close

Вход

Забыли?

вход по аккаунту

?

Патент USA US3090008

код для вставки
May 14, 1963
3,089,999
1‘ K. DORTORT
BIAS FOR CURRENT TRANSFORMER
Filed Oct. 20, 1958
ICE-.5.
IE5.
153:1
J; 35
if
34
33/
ED.FO mm.mmweE
MCAU6%mmT
NET
EFFECTIVE
NEGATIVE
MAGNETIZING
CURRENT
CURRENT
FCROUEO RTN
RRC
WG
MC
RMDTRw
57/“,
ADJUSTABL E
PHASE
SHI FTER
SQUARE
WAVE
'— GENERATOR
36
15-. 5_
”w m
BY
35'
W
E.4” ,/
m.”a
m
MMM
/J
United States Patent 0
3,089,999
re
‘ ICC
Patented May 14, 1963
1
2
3,089,999
ble manner in which the current transformer of FIGURE
3 can be constructed.
FIGURE 7 shows a second embodiment of my inven
BIAS FOR CURRENT TRANSFORMER
Isadore K. Dortort, Philadelphia, Pa., assignor to I~T~E
Circuit Breaker Company, Philadelphia, Pa., a corpo
ration of Pennsylvania
Filed Oct. 20, 1958, Ser. No. 768,312.
6 Claims. (Cl. 323—56)
My invention relates to a highly accurate current trans
former which utilizes a D.-C. bias and is a continuation
in-part application of my copending application Serial No.
587,122, ?led May 24, 1956, now Patent No. 2,883,603,
tion for an A.-C. type of current transformer.
Referring now to FIGURE 1, a commutating reactor
core 20 is shown as having a winding 21 connected in
series with a contact 22. Contact 22 may be mechani
cally driven into and out of engagement in synchronism
with ‘the A.-C. source 23 so as to deliver an average D.-C.
10 voltage to the D.-C. load 24.
As may be seen with reference to Patent No. 2,693,569
issued November 2, 1954 entitled Commutating Reactor
entitled Cancellation of Break Step Current ‘for Contact
to Edward J. Diebold, as the load current 24 decreases
through a zero value, the commutating reactor 20 will
Converters and assigned to the assignee of the instant
invention.
15 unsaturate to thereby provide a low current step within
which the contact 22 may be opened.
As is well known in the art, the accuracy of current
So that this contact may interrupt a substantially zero
transformers is limited by the magnetizing current of the
current, I provide a current transformer having the sec
transformer. That is, the ampere turns generated in the
ondary Winding 25 to measure the magnetizing current
of the commutating reactor 20 and to thereafter impress
this secondary output current across the contact 22 in
series with a current limiting means 26. The current
mary current magnitude so that it is not possible to make
transformer having secondary 25 is more speci?cally a
the secondary current vary in direct proportion to the
current transformer which could have a one-to-one turns
primary current. Therefore, a certain inaccuracy is in
25 ratio so that it will induce a current as shown by the
herent in current transformers.
arrow which is of the same shape and magnitude as the
The principle of my invention is to substantially sup
magnetizing current of commutating reactor winding 21
ply the current transforrner magnetizing current from an
secondary winding is equal to the ampere turns in the
primary winding minus the magnetizing current ampere
turns. The later value is relatively independent of pri
auxiliary source whereby the primary and secondary cur
and flows through the contact 22 in a direction opposite
to the magnetizing current. Hence, complete cancella
rents will vary linearly with respect to one another.
In a preferred embodiment of my invention, the cur 30 tion of the current through contact 22 may be obtained.
The current limiting valve 26 is required in the cir
rent transformer core is formed of a material having a
cuit so that after contact operation of contact 22 to a
relatively rectangular hysteresis loop and the primary cur
disengaged position, the reverse voltage appearing there
rent is a unidirectional pulsating current whereby its mag
across will be impressed across this current limiting valve
netizing current can be supplied from a simple D.-C.
source. However, if the primary current is an A.-C., 35 26. Hence, valve 26 is, as will be shown hereinafter,
provided with the property of opposing current flow there
then the bias could be an A.-C. pulse type bias which
through when the contact 22 is opened and still provides
is reversed each half cycle so that the bias is in a proper
a substantially zero impedance circuit for current flow
direction for each half cycle. Furthermore, if the core
of smaller value in the same direction during the break
is made of a relatively non-rectangular hysteresis loop
step from the current transformer secondary winding 25.
material as by using a normal transformer iron core,
FIGURE 2 shows a second embodiment of my novel
then the bias could be formed of a current which initiates
invention wherein a current transformer seen generally
this relatively complex shape so that the magnetizing cur
at 27 is comprised of a core 28, a primary winding 29,
rent of the current transformer is always supplied from
and a secondary winding 34}. An auxiliary current trans
the auxiliary bias circuit.
