The Saint Paul globe. (St. Paul, Minn.) 1896-1905, 1903-02-27
ELECTRIC MAGNETS
OF WONDERFUL POWER
Enormous Ones Used to Lift Great Mass
es Of Iron.

Electro magnets, as now in use differ
considerably in design, but the most pop
ular form is simple horseshoe, with one
limb so developed as to form an envelope
Tor the rest of the magnet. This type,
however, proved inadequate for certain
grades OF work, notably plate handling
on account of the shape of the pole face
and the excessive leakage from pole to
| pole. In the experiments made to de-
wise the most efficient form of magnet
many surprising disclosures were made
For instance. it was demonstrated that a
| round magnet which would on a straight
pull easily lift five tons was incapable of
picking up long thin plate weighing only
| half ton. After thorough Investigation
most engineers have adopted a group Of
rectangular poles as the best for plate
handling, which, as previously intimated
constitutes the most important use to
which the lifting magnets have yet been
! put.
One of the most interesting qualities Of
the electro-magnet is found in its capabil-
| lty, under regulation Of the strength of
the magnet; to pick up several objects or
only one. This may be ACCOMPLISHED bv
means of q rheoStat In series with the
| winding, but the preferable method is for
the operator to drop off superfluous mate
| rial by opening the switch and suddenly
| closing it. The current consumption of q
| lifting magnet is dependent of course
| upon the winding of the coils but as a.
rule a magnet operated on / 600 watts will
| have a capacity for handling fully 5000
| pounds of Sheared plates under any and
all conditions, and may, under exceptional
| tons.
In many horseshoe types of electro
| magnets horns are provided at the sides
| for attaching sling chains in case of the
| displacement of the magnet. AS indicat-
| Ing the capabilities of even the less per
| rect magnets, 1t may be cited that at a
| horseshoe design whose large size natur-
| ally entailed low ratio of lifting power
| to weight lifted a load in excess Of u
| tons with 13 amperes at 25O volts or g 250
watts. The weight of this magnet is j, 235
| pounds, which renders the ratio of weights
IN the case Of the test in question about
Tests Of a representative bi-polar mag
net In use at the plant of the Illinois
| Steel company, the magnet weighing /, 200
| pounds. demonstrated its capabiiitv Of
| lifting six tons with six and one-quarter
amperes at $50 volts or 1852 watts. This
magnet is capable of picking up several
| plates at a time. Tests such as those
above obtained are not, however, of much
| value as criterions of the practical work
ing efficiency Of magnets, as may be sur
missed from the fact that the round mag
net which at the test showed a ration Of
| 10 is not, under actual working condf-
lions; anything nearly as satisfactory as
this particular test was but 10. AS afford
| Ing further comparison, 1t may be noted
that the coil of the round magnet involves
! 1904 turns of wire, weighing approxima te-
ly PIT pounds, whereas the two coils Of
| the long magnet embody 1852 turns, and
weigh 176 pounds.
present time the favor4te type of magnet
| is a pole piece of five inches cross section
and three and one-half inches length. with
the coils surrounded to depth of fully
three quarters of an inch. The magnet
! face is rectangular in form The weight
! OF this magnet is but 30G pounds, and in a
test corresponding to that to which the BIZ
polar magnet previously mentioned was
subjected it lifted four tons, indicating a
ratio Of q. This magnet can be operated
| with four amperes at 230 volts or 920
| watts, but usually takes 4 amneraS a =
ESQ volts or LOO watts.-New York Eve
| ming Post.