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Патент USA US2114865

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April 19, 1938.
I
2,1 14,865
o. c. TRAVER
PEAK ALTERNATING CURRENT MEASURING APPARATUS
Filed Feb. 6, 1957
2 Sheets~Shect l
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JCJCOT‘Qey.
April 19, 1938.
2,1 14,865
10. c. TRAVER '
_IPEAK ALTERNATING CURRENT MEASURING APPARATUS
Filed Feb.- e, 1937
2_ sheets-sheet 2
Figm.
Figl l.
lhver'atof“:
Oliver~ C.Tr~avef7
His Attorney. -
atente Apr. 19, 1938
2,114,865
so STATES
PATENT OFFlC‘E‘
2,114,865
PEAK ALTERNATING CURRENT MEASURING
'
APPARATUS
.
-
Oliver 0. Traver, Drexel Hill, Pa, assignor to Gen
1 eral Electric Company, a I corporation of New
York
Application February 6, M37, Serial No. 124,398
9 Glaims. ' (61.1'75-183)
'My invention relates to current-measuring ap
paratus for use on alternating-current circuits
and particularly apparatus for measuring various
surge current values, components, and relations
5 which occur only momentarily during transients
caused by short circuits, lightning strokes, switch
apparatus for measuring the peak value of a cur
rent surge regardless of its polarity; Fig. 2 illus
trates apparatus for measuring the positive and
negative peak values of the current surges or
their sum or di?ercnce; Fig. 3 represents an oscil
lograph ‘ record' of .a typical transient current
ing, etc. Such measurements are of value to elec __ caused by a short-circuit condition on an alter
trical engineers in connection with problems that nating-current line; Fig. 4 shows a simpli?ed
concern the ‘safety, protection, and design of transient current pick-up circuit embodying the
10
various
electrical
apparatus, switching pro
cedure, maintenance of service, protection of op- '
erators in determination of the location of faults,
etc.
‘
'
.
, present invention; Fig. 5 illustrates connections 10
and apparatus assembly for three-phase .surge.
measurements; Figs.» 6 and 7 illustrate different
arrangements embodying phase-shifting devices
Animportant object of 'my invention is to pro- ’ ' for obtaining measurements of the maximum os
vide simple and reliable surge current-measur- - cillating component of surges; Fig. 8 represents 15
surge current curves explanatory of the opera
tion of Figs. 6 and 7; Figs. 9 and 10 show circuits
'for obtaining an approximate measurement ‘of
the sum of positive and negative components of
cost recti?er apparatus. ~
Another important object of my invention is to an oscillation‘; Fig. 11 represents a modi?cation 20
20 provide standard apparatus of the character.
of my-invention which includes tuned circuits
speci?ed which may be used in a large variety of ' whereby measurements indicative of the fre
ways for measuring numerous quantities without. quency of an oscillatory surge may be obtained;
burdensome installation and maintenance ex-_ and Fig. 12 represents the elements of a magnetic
ratio instrument for determining the average 25
25
Other objects of the invention will appear as frequency of an oscillatory surge using pick-up
magnets energized in the system of Fig. 11.
the description proceeds.
In Fig. 1, I have shown apparatus for measur»
In carrying my invention into e?ect, I make
use of the inexpensive copper oxide, or other type/ ing' the peak value of an alternating-current
surge that subsides too quickly to be measured by 30
30 of recti?er for segregating positive and negative
the conventional iorm of measuring apparatus.
surge currentcomponents and I use pick-up de
vices composed of units of permanent magnet In Fig. 1, l0 represents an alternating-current
material which are temporarily permanently line inwhich a current surge may occur due to a
magnetized in response to the segregated surge short circuit, a lightning stroke, or some otherv
current components under investigation. The transient condition. H is a'current transformer 35,.
strength of such permanent magnets can be which has its secondary connected througna full
measured at‘ leisure and the surge current wave recti?er bridge I! to the coil l3 of a special
values thus ascertained. Before any magnetic current-measuring device which gives a semi-per
pick-up device is used again, it is demagnetized.‘ manent indication of the maximum current that
ing apparatus which distinguishes between posi
tive and negative transient current values and
components without the necessity of using high
penses.
-
'
40 The degree‘ at which the magnetic pick-up de
has ?owed in line Ill.
