Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
114~Z26
Core Lamination for Shell~type cores,
particularly for Transformers.
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The invention relates to imp~ovements in magnetic
core laminations of two piece EI configuration providing
three legs and two end yokes, for shell type magnetic cores
utilizing a plurality of said EI laminations provided in
layers, said layers being provided with an E
and an I part, the E parts having a center leg and two
outer legs parallel thereto at a distance and an integral
yoke, which will be called the integral yoke and the ends
of said legs abut one side of the I parts, constituting
the other yoke, which will be called the separated yoke,
and wherein lower reluctance, reduced magnetic leakage and
higher efficiency is achieved by means which are described
hereafter.
Namely, in addition to the so-called M type of core
laminations for shell-type cores, there is also another
very widely used type, namely the so-called EI core
lamination, for instance according to US-Patent 3,546,571;
~th December 1970; USA Fletcher et al. Core laminations
o~ the EI type are distinguished in particular by very
economical manuacture because they can be stamped with
litt'le or no waste at al], and I parts being obtained from
the waste left after the E parts have been stamped.
By far the greatest majority of known art magnetic
core laminations for shell-type cores of two piece EI
construction are provided with a ratio of the center leg
width being twice the width of'each outer leg and also
twice the width of each of th~ end yokes which are of the
same width as the outer legs, that is half the center leg
width.
It is the object of the invention to provide new
and improved magnetic core laminations of two piece EI
construction, so that a core comprising such lam;nations
will be characterised by lower reluctance, reduced maynetic
leakage and higher efficiency.
According to the invention this object is achieved
by ~roviding a core laminations comprising an E
11~()226
pa,rt .~nd ,3,n :I: p3rt;, . r,a.rts and I
parts b-^in~r,~orned hy ,i.-~u].tareous stampin-,-to minimize
~aste9 ~rovidin, t'n-~e l,e rS end t~ o end -~rokDs and quita.bl.D
for ,hell-typa m.~,net~c coresf -~arti,cularly for transformer--"
the -~ rt havin-~, a Crnter 1 ~? r and tl~,o outer le rS ~arallel
t,hereto at ~1 di.,tance ~nd an interra.l yoke, ~hich ;~7ilL be
called the interral ~Joke, .r.d the ends o.f .-,aid le-rs a.butti,n r
one side of the '~ par-t con.,ti,tutinr~ the other ~olce9 whi.ch
.~;ill be called the ~se~r,ltrd ~olA~e~ characterised in that
the width (cl) o.f saicl inte,rral yoke i.s rreater tha.n the
~ridth (c2) of said se~arated yokr, (cl ~c2) and -rreater -than
half the center ler~idth (cl~f'/2) and the width (b) of
the two outer le rs i5 ~,reater than half the center le r I~Jidth
(b ~f~2).
I~oreover, these rneasures not only suppl~y an
advantageous .,olution -to the ,iven prob]em, but also provide
core laminations of ~uite reneral, applicati.on. ~tacked
alternately, these core la.minations yield transformers
o.f much improved marnetic and electrical characteri,tics;
and stacked in the same direction, they can be used to
advantaTe to make weldecl cores, cemented cores or clamped
cores. rhis a;~r)lies particularly to EI laminations ~hen
the width of the inte,.rral yol,ce is rreater than half the cent~r
l,e r ~idth9 preferabl~ hen the su~n of the ~idths of the two
yokes is at least 1.3 times, maximlm l.L~ times the center
le-~ idth and the outer le~ idth is at least 1.2 ti.mes7
maxi.mum 1.3 times hal:f the cen~er le~ idth. ,,~ 5,'' increase
o:f the width o:f the i,nte,-r,ral yoke with refererce to the width
of the se~arated yoke yields fair resul,ts, a 1~-,.,~ increase
yields -,ood results, a 2'~ i,ncrease yields exce1,lent results.
