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Патент USA US2110418

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Màrch .8, 1938.
Filed March 26, 1936
.'5 Sheets-Sheet l
Mmh s, 1938.
s, s. GREEN
mmm lènguggpnm
-Marçh 8, 1938.
Filed March 26, 1956
3 Sheets-Sheet 3
’Patented Mar. 8, 1938
' 2,110,418
Enno'rmo METER
„Stanley S. Green, La Fayette, Ind., assignor to
Duncan Electric Manufacturing Company,
La Fayette, Ind., a corporation of Illinois
Appiication March ze', 193s, serial No. 70,951
17 Claims.
(Cl. ITI-'5264)
way of producing ad
This invention relates to velectric watthour
meters and has been illustrated as being embodied jacent fields of opposed polarity and adequate
in a two-element meter. In most of its aspects strength was to provide'a large magnet having
it is equally suitable for single element meters, both of its poles above the disc, with an arma
Y5 and in fact one of the important advantagesof ture below the disc opposite said poles, the ilux 5
the illustrated form ,is the readiness with which y passing downwardly from one pole into the arma
it may be converted to a single element meter. . ture and upwardly from the armature to the other
For many years efforts have been made to pro
duce metersy so that they would be'not only more
10 satisfactorylin operation but also more econom
ical in manufacture and more economical in use
, from the standpoint of taking up the minimum
pole. This was a fairly economical manner of
attaining this result, but it had several draw
backs which caused 'it to be discontinued com
Due to the fact that the magnets, in order to
be large enough to have adequate strength, ex
amount of Wall space. In my copending »appli
cation Serial No. 33,116, I disclosed a polyphase tended close to the sides of the meter case, it was
impossible to mount several meters side by side
meter Which takes up only the Wall space hereto
fore required by a single phase meter, while at in closely spaced relationship without introduc
ing what was called an “adjacency error”, be
the same time conforming to present high stand
ards in electrical performance. That application' cause large portions of the damping magnet of
covers the «interference-proof disc for polyphase one meter were so close to those of another meter
that there would be appreciable flux leakage be
20 meters, and a novel arrangement of the major tween the two magnets. According to the pres
parts which is -more eñlcient and satisfactory,
especially from the manufacturing standpoint and ent invention this is overcome by using a small
in requiring‘the minimum of Wall- space. The and properly positioned magnet made of a high
present application is intended to cover various coercive magnetic material instead of a large
magnet `of a metal conventionally used in watt
25 improvements, most of which are made possible hour meters, such conventional metals having
by using this latter feature, and involve the use
'of very high coercive permanent magnet steels. relatively low coercive characteristics; This
Although the metals themselves are not new, their small but high-coercive magnet is placed at a
use in kilowatt-hour meters is new -and has var
30A ious advantages which are peculiar to electric
The type and arrangement of damping mag
position suiilcientlyf removed from the periphery
of the meter case, as shown at 32 in Fig. 1, so 30
that there is no appreciable meter adjacency
error; At the same time the efficiency obtained
nets is an importantfeature of this invention, by having two opposed fields from one magnet
but to make its significance clear, it is necessary .is retained by having both poles on one side of
the disc, as seen in Fig. 6. This is in contrast to
35 to briefly explain the action of damping magnets
in an electric'meter. A damping magnet sets up another prior practice in which'the adjacency
a magnetic ñeld for opposing the rotation of the error due to the use of one large magnet was
disc to make its speed proportional to the power avoided by using two smaller magnets, one for
vconsumptionmeasured by the meter. _ The disc
' 40
does not touch the> magnets, and in fact rotates
With as little friction as possible. It is.common
practice in damping magnet arrangements to
provide` two adjacent fields of opposite polarity
through `which the,- meter disc rotates. The
45 ldamping effect depends upon the speed of change
of vilux in a given portion of the disc as it passes
vthrough these ñelds. This speed of change de
pends, in turn, not only on the total magnetic.
ñux in these fields, but- also on their concentra
tion and proximity. The most important parts
of the two ñelds are those parte which are ad
jacent to one another, since the stronger these
two parts are, the more rapid will be the change
yof iiux’through a given portion of the disc as it
from one to the other.
each of the two opposed iields,v each magnet
straddling the disc, having one pole above the
disc and the other below, and the two magnets
being alined and positioned almost end to end. >
Thisconstruction, however, was more expensive,
partly because of the difllculty of accurately
mounting the two magnets as well as the -extracost of fabricating two magnets, instead of one.
Such a construction is alsoespecially unsatis
factory when economy of space about the disc is
necessary. Nevertheless this isthe practice which
has been universally followed in recent years in
all meters ofthehighest quality.
The large single magnet of the discontinued
prior art also failed to make the best use of the
available magnetic flux, since it failed to -con
- centrate the iiux from the two poles in the zones
adjacent one another as thoroughly as this should
be done. A According to the present invention the
meter case, showing the meter element in side
fluxes are very concentrated in these most ef
fective zones, as seen in Fig. 6.
meter adjusting armature.
Fig. 5 is a horizontal sectional view through the
One methodof
accomplishing this is shaping the magnet so that
only the faces of the poles are adjacent to the
disc, the magnet extending upwardly from these
poles instead oi’ substantially parallel to the disc
as did the large single magnets ofthe prior art
mentioned. Another feature which contributes
same; and
Fig. 6 is .a side view of a magnet comprising
one feature of this invention, with an armature
'and a »fragment of a disc adjacent thereto, and
the direction of flux indicated.
Fig. 7 is a chart showing magnetic character
istics of metals.
Fig. 8 is a fragmentary plan view of a preferred
form of meter disc.
toward the same end of concentration of iiux is
shaping the magnet so that its cross section ad
jacent its poles is less than its cross section else
Fig. 4 is a Vertical sectional view through the
where, especially at its central portion (the upper
half of the magnete). It is obvious that except
for leakage, the ñux of the/entire magnet is thus
concentrated in the relatively small pole pieces.