Accordingly, a primary object of my invention is to 45 former is then provided comprising the primary winding
31 and the secondary winding 32, this secondary wind~
provide a highly accurate current transformer.
ing 32 supplying the compensating current for the con
Another object of my invention is to provide a novel
current transformer in which its magnetizing current is
tact 22.
supplied from an auxiliary source.
It may be desirable that a system such as that seen
A further object of my invention is to provide a novel 50 in FIGURE 2 be utilized wherein the turns ratio of the
current transformer in which an auxiliary source of power
current transformer is not the exact one to one turns
ratio described in conjunction with FIGURE 1, but a
supplies the magnetizing current in the same direction as
turns ratio which is so adjusted as to have an output
the primary current.
These and other objects of my invention will become 55 current from secondary winding 32 which is of a slightly
greater magnitude than the primary current through wind
apparent from the following description when taken in
ing 29. This may be desirable in order to assure that
conjunction with the drawings, in which;
FIGURE '1 shows a recti?er circuit which requires a
current transformer means of the type to which my in
a very slight positive current flows through the contact
22 during the break~stcp so that in the event of an arc
during contact disengagement, this arc will be extinguished
vention is directed.
upon a subsequent passage through zero current. More
FIGURE 2 shows a modi?cation of the circuit of FIG
over, the current transformer .27 is by this means ap
URE 1.
proximately compensated for its magnetizing current.
FIGURE 3 schematically illustrates my novel current
A turns ratio which is slightly different from an exact
transformer construction.
one-‘to-one ratio would in a practical case be di?icult to
65
FIGURE 4 illustrates the operating characteristic of
obtain when utilizing a single current transformer as
the current transformer of FIGURE 3 for the case of
shown in FIGURE 1 in view of the relatively high cur
circuit of the type of FIGURE 1 or 2.
rents conducted in mechanical recti?er or contact con~
FIGURE 5 speci?cally shows the current transformer
verter devices. That is to say, the number of turns of
of FIGURE 3 as applied to a circuit of the type of FIG 70 the primary and secondary windings will be substantially
limited so that a ?rst current transformer of FIGURE 2
URE 1.
which may be a one-to-one ratio current transformer may
FIGURE 6 is a cross-sectional diagram of one possi
3,089,999
3
cause energization of winding 31 of an auxiliary current
transformer, which winding may have a relatively high
number of turns.
Hence, winding 32 may have a number of turns only
slightly different from the number of turns of winding 3];
to thereby effect a turns ratio slightly less than one-to
one between the primary winding 29 of the ?rst current
4
and the secondary current is larger than the primary by
that amount.
FIGURE 5 shows the type of current transformer of
FIGURE 3 as being applied to the contact converter of
FIGURES 1 and 2 and further shows a particular type
of current limiting valve which comprises the resistor 40,
reactor 41 and diode 42. This system operates in a man
transformer and the second winding 32 of the auxiliary
ner similar to the system described in copending applica
current transformer. Hence, the output current of sec
tion Serial No. 490,319. Reactor 41 is charged by the
ondary winding 32 may be slightly greater than the mag 10 inverse cycle current i1 which ?ows due to the inverse
netizing current of the commutating reactor 2-3, which
voltage across the contact 22 while it is open and will
flows in current transformer primary windin g 29, and the
maintain a current flow in the forward direction of
net current through contact 22 will always be a very
diode 42, this current being shown as the current i2 when
the inverse voltage disappears, as when the contact closes.
It is understood that in order to have an exact or sub 15 In the event of unsaturation of the commutating reactor
stantially exact reproduction of the wave shape of the
core 20, the current transformer secondary winding 34
magnetizing current for the output of the compensating
will cause a compensating current I}, to ?ow through the
circuit, the current transformer utilized must be highly
contact 22 in a direction to buck down the current i2
linear in the period during which that current flows.
?owing through diode 42.
In order to provide a current transformer having this 20
By providing the type of valve means shown in FIG
high degree of linearity, I propose the use of a current
URE 5, it is now seen that during the ?ow of compen
transformer as may be seen in FIGURE 3 wherein the
sating current that this current is merely effective to buck
primary winding 33 which is the bus connection between
down an existing current through a semi-conductor and
the commutating reactor and the contact is surrounded
in view of this, it will be a very small impedance.
25
by a core 34 constructed of highly saturable type mate
Hence, when the net contact current id, which is the dif
rial. The core 34 is preferably constructed to have a
ference between the magnetizing current of commutat
relatively small radial thickness to thereby effect a highly
ing reactor winding 20 which flows through the contact
rectangular hysteresis loop for the core.
