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‘
NOV.l2_,1946."
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sTmsgNi
2,411,010
. ELECTRICAL MEASURING INSTRUMENT
Filed June 9, 1944 ,
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Inventor. _
Allen 6. stims'oh,
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by
" ‘His Attorneg.
NW- 12,1946-
‘A. G. STIMSCN
' ' "
‘2,411,010
ELECTRICAL umsunms INSTRUMENT ,
Filed June 9, 1944
s Sheets-Sheet 2 ‘
Inventor:
Allen 6. Stimson,
by ~ mttorneg.
Nov. 12, 1946.
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J’
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A. G. s'nMsoN
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1, 2,411,010
ELECTRICAL‘MEASURING INSTRUMENT
’
Filed June 9, 1944
3 Sheets-Sheet 3
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. Iriv‘entor:
. Allen 6. Stimson,
‘
Hus Attorneg.
.
. Patented Nov. 12, 1946
2,411,010 '
UNITED STATES PATENT OFFICE "
MTZTZZIZI'Z?ZZGMZT
213:?..
General Electric Company, a corporation of
New York
Application June 9, 1944, Serial No. 539,546
’ 1 Claim.
2
(01. 172-245)
,
2
.
My invention relates to, electrical measuring
in'series‘and, except for the split arrangement‘
instruments and particularly to miniature instru
to balance the coil assembly with respect to the
‘ments for measuring frequency, although certain
armature shaft, might be considered as a single
features of the invention areapplicable to measur
coil, since they are connected in boosting relation.
ing instruments generally. An important object 5 The armature circuit includes a condenser ‘l, a
of my invention is to provide a compact, rugged,
. variable resistance 8, and a variable reactance 9.
lightweight measuring instrument of goodac
The armature circuit thus comprised is connected
in parallel with the ?eld coil I0 across the source
curacy which is easy to assemble. The instru
ments to be described were designed for use on
aircraft where it is especially, desirable that in
struments be small insize and light in weight.
The features of my invention which are believed
to be novel and patentable will be pointed out in .
I I, the frequency of which is to be measured. For
the purpose of representing a, practicable example,
it will be assumed that the normal frequency of
the source of supply is 400 cycles and'that the“
scale range of the frequency meter is from 350
the‘claim appended hereto. Certain structural
to'45‘0 cycles.
features of the instrument described herein are 15
The ?eld coil I 0 is of high reactance and its
claimed in a divisional application Serial No.
current represented by vector 12, Fig. 2, lags ap
588,196, ?led April 13, 1945.
For a better understanding .of my invention,
reference is made in theiollowing description
to the accompanying drawings in which Fig. 1
represents an improved circuit arrangement for a
frequency meter embodying my invention; Fig. 2
is a vector diagram explanatory of the theory of
operation of the frequency meter of my inven
tion; Fig. ,3 is a diagrammatic representation
of a frequency meter embodying my invention;
Fig. 4 represents connections for a wattmeter em
bodying'certain features of my invention; Fig. 5
represents a plan view and Fig. 6 a side view of a
measuring instrument embodying my invention,
the latter view‘showing a portion of a casing for
, the instrument; Fig. 7 is an exploded view of
the coil, laminated ?eld core, and supporting
plate used in my invention; Fig. 7a shows one
half of the ?eld core assembled; Fig. 8 repre
sents an exploded view of the armature assembly
and supporting structure used in the frequency
meter of my invention; Fig.9shows the preferred
shape of‘ ?eld pole tips and armature core for use
in a, wattmeter; Fig. 10 represents ‘the type of
armature used in a wattmete'r; Fig. 11 shows the
armature circuit of the frequency meter ener
gized from a secondary coil on the ?lled core to
proximately 90‘degrees behind the applied voltage
represented by‘vector l3. The armature circuit
is tuned and the phase angle of its current varies
20 with the frequency. At app'roximatelyrated fre
quency of 400 cycles the armature circuit is
I preferably tuned for resonance ‘so that its current
represented by vector‘ I 4 is in phase with the
voltage l3 at this time. Since I B is 90 degrees out
25 of phase with the ?eld current I2,_no torque due
to current flow will be present at this ‘time. The
armature, however, is provided with a tiny mag‘
netic vane l5 positioned with its magnetic axis
at right angles to the axis of the armature coils,
30 which vane is attracted by the ?ux across the
armature air gap and positions the ‘armature
so that its coil axis is at right angles to the ?eld
7. ?ux axis across the gap under these conditions,
and at this time the pointer is positioned to'read
35 near the center of the scale at the 400-cycle
graduation. Now when the frequency goes below
400 cycles, the armature current will leadthe .