With the large prior art magnet mentioned,
Although this invention may' take` numerous.
forms, only one has been chosen for illustration.
In this -form the meter includes any suitable
meter base II and cover I2 as well as the meter
mechanism mounted on said base and enclosed
by said cover. 'I'he meter mechanism includes 20
one factor which detracted from concentration
20 of iiux in the most effective zones was the use
of a round amature, this armature being round
an inner driving unit having a laminated core I3
which is mounted on the base in any suitable ‘
so that it could be turned on a screw to be screwed
toward or away from the meter disc and the
manner, a frame I4 mounted on the _core I3 of the
magnet beyond ,the disc for the purpose of adjust Y inner driving unit, an outer driving unit having
25 ment. According to the present invention the
a laminated core I6 mounted on said frame Il,
armature is made generally rectangular corre
a meter~ disc 2| rotatably carried by the frame,
spending in shape to the desired zone of con- ' the 'damping magnets 32 and their armatures
centration, so that it need not have any parts . 41 and 48 forming an important part ofA this
drawing the magnetism away from the zone of invention, and a register indicated diagram
30 concentration. For the purpose of adjustment, matically at 23. The driving units may be identi 30
the armature may be divided, and one part of it cal with those shown in my copending applica- .
moved parallel to the disc relative to the other tion Serial No. 48,713, although the laminated
part. The two parts of the armature are thus coresv I3 are preferably made»- up of a thinner
`partially separated to impede the flow of flux stack of laminations than was illustrated in that
application. Each driving unit includes a voltage 35
35 through the armature.
Another drawback to the magnets heretofore coil 24 and a current coil 26. In the preferred
used in meters is their requirementfor a. sub
form the laminations are secured together partly
stantial amount of temperature compensation,
by spacer rivets 68 which also secure attachment
which compensation takes the form of divert
40 ing part of the iiux of the magnet from its useful
channels. According to the present invention the
lugs 18 and 'I9 to the cores.
Arrangement of parts
An important feature of the preferred forml
magnets are made of a type of metal which -re
quires relatively little temperature compensation
of this «invention is the arrangement of the driv
ing units and permanent magnets 32 as shown,
with the driving units at opposite sides of the 45
disc and the magnets 32 between the driving
units and at opposite sides of the disc axis from
one another, with these damping magnets having
both poles adjacent one face of the disc (by which
is meant that both poles> are above or both poles
and therefore can use a relatively greater amount '
45 of their flux for the damping eiïect.
An additional objection to the magnets of the
‘prior art is that to prevent their being per
manently weakened by stray ñelds, as a ñeld from
the current magnet if there should be- a short
50 circuit, it was necessary to protect the permanent`
magnet from said field either by considerable
are below the disc) and their armatures on the
distance or by a suitable shield. Either form of opposite face of the disc and alined with their
protection involved expense and inconvenience. poles. This arrangement 0f parts permits se
According to the present invention the magnets . curing adequate damping torque for a two
element meter in a minimum of space, without 55
55 are, of such nature that this protection is not
any material adjacency error, and at exception
ally low cost. 'I'his feature of arrangement is
A necessary, a high-coercive material being used.
The objects of. the invention are not only t0
covered in applicantfs copending application pre
viously mentioned, and it should be borne in
overcome the difficulties previously mentioned,
ybut also 'to provide a more economical and satis
60 factory meter construction aside from these
mind that many of the remaining features may
be used without this feature.
particular considerations. One speciñc object,
for example, is to provide an improved form of
Meter frame
meter adjustment which, though very economical,
is exceedingly delicate and accurate and capable
'I'he desirable'arrangement with damping mag-~
nets between drivingmagnets is attained largely
65 of utilizing substantially all of the available flux.
Other ‘objects and .advantages of my invention
will be apparent from the following description,
taken with the drawings, in which:
Fig. 1 is a front sectional view of the form of
70 meter chosen for illustration, >taken approxi
mately through the line I-I of Fig. V3, with a
portion of the case broken away.
. f‘
` Fig. 2 is aperspective view of the meter frame
shown in‘Figl
Fig. 3 is a vertical sectional view through the
through the use of the frame I4 which is secured
to the spacer rivets 68 and 14 of core I3 in any
suitable manner.
'I'he frame I4 is constructed
as shown clearly in Fig. 2 and is cast of a non
magnetic.v material such as aluminum. 'It in 70
cludes a pair of inclined seats 3| against which
the magnets 32 are secured. There may desirably
be a raised boss 33 on each of these seats 3|,
through which is drilled a hole suitably threaded
for a screw -which holds the magnet in place. 75
A washer‘36 of non-magnetic material may de
sirably be provided between the head of the screw
andthe magnet. The seats 3I are extended up
wardly and integrally connected to mounting
lug 38 and to brackets 4I. The brackets 4I sup
port the upper disc bearing as is described below.
Extending downwardly from -the seat 3| is an
integral extension in the form of a loop 43, which
, loop extends around and under the meter disc'
10 44 and includes at its bottom portion seats 46 on
which are mounted the armatures 41 and 48 as
explained below. The central portion of the loop
43 forms a support for the lower bearing holder
5 I. This bearing holder is not new with the pres
15 ent invention andi therefore need not be described
the segment 6I and> also in the segment 48 but,
due to the differential pitch, it screws to the right
inthe segment-6I faster than in the segment 48,
and thus draws the segment 48 towards the seg
ment 6I.
Likewise when the screw 62 is turned in the
`opposite direction, it screws to the- left in seg
ment 6I faster than in segment 48 and hence it
separates the segment 48 from the segment 6I.
This movement is limited, however, b_y engage 10
ment of threads 64 with the segment .48 since
the threads 64 will not ñt the threads in the seg
ment 48 which engage the threads 63. It isvthus
seen that the length of the unthreaded or re
duced portion 65 between the threads 63 and
64 may be utilized together with the difference in
pitch to determine the maximum amount of sepa-I
ration of the two armature portions 48 and 6I.