22 and the compensating current of winding 34, is broken,
The current transformer shown in FIGURE 3 may be
the circuit will have an extremely small impedance in
constructed in the manner shown in FIGURE 6 wherein 30 parallel with the disengaging contacts and the voltage
‘the secondary bus is comprised of portions 33a and 33
drop due to the compensating circuit in parallel with con
which are connectible by the threaded current carrying
tacts 22 will be negligible.
connection 330. The core 34 which is preferably con
As has been desecribed above, my novel invention may
structed of a wound tape is then positioned to encircle
35 be applied to an A.-C. type of current transformer. This
small positive value.
the current carrying protrusion of the bus portion 33a
construction is schematically set forth in FIGURE 7 in
and carries therearound the single turn windings 35 and
36.
which an A.-C. system including voltage source 50 and
load 51 has a current transformer 52 connected therein
In FIGURE 3, the secondary winding 35 (which is
for measuring the current of the system. Current trans
equivalent to winding 25 of FIGURE 1) is to be con 40 former 52 is constructed of a core 53 which is prefer
nected to the contact 22 of FIGURE 1 through the cur
ably of a highly saturable type of material with primary
rent limiting means 26 and winding 36 is connected to
be energized through the adjustable resistor 37 to a
D.-C. voltage source as the battery 38. This type of con
struction offers a current transformer of an extremely
high degree of linearity as may be understood with refer
ence to FIGURE 4.
In FIGURE 4, the hysteresis loop of the core 34 of
FIGURE 3 is seen with the magnetizing current of the
winding 54, secondary winding 55 and a compensating
winding 56 wound thereon. The secondary winding 55
is connected to an output load means 57 which could in
45 clude an instrument for indicating current in the usual
manner.
The compensating circuit for energizing the
compensating winding 56 includes an auxiliary voltage
source 57 which could be derived from the main voltage
source 56. The voltage of source 57 is connected through
commutating reactor superimposed thereupon, and seen 50 an adjustable phase shifter 58 and a square wave gen
as the curved line 39. The D.-C. bias winding 36 is then
erator 59 so that a relatively square wave current is sup
so energized as to magnetize core 34 in the same direc
plied to compensating winding 56. Since both the phase
tion as it Would be magnetized by the ?ow of magnetiz
ing current from the commutating reactor. Hence, the
shifter 58 and square wave generator 59 are well known
devices and their structure would be obvious to those
skilled in the art, details of their construction are not
net effective magnetizing current of the current trans
former assembly is the small difference between the bias
current of Winding 36 and the magnetizing current of
given herein.
core 34, which is the very low value seen in FIGURE 4.
a rectangular hysteresis loop similar to that illustrated in
The core 53 of current transformer 52 preferably has
Since the core 34 has a highly rectangular shape, then
FIGURE 4. The true magnetizing current of this core
this effective magnetizing current, as is further seen in 60 is essentially a square wave current which is in phase with
FIGURE 4, is relatively constant throughout the dura
the developed voltage of the transformer. The phase
tion of unsaturation of the core 34. In view of the very
relationship between the magnetizing current of the core
low e?ective magnetizing current of the current trans
and the primary current of winding 54 is determined by
former of FIGURE 3, it is then realized that an extreme
the power factor of the load 57 connected to core wind
ly linear current transformer device is obtained; a char 65 ing 55'. Generally, this power factor is ?xed except un
acteristic which is very desirable for either of the em—
der extreme load conditions and can be readily deter
bodiments of FIGURES l or 2.
mined. However, the phase shifter 58 is preferably inter
When the bias is equal to the uncorrected magnetizing
current of the current transformer, the secondary cur
posed between the auxiliary voltage source 57 and com
pensating winding 56 so that the phase of the compensat
rent is exactly equal to the primary current. When the 70 ing current is adjustably controlled to be in phase with
bias is smaller than the transformer magnetizing current,
the magnetizing current of the core 53.
the net magnetizing current is a small positive value and
The operation of the circuit of FIGURE 7 will be
the secondary current is smaller than the primary by that
identical within each half cycle to the operation of the
amount. If the bias is greater than the transformer mag
circuit of FIGURE 3. That is to say, when the mag
netizing current, the net magnetizing current is negative,
netizing current of core 53 is positive, winding 56 will
3,089,999
conduct a compensating current which Will serve as a
source of magnetizing current for the core.
Thus, the
current in winding 54 and the current in winding 55 will
be substantially directly proportional to one another.
When the magnetizing current of core 53 reverses, the
square Wave compensating current applied to winding 56
will reverse and the same compensating process described
above will continue.
Clearly, the basic concept shown in FIGURE 7 may
6
turns to supply the same ampere turns that would be
required of said primary winding in the absence of said
compensating means.