.~n embodiment of the invention is re~resert~d
d;.~r,rlmm,~t;.~,~.l.'.~r ir. t,he dra~in^r, in ~Ihich:
'~ir,. 1 is the ~lan vi.el,~/ of one laver of '.~:;l core laminations~
~; r,. 2 i 5 the plan vie~ of a ,,hell-t,r~e core cons;,stin~ of
,ernatel-y staclce,d El core lamin-ltions.
i~i r,. 3 sho~s the sheJ.l- t~Tl~e core accordin-r, to ~ r,~ ~
J..ockin-r".n the direction of arrow III in ?i-~r. 2.
rhe embodir1ent accordin, to ~i-r,. 1 sholJs a layer of
,o-cal] ed r core 1,~ i.nat,i.ons f~riron cores ln shell.-t~ P
~,ran:,:rormers or thP li'.~.e con~,i.C,tinr of an ~' ~art ,A, l~`.'hi.Ch
..1 _
114(~226
has a yoke 5, a center leg 1 and two outer legs 2 and 3
width of the yoke ~ which forms t-he I part B. This means
that the window widt'n h is e~ual to or greater than the
width c2 of the I part B because this is the only
possibility of obtaining the I parts B from tne window parts
stamped out of the E parts A and hence of cutting the
stamping waste to a minimum. Two E parts A are stamped
simu]taneously, with their legs pointing toward one another,
so that the two window stampings, i.e. the two I parts B,
will be of the necessary length. Thus the waste amounts to
no more than twice the window length e minus the length a
of the I part B of the free yoke 4.
The integral yo~e 5 of the E part A holds the legs
1, ~ and 3 together, its width cl being greater than the
width c2 of the separated yoke 4, i.e. the I part B.
The width of the two outer legs 2 and 3 and of the
two yokes 4 and 5 is greater than half the width f/2 of
the center leg 1. The width b of the outer legs 2 and 3
is preferably 1.2 to 1.3 times half the width f/2 of the
center leg 1 whereas the sum of the widths cl and c2 of
the two yokes 4 and 5 amounts to 1.3 to 1.4 times the
width f of the center leg 1.
The center leg 1, the two outer legs 2 and 3 and
the two yokes 4 and 5 enclose the windows 10 and 11, being
of window length e calculated in the direction of the
longitudinal axis 9 of the center leg 1.
The windows 10 and 11 are asynunetrical to the
transverse axis 6 because the width c1 of the integral
yoke S is greater than the width c2 of the separated yoke
4, i.e. the I part B.-
The shell-type core according to Fig. 2 and 3
contains core ]aminations according to Fig. 1, said core
laminations being stacked alternately. The inside edges
12 of the integral yoke 5 of the E parts A are in contact
with the winding and its supporting coil form respectively.
Said winding and coil form are not shown in the drawings.
In contrast, the inside edges 15 of the separated yoke 4,
i.e. the I parts B are spaced away from the winding and
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226
its coil form respectively; by an amount corresponding to
tlle yoke width dirference cl - c2. The inside length eK
of the windows in the shell-type core is shorter, by the
yoke width difference cl - c2, than the length e of the
windows 10 and 11 of the individual core laminations. This
form of stacking the core laminations serves to modify the
poor, separated yoke cross-section in favour of the
heneficial, integral yoke cross-section, without any
substantial disadvantage having to be taken into account.
There is no change in the amount of material, stacking
time, yoke cross-section or coil form.
In a core comprising ~ alternately stacked
laminations of the above kind, the abutting joints are
located within the yokes so that some of the magnetic flux
can flow out of the yoke in an undivided stream before it
even reaches the abutting joints, so diminishing the
adverse influence due to said joints. This influence is
diminished still further by making the outer legs wider
than half the center leg.
It is also possible to stack the EI laminations of
the invention in the same direction in the core, the E
parts A and I parts B then being cemented, clamped or
welded together after the insertion of the winding and its
supporting coil form, respectively. This procedure is
particularly adopted in cases where the benefits to the
manufacturing process have priority over the electrical
characteristics. ~lere again, advantages are obtained by
using the core laminations according to the invention.
The magnetic leakage of a shell-type core constructed thus
is very low at the end with the integral yokes, firstly
because the latter is of larger cross-section and hence of
lower reluctance and secondly because all the abutting
joints are situated at the other end in the separated yoke
part of the shell-type core.
The invention thus provides magnetic core laminations
cornprising of two piece EI configuration, wllich are of
really universal application, which according to the
invention, will be suitable for practically all purposes.
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