The recti?ers used are of 40
vices are'magnetized by, the surge currents is
within the range belowv complete saturation, so
the inexpensive, dry, copper oxide contact type.
that the permanent magnet strength remaining
strument is made from ‘permanent magnet steel " I
current under investigation. Owing to the sim
plicity and low cost oi these devices and the ?exi
bility with which they may be used, a variety of
novel‘ and useful measurements become possible
direct current which flows in coil l3' from the 45
recti?er I2._ This pick-up core may be of the
The core l4,_or a portion thereof, of this in
in the pick-up device is proportional to the surge . so that it is permanently magnetized by the
by their use.
'
-
The features of my invention which are. be
nature of the magnetic pick-up elements de
scribed in United States Patent No. 1,942,052,
Faust et 9.1., January 2, 1934. The coil l3 must
have a su?icient number of turns as compared to 50
lieved to be novel and patentable will be pointed the cross-section of the pick-up core element vto
out in the claims appended ‘hereto. For a better cause proper magnetization thereof by a. surge
understanding of my invention, reference is made current when reduced by the current transformer
in the following description to the accompanying \ to a ‘value that‘ can be properly handled by the
55 drawings in which Fig. 1 illustrates measuring type '01.’ recti?ers used. The strength of the 55
2
2,114,865
permanent magnet thus produced will be propor
tional to the maximum current through coil I3
and, hence, to the maximum peak value of any
alternating-current surge that occurs in line l0.
Between the pole pieces of such permanent
magnet is an iron vane type of armature l5,
which is biased out of alignment between the pole
pieces by a spiral spring. The armature tends to
turn to align its magnetic vane with any ?ux
10 crossing between the pole tips and, hence, it will
produce a de?ection which is a measure of the
strength of the permanent magnet. Such
measurement de?ection will persist after. the
maximum surge current has passed until the
15 core It has been demagnetized. .
The instrument is provided with a scale l6 and
pointer I1 calibrated to indicate maximum surge
current values in line it. After a surge of a
predetermined magnitude has occurred and its
20 value is ascertained from reading the instrument,
it will be desirable to demagnetize the core I‘
to place the device in condition for measuring the
next surge that may'occur. For this purpose, we
may provide a second coil I8 which is to be ex
25 cited by a gradually decreasing value of alternat
ing current from a source IS, a rheostat 20 being
provided to control the demagnetizing current.
proposing changes in given systems to minimise
the effect of such disturbances.
Fig. 2 represents a device in which the positive
and negative current surge values are segregated
and arranged to energize separate coils of the
pick-up winding and to magnetize separate
permanent magnet core parts 23 and 24 shown
connected in series inv the magnetic circuit of the
measuring instrument. In this representation,
the pole pieces and the keeper 25 may be of soft 10
iron. If the cores 23 and 24 are magnetized while
in place, the keeper 25 should be removed until a
reading is taken. In this example, it will be
evident that the surge of one sign which we may
designate “plus.” will pass through. recti?ers 28 15
and 21 to magnetize core part 23, and the surge
of the “negative” sign will pass through recti?ers
28 and; 29 and magnetize core part 24. Thus,
there is full wave recti?cation. Where the core
parts 23 and 24 are connected to pass their ?uxes 20
in the same direction in the magnetic circuit, the
instrument will measure the sum of the plus and
_minus surges or the maximum value of the os
cillatory surge that is (I+max.) +(I—max.),
Fig. 3. After such measurement, core part 23
may be reversed to obtain a measurement corre
sponding to (I+max.)—-(I—max.). Thus the
This coil will normally be open-circuited and used summation measurement may be algebraic.
only when the instrument is to be demagnetiaed Then core parts 23 and 24 maybe replaced by soft
80 and its indication brought back to zero. It will iron parts, like part 25, and the'permanent mag 30
be understood that it is not intended that this net 23 placed where soft ‘iron core part 25 is
apparatus will be used to measure the ordinary full " in Fig. 2 to obtain a measurement of (I-i-max.)
load current of line l0 and, while such current will alone. Then, substitute permanent magnet 26
produce some magnetization of core iii and possi
in place of permanent magnet 23 in this last ex
.36 bly a slight de?ection of the instrument, this will
ample and obtain a measurement of (I-maxJ.
not interfere with its use for measuring occasional, Also, we might provide a soft iron shunt part for
much higher current surges because the strength one of the core parts 23 or 213 to obtain the
of a permanent magnet depends upon the maxi
measurements (I-i-max.) or (,I-max). The
mum value of the exciting direct-current ampere calibration of the instrument should be checked
40 turns and the device will be designed to produce ‘ under these different measurement conditions and 40
a substantial de?ection only after an overload cur
the calibration suitablylmodi?ed to give consistent
rent condition has occurred.