voltage 83 as represented by vector M’, and a
down-scale instrument torque represented by"
vector‘ 56' will exist, producing a down-scale
de?ection. At frequencies above 400 cycles thev
> armature current will lag the voltage l 3 as repre- '
.sented by vector l4", and an up-scale torque
represented by vector I6". will move the pointer
is a vector explanation thereof. .
‘
45 up-scale from center. The magnitude of this
First, I will explain ‘the theory of operation
up-scale and down-scale torque may be increased
of my frequency meter in connection with Figs.
for a given armature current by increasing the
1, 2, and 3. The instrument has a stationary
values of capacitance and reactance in the arma
provide temperature compensation; and Fig, 12
U-shaped?eld core i energized by a voltage coil ‘
ture circuit in comparison to the resistance, and ‘
and has a moving armature winding split into 50 the scale distribution changed accordingly. When
two coaxial coils 2 and 3 mounted on either side
the details of the armature assembly are de- '
of the armature shaft it and a pointer ,5 cooper ‘ scribed, it will be pointed out thatthe torque
ating with a scale 5. The connections for measur
of the magnetic vane 15, which opposes the
ing frequency are as represented in Fig. 1 where
‘up-scale and down-scale instrument torques de- I
it is seen that the armature coils are connected 55 scribed, is alsoadjustable. The center restoring
2,411,010
torque furnished by vane I 5 varies with the voltage
and makes the frequency meter substantially
independent of voltage variations.
'It is desirable that the armature current be
kept at a low value and that the physical dimen
sions oir the circuit elements ‘I, 8, and 9 be small
After the initial calibration
adjustments these circuit elements have ?xed val
a and light in weight.
4
,
to the supporting plate II by screws 33 and-ll
‘which also clamp the support I! for the arma
ture assembly to the upper pole piece surface of
the ?eld core as shown in Figs. 5 and 6. The
openings for the screws 33 and 24 are numbered
33' and 34' respectively. The supporting plate
ll has peripheral recesses at ‘26, 21, 28, and II
positioned to receive the large heads of the rivets
40 (see Fig‘. '1) which are used-‘in the holes 2|,
ues. Without intending to limit my invention but
25, etc., to rivet the laminations together. This
to give a practicable set of values for the dif m facilitates quick assembly and aids in a rigid eon
ferent circuit elements and assuring a 110-volt
structlon.
supply, I may use a coil at l0 having 1800 turns
replacement and repair of the coil and low-cost
The splitcore arrangement facllitates- .
of 0.008 inch copper wire, .425 henry, and‘ 56
assembly of laminations, since each stack can be
ohms resistance. The two armature coils may
assembled and each half of the split core assem
15
have 600 turns each of copper wire, the induct
bled before the coil is added.
ance 9 may have 5 'henrys, ‘and the capacitance
It will be ‘evident that the generally U-shaped
at "I may be a .03 microfarad condenser. The re
> ?eld core described above has its laminations par-v
sistance of the armature circuit is of the order
allel with the plane of the U and is appreciably
of 11,500 ohms. ‘Under these conditions the ?eld 20 thicker and of larger cross section in the pole
current will be of the'order of 120 milliamperes
piece portions than in the yoke portions by rea
and the armature current of the order of 10 mil
son of the pole piece parts I8 and is, Fig. '1,
liamperes at rated voltage and frequency and
which lie entirely above the plane of the remain
with the aid of features to be‘ described herein
der or the core in a direction at right angles to
after, the entire instrument and ‘circuit devices
the plane of the laminations. The thickness of '
25
may be housed in a cylindrical casing having out
the pole piece portions or the core is increased
side dimensions 2% inches in diameter and 3
with respect to the yoke portion of the core by
inches in length. I desire to point out at this
the depth of these laminated ‘pole piece stacks
point that the instrument above‘ described may
l8 and it. One advantage or this is that I can
be used as a position indicator by maintaining
operate the yoke portion of the core at a higher:
the voltage and frequency constant and varying 80 ?ux density than would be advisable for the pole
the tuning of the armature circuit as by varying
piece portions and thus save material in the yoke
the reactance I, for example.
