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(c)
Actuator
The actuator'
(1,
Fig.
4) supplies
the force needed
to move the throttle
valve
as required
to maintain
a constant
engine
speed.
The actuator
is oFrated
by a DC signal
from lphe control
unit.
,
*
(d)
Throttle
valve
assembly
An auxiliary
throttle
valve, assembly
(3,
Fig.
4) is mounted
on the intake
manifold
be low the carburetcr
.
The valve
is operated
by the actuator
to con-
trol engine
speed for close regulatibn
of generator
output
frequency.
The valve
shaft is mounted
in needle
roller
bearings
which
offer less
resistance
to shaft movement
than sleeve
bearings
and allow
the actuator
to move the valve
quickly
and easily
for close speed regulation.
The
valve
body is heated
by engine
coolant
to assist in preventing
valve
icing
when ambient
temperature
is near or below
freezing.
(2)
Engine
safety
shut-down
devices
Electrical
safety
devices
are connected
in the primary
ignition
circuit
to stop
the engine
in the event
of low oil pressure,
overheating,
or overspeed.
(a)
b)
(4
Coolant
temperature
switck
This is a bi-metal,
bulb trp!
temperature
switch
(2,
Fig.
4) mounted
in the
water
manifold
near the front of the engine.
It is connected
in series with
other
safety devices
in the primary
ignition
circuit.
A coolant
temperbture
of 225 deg.
will
cause the switch
contacts
to OPEN
and stop the engine.
Oil
pressure switch
The oil pressure switch
(20,
Fig.
4) is mounted
in the engine
lubricating
oil system at the oil filter.
It is diaphragm
operated
and is held
in
'
CLOSED
position
at pressures above
12 PSI.
It,
too,
is connected
in
the primary
ignitim
and OPENS
at pressures below
12 PSI
to
stop the
engine.
Engine
overspeed
device
The engine
and generator
are protecied
against
the danger
of overspeed
by a solid-state
electrical
overspeed
device
(4,
Fig. 4) connected
in the
primary
ignition
circuit.
.Direct
current
to-the
.ignitim
coil
is conducted
'I,
through
the contacts
of a relay
in the ,device.
The solid-state
circuitry
',
is designed
to sense the pulsating
current
in the primary
circuit
and to
signal
the relay
to OPEN
and stop the engine
when pulses redch a value
equivalent
to approximately
2750 RPM.
)I\
1
.
_
*
..-
i
July
l/76
l-l
Page 11
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