results if found necessary. It will be understood
If desired, the instrument pointer may be pro
that the permanent magnet core parts 23 and 25
vided with a target, shown in dotted hues at My may be magnetized in coils which are no part of
46 which, for low permanent magnet values, is
the instrument shown and, after being so mag 45
hidden from view by a screen 22. Such a target
netized, assembled in the magnetic circuit of the
will move into view from behind the screen when instrument, as explained above, to obtain any one
a surge of su?icient value to be interesting occurs or more of the measurements described. This is
and will indicate that the surge value should be represented in the simpli?ed recti?er magnetiz
50 recorded and the instrument demagnetized.
.
ing circuit of Fig. 4 where full wave recti?cation is 50
It will be evident that the device of Fig. 1 will obtained but only two recti?ers are required. In
measure the maximum current surge value
any case, where the secondary current of trans
whether it be positive or negative and will not former Ii is likely to be in excess of that which '
distinguish between positive and negative values. may be handled by a standard recti?er, a suit
55 Thus, it will measure the value (I+_max.) of the
able shunt Ila may be connected across the
oscillatory surge represented in Fig. 3. It may be secondary circuit as indicated in Fig. 4, or an
stated that the curve of Fig. 3 represents an os
auxiliary current transformer may be used as at
cillograph record of a typical short-circuit cur
65,.Flg. 5.
.
,
rent having positive transient displacements such
In Fig. 5, I have shown apparatus for mag
60 as often occur on alternating-current circuits
netizing six permanent magnet pick-up devices in
where the short circuit began at time t- The
dotted line d represents the nature of the dis
placement of the oscillatory surge fromthe zero
response to positive and negative surge currents
in the three lines of a three-phase power system.
- current line ll.
After about four oscillations,
the transient displacement or direct current com
ponent of the wave has practically all‘ decayed
away at time t’ and the time t to t’ may be con
sidered the time during which a. circuit breaker is
opening to clear the short at time t’ by which time
70 the surge current has reached a steady state and
the maximum negative value (I-max.) .. ' Experi
ence has taught engineers how to make use of the
values (I+max.) and (I-max.) in determining
the approximate lino location of the short circuit,
in designing proper line protective devices and in
The six pick-up core pieces of permanent magnet
material, such as core piece 23 of Fig. 2, being
initially demagnetized will be inserted in the six
pick-up coils 30 to 35. The recti?er units 36 to
‘I may be assembled in a stack as is customary
in assembling a number of small, dry disk type
copper oxide recti?ers. Where the line current
transformers 42, 43, and 44 are standard five 70
ampere secondary current transformers. addi
tional transformers 45, 43, and 41 may be in
serted between the line transformers and the
recti?er pick-up coil circuit to reduce the recti
?er currents expected to economically match the
_3
2,114,865
current rating of the standard sized copper oxide
dry disk recti?er. It will be evident from the
connections shown that pick-up coil 30 will be
pick-up coil 50 at the same. time the retarded
positive wave passes through recti?er bridge i2’v
to the pick-up coil and these components are
traversed by currents proportional to surge cur
rents of one sign in the primary of line trans
former 42 and that pick-up coil 3l- will respond
to surge currents of the opposite sign in the pri
mary of line transformer 42 utilizing recti?er
added. This recti?ed summation is represented
in the lower curves of Fig. 8 and it will be evident
that A1 max. plus B: max. andAz max. plus B1
max. are equal to and represent the distance In
from the tip of positive wave A to the tip of
units 38 and 31. The full line arrow heads repre
10 sent the current circuit for pick-up 001130 and the
dotted line arrow heads represent the current cir
cuit for pick-up coil 3!. The nature of current
flow and circuits for the remaining pick-up coils
' will be evident from the connections without fur
15 .ther explanation. It is seen, thatcthe number of
connections and recti?er units are reduced to a
minimum and that a compact, relatively low cost‘, ‘ ~
three-phase surge current measurement out?t is
'
provided.
Figs. 6 and 7 show embodiments of the inven
20
tion for obtaining a measurement of the maxi
mum oscillation surge component (IomaxJ , Fig. 3.‘
in a single pick-up device. -In Fig. 6, line lli_ is
negative wave‘ B.
_
.
' In Fig. 8, the two full waves of the surge have 10
been represented as of equal magnitude for the
sake of simplifying the explanation of Fig. 6.
If '
the surge is of usual character, the value In. will
vary, as is evident from Fig. 3 and, when apick
up magnet is inserted in coil 50 of Fig. 6 and a 15
surge such as is represented in Fig. 3 occurs, the
pick-up-magnet will be magnetized in accordance
with sul?stantially the maximumsurge oscillation
or (Iomax.) , Fig. 3.
The value (IumaxJ. is in this
case less than (I+max.) +(I—max.), and thus it 20
is seen that the arrangement of Fig. 6is for
measuring the former quantity although there
‘may be surges where these quantities happen to
provided with a current transformer 42. The
25 secondary of the current transformer is connected
to a step-down current transformer 45 and its
secondary is connected to parallel phase-shifting
full-wave recti?er circuits. One of these circuit-s
includes the inductance 48 in series with full-wave
be equal.
'
-
Fig. 7 shows a connection by means of which 25'
results similar to those obtained with Fig. 6 may
be had. . Inductance 48 and condenser 49 are
connected in series and in parallel with recti?er
bridges l2 and i2’, respectively. Current through
bridge I2 will be leading and current through 30
30 recti?er bridge I2’. The other parallel circuit
includes the condenser 49 in series with full-wave ' bridge I!’ will be lagging to accomplish the phase
recti?er bridge i2. The direct-current output
circuits of both recti?er bridges are connected in
parallel to the pick-up coil 50 such that the direct
current from both bridges ?ows in the same direc
tion in coil 5t.
.
'
Assume now that line it is traversed by an
' oscillatory surge having a positive displacement
such as is represented in the top curve of Fig. 8,
A representing the positive component and B the
shifts desired. Another difference, which; how
ever, could be applied to Fig. 6, is that the cur
rents from the two recti?er bridges are fed to
separate pick-up coils 52 and 53 comprising the
‘pick-up winding. When these coils are connected
to produce flux in the same direction in the pick
up magnet, the results‘will be the same as with
Fig. 6. However, one coil may be reversed to ob- -
tain a measurement in the pick-up magnet of 40
(I-l-max.)——_(I—max.), Fig. 3, or A-B, Fig. 8,
‘the maximum displacement component of the
nected phaseeshifting recti?ercircuits. Positive. surge. This may also be termed the maximum
direct-current component of the surge.
surge component A is advanced in phase in trav
In Figs. 9 and 10, I have shown arrangements’ 45
ersing condenser circuit 49 and may be repre
negative component of such surge.
InFig. 6, this '
surge is impressed on both of the parallel con
sented as A1 in the middle set of
. Likewise, the negative component
in phase and is correspondingly
' represented‘ at B1 in the middle
for accomplishing an approximate summation
curves, Fig. 8.
measurement of the positive and negative compo
B is advanced nents of an oscillation by using inductance in the
displaced and recti?er pick-up circuit to prolong the effect of
set of curves,
a current impulse of one sign so that the follow
Fig. 8. The surge in traversing the circuit in
ing impulse of opposite sign will be superimposed
cluding inductance $8‘ is retarded in phase and thereon to a large degree. Thus, in Fig. 9, as
its positive and negative components may belrep ' sume a positive current ?ow through a large in
resented at A2 and B2 in the central group of ductance 66 ‘followed by a negative current ?ow
curves, Fig.- 8. If the phase shift in each case ' through pick-lup coil 55 of small inductance. The 55
55 is 90 degrees, and it may be made su?iciently
positive current impulse will die out slowly be
near that amount for good measurement results, ' cause of the inductance 64 and thus tend to feed
the positive'portions of the ‘advanced wave and current through the pick-up coil 65 during the 7
the negative portions of the retarded wave will
occur
simultaneously.
Likewise,
the
negative >
portions of the advanced wave will occur simul
taneously with the positive portions of. the re
tarded wave. Thus, A1 and B2 occur simultane
ously and A: and B1 occur simultaneously. ‘The
negative components in passing through the rec
ti?er bridges are recti?ed and ?ow to ‘pick-up
coil 50 simultaneously with those positive com
ponents which occur simultaneously. Thus, the
retarded negative wave B2 is recti?ed in bridge
unit l2’ simultaneously with the passage of the
70 advanced positive wave Al through bridge 12 and
corresponding currents ?ow to and are added in
pick-up coil 50 simultaneously. Likewise, 180 de
75
grees time phase sooner or later, advanced nega
tive wavev B1 is recti?ed in bridge I! and ?ows to ’
negative current impulse therethrough. This will
produce a summation magnetization effect on the
pick-up‘ magnet proportional to the sum of the
positive and negative impulses.
In Fig. 10, the pick-up magnet has two coils
66 and 61, and inductances 68 and 69 are em
ployed in series with the pick-up coils and recti
65
?ers as shown. .1 Assume a positive ‘impulse
through inductance 68 and coil 66 followed by a
negative impulse through inductance 69 and coil
61, both tending to magnetize the pick-up mag
net in the same direction. Due to the induct 70
ances, the impulses will die out slowly and will '
thus exist in the pick-up coils in overlapping re
lation, producing a summation measurement
e?'ect.
'
'
'
‘
‘ In Fig. 11", I have shown an‘ embodiment of my 75
4
2,114,865
invention for distinguishing between high and
low-frequency oscillatory surges. It will be noted
current recti?er means-included in the circuit be
that‘pick-up coils 54 and“ are connected in the ' tween said transformer secondary and pick-up
recti?er circuit to pick up positive and negative
_ surge components which ?ow through the series
connected predominating tuning inductance 56.
Also pick-up coils 51 and 58 are connected in par
allel with pick-up coils 54 and IS in the recti?er
circuits but in series with a predominating tuning
10 condenser 59.
The two tuned circuits thus
formed are connected in parallel to be energized
"15
from the secondary of current transformer II.
There may also be ‘included plus or minus surge
pick-up coils ill and Cl through which all of the
surge current of corresponding sign must ?ow.
An oscillatory current will divide between the two
tuned circuits in a manner which depends upon
the frequency of the surge and the manner in
which the circuits are tuned. Let us assume, for
20 example, that the condenser circuit 59 is tuned
to a high frequency HF, and that inductance cir
cuit It is tuned to pass lower frequency surges
.
Let us further assume that the tuning is
not so sharp but that both circuits will pass some
25 current at intermediate frequencies. It will now
be apparent that the various pick-up device
measurements will show the following:
30
Device 60 maximum positive surge current.
Device 54 maximum positive Ll‘I surge current
component.
.
Device 57 maximum positive HF surge current
component.
'
_
, Device 61 maximum negative surge ‘current
component.
' Device 55maximum negative LF surge current
component.
'
Device 58 maximum negative HF surge current
a component.
From a comparison of high and low~frequency
40 component measurements, we can determine ap
proximately the average frequency of the surge
oscillation. If desired, the pick-up magnets 54,
55, S‘Land 5| may be transferred to a magnetic
vane ratio instrument as represented in Fig. 12,
45 which then measures the ratio between the re—
sultant strength of the LF magnets 54 and 55
and the resultant strength of the HF magnets 51
and 56. and gives an indication calibrated in
terms of frequency. Also, in Fig. 12, the negative
50 surge measurement magnets 55 and 58 may be
removed to obtain a ratio measurement of only
the positive 'high and low-frequency pick-up
magnets in terms of fr'cguenc . Similarly, pick
up magnets I4 and I‘! may be removed to obtain
,55 a comparison measurement of magnets 55 and
n.- Such an instrument may be provided with
coil for the. purpose of permitting current to flow
in only one direction in said coil, and a mag
netizable core element of permanent magnet ma
terial within said pick-up coil.
2. Apparatus for use in measuring the char
acter of current surges comprising, a current
transformer, a pick-up winding connected to be
energized from the secondary of said transformer, v10
full-wave recti?er means included in circuit be
tween said transformer secondary and pick-up
winding, andcore means of permanent magnet
material positioned to be magnetized by the recti
?ed current ?owing in said winding.
3. Apparatus for use in measuring the char
acter of surges comprising, a current transformer,
pick-up winding means energized from the sec
ondary of said transformer, dry contact type me
tallic recti?er means for rectifying the current 20
supplied by said transformer to said winding
means, and a core element for said pick-up wind
ing made of a material capable of being perma
nently magnetized by and in proportion to the
maximum recti?ed current impulse in the pick 26
up winding means.’
4. Apparatus for use in measuring the char
acter of surges occurring on polyphase alternat
ing-current circuits comprising, a current trans
former for each phase of such circuit, a pair of 80
pick-up coils for each transformer connected in
parallel with the secondary winding thereof, and
a recti?er connected in series with each pick-up
coil such that the current impulses ?owing in one
direction in a transformer secondary ?ows only 85
in one pick-up coil of its pair and the current
impulses flowing in the opposite direction in this
transformer secondary ?ows only in the other
pick-up coil of its pair, all of said recti?ers being
of the copper oxide type and arranged in a stack. 40
5. Apparatus for use in measuring the char
acter of current surges comprising, a current
transformer having a primary traversed by the
surge to be investigated, and a secondary for ob
taining a lower current proportional to the surge 45
current, a pick-up coil provided with a core ele
ment of a material capable of being permanently
magnetized for determining the maximum posi
tive component of a surge, a second pick-up coil
and core element similar to thel?rst for deter
mining the maximum negative component of .the 50
same surge, said pick-up coils being connected in
parallel to the secondary winding of said trans
former, and rectifier means included in series
with each pick-up coil for directing the positive
and negative surge currents induced in the sec
a scale calibrated in per cent positive surge com
ondary of said transformer to the positive and
ponent for comparing positive and negative pick
negative component pick-up coils, respectively. '
up units which have been magnetized accord
_6. Apparatus for measuring characteristics of
ingly, for example, pick-‘up units Cl and ’ 6|,‘ current
.surges "comprising, a current-reducing 60
Fig. 11.
'
transformer having a primary forming a part of
In accordance with the provisions of the pat
a surge-current circuit, a pair of pick-up coils
ent statutes, I have described the principle of energized from the secondary of said transformer,
operation of my invention, together with the recti?er means included in the energizing circuits
apparatus which I now consider-“to represent the of said coils for segregating reverse current im
best embodiment thereof, but I desire to have it pulses from said transformer and directing cur
‘Understood that the apparatus shown is only ' rent-impulses of onesign
only through one pick
illustrative and that the invention may be car
.up coil and current impulses of the other sign
only through the other coil, removable core ele
ments for said coils composed of material capable
Letters ‘Patent of the United States is:
of being permanently magnetized by and in pro-' 70
1. Apparatus for use in measuring the char
portion to the maximum current impulse through
acter of current surges comprising. a current said coils, and a magnetic field measuring instru
transformer, a pick-up coil connected to be ener
75 gized from the secondary of said transformer, ment designed to compare the relative strengths
of the permanent magnet field of said core ele
76
ried, out by other means.
. What I claim as new and desire to secure by
15
2,114,865
5
ments and calibratedtherewith and with said
current transformer and pick-up coils to give an
indication of the magnitude and polarity of the
maximum surge current through the primary of
said transformer.
7. Apparatus for use. in measuring the char
acter of current surges comprising, a current
transformer, full-wave recti?er means connected
with the secondary winding of said transformer,
substantially simultaneously as recti?ed current
impulses in said pick-up winding means, and core
means of permanent magnet material magnetized
by said pick-up winding means in accordance with
the summation of the substantially simultaneous 5
10 a pick-up winding, and core means of permanent
nected to be supplied from the secondary of said 10
transformer, pick-up winding means supplied by
recti?ed currents from said pair of recti?er
magnet material positioned to be magnetized by
the current ?owing in said winding, said winding‘
being energized from said recti?er meansv in such
manner as to magnetize said core‘ means substan
tially in accordance with the summation of re
verse current impulses ?owing in the secondary‘
of said transformer.
8. Apparatus for use in measuring the char-_
acter of current surges comprising, a current
20 transformer, full-wave recti?er means connected
with the secondary of said transformer, pick-up
recti?ed current impulses therein.
'
9. Apparatus for determining the character- .
istics of current surges comprising, a current
transformer, a pair of full-wave recti?ers con
means, phase-shifting means associated with the
supply connections to said recti?er for advanc
ing the current impulses through one recti?er 15'
and retarding the current impulses through the
other recti?er to the extent necessary to cause
consecutive reverse current impulses from said
transformer to' be recti?ed substa'ntially'simul
taneously by said pair of recti?ers, and core 20'
means of permanent magnet material positioned
winding means connected to be energized by
in said pick-up winding so as to be magnetized in ‘
recti?ed current from said recti?er means, phase
accordance with the'summation of the substan
tially simultaneous recti?ed current impulses”
shifting means included in the aforesaid connec
tions for causing consecutive reverse current im
pulses from said transformer secondary to appear
OLIVER o. TRAVER.
26
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