Note: Descriptions are shown in the official language in which they were submitted.
GENE~L STATEMENT OF T~IE INVENTION
~his inven-tion relates to a large separation type electro-
magnet which is entirely air cooled by normal convection.
In accordance with the invention in one aspect there is
provided an electromagnet comprising, a back plate, a circular
bottom plate and a wear plate supporting said bottom plate, a
shell disposed between said back plate and said wear plate and
fixed to said back plate, heat dissipation fins disposed between
said back plate and said wear plate and adjacent said shell and
extending radially outwardly from said shell, a winding disposed
in said shell adjacent said back plate, said winding and said
shell defining a space therebetween, said space being filled
with an epoxy material that is filled with grains of material
having a high coefficient of thermal-conductivity.
In a typical embodiment the heat energy developed by the
magnetic winding is transferred to the external convecting
surfaces by a resin filled with high thermal-conduction material.
The coil is wet~ wound with the empotting material. The said
resin is heat cured to a solid, dry mass having heat transfer
characteristics of -the order of ten BTU/in. per square foot per
hour F. Previous magnet designs have commonly been cooled by
circulating dielectric fluid, such as mineral oil or askarel,
or by heat conduction through the dry-wound unpotted winding to
the external convecting surfaces, The type of coil cooled by
, . : - . .. , . . ... ,~ . : : : :. ,, . :
3~J
dielectric fluid sufers the major disadvantages of being
complex due to the necessi-ty of providing means for circulation
of the fluid and for its e.xpansion upon being heated; w.hile the
dry wound unpotted types suffer the major disadvantages of being
bulky, expensive, and inefficient due to the necessity of
providing a coil with low wattage in order to minimize the in-
ternal hot-spot temperatures.
Further, with the fluid-cooIed type, it is extremely
difficult to make the system explosion proof for hazardous gassy
atmospheres in accord with modern-day standards for such equipment.
The fluid that is used must be the non-flammable askarel, a
material that has recently been found to be so dangerous to the
environment in the event of leaks that it is now being phased out
as a coolant in fluid-cooled systems.
With the dry-wound unpotted type it is extremely difficult
to make the unit dust-tight for haæardous dusty atmospheres and
still retain the necessary heat transfer to the outside convecting
surfaces.
The invention disclosed herein makes it possible to
design a large explosion-proof, dust-tight magnet coil with coil
depth as great as 16", while still operating at normai wattage
and with a coil of moderate size for the magnetomotive force to
be developed. Coils according to previous designs were impractical
above a maximum depth of 6" for a dry wound unpotted coil
operating at a normal wattage level.
Other features of the invention which enhance the oper-
ation of the coil are the solid welds that join the magnet back
bars, the corner fins~ the bottom plate and the shell and the core.
Heat transfer from the coil hot spots to the fins is through the
resin-saturated coil and the surrounding resin which is potted
between the outside of the saturated winding and the shell. The
steel shell is made cylindrical in form in order to better with-
stand the effects of internal explosions as well as to provide
- 2 -
1~23~o
short co~duction paths to the shell. The cylindrical shape of
the shell also saves potting material. The steel corner support
fins serve several purposes. (lj provide additional exterior
convecting surfaces, (2) support the wear plate, (3) provide
additional shell support at the four corners, (4) improve the
appearance of the electromagnet, and (5) provide a supporting
means for auxiliary hardware.
OBJECTS OF THE INVENTION
-
It is an object of the invention to provide an improved
electromagnet.
Another object of the invention is to provide an electro-
magnet with high heat dissipation characteristics.
Another object of the invention is to provide an improved
electromagnet that is simple in construction, economical to ~;
manufacture and simple and efficient to use.
With the above and other objects in view, the present
invention consists of the combination and arrangement of parts
hereinafter more fully described, illustrated in the accompanying -
~drawings ana more particularly pointed out in the appended
claims, it being understood that changes may be made in the form, -
~size, proportions, and minor details of construction without
departing ~rom the spirit or sacrificing any of the advantages
of the invention.
GENERAL DESCRIPTION OF DRAWINGS
-
Fig. 1 is an isometric view of the electromagnet accord-
ing to the invention;
Fig. 2 is a longitudinal cross-sectional view taken on ~ -
line 2-2 of Fig. 3;
Fig. 3 is a cross-sectional view taken on line 3-3 of
Fig. 2.
DETAILED DESCRIPTION OF THE DRAWINGS
Now with more particular reference to the drawings, an
- 3 - ;~ ;
.~
~IL08Z:~)0
electromagnet 10 is shown suitable for mayne-tically removing
scrap iron from non-magnetic materials, such as on belts.
The magnet is made up of a steel major bac~ bar 11 that
is generally a square plate in configura-tion and a steel minor
back bar 12 supported on the major back bar 11. The circular
bottom plate 13 is made of non-magnetic s-tainless steel and has
wear plate 14 fixed to it. Wear plate 14 is disposed in a plane
parallel to the bottom plate. Wear plate 14 is likewise made of
stainless steel.
Cylindrical core 15 is made of magnetic material and is
fixed to the major back bar 11 and extends generally perpendicular
thereto. A winding 17 is wound on core 15 and is disposed in
the space between the core 15 and the shell 19. The space 18 be-
tween the winding and the shell 19 contains an epoxy material
filled with grains of high-heat-transfer material. A filled
epoxy material contemplated for potting the winding is a material
known as "Stycast". This material is an epoxy which is filled
with grains of aluminum oxide, tabular, flat, relatively thin
platelets having a particle size of 325 grit, about half of
said grains overlapping each other, which is an excellent
conductor of heat.
The magnet may be supported above a belt 22 by suitable
cable or line (not shown), connected to the ears 20. A suitable
explosion-proof dust-tight wiring box 21 is fixed to the cylindri-
cal shell 19 which houses the terminals connected to the
winding 17. The plate-like corner supports 16 are fixed pre-
ferably by welding to the major back bar 11, to the bottom plate
13 and to the cylindrical shell 19, thereby providing a large
amount of heat dissipation surface in good heat conductive
relation because of the welded parts.
Fins are located at the corners of the electromagnet.
These fins not only act as strl~ctural members, but also as heat
' ~
~8~3~0
disslpation means exposecl to air convection curren-ts for trans~
ferring the hea-t away from the electromagnet. The high heat
dissipation capabili-ty of the magne-t, due to its construction
set forth above, makes it possible to build dry electromagnets
of substantially larger sizes than are possible to build with
conventional heat dissipation techniques commonly used.
The foregoing specification sets forth the inven-tion in
its preferred practical forms, but the structure shown is
capable of modification within a range of equivalents without
departing from the invention which i5 to be understood is broadly
novel as is commensurate with the appended claims.
. ~;.
- 5 - ;
.