It should be observed that the diiîerential`
er 5I preferably has a jewel bearing on which y thread arangement may be designed to give any
the meter disc 44 rotates. The upper end of the desired degree of delicacy of adjustment, even
shaft 52 of the meter disc is kept in the vertical though both of the threads may be fairly large
position in a substantially frictionless manner ' and strong. If the pitch of one thread differs
by an upper bearing pin which is held in a bear
from that of the other by only a hundredth or a
in detail. It passes through the bearing support
portion 49 and screws into the same, having an
annular shoulder which seats against the bot
tom of the support portion 49. The bearing hold
ing holder 54. v The preferred construction of . thousandth of an inch per revolution, the arma
this bearing holder is adequately illustrated in tures will be separated by only the corresponding
my said copending application Serial No. .48,713. y amounts. Expressing this differently and giving
This bearing support 54 screws into a plate 56 a typical preferred example, if the thread 64 has
which is shown as secured to the brackets 4I as a pitch of twenty-four turns to an inch, and the
thread 63 has a pitch of thirty-two turns to an 30
30 by suitable screws 51, though the plate may be
then in one revolution oi' the screw it will
4an integral part of the frame I4. Y
one twenty-fourth of an'inch in the block
Damping magnet armatures
6I, but it will/move one thirty-second of an inch
lThe armature 41 is preferably a rectangular _in the other block 48. The net movement of the
35 block of metal. of high magnetic permeability block 48 will therefore be one twenty-fourth of an
such as commercially pure iron. Its upper face >inch minus one thirty-second of an inch, or, in
is preferably directly opposite the faces of the other words, one ninety-sixth of an'inch.
poles of the adjacent permanent magnet 32 and
vOperation of adjustable armature
coextensive with the outer edges of the poles.
'I-'he armature 41 is secured in place'in any de
The operation and effect oi the adjustable ar
sirablemanner as by screws 56 extending through maturegare quite simple. As the two portions are
the~ seat 46 and screwing into the armature 41.v separated,- the reluctance ofthe armature flux
It is evident that the disc 44 rotates between the path is increased and therefore less iiux passes
magnet 32 andthe armature 41. `
from themagnet through the disc to the arma
The armature 48 may be 'the same as the arma vture and back through the disc to the magnet
ture 41 but it is preferredA that it be in two rela
than with the armature portions closer together.
tively movable parts to provide for adjustment of It follows that the damping effect is reduced. It
the meter, unless other adjustment of this type is is possible that part of the reduction in damping
provided. It should be understood that it is com
effect is vdue to shifting the position of the fluxy
mon practice to adjust' meters by varying the as,well as to decreasing the amount of the' flux,
amount of damping ñux which passes through inasmuch as when the portion 48 is moved away
the meter disc. In the present instance this 'is . from the portion 6I itis no longer directlyoppo
accomplished by shifting that part of the arma- ‘ site the face of the pole of the magnet 32 and
ture to which the numeral 48 is applied toward therefore the iiux` may no longer be concentrated
or away from the other part which is designated at its most 'effective position.
by the number 6I. The portion 6I may be se
Mounting of frame
cured` to its seat 46 inthe same manner as the
armature 4'_I is secured to the other seat 46. The
The frame ' I4 is secured at its top to the core I3
portion 48 may slide on the seat 46 and is ad
of one driving unit by means of a bracket 66
justable towards and away from the armature which may be secured to the 1ug`38 by a screw
portion 6I by means of a screw 62 engaging both 6.1 and to spacer rivet 6_6, by a screw 63. The
y portions of the armature.- Various screw are bracket 66 may desirably have a leg 1I extendingrangements’may be used such as having the screw beyond the spacer rivetv 68 and against the core
threaded in one member and simply pivoted in 'I3 for further rigidity. The frame I4 is further
the other member `without being longitudinally secured to the core I3 by screws 12 which may`
movable therein. To permit more delicate ad '_ desirably pass through bosses 13 formed on the
justment, however, the
ent shown' in frame, and screw into spacer rivets 14 on the
Figs, 4 and 5 is preferred.
According to this construction the screw 6_2
70 has two differential or independent threads 63
and 64 formed thereon, both-of which are right
hand threads, though both may be left hand
threads. The thread 64 has slißhtly greater pitch
than the thread 63. It follows »that when the
laminated core structure
Mounting of front driving unit
The front driving unit is secured to the frame
in a manner _similar to the mounting of the in
ner unit, or rather it is secured to-a link 15 se
cured to post 16 which is formed on the lug 38 75
-of frame It, and to _the posts Tl formed on the
looped portion of the frame i6. -The driving unit
-I6 is provided with an attachment lug 'I8 through
which a screw is passed and screwed into the
bracket 1E.
It is likewise provided with out- .
metals are able to force much more flux through
the meter disc than chrome steel or others of its
class, if each were made up in a magnet of a
given size.
Although various general characteristics of
standing attachment lugs ‘I9` through which
these metals have been known almost asV long as
screws may be passed and screwed into posts 11.
the metals themselves, the metals have certain
It will be observed that the two core structures` advantages peculiar to kilowatt-hour meters not
i3 and I6 are identical, even as to the lugs pro ' known before the present invention. This is
vided for mounting. As a mattei' of fact, spacer
partly because all the higher coercive materials
rivets 0l on the front core i6, similar to the spacer are much greater in cost on a weight basis than
rivets it, may be used for mounting the register
23 and name plate 82, both of which are secured
the commonly used chrome variety. Radical
changes in mode of application to the watthour
to mounting plate 83 which is secured directly to
meter mechanism have been necessary to make
15 said spacer rivets.
.their use commercially possible, since high-co
ercive steel used along the lines of recent meter
Damping ‘magnets
designs would have had much more total coercive
For many years a chrome steel of relatively low force than could be used effectively, and hence
coercive force has been used in meter magnets much higher cost than would have been justified.
