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Патент USA US2117991

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May 17, 1938.
L. H. PALMER
2,117,991
DEFINITE POLE ALTERNATOR
Filed-March 7, 1936
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Zeray H. Pa/merf
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BMW .
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ATTORNEY
2,111,991
Patented May 17, 1938
PATENT ‘OFFICE .
' ‘UNITED I STATES
2,111,991
um row amnami'roa _
Leroy u. Palmer, Bell, Calif.‘
Application March 7, iasejseml No. 67,664
'6 Claims.
(Cl. 171-252)
This invention relates to a de?nite pole alter
Figure 1 is a front elevation of an alternator
embodying the invention, some, of the parts being
nator.
Such alternators in general have been in corn- - broken away and a part of the rotating ?eld struc
mon use for a long time. They usually involve a
5 stationary armature and a rotating ?eld struc
> ture, excited by. direct current. Di?iculties in the
design of such alternators are inherent when the
problem of regulation is considered. As the load
increases, the armature reaction increases; and
10 ‘its effect in turn depends upon the power factor.
This reaction results in a modi?cation of the ef
fective ?eld magnetism, and there is usually a
decided drop in the generated electromotive force
as the load increases. It has been customary in
the past to provide some means for compensating
for this drop, which can be operated to vary the
?eld excitation.
It is one of the objects of this invention to
reduce very materially ‘the effect of this arma
v 20 ture reaction and thereby to ensure good regula
tion of the electromotive force between no load
and full.load without ‘the necessity of varying
the ?eld excitation.
.
This object is attained by special reference to
the design of the ?eld spider and of the air gap.
In the past it has been almost universal to em
ploy relatively large gaps in an attempt to re
duce armature self-induction. It has been found
however, on actual tests, that an alternator built
30 in accordance with this invention, and in which
the air gap is very small can be operated with
very little reduction in the electromotive force at
full load. It is believed that this effect is due
to the very low magnetic reluctance in that path
which includes the pole pieces, as compared with
the path intermediate the pole pieces.
Accordingly, it is another object of this inven
tion to provide a de?nite pole alternator in which
the magnetic circuit is designed to provide a mag
40 netic reluctance through the pole pieces that is
very low as compared with a path intermediate
the poles.
_
I
This invention possesses many other advan
tages, and has other objects which may be made
45 ‘more easily apparent from a consideration of one
embodiment of the invention. For this purpose
there is shown a form in the drawing accompany
ing and forming part of the present speci?cation.
This form shall now be described in detail,» illus
50
ture being in section;
Fig. 2 is a vertical sectional view taken alon
the plane 2-2 of Fig. 1; and
'
Fig. 3 is a detail section illustrating the manner
of attaching the pole pieces to the revolving ?eld
structure, as seen along the plane 3-3 of Fig. 1. a
In the present instance, the armature core I
is shown as being made up of a series of lamina
tions and appropriately supported by a frame 2.
This frame 2 has the end housings 3 and 4, pro
vided with feet 5. The shaft 6 is appropriately
supported as by ball bearings, in the housings 15
3 and 4. The armature winding 1 is‘ indicated
in diagrammatic fashion only.
The ?eld structure is supported upon the shaft
6 by the aid of a spider or hub 8, which may be
pressed onto the shaft 6. This spider 8, as well 20
as the pole pieces 9, can be formed of appropriate
magnetic material such as mild steel, either cast
or forged. Such mild steel may be of low carbon
content, such as 20 points of carbon.
In the present instance the alternator is shown 25
"as having six poles. Each of the pole pieces is
surrounded by a ?eld coil i0. Excitation for the
?eld can be obtained by way of the collector rings
l2 and brushes I! in the conventional manner.
Each of the pole pieces 9 can be provided with
‘ a pole tip ii having an arcuate exterior surface.
One of the important features of this invention
resides in the fact that the air gap between the
pole tip- ii and the armature structure I is, of
very low value; of the order of 21/2 or 3 thou-.
sandths of an inch per inch of radius of the re
volving ?eld.
-
I
The manner in which the individual pole pieces
'9 are fastened to the spider or hub 8 is such that
a very low magnetic reluctance is provided at the
joints. For this purpose, each of the pole pieces
9 may be provided with an inwardly radially ex
tending projection ll. These projections?t very
snugly into corresponding radial recesses l5
formed in the hub or spider 8; In order to lock
the pole pieces in place, a transverse locking pin
I6 can be used, which passes transversely across
the recesses l5 and through the projections H.
trating the general principles of the inventlon;~
These locking pins are preferably made of low
‘but it is to be understood that this detailed de-‘
magnetic reluctance material, and should have a
scription is not to be taken in a limiting sense,_ -tight ?t in the apertures provided threfor.
