
box receives
two signals;
one from the potentiometer
(2RH),
and one from the MAGNETIC
PICKUP.
The control
box sends a signal
to the ACTUATOR.
The voltage
value of the input signal
from the potentiometer
(2RH) deter-
mines the governed
speed of the engine.
The potentiometer
signa I enters
the box through
terminals
9 (+) and 10 (-).
The value of this signal
may be
varied
from 0 V DC (minimum engine speed) to 1.5 V DC (maximum engine
speed).
Voltage
(and engine
speed) is increased
by turning
the "pot" ad-
justing
screw CLOCKWISE.
It is decreased by turning
the screw COUNTER-
CLOCKWISE
(Ref.
2-3,
Fig.
12).
Twenty-four
complete
turns (revolutions)
of the screw are required
to move the adjusting
slide from minimum to max-
imum speed setting.
There are no stops,
as such,
on this potentiometer;
however,
the adjusting
screw will
"slip"
to prevent
damage to internal
parts
when the slide reaches either
end of its travel..
In schematic
diagram
(Figure
3) the potentiometer
adjusting
slide
is shown in maximum voltage
(and speed) position.
The potentiometer
signal
is amplified
after
it enters
the control
box and becomes the speed setting
signal
voltage.
The other
signal
which enters
the control
box is an AC signal
fromihe
magnetic
pickup,
which
is a device
for sensing the speed of th,e engine.
The pickup
is mounted
in the flywheel
housing,
with the tip (magnetic
field
end) very close to the
starter
ring gear.
The device will
produce a voltage
output
when any mag-
netic
material
moves through
its magnetic field.
Thus,
as each tooth on the
ring gear passes through
the magnetic
field,
an electric
pulse is sent to the
control
box.
act
30/73
3-l
~
Page 5
Advertisement
Chapters
Table of Contents
