FRANTZ® Low Field Control
(Model LFC-2)
The Frantz Low Field
Control is an accessory unit for
installation in the electrical circuit
supplying direct current to the
coils of a Frantz laboratory
magnetic separator (the Barrier
or the Isodynamic). It provides
the conditions required for
separating ferromagnetic
materials according to differences
in their magnetic properties.
The Control comprises
means for reversing the direction
of the current to the separator's
coils, for sensing a zero field
condition in its working space, for
regulating and monitoring current
f r o m z e r o to a b o u t 100
milliamperes and for pulsing the
current at selected frequencies,
between selected values.
F R A N T Z MODEL L F C - 2
LOW F I E L D CONTROL
FIELD
SENSOR
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N. SI*?**
(-1
REVERSING
The magnetic field in the
working space of the separator
with no current flowing, which
results from residual
magnetization of its circuit, is
h i g h e n o u g h to c a u s e
ferromagnetic materials to
agglomerate and stick in the chute.
Reversing the direction of the current serves
to eliminate residual magnetization. By a series of
current reversals a minor hysteresis loop is
established and stabilized, so that the direction and
strength of the current which results in a zero field
condition in the working space of the separator may
be recorded and repeated. Low field intensities in
the 0-1000 Gauss range can then be selected and
any selected field intensity can be repeated.
Current can be pulsed between selected high
and low values at selected frequencies in a range
from 3 to 35 hertz. When current is pulsed through
the zero field value polarization of ferromagnetic
particles reverses with each pulse, causing trees of
ferromagnetic particles to collapse and release
entrained particles.
MAGNET CURRENT
PULSER
FREQUENCY
Off
As with paramagnetic and diamagnetic
materials the magnetic properties of some
ferromagnetic materials are too closely alike for
separation by magnetic means. With the Low Field
Control, however, the separator becomes highly
sensitive to small differences in magnetic
properties.
The model LFC-2 is 8 inches high. 8-1/16
inches wide and 7-15/16 inches deep. A 0-100
milliampere meter is mounted on its sloping control
panel. A pilot light on the panel is connected to a
reed switch attached to the magnet poles, which
opens when the field approaches zero.
A stabilized minor hysteresis loop measured
for the magnetic circuit of the separators is shown
on the reverse.
The diagram shows a stabilized minor
hysteresis loop for the magnetic circuit
which serves the Isodynamic and the
Magnetic Barrier Laboratory Separator.
Field intensity is measured between plus and
minus seventy milliamperes. The width of
the loop is significant for low intensity fields.
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In this stabilized loop the field in the gap of
the separator is about 1,100 Gauss at plus
70 mA (point A) and about 1,000 Gauss at
minus 70 mA (point E). As current is
reduced from plus 70 mA, the field declines
to about 100 Gauss at zero mA (point B),
but does not reach zero Gauss until, after
direction is reversed, current is increased to
about minus eight mA (point C).
D
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S. G.
FRANTZ
CO.
INC.
P.O. Box 1138 • Trenton, New Jersey 08606. USA
Telephone (609) 882-7100
Fax: (609) 882-3047
If current is pulsed on the negative side of
the loop between, say, zero and minus 40
mA, the field pulses between a maximum
value of about minus 500 Gauss (point D),
through zero, to somewhere between plus
50 and 100 Gauss, the value of the residual
field with no applied current. As the
direction of the field changes from minus,
under applied current, to plus, the direction
of the residual field, polarization of
ferromagnetic particles reverses direction,
causing "trees" of agglomerated particles
to collapse. The collapse of trees is visible
at lower pulse frequencies.