20 because the meter designs were not such as to
The primary change has been the use of a new 2
take advantage of the high-coercive steels which - magnet of short total length compared with the
have been available in thelast few years. ` One
gap length. With the chrome steel the ratio of
typical such steel contains 8.50 percent chro
useful magnet length to gap length has usually
mium, .90 carbon, .33 manganese, .101 phosphor
exceeded 50 to 1. In the present preferred form
25 us, .015 sulphur, .29 silicon, .20 nickel, and the of the invention I have found a ratio of even as
rest iron.
low as ten to one to be sufficient. - This has been
Some of the permanent> magnet steels which . the basis ~for the selection of a small length mag
have become available commercially having much net oi' general horse-shoe shape but of heavy
higher coercive force values, are the high cobalt ‘ cross-section in which the flux is forced through
30 steels and the nickel aluminum steels. Qne form the disc gap twice, thus, in reality, doubling the
of the latter group which vhas become available actual length of gap as far as the flux path is
commercially is known by the trade designation concerned. Such extra gap length is the means
of “Alnico” because in addition >to about 20% by which the high coercive force of the steel is
nickel and about 12% aluminum it also contains utilized. It may be noted at this pointv that if
35 about 5% cobalt, the rest being iron. A good
the armature is fixed with respect to the magnet,
survey of the iield of such available materials >to
Vas is armature 41, the available coerciveforce in
gether with a bibliography is contained in an ar
a magnet may be more fully used, since it is not
ticle by C. S. Williams in the January, 1936, issue necessary to provide an excess to take care of
of Electrical Engineering and need not be further adjustment. For this reason other means of ad
discussed here. Therel are numerous patents justment than varying the, armature may be pre
purporting to relate to high-coercive steels, in
ferred. _The departures in fundamental gap re
cluding Patents Nos. 1,633,805, 1,947,274, 1,989,
lations and shaping have resulted' in a damping
551, 1,968,569, 2,027,994, 2,027,995, 2,027,996,2
magnet so radically different from former watt
027,997, 2,027,998, 2,027,999, and 2,028,000.
hour meter practiceas to introduce entirely new
For reference, the following table of typical space Aand arrangement problems in its applica
coercive values of different» common materials is tion to the meter disc. The solution of these has
resulted in a meter ofl great flexibility, light
weight, low cost, and simplicity of assembly, to
Coercive Aälä‘ääïœ
-force in
Low-coercive steel:
. oerqœds
residual tlux
in kilcgauss
The use of a smaller magnet permits the most
advantageous positioning of these magnets, es
60 to 64
36% cobalt steel _____________ _.
240 to 250
420 to 440
9. 4
within the space above the disc rather than pro~
10. 2
jecting outwardly beyond the disc, and thus it
Alnico ......... ____ __________ __
pecially in that it permits their being included
Old or usual form of chrome steel- -.._
Higlrcoerclve steels:
gether with the other advantages mentioned
It will be observed that the chrome steel can
overcomes the'tendency to adjacency errors when
two meters are located closely together.
To get the best use of a given weight of metal,
not be considered as in a class with the latter two
the magnets are preferably shaped substantially
materials, since these are characterized by having
as shown in Fig. 6, in which it is seen that thev
a coercive force value of at least three times that
of the chrome variety that of Alnico being over six
magnet, though of general horseshoe shape, is
thicker at its center top portion than at its poles.
times. There are, of course, steels _between those
mentioned above, such as 17% cobalt steel, but
The larger cross section of the magnet near the
65 this table _shows the diñerence between low and
flux which crosses the gaps,'but also the leakage
high coercive steels.
It will be noted from thev second column that
the residual flux values of the Alnico are some
what lower than for the other materials but this
70 is more than made up for by the highl coercive
value for the material when used in accordance
with this invention because the structure, gap and
shaping of the magnet in this case is such as to
capitalize on or take advantage of this factor
75 .rather than to throw itv away. 'I'he- last two
midpoint must carry not only the useful ldamping
iiux between the poles. Thus the crossvsection
near the poles need not be as great to secure op
eration of the magnet at the „most efficient point
of substantially uniform ñux densityfthroughout
its length. Moreover, this taperinggof the-polesy
has the additional advantage of causing the flux
density at the poles to be as great as further
back in the magnet and, as has been pointed-out,
this concentration of flux density at the gap'
greatly increases the damping effectiveness 'of a 7|
given amount of ñux, especially when the concen
trated flux zones of opposite direction are closely
adjacent to one another. The shape of the mag
net shown would give approximately uniform flux
density throughout the magnet.
Referring to Fig. 6, it is seen that to the left of
the line A-A the flux is all downward, and to
4the right of the line A-A the flux is all upward.
Thus as a given. portion of the disc 2"I lies under
the pole S, the flux> will be passing downwardly
perature compensating clip 9| may be provided.
These clips may be secured underneath the
washers 36, one ,under each washer, an'd may be
‘somewhat U-shaped if desired so as to 'extend
closer to the faces of the poles of the magnet, 5
thus straddling the horizontal portion of the
frame Il as do‘ the magnets themselves. The
washers 36 may be specially shaped, being ñat
tened along their lower side so as to fit above
the horizontal portion of the frame I4 and, ii' 10
desired, being recessed on their inner faces to
through it, but when said portion moves to lie
receive the clips- 9i. As is Well known, these _
under the pole N, the ñux will be passing upward
ly through it. It is this change in the direction of temperature compensating clips may be made of
flux passing through a given portion of the meter any magnetic metal having a negative tempera
disc which produces the damping eiïect, and the ture coefiicient such as nickel steel. One >well 15
more rapid the change is, the greater is the damp ’ known steel widely used for this purpose con
ing effect. In other'words, it is the intensity of tains 29.5% nickel and approximately 69.5% iron. »
Certain important advantages of mounting the
flux just to the leftA of the line A--A and just to
the right of the line A-A‘ which is most impor- ' damping magnets above the disc and with arma- `
tures below, have already been discussed: ,it per- 20
tant in the damping effect. Due to leakage be
tween the poles S and N, it is not possible to get mits avoiding adjacency error, makes a compact '
high concentration of flux exactly adjacent to the arrangement of parts possible, >and provides ad
li?e A---A, but it is possible to concentrate the jacent opposed ñelds from a single magnet. 'I‘here
flux approximately under the faces of the poles are, however, at least two other important ad
vantages as comparedr to using two adjacent 25
Ul by means of the use of the armature 41. Since
greater concentration of the flux close to the line magnets each having one pole above and one be
»A-A‘ produces greater damping effect, it- follows low the disc. One is obtaining the desired width
that by tapering the poles, the iiux is less spread of gap and the other is in the adaptability of a
out and is l'therefore concentrated under the two-elementl meter to a single-element meter.
