Dual CS 731 Q - EDS 920 Direct Drive System

EDS
920
direct
drive
system
The
newly
developed
direct
drive
system
of
the
CS
731
О
turn-
table
is
a
successful
synthesis
of
our
well-known
motor
principle
and
a
highly
sensitive
electronic
system
which
receives
its
accu-
racy
from
a
quartz
crystal.
The
drive
motor
is
a
DC
motor
with
по
commutator
in
which
commutation
is
carried
out
by
two
Hall
generators
which
detect
the
position
of
the
rotor
equipped
with
an
8-pole
ring
magnet
and
which
also
actuate
the
corresponding
windings
of
the
rigid
flat
coils.
The
synchronously
rotating
mag-
netic
return
circuit
plate
and
the
ring
magnet
enclose
with
a
small
air
gap
the
non-ferrous
coil
arrangement
so
that,
on
the
one
hand,
the
drive
system
displays
an
extremely
uniform
running
characteristic
without
pole
sensitivity
and
which
displays,
on
the
other
hand,
a
high
torque
in
spite
of
the
economical
energy
supply.
After
the
nominal
speed
has
been
attained,
the
energy
supply
required
for
maintenance
of
rotation
is
less
than
50
mW.
Fig.3
Description of function
At
a
motor
speed
of
33
1/3
rpm,
the
200-pole
frequency
genera-
tor
rigidly
coupled
to
the
motor
delivers
a
frequency
of
111
Hz
which
is
amplified
in
the
input
amplifier
and
prepared
in
the
cam
form.
This
signal
is
applied
as
an
actual
value
to
the
PLL
circuit.
An
oscillation
frequency
of
4.608
MHz,
which
is
controlled
by
a
highly precise quartz crystal,
is generated
in the quartz oscillator.
The
actual
reference
frequency
—
that
is
to
say,
the
set
value
—
is
derived from the oscillator
frequency
by a multi-stage
divider.
In
the
PLL
circuit,
the
actual
value
and
set
value
are
compared
with
one
another
as
regards
amount
and
phase.
In
the
case
of
the
slightest
deviation,
a
control
pulse
is
applied
to
the
digital/analog
converter
which
obtains
from
this
an
analog
control
signal
which
is
converted
into
a
current
alteration
in
the
subsequently
connec-
ted
motor
control
circuit.
In
the
drive
motor,
this
current
altera-
tion
causes
spontaneous
stabilization
of
the
minimal
speed
devia-
tion.