4-. A conilensating means for a current transformer;
said current transformer comprising a magnetic core hav
ing a primary winding and a secondary winding thereon;
said secondary winding having a current ?ow induced
therein which is functionally related to the current flow
through said primary Winding; said compensating means
be modi?ed for cases in which winding 56 will carry any 10 including a current source, and winding means associated
with said magnetizable core to generate ampere turns in
shape current to compensate for a similar shaped mag
said magnetizable core; said current source generating a
netizing current of ‘the current transformer core.
current having substantially the same shape as the mag
In the event the circuit is such that phase angle of load
57 is variable, it will be obvious to those skilled in the
art that feed-back control means from load 57 to phase
shifter 58 could be applied so that the proper phasing of
the energization of winding 56 will be maintained with
respect to the magnetizing current of the core.
In the foregoing, I have described my invention only
in connection with preferred embodiments thereof. Many
variations and modi?cations of the principles of my in
vention within the scope of the description herein are
netizing current required for said magnetizable core; said
winding means being constructed to have sufficient turns
to supply the same ampere turns that would be required
of said primary Winding in the absence of said compen
sating means; said core being of relatively high perme
ability material having a rectangular hysteresis loop; said
current source generating a relatively constant current.
5. A compensating means for a current transformer;
said current transformer comprising a magnetic core hav
ing a primary winding and a secondary winding thereon
speci?c disclosure herein but only by the appending 25 and a rectangular hysteresis loop; said secondary wind
ing having a current ?ow induced therein which is func
claims.
tionally related to the current flow through said primary
I claim:
winding; said compensating means including a winding
1. Means for reducing the effective magnetizing cur
obvious. Accordingly, I prefer to be bound not by the
rent of a current transformer; said current transformer
comprising a core of saturable type material, a primary
winding, a secondary winding and a D.-C. bias winding;
said primary winding being energizable from a source of
unidirectional pulsating current; said D.-C. winding being
energizable from a D.-C. power source; said core of
wound on said magnetic core and a current source there
for to magnetize said core in the same direction as the
current through said primary winding Which is to be
reproduced in said secondary winding; said compensat
ing means generating the magnetizing ampere turns nor
mally supplied by said primary winding; said current ?ow
saturable type material having a relatively small radial 35 through said primary winding being an alternating cur
rent; said magnetizing ampere turns generated by said
thickness to effect a highly rectangular hysteresis loop
compensating
means being a square wave current.
for said core; said D.-C. bias winding and said primary
‘6. A compensating means for a current transformer;
winding being connected to magnetize said saturable core
said current transformer comprising a magnetic core hav
in the same direction during that portion of the primary
wave where high accuracy is desired responsive to ener~ 40 ing a primary winding and a secondary winding thereon
gization by their respective sources.
2. A compensating means for a current transformer;
said current transformer comprising a magnetic core hav
and a rectangular hysteresis loop; said secondary winding
having a current ?ow induced therein which is function
ally related to the current ?ow through said primary
winding; said compensating means being magnetically
ing a primary winding and a secondary winding thereon
and a rectangular hysteresis loop; said secondary Winding 45 connected to said magnetic core to magnetizc said core
in substantially the same direction as the current through
having a current ?ow induced therein which is function
said primary winding which is to be reproduced in said
ally related to the current ?ow through said primary
secondary Winding; said compensating means generating
winding; said compensating means including a winding
the magnetizing ampere turns normally supplied by said
wound on said magnetic core and a source of current
for said winding to magnetize said core in the same di 50 primary winding; said current flow through said primary
rection as the current through said primary winding which
is to be reproduced in said secondary winding; said com
pensating means generating the magnetizing ampere turns
winding being an alternating current; said magnetizing
ampere turns generated by said compensating means
being a square wave current; and phase shift means con
nected to said compensating winding for controlling the
phase shift of said magnetizing ampere turns generated
55
of current supplying a constant current over any half
by said compensating means with respect to the induced
cycle.
voltage of said magnetizable core.
3. A compensating means for a current transformer;
normally supplied by said primary winding said source
said current transformer comprising a magnetic core hav
References Cited in the ?le of this patent
UNITED STATES PATENTS
ing a. primary winding and a secondary winding thereon;
said secondary Winding having a current ?ow induced 60
therein which is functionally related to the current flow
through said primary winding; said compensating means
including a current source, and winding means associated
with said magnetizable core to generate ampere turns in
said magnetizable core; said current source generating 65
a current having substantially the same shape as the
magnetizing current required for said magnetizable core;
said winding means being constructed ‘to have su?icient
2,746,003
Wegener ____________ __ May 15, 1946
2,773,133
Dunnet ______________ __ Dec. 4, 1956
2,866,158
Petzinger ____________ __ Dec. 23, 1958
OTHER REFERENCES
IBM Technical Disclosure Bulletin, August, 1958,
page 7.
'
‘
Документ
Категория
Без категории
Просмотров
0
Размер файла
602 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа