Sorvall RT/T6000D - Page 126

SORVALL®
Centrifuges
6-24.
200 RPM
Switch
(refer
to
figure
6-22)
System
Descriptions:
Electrical
The
200
rpm
switch
ensures
the
rotor comes to
a smooth,
complete
stop
below
200
rpm.
This
switch is
hardware-controlled and therefore
cannot
be defeated
by any
switch and
or calibration.
Hardware
circuitry
that includes the
>200
rpm
comparator on
the Control
P.C.
Board
senses
when the
actual
speed
(rpm)
drops
below
200
rpm.
When that
happens,
the
signal
causes
the
brake enable
opto-isolator to
shut
down,
thereby
removing
power
to
the
brake
transformer.
The rectified
dc
voltage
created from
the
brake
transformer secondary
winding is
then
prevented
from
being
injected into
the
motor
field
windings.
The
flux lines
collapse
in
the
motor
field
windings,
allowing
the
armature to continue coasting towards
zero
rpm
with
no resistance.
Figure
6-22.
200
RPM
Switch