Surrounding each of the projections I‘ there
since the scope of this invention is best de?ned
_ by the appended claims.
66
Referring tothe drawing:
"
,
is a shoulder H on each of the pole pieces 9. This
shoulder contacts snugly with'the corresponding
2,117,991
3. A de?nite pole alternator having ‘an arma
‘surface of the spider 8, which is: formed with
?at sides for this purpose.
ture core structure as well as a magnetic ?eld
4
structure with a central element and de?nite pole
pieces attached thereto, one of the structures be
ing rotatable, characterized by the fact that the
air gapibetween /the structures is reduced to a
value of the order of two and one half thou,
It is seen that the area of contact between‘each
' of the pole pieces 9 and the corresponding area
on the hub 8 is made quite *large, and an intimate
contact is provided by accurate machining of the
?at surfaces and of the cylindrical surfaces form
ing‘ the projection i4 and the recess ii. In this sandths of an inch per inch of radius of the ro
way, a very low magnetic reluctance is provided‘ tating structure, and that the magnetic reluc
10 for the magnetic path through a pair of adjacent tance through the magnetic path including the 10
pole pieces and the intermediate portion of the pole pieces is further reduced to a very low value
hub B. By providing the small air gas as de?ned by ensuring a large and intimate contact between
above, in conjunction with this low reluctance, it the pole piece surfaces that contact with the cen
has been found that the problem of regulation is tral element.‘
4. A de?nite pole alternator having an arma
15 avoided;- and tests have shown that from no lead
ture core structure as well as a magnetic ?eld
to full load’ conditions the generated electrome
tive force does not vary by more than a few per
cent.
‘
'
Apparently the armature core structure and
g. the ?eld core structure cooperate to reduce the
inherent effects of the armature reaction upon
regulation.
'
‘
,
1
‘ What is claimed is:
1. In a definite pole alternator, an armature
having a magnetic core, and a field structure co
operating with the armature and having a mag
netic core, said ?eld core’ having a series of pole
pieces as well as a hub support for the pieces, said
structure with a central element and) de?nite pole
pieces attached thereto, one of the structures be
ing rotatable, characterized by the fact that the
air gapbetween the structures is reduced to a
value oi’ the order of two and one half thou
sandths of an inch per inch of radius of the r0.
tating structure, that each of the pole pieces and
the central element are joined by the aid of a pro
jection telescoping into and closely contacting
substantially all surfaces of a corresponding re
cess, and that there is a shoulder surrounding the
projection in intimate contact with the corre
sponding surface on the other element.
5. In an alternator, “an armature core struc
radial projection extending from one of the ele
~ments into a closely contacting recess formed in .' ture. and a ?eld core structure, one of said struc
[hub support and pole pieces being joined by a
the other element; there being a shoulder surface -
tures being rotatable, said iield core structure
forming an air gap with the armature core of
and a ?eld-core structure, one of said structures
having definite pole pieces and a hub supporting
formed around the projection in intimate con
tact with the corresponding surface on the other said pieces, the air gap between the structures
element, to provide a tight joint at these surfaces, , being of the, order of three thousandths of an inch
and the air gap between the pole pieces and the per inch oi’ radius of the rotating structure, and
armature being of the order of two thousandths of each of said pole pieces being joined to the hub
an inch to three thousandths of an inch per inch so as to form large contacting surfaces between
the pole piece and the hub and held in ciosecon
of radius of the rotating element. F
2. In a de?nite pole alternator, an armature tacting relation to each other for reducing the
mag etic reluctance through the de?nite pole
having a magnetic core, and a?eld structure co
stru ture.
a
,
operating with the armature and having a mag
6. In an alternator, an armature core structure,
netic core, said ?eld core having ?eld-pole pieces
being rotatable, said ?eld core structure having
' thousandths of an inch per inch of radius of the .deflnite pole pieces and a hub supporting said
rotating element, said ?eld core having’ a hub pieces, the air gap between the structures being
provided with radial recesses, and the pole pieces of the order of three thousandths of an inch per
inch of radius of the rotating structure, and each
having projections closely contacting substan
tially all surfaces of the recesses, said ‘pole pieces of said pole pieces being joined to the hub by a
also having a shoulder surface around the pro-'. ‘radial projection extending into a closely con
tacting recess, there being a shoulder surface
jections in intimate contact with the correspond
formed around the projection, and urged into in
ing hub surfaces; said ?eld core also having lock‘
ing means extending across the recesses and timate contact with the corresponding surface.
55 through the projections and made from magnetic
LEROY H. PALMER. .
material, to hold the contacting surfaces in inti-f
mate relation to each .other.
45 the order oftwo-thousandths of an inch to three- _ -
15
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