Du Pont SORVALL RC-5 Service Manual page 99

Drive
System
CircuitSorvall®
CentrifugesWhen
relay
Kl Is
energized,
28 Vac
passes
across contacts 11-1, then goes to
bridgerectifier
CR202. where
the
output
is used to
energize
the
door solenoid L301.
allowingthe
door
to
be
opened.
When the door is
opened.
+5 Vdc is removed from the
RUN
tem¬perature
control
circuit which disables the RUN
circuit.At
rotor
speeds
exceeding
100
rpm.
the
output
of
tachometer generator
TG301 is
recti¬fied
directly
by
the tachometer bridge detector on
PC
20126. This
output
overcomes
thepositive
offset
voltage
which disables the
relay
driver
Q5
that
deenerglzes relay
Kl.When
Kl
is deenergized.
+28 Vdc
is removed
from
the door solenoid circuit, locking
thedoor
in the closed
position. Relay
Kl also
applies
+5 Vdc
to
enable the RUN
temperaturecontrol
circuit.4-8.
Ovcrspeed Detector
CircuitThe
overspeed
detector circuit
consists
of
tachometer generator TG301, bridge
rectifierZ4,
a
differential
amplifier circuit, a relay driver Q24 and relay
K6.IN
OVER
TEMP.DETECTCIRCUIT0<C0L--L--JK6t
10 V dc
FROMZERO
SPEEDDETECTION
CIRCUIT7
79PCS
36Figure
4-7. Overspeed Detector
Circuit,
Simplified Schematic
Diagram4-18