section, and correspondingly reduce the inner and
outer diameters of the coil II and the volume
Field structure
and weight of copper used therein for a. given
The laminated magnetic ?eld core i is de
number or ampere turns and coreloss. At 400
signed for minimum weight for a given iron loss,
cycles, for which the frequency meter is intended,
to facilitate assembly in a prewound coil and
the core loss is likely to be considerable unless
'
of
the
assem
. to reduce the space requirements
certain precautions are taken. The construction
bled instrument. The core with its coil i0 and go permits of an accep 'ble
core loss without sacri
‘
coil supporting plate I1 is shown disassembled
?cing coil space. The laminations 2| and 22
in Fig. 7. The core comprises six stacks of la'm- I which thread the coil III are preferably made of
The stacks 2| and 22
the order of only 0.005 inch in thickness, which
inations I. to 22 inclusive.
are similar and may be stamped with the same
reduces the core loss in the higher flux density
piece sections integral , at‘ die, and include pole
45
yoke
part of the core, while the laminatlons 01'
one end with the yoke or coil enclosed parts which
parts I8, It, 20, 22 which operate at appreciably
are the‘ longerleg portions thereof and which
lower flux density and where there is greater need
are assembled side by side. The stack sections
of- structural rigidity, are preferably made of the
ll, 2|,, and 22 are assembled as one group or
unit as shown in Fig. ‘la, and comprises one pole
order of 0.014 inch in thickness. It is to be noted
50 that the laminations of the different core parts
are not interleaved, as this would not permit of
piece and one half the yoke, part‘ 22 being be
tween parts II and 22, and these parts riveted to
different thickness laminations in parts Y20 and
gether by rivets that pass through the aligned
2|, forexample, which lie in the same plane, nor
rivet holes 24 and 25. the. same rivet passing
would it permit of the ease of assembly and dis
through the holes which are numbered alike
55 assembly obtained. Instead of interleaving the
inrlg?l.
laminations, certain core parts as a whole over
Core parts ll, 2i, and 22 are assembled as a
lap and abut against other core parts at the junc
group with part 2| between I! and 23 and riv- . ' tion of pole pieces and yoke sections and are
the
other
pole
piece
and
eted together to form
then clamped rigidly together.
one half of the yoke. The non-polar ends of the
To reduce further the core loss of the lamina
two half yoke portions are then slid through the w tions, the rivets and screws used therethrough
coll I! from opposite ends, part 2| above and flat
are kept as near the periphery of the core and
against part 22, until the facing surfaces at 20,
out of the main ?ux pathv as is possible. As
Fig. ‘I, abut and the facing surfaces at 21 abut.
shown at 28 and 29 in laminated parts 2i and
and the bolt openings numbered 2! are aligned
and as 22,.1-espectively. the bolt openings are not closed
andthose numbered 2| are aligned. Bolts 22'
‘ by magnetic material. _-where ?ux can pass out
22', Fig. 5, are then passed through the openings
side of a bolt or rivet, it will be noted that the
respectively, and the corresponding
cross section of the magnetic material op the
numbered openings in the plate II. The assem
outside of all rivets and bolts is substantially the
bled eore structure with its supporting plate i1
same. _ Hence, it any flux does go outside the
is then clamped together and against the upper 70 bolts
and rivets, that part of the flux will evident
‘ ?at surfaces (see rigs. 5 and 6) of pedestals 3|
ly stay outside all rivets and bolts around the
insulating support and wall
rising from a circular
ll adapted to. ?t into a cylindrical casing 32 as
entire periphery of the core. which would tend to
induce currents therein oi the same phase and
best shown in Fig. 6. The pole piece parts of ‘(5 magnitude but without a return circuit and as
the assembled core iaminations are also clamped
2,411,010‘
5-
-
.