poles, and hence closer to the line A-A than if- Resistance of damping magnets to magnetic disw 30
`the poles, not being tapered, extended further
away from the line A--A. In order to obtain a
magnet having this tapered shape economically,
When meters are installed under practical
it is preferred to use a magnetic metal which may
be cast or molded to this shape. It should be"
noted that the proportions shown in Fig. 6 are
approximately those of an alnico magnet which
has been found to be satisfactory. The outer face
conditions on the utilities’ supply lines to service
customers, they are likely to be subjected to two 35
classes of magnetic disturbance. In the iirst of
these, a short circuit occurs- on the load side of
the magnet is tapered too much, its eñiciency
rated current of the meter to ñow through the
the meter (that is on the consumer’s side) which
’is shown, and is slightly'longer than the inner ‘ may cause a transient current of from one hun- i
face on account of the slant of the magnet. If dred'to even one thousand or more times the 40
might be impaired on account of increased ñux
current `coils, (depending upon the short-circuit
capacity of the supply system and the severity of
The use, in accordance with this invention, of the short-circuit). In the second of these classes
of magnetic disturbances, the potential circuit 45
the rectangular armatures 41 and 48 substantial
ly no larger than the spread of the poles, also l of the meter is subjected to a transient over-volt
contributes to the concentration of flux, since if age of very' short duration, usually- because of a
the armature extended beyond the area of de
sired concentration it would draw some of the
flux away from this area'. As a matter of fact. it
may be desirable to have the armature slightly
smaller inthe direction concentric with the disc
than the dimension across the pole faces of the
magnet in this direction. It might also be better
to have the outer opposite sides of the poles and
of the armatures radialrather than parallel.
From Fig. 1 it will be observed >that the mag
nets 32 are slightly inclined. The chief advantage
of this is thaty the average spacing between ad
jacent magnets .of adjacent meters is greater,
although the faces of the magnets are kept at
the most effective position close` to the edges of
surge caused iby lightning.
"These lightning
surges may be of all‘magnitudes up to a value
sufficient to burn. up the meter, but the great 50
majority of surges are insufiicient to do this, and
dissipate themselves by causing abnormally large
transitory currents in the potential windings.
When either one or a combination of the above
two classes of abnormal surges occur, strong mag- ` 55
netic ñelds are set up around the meter coils
and their core structuresmay become completely
saturated, causing strong leakage fields. These
transient fields may be of the order of hundreds
or even thousands of times the normal value .of 60
the leakage fields to which the damping mag
nets are subjected in usual operation. These
transient fields are usually produced by alter
the meter discs. As a matter of fact, it is pre
nating current (and in consequence are demag
ferred that the corners of the poles of the mag
nets extend approximately to the edge of the netizing.
In prior art meters, designers have always
disc so as to obtain the greatest damping torque.
As previously stated, magnets made with the guarded against such fields by keeping the damp
ing magnets as far away as possible from the elec
preferred metal have very little temperature er
tromagnet coils (usually on the diametrically op
ror, since they have a relatively low temperature
coeiñcient with respect to the magnetic ilux posite side of the meter disc). Even further than 70
this, they have (in. the best quality of meters) al
which they produce. They do have a slight tem
perature error, however, and the remaining parts ways provided some form of shield vof magnetic
of the meter such as the cores I3 and I6 also , material (usually cast iron) between the electro
have very slight temperature errors. To compen
magnet and the permanent magnet'. Thus, prior
sate for these errors and overcome them, a tem
art meters have often or usually had the frame 75
of the meter of lcast iron. The shielding eiïect
has only guarded against magnetic surge elfects
partially as it is practically impossible to com
pletely guard against a magneto-motive-force by
magnetic shield means.- (Distance between the
electromagnet coils (where the disturbance origi
nates) and the permanent magnets has been an
Vchrome _____________________________ _'_ 33-42
Amico _______________________________ „_ 831-100
not function eiîectively).V It is therefore evi
dent that the two most important safeguardsv
of the prior art are completely absent, and a com
mercially acceptable job in the reduced space
20 would be impossible except for the greatly aug
mented use of a third safeguard.
.This third safeguard may be more easily un
derstood by reference to Fig. 7, and especially the
.left hand portion thereof. Chrome steel `has
usually been magnetically “aged” before its ap
plication to a meter. This “ageing” has consisted
'in the application of a demagnetizing force
(usually in the form of a magnetic ñeld produced
Ui. Ul
In this example the'Alm‘co had not been knocked
down nearly to the point Y but instead was be
ing operated at a point at about Z. .ObviouslyI if
it is no_t necessary to go to Y, there is some econ
omy by operating at a point such as Z-"
It can be shown by expert and detailed analysis
that the knockdown ampere mms per unit of
length are a close measure of the degreev of im
munity of a given magnet to demagnetizing in
iiuences such as the aforementioned surges.
Therefore it can be seen »that »the Alnico mag
net,--depending upon what A. C. knockdown isy
deliberately given to it,'-.can be made atleast
two times as resistant as magnets of the prior
art while producing almost as much ilux, even in
'a closed circuit, or three or more times as re
sistant while having much greater energy value.
Actual tests vhave vshown that the utilization of
this third and last factor, to the necessary de
by an alternating current). This force has gree, is the most reliable way of guarding against
usuallyI been one sufficient to bring the residual ' surges. The inventor has constructed and tested 30
flux down to approximately the point X on the ‘a meter with spacings and arrangement accord
curve. It will be seen that this point is at the ing to this invention which was actually more re
value of B and -I-I where the maximum energy sistant to surges than any prior art meter, not
product PX is produced for the chrome steel. The withstanding the close spacing.
maximum energy product of a magnet is the high- v
The present invention marks the ñrst time that
est product obtained by multiplying the coercive damping units and driving units have ever been
force at any point on its hysteresis curvev iFig. 7)
successfully used in close proximity and Without
by the flux intensity at that point. At the top of shields between them of magnetic material.
the curve the product is 0 because the coercive
Material used in meter frame
yf_orce is 0. At the bottom of the curve the prod
uct is 0 because the flux is 0. Somewhere be
It has previously been mentioned that the
tween there is a maximumenergy product. Of meter frame is made of aluminum. Of course
course X could be brought down still further on many other non-corrosive non-magnetic metals
the curve but not much further without consid
of adequate strength which can be cast to shape
erable sacriñce in energy product and hence in may be used as well. As has just been discussed, 45
damping eiîectiveness. \With the chrome steel the use of a high coercive material ln the damp
this demagnetizingforce applied is about forty
ing magnets makes possible this use of a frame
flve oersteds (gilberts per centimeter). Against which does not act as a' shield for the magnets,
demagnetizing forces up to but not exceeding this, although the arrangement of parts is so compact
the magnet would be immune.>
that shielding would be necessary otherwise.
'With Alnico, the demagnetization 'can be> con
'I'here are numerous advantagesl in the use of
tinued without great sacrince of damping eili
this type of frame which greatly enhance the
ciency to the point Y where a value of about 320 value of the use of the high coercive metal which ,
oersteds is obtained (or over seven times the value permits the use of the frame. For the ñrst timev
with chrome steel), with approximately the max
it has been possible to get along without added ëö
imum energy product Py.
clamp members or the equivalent. Now itis pos
Of course it may not always be necessary to go sible to secure the permanent magnets directly
to the extreme of descending on the Alnico curve to the frame without increasing the flux leakage.
to the point Y but if necessary it can be done.
'I'he manner ofvobtaining gap accuracy is ex
'I'he result would be a magnet immune to demag
plained under _the next heading.
_ netizlng forces up to approximately 320 oersteds.
In this connection it should be noted that some
of the available coercive force of the magnet is
consumed in driving the useful or damping flux
across the gap, but in general- much of it re
mains to be fully available as a safeguard against
demagnetizing stray ñelds.
Some examples may make this matter of age
ing more clear. A chrome steel magnet in wide
use (by the applicant’s company) has a devel
oped length of six inches, a single gap of .100",
and withstands from 200 to `250 ampere turns of
alternating current demagnetizatlon (or knock
doyvn, as it is commonly'called) .
veloped length for' the two are: i
the prior art.
room for the addition of magnetic shields (and
15 without greater space as well, the shield could
.125"> each and Withstands 250 to 300 ampere
turns of alternating current knockdown. The
knockdown ampere turn values per in_ch of de
even more important factor than the shielding of
In the present invention the damping magnets
are placed in- close proximity to the electro
magnet coils. Moreover. the frame of the meter
is'preferably of cast aluminum, and there is no
vention, has the same damping power, has a de
veloped length of three inches, with tWo gaps of
An Alnico magnet, preferred in the present in»
Another advantage is the elimination of trou
blesome magnetic particles which always are l
likely to get into the meter with any machined
parts made of a magnetic metal such as the old
cast iron frames. These particles could not be
removed reliably in any commercially practi
cal way, and in a meter they were especialy like
ly to accumulate on the poles of the magnet, thus
affecting the speed of 'the disc.
Another advantage is that the frame does not` 70
need to be painted, since it is inherently non-cor
rosive. AThere has always been trouble in the
past with paint chipping oil? and getting in the
bearings or gap as well as leaving the frame ex
posed to corrosion. yIn this connection it may be 75
mentioned that the Alnico magnets are also rust - rather than to limit the invention to these fea
tures, except- as the prior art may require.
' proof, so that paint may be omitted from- them
I claim:
’ The advantage in reduction of weight in the
use of an aluminum frame 4(andinthe use of any
1. An electric Watthour meter including a con
tinuously rotatable disc, a, plurality of driving
units acting on said disc and having approxi
frame of its skeleton nature)~ is obvious.>
mately parallel core' structures adjacent diametri
Obtaining desired gap width
' cally opposed peripheral portions ofthe disc, and
With the magnet arrangement shown, it is not an upwardly extending damping magnet located
10 necessary to grind the gap between the poles to
the desired size as when the disc must rotate
through this gap. With the present construc
between the cores with its pole pieces adjacent
one face of the disc, and an amature adjacent
the other face of the disc and alined with said
tion, the desired gap width can be obtained with'
adequate accuracy simply by applying the arma
pole pieces,_ said magnet slanting from the disc`
‘ tures 41 and 48' and magnets before the disc is
in place. A spacer gauge is placed on each arm
metal having a `coercive strength higher than one
inwardly,v and said- magnet being formed oi' a
hundred eighty oersteds.
ature and the corresponding magnet 32 is slid->`--- " 2. An electric Watthour meter mechanism in
along its seat 3| until its rests on the spacer cludingh a disc mounted for continuous rotation>
about a given axis,- a plurality of driving units
gauge and then the screw 3l is tightened to main
acting on said disc and having approximately 20
20 tain- this spacing. The gauge is then removed
parallel core structures adjacent diametrically
- Í`and the assembly of the meter is completed.
opposed sides of the disc, a damping magnet sub- -
Uonversz'on to single-element meter
Another advantage of the type of magnets
25 here used, and one which is newly attained by
stantially within a cylindrical _space subtended
by the disc extending steeply away from the disc,
and having its poles close’together and both ad 25
- the present invention is that a two-element meter l ’jacent the same face of the disc and spaced sub
mechanism such as Vthe polyphase meter illus
trated, may be converted to a single element me
stantially equally from `said axis, and an arma
ture opposite said polesv and adjacent the oppo
ter simply by removing the front driving unit
site face of said disc and constituting a low re
30 I6 and the lefthand one ofthe damping mag _ luctance path for causing the ñux to pass through 30
nets 32., Perhaps more important than this from ` d the disc in opposite directions in passing from one '
the lstandpoint of the user of meters, a single
phase type can be changed into a polyphase meter
by Aadding the front electromagnet element and
one damping magnet, and of course changing
pole of the magnet to the other, said damping
magnet being made of a magnetic material >having a coercive strength of at least“ 180 oersteds
and b‘eing in a magnetic state corresponding to 35
the connections for the outside circuit according - its having been previously magnetized and then
`ly. Also, a manufacturer can make either> single subjected to a knockdown force equivalent to at
phase- or polyphase` meters from the same stock least 120 oersteds.
3. A watthour meter includinga driving unit
of parts.- As a matter of practice, the disc will
usually be changed, since for the polyphase meter for rotating a disc,` a suitably ysupported frame of
it is preferred to use an interference proof disc
non-magnetic metal. a disc mounted on said -
such as that shown in Fig'. 8 having live insulated
laminations, each- having ñve radial slots ex
tending from the outer edge nearly to the center
of the. discs. Such discs are expensive and are
not necessary in single phase meters. The ad
frame for continuous rotation, a damping magnet
secured directly to 'said frame and having both
poles adjacent one face of the disc for retarding
the rotation of the disc, said frame extending
around to the opposite face of the disc from said
magnet, and an armature secured to said frame
vantage of havingv the other parts standard for
both single phase and polyphase meters is very
opposite said magnet but adjacent said opposite
important nevertheless.
face of the disc.
4. A watthourmeter comprising a torque pro
ducing electromagnet, a disc drivenby the elec
Torque-balanced disc .,
lAnother novel result of the illustrated arrange
ment of parts is that the forces around the disc
are balanced in such a way that there is no radial
pull on the disc shaft when the two driving ele
ments are measuring equal power consumptions,
no matter how great the torque may be. The
two driving elements act on the disc as a whole
'in exactly opposite directions (one to the right
60 and one to the left), and the two damping mag
nets also act in exactly opposite directions, so
l_that each set of forces is balanced except as to
torque. With suitable bearing design, this saves
wear on the bearings of the disc, as compared to
a construction in which both the damping mag
tromagnet andcapable of continuous rotation,
anda damping magnet for said disc, said'magnet
being of general horseshoe shape with its end
faces comprising pole faces both of which are ad“ 55
jacent one face of the disc and having an arma
ture cooperating with said pole faces adjacent the
opposite face of the disc, said magnet being made
of a material having a coercive force of at least
180 oersteds and being of such size and so posi
tioned with ` respect to the armature that the
ratio of the length of the flux path in the co
ercive portion of the magnetic circuit to the com
bined length of the> air gaps in the path through
the 'air to the armature and return is less than
net and the driving element being on opposite 25 to l.
5. A watthonr meter comprising a torque pro
sides of the disc, tend to shift the disc bodily in
ducing electromagnet, a disc driven by the elec
one direction so that the bearing has to counter
. tromagnet and capable of continuous- rotation,
act this force.
Although but one embodiment of my invention and a damping magnet for said disc, said mag 70
has been herein“ shown and described, it is to net being of general horseshoe shape with its end. .
be understood that the invention is not limited faces comprising pole faces both of which are
thereby, but is 'to be limited only` by the prior art. adjacent one face of the disc» and having an
The following claims are intended to point out armature cooperating with said pole faces adja
75 some of the features now recognized as new, cent the opposite face oí the disc, said magnet
being made of a material havingacoercive force
face of the disc, said magnet being formed of a
and so positioned with respect to the armature
that the ratio of the length of the flux path in the
'coercive portion of the magnetic circuit to the
combined length of the air gaps in the path
through the air to the armature and return is
than 180 oersteds and capable of operating above
the point of its maximum energy product after
being knocked down with a force corresponding
less than 15 to 1.
meter mechanism mounted on said base, said
oi at least 180 oersteds, and being of such size ` magnetic material of coercive strength. higher
6. A watthour meter> comprising a torque pro
ducing eiectromagnet, a disc driven by the elec
tromagnet and capable of continuous rotation,
and a damping magnet for said disc, said magnet
beingA of generalhorseshoe shape with its end
faces comprising pole faces both oi' which are
adjacent one face of the disc and having an
armature approximately coinciding in shape with
the outer edges of the pole faces cooperating with.
said pole faces adjacent :the opposite face of the
disc, said magnet being made of a material
20 having a coercive force of at least 180 oersteds
and being of such size and so positioned with
respect to the armature that the ratio of the
length of the iiux path in the coercive portion of
the magnetic circuit to the combined length of
the air gaps in the path through the air to the
armature and return is less than 25 to 1.`
7. A watthour meter comprising a torque pro
ducing electromagnet, a disc driven by the elec-_
tromagnet and capable of continuous rotation, a
damping magnet for said disc, said magnet being
made in general horseshoe shape with its legs'ta
to at least 120 oersteds.
10. A watthour meter including a base and a
mechanism including a driving unit, a unitary
frame formed'of a non-magnetic material re
movably secured' to said driving unit, a pair of
spaced bearings carried by said frame, a disc ro
tatable in said bearings and positioned by said
`frame to be inductively acted upon by said driv
ing unit, and a damping magnet carried by the
frame with closely spaced poles adjacent one face
of said disc, said frame extending around the.
edge of said disc adjacent the pole portions of
said magnetkand an armature carried by said
frame opposite said magnet but adjacent the op 20
posite face of the disc.