a consequence of the arrangement, negligible
eddy current loss is occasioned by the presence of
the bolts and rivets. For 400-cycle service I pre
fer to use laminations made of the high per
I by the flux is inserted an aluminum damping
vane 58 secured on the armature shaft 59.
The armature
meability nickel iron alloy known to the trade UK
as
Nicaloi.
.
A
‘
It will be noted that the damping vane 58 is
of an open or half cup shape between the point
wherev it is fastened to shaft 59 and the ?at
- outer peripheral portion, with the shaftinserted
through the bottom of the cup and the cup open
In Fig. 6 the upper half of the nearly square
yoke section is outlined by dotted lines, while
the lower half is shown in full‘ lines. It is to be
noted that the pole piece portions of the core are
offset from the center of the coil in one direction
ing upward. This cup shape provides added
strength and rigidity to the damping vane and
at right angles to the plane of the laminations -
provides space and‘protection within the cup '
towards the scale plate 6. This has the advan
tage that the scale plate may be placed lower
for the upper spiral lead-invwire 60 and the
collar
‘to which the pointer 5 and the balancing
down than would be the case if the coil were 15'
arms 6i are secured.
centered in the vertical direction with the pole
The balancing arms Bl
are at right angles to each other and 45 degrees
pieces, ‘as viewed in Fig. 6, and requires less off
from the pointer forward of and in the same plane
set of the pointer 5 and saves a corresponding
with the damping cup member 58 where they
amount of space in the over-all height of the in
are accessible for adjustment of their weights.
strument as picturedin Fig. 6.
20
This arrangement allows of balancing with two
The armature assembly and support
counterweights instead of three as is usual. It
also allows of quick balancing with few opera
All parts of the armature, its pivots, lead-in
' tions as follows: With the instrument shaft held
spirals, magnetic damper, armature stop, zero
adjustment, and scale plate are supported by the 25 horizontal and with one balancing arm vertical,
the armature is balanced with the other vor hori
support 35 (see Figs. 5, 6, and 8), and all of these
zontal balancing arm weight. Then the‘ arma
parts are removable from the instrument as a
ture is rotated 90 degrees so that the other bal
unit by taking out the two screws 33 and 34.
ancing arm is horizontal and its counterweight
The support 35 is an integral die casting of non
magnetic, corrosion-resisting material such as 30 is shifted until a balance is obtained.
Theinstrument shaft 59 is a hollow bronze
aluminum. The scale plate 6 is fastened there
tube with the upper and lower pivots 62 and 53
to by two screws 4! (see Fig. 5). The support
pressed into its upper and lowerrends. The mag
35 has a lower forward horizontally extending
netic vane‘ I5 is secured to the shaft within the
part 52 which supports the lower bearing 43 and
35 coils and is adjustable about its .center support
stud which goes through the shaft 59 so that
The upper bearing 85 and '
. the effective length of the vane and its torque in
upper lead-in spiral adjusting means 46 are sup- the ?eld ‘of the instrument may be 'varied. The
lower armature lead-in- spiral supporting and ad
justing element 55.
ported by a strap 6‘! which is fastened to the
lateral and forward extending top part of the
support 35 by screws 58 entering into threaded‘ 40
openings 59. The two spiral adjusting means
85 and 45 are clamped in place coaxially with the
axis of rotation of the armature under the come
pression of resilient slightly dish-shaped fric
tion washers 50 which permits‘ of their being
rotatively adjusted readily but without danger
of accidental movement from adjusted position
by vibration.
\ '
‘
Beneath the top bearing bridge strap 57 there
is a central recess in the support 35 into which
there loosely fit a kidney-shaped permanent mag-v
net 5i and spaced return flux keeper 52 com
prising the stationary part of a magnetic damper
for the armature. The damping magnet parts 5|
and 52' are secured near‘ the upper end of a
strap 53 which ?ts into an elongated vertical
slot 55 in vthe rear side of support 35 as viewed
in Fig. 8, and secured in place by a screw which
enters through a hole '55. The damping mag
net parts may thus be polarized as a unit and
added last during assembly of the instrument
parts and kept clean'of magnetic particles. ‘The
strap 53 in the ‘frequency meter also supports
a removable armature stop 56. The stop‘ 55 has
45-degree position of the. vane shown inFig. 8
gives approximately the correct restoring torque
for the frequency meter described. When cor
rectly adjusted it is permanently secured in
place.
,
g
y
The armature coils 2 and 3 are shell-less and
are held to the shaft by two ?at-surfaced bush
ings 64 of insulating material ?tting against
the inner surfaces of the coils and to which the
coils are secured at top and bottom by cement
andlashings. The armature coils are wound
with formex wire with the turns cemented to
gether into a solid mass andv are su?iciently
stiff to provide their own support without using
a shell or other coil ‘form support. This gives
an exceptionally high ratio of useful armature,
torque to armature weight and space. On the
shaft below the coils theremay be a washer 65
of mica to protect and, insulate the lower lead
in spiral 56. The lead-in spirals of the fre- v,
quency meter are adjusted to have minimum torque.
,
,
In order to give a better idea of dimensions, it
may be stated that the total length of the ar
mature coils is' 1% inch, with other dimensions in
the proportions pictured in the exploded view
of Fig. 8.
When the parts shown in Fig. 8 are
a screw part threaded in the support 53 and a 65 assembled, the total height of the assembly is.
forward'ceram'ic' bushing part of insulating ma
terial which extends freely through the open
ing 57 in the support 35 and into the path of
‘approximately 1% inches. This assemblyyto
gether with the scale plate which is omitted in
Fig. 8 may be removed as‘a unit from the pole
piece assembly by removing the two dowel screws
of the armature as viewed in Fig. 8, and serves 70 33 and 3.5, Fig. 5, and when this‘ assembly is in
to stop their swing at suitable limits in both
place in the ?eld and the dowel screws are
directions. The permanent magnet 5| is po
tightened, the armature coils are correctly po
larized as indicated in Fig. 8 so as to produce
sitioned in the ?eld air gap.
swing of the armature coils 2 and 3 to the rear ‘
a flux across the air gap between it and the flux
‘ The circuit elements of the frequency meter
return part 52, and into this gap so as to be cut 75 comprising the condenser l, the resistance 8,
£2,411,010
and the reactance 9 are housed'in the same
a secondary winding" inductively coupled with
insulating partition base 31 which supports the
the ?eld coil ill instead of being connected across
the line II as in Fig. 1. In case the coil l0, Figs.
1, 3, and 11, increases considerably in tempera
instrument as indicated. The supporting en
closure for the condenser 1 may be held be
tween the partition SI and a cross plate indi
cated at'i'l by bolts 68. The casing 32 may com
likely to shift as represented by the dotted vector
12', Fig. 12, at any given frequency. If the ar
casing 32 (see Fig. 6) with the instrument and
are preferably mounted on the rear wall of. the
ture so that its resistance component increases
in comparison to its reactance, the field flux is is
mature circuit is connected across the line as in
Fig.
1, there is no corresponding shift in its phase
'10
10 both secured to the base partition SI of the
prise two telescoping cylindrical parts 89 and
instrument. Casing part ‘Iii which is the outer
rear telescoping part is held in‘ place by nuts on
bolts 68. Casing part 69 is held in place by
position due to temperature rise. If, however,
the armature circuit, including coils 2 and 3, is
energized inductively by transformer action from
?eld coil in acting as a primary of a transformer.
screws, one of which is shown at ‘H, and which
are accessible when the casing part ‘I0 is re 15 any shift in the'phase position of the flux in the
core i due to rise in temperature of the winding
It will produce a corresponding shift in the ar
of the instrument. Frequency meters and
mature voltage because here the armature volt
wattmeters such as described are now being
age is referred to the field ?ux I: rather than
built for use on airplanes, enclosed in cylin
to
the linevoltage ii. Thus, at a given fre
drical casings less than'three-inches in total 20
quency, if the field ?ux shifts from It to II’, Fig.
length and about 2% inches in diameter.
moved. 12 represents the electrical terminals
12, the armature voltage phase position will shift
When used as a wattmeter the connections are
as represented in Fig. 4.‘ The wattmeter ar
from H to ll’, which tends to compensate for
the temperature error that would otherwise exist
mature coil is represented at 13, and the arma
ture circuit is the potential circuit and contains 25 due to this shift in the ‘?eld ?ux phase position, .
since in Fig. 11 the phase relation between the
an adjustable resistance H for calibration and
?eld flux and armature current-is substantially
a‘ ?xed inductance 15 to obtain correct phase
unaffected by the changes in field resistance with
angle adjustment between the ?eld and arma
temperature changes. The armature circuit is
ture. ?uxes. The field 16 is preferably ener
gized from a current transformer 11 connected 30 nevertheless tuned and shifts as in Fig. 2 with
frequency‘ variations. The change in power
vin the current circuit of the line 18 metered.
factor of ‘the secondary armature circuit in Fig.
In the wattmeter I prefer to use an iron core
11 due to changes in frequency has an insis
19 in the ‘armature and change the shape of
ni?cant effect upon the power factor of the pri
the pole pieces to that represented in Fig. 9.
The same split core and offset pole piece assem 35 mary field coil circuit ll, because the secondary
transformer burden represents a very small‘
bly of the laminations are employed as in the
percentage of the input to coil vl0.
frequency meter, the only difference being in
In accordance with the provisions of the pat
the pole face shape of the pole piece laminations.
ent statutes I have described the principle of op
In the frequency meter the pole tips were square
to obtain better magnetic vane, center restor 40 eration of my invention together with the ap
paratus which I now consider to represent the
ing torque. A conventional style of wattmeter
best embodiment thereof, but I desire to have
armature is used as represented in Fig. 10, but
it understood that the apparatus shown isv only
the cup-shaped damping vane 58 and armature
illustrative and that the invention may be car
balancing arrangement 6| previously described
is used thereon. The lead-in spirals 60 and 88 45 ried out by other means.
What I claim as new and desire to secure by
Letters Patent of the United States is:
An alternating current electrical measuring in
strument comprising ‘a magnetic field core struc
in Fig. 8 are used. The opening 51 in support
35 which ‘in the frequency meter contained a 50 ture and energizing coil therefor, a moving coil
armature within the field produced by the field
removable armature stop is used in the watt
core structure, said armature having a tuned
meter to hold a screw which supports a ceramic
circuit and the instrument operation being due
armature stop 80 (Fig. 9) and a holding screw
to changes in the phase angle of the fluxes pro
ill entering from the rear of such opening is
threaded into support 35 to securely hold the 55 duced by the field and armature by reason of a
shift in the phase angle of the armature flux in
part 53 in correct position. The core is held in
response to a variable to be measured. and a sec
place between parts one of which is shown in
ondary coil on the field core, from which said
part at 82 (Fig. 9) which extend laterally from
armature circuit is energized by transformer ac
the support 35 just inside the armature coil and
tion from the field coil acting as a primaryin.
grasp the core ‘I! from the top and bottom.
order to maintain a substantially ?xed phase
In case the frequency meter is likely to be sub
relation between the field flux of the instrument
jected to considerable temperature variations, a
are here used in place of an iron vane for zero
restoring torque. The same armature assem
' bly support 35 and damping magnet SI, 52 shown
further improvement may be had by employing
- and the excitation voltage of said tuned arma- _
the circuit shown in Fig. 11 where the armature
circuit, including coils 2 and 3, is energized by 65
ture circuit.
'
ALLEN G. S'I'IMSON.
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