‘ 11. A watthour meter including abase and a
meter mechanism mounted on said base. said
mechanism including Va driving unit, a frame
formed of a non-magnetic material removably se 25
cured to said 4driving unit, a pair of spaced bear
ings carriedby said frame, a disc rotatable in
said bearings and positioned by said i'rame to be
inductively acted upon by said driving unit, and
damping magnet means carried bysaidl frame- 30
on the outside thereof and including closely
pering toward their ends over a substantial por
spaced opposed pole portions adjacent the same
tion ofd their length and with its end faces com->
prising pole faces both of which are adjacent 'one
face of said disci; said frame extending from the
inside of .said damping magnet meansr between
face of the disc and having an armature cooper
said opposed pole portions and aroundlthe edge 35
ating with said pole faces adjacent the opposite
of said disc.
7 face of the disc, said magnetl being made of a
material having a coercive force of at least 180
oersteds, and being of such sizeand so positioned
40 with respect to the armature that the ratio of
the length of the flux path in the coercive portion
of the magnetic circuit to the combined length of
the air gaps in the path through the air to the
armature and return is less than 25 to 1.
8. A Watthour meter comprising a torque pro-y
12. A watthour meter having a continuously
rotatable disc, an electromagnet driving unit
having current and voltage windings subject to
abnormal surges, a damping magnet in close 4,0
proximity to such windings and in substantially
unshielded relation with respect thereto. said
damping magnet being in a magnetic state cor
responding to its having been previously sub
jected to knockdown force of at least '10 ampere 45
turns per -fnch of developed length of the mag-'
Itromagnet and capable of continuous rotation, net and suilicient in magnitude for the magnet
and a damping magnet for said disc, said magnet to withstand, with immunity ,from permanent
being of general horseshoe shape with its end - weakening, the magnetic surges to which it is
faces comprising pole faces both oi' which are ad- ' likely to be subjected in service in its environ 50
ment in the meter, the magnetization of said
jacent one face of the disc and having an arma
ture cooperating with said pole faces adjacent magnet being still above ,a value at which it has
the opposite face of the disc, said magnet being approximately its maximum energy product.
13. A watthour meter having a continuouslyv
made of a material having `a coercive force of at
least 180 oersteds, and being of such size and so rotatable disc, an electromagnet driving unit hav-à 55
positioned with respect to the armature that the _ing currentand voltage windings subject to ab
ratio of the length of the flux path in the coercive normal surges, a damping magnet in close prox
portion of the magnetic circuit to the combined imity to such windings and in substantially un
length of the air gaps in the path through the shielded relation with respect thereto, said damp
ing magnet being made of a material having a 60
60 air to the armature and return is less than 25 to
coercive strength of at least 180 oersteds and
1, and the entire magnet being located a sub
stantial distance from the peripheral boundary being in ,a magnetic state corresponding to its
>of the meter case wherebyl adjacency error is having been previously subjected to a knockdown
. ducing electromagnet, a disc driven by the elec
substantially eliminated.
9. A watthour meter forpolyphase measure-'
ments comprising a plurality of independent
y torque producing electromagnets, a disc driven
bythe electromagnets, capable of continuous ro
tation, and including a plurality of overlapping
.sections substantially electrically isolated from
force of at least 70 ampere turns per inch of
developed length of the magnet and suiilcient 65
in magnitude for the magnet to withstand, with
immunity from permanent weakening, the ymag
lnetic surges to which it is likely to be subjected
in service in its environment in the meter.
14. A watthour meter having a continuously
one another and each acted upon by only one of » rotatable disc, and an electromagnet driving unit
the driving magnets at a time, damping magnet > having current and voltage windings subject to
means forming two adjacent opposed fields pass
ing through said disc, and including at least one
75 magnet having both poles adjacent the same
abnormal surges, a damping magnet system in
close proximity to such windings having a mag- ‘
netic circuit forming an air gap through which 75
the disc rotates and including a magnet made
of a material having a coercive strength of at
being in a magnetic state
_ least 180 oersteds and
corresponding to its having been previously mag
netized and then subjected to a knockdown force
of at least '70 ampere turns per inch of developed
length of. the magnet; the remainder of the
magnet system having substantially no coercive
strength, and the ratio of the length of the coer
cive portion of the magnetic circuit to the total
10 air gap length in the magnetic circuit being less
than 25 to 1.
15. A watthour meter including a continuously
rotatable disc, a driving unit for rotating said
15 disc, and a damping magnet system including a
tarding the rotation of said disc, said damping
magnet being made from a magnetic material
of coercive strength higher than one hundred
eighty oersteds, having closely spaced poles ad
jacent one face of the disc and being positioned
substantially between vertical planes on each side
of the meter passing through the periphery of
the disc, and an armature opposite said magnet,
adjacent the other face of the disc and directly
bridging the poles.
17. A watthour meter including a continuously
rotatable disc, a driving unit for rrotating said
disc, and a U-shaped damping magnet for re
tarding the rotation of said disc, said damping`
magnet being made from a magnetic material of'
coercive strength higher than one hundred eighty
closely spaced poles adjacent
damping magnet for producing opposed and ad
one face of
the disc and being positioned sub
jacent concentrated iields cutting the disc, said‘V loersteds,
damping magnet being made from a magnetic
material of coercive strength higher than one
hundred eighty oersteds, and said damping mag
20 net system being positioned between vertical
»planes on each side ot the meter passing through
the periphery of the disc.
16. A' watthour meter including a continuously
a driving unit for rotating said
g5_ rotatable
disc, and a U-shaped damping magnet for re
stantially between vertical planes on each side
of the meter passing through the periphery of
the disc, and an armature opposite said magnet,
adjacent the other face of the disc and approxi
mately coinciding in shape with the outer edges
of the pole faces of the magnet.
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