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Патент USA US2115595

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April 26, 1938.
2,115,595
S. TANIA]
‘ SYNCHRONIZING APPARATUS
Filed May 9, 1936
2 Sheets-Sheet l
Fig. I.
Inventor‘:
Seiichi Tan'iai,
b9
537%
His Attorneg.
April 26, 1938.
s. TANlAl
2,1 15,595
SYNCHRONIZING APPARATUS
Filed May 9, 1956
2 Sheets-Sheet 2
Fig. 2.
Fig.3.
Inventor: ‘
Seiichi Taniai,
Time
by”
5194M
His Attorneg.
Patented Apr. 26, 1938
_
2,115,595
UNITED STATES PATENT OFFICE
2,115,595
SYNCHRO-NIZING APPARATUS
Seiichi Taniai, Yokohama, Japan, assignor to
General Electric Company, a corporation of
New York
Application May 9, 1936, Serial No. 78,814
In Japan October 9, 1935
13 Claims. (Cl. 171-118)
_ My invention relates to improvements in synchronizlng apparatus and has for an object the
controlled by a relay 5 having normally open con
tacts which are closed when the relay is ener
provision of improved synchronizing apparatus
gized.
for so controlling the operation of connecting
5 two alternating current circuits as substantially to
I
For controlling the closing of the circuit break
er 3 so as to effect a connection of the circuits l '5
eliminate the possibility of effecting a connection
and 2 under synchronous conditions thereof, any
at the wrong instant.
In order to avoid any appreciable disturbance,
suitable manual or automatic means, examples
of which are well known to the art, may be em
two alternating current circuits should be con-
ployed.
I have chosen to illustrate an automatic 7
10 nected when their electromotive forces are substantially alike in phase and frequency. It is
means which is similar to the synchronizing ap- 1O
paratus disclosed in United States Letters Patent
also preferable that they be substantially alike
in magnitude. Inasmuch as the closing operation
takes an appreciable time, it is desirable to start
15 when the frequency difference is small enough
and also suf?ciently prior to phase coincidence to
1,630,754, issued August 14, 1928, but it Will be
obvious that the application of my invention is
not limited to this particular apparatus. Thus,
a synchronizing relay 6 is connected to be ener- 15
gized by corresponding voltages of the circuits I
allow for the time necessary to make the connection. The closing time of circuit breakers for
high voltage, large capacity circuits is so long
that the frequency di?erence may undergo such
changes as to render the completion of a closing
operation undesirable. This is also true, even
with shorter closing-time circuit breakers, where
the circuits are subject to large frequency varia-
and 2 through suitable means such as potential
transformers 1 and 8 so as to operate in depend~
ence on the sum of and the difference between the
two voltages. The normally open contacts 9 and
iii of this relay will close When the frequency dif- 2O
Terence and the voltage and Phase difference be
tween the electro-motive forces of the circuits i
and 2 are below predetermined values. Besides
25 tions as, for example, in some low head hydraulic
plants. Also errors in judgment of the operator
in manual. control or errors of the synchronizing
the synchronizing relay 6, there may be employed #25
an auxiliary synchronizing relay H whose. ener
sizing Winding iS Connected to the Potential trans
2.o
device in either manual or automatic control may
make it undesirable to» complete the closing oper-
f0rmer5 T and 3 S0 as to be energized in accord“
ance with the vector difference between two cor
30 undesirable
ation. In order
closing,
to eliminate
I provide,the
in accordance
possibility ofwith
an
responding
and 2. Thiselectromotive
relay can be forces
set to close
of the
itscircuits
contactsl
my invention, means for determining the state of
synchronism after the closing operation has been
started such that if conditions are unfavorable,
the closing operation is interrupted or checked.
30
My invention will be better understood from
the following description when considered in connection with the accompanying two sheets of
drawings, and its scope will be pointed out in the
'40 appended claims.
i2 when the phase difference between the elec
tromctive forces of the circuits is less than a pre
determined value. Thus, if the. contacts 9, H),
In the accompanying drawings, Fig. 1 illustrates diagrammatically an automatic synchronizing arrangement embodying my invention;
Fig. 2 illustrates diagrammatically a modi?ca45 tion of the embodiment of my invention Shown
in Fig. I; Fig. 3 is a switch closing time-travel
curve explanatory of my invention; and Fig. 4 is
a voltage vector diagram explanatory of my invention.
50
In Figs. 1 and 2, two alternating current circuits l and 2 are arranged to be connected by
suitable switching means, such as a circuit breaker 3, which is illustrated as having a mechanically trip~free operating mechanism including a
closing coil 4. The circuit of this coil may be
synchronizing relays 6 and N, there may be
used a normally open circuit-closing auxiliary re
lay l3, which has a resistance M in the circuit of
its Operating Winding '5, a portion of the resis
tance being short-circuited when the contacts 45
9. l9. and '2 0f the Synchronizing relays are
simultaneously closed. For controlling the relays
5 and I3, there may be provided a normally closed
circuit-opening relay 16 which opens and closes
its contacts I‘! with a de?nite time delay when its 0
operating coil I8 is energized and ?le-energized.
For energizing the various control devices, there
is provided an auxiliary control bus CB which
may be energized from a D. C. source. The oper
ating coil 15 of the auxiliary relay I3 is normally 55
and I2 of relays 6 and H are connected in series >
in a control circuit, as shown, the sticking of the 35
contacts of one will not cause false synchronizing
if the Contacts 0f the other are Open
In order to obtain a control dependent on the
instantaneous positions of the contacts of the 40
2
2,115,595
energized in a circuit from one side of the control
bus CB through a conductor l 9, the resistance M,
the winding l5 of the auxiliary relay l3, and the
contacts I‘! of the time limit relay I6 to the other
side of the control bus CB. However, as the re
sistance l4 limits the value of the current in this
circuit, the auxiliary relay I3 is not su?iciently
energized to close its contacts 20 and 2 I.
When the voltage and phase, and frequency
10 differences between the eleotromotive forces of
the two circuits l and 2 decrease to the values for
which the synchronizing relays 6 and H are set
to respond, their contacts 9, Ill and I2 will be
closed at some instant. A part 22 of the re
15 sistance I4 in the circuit of the operating wind
ing [5 of the auxiliary relay i3 is thereby short
circuited and the operating coil I5 is energized
sufficiently to cause the relay l3 to close its con
tacts 20 and 2|, thus completing the circuits
20 of the control relay 5 and the time limit relay
I6 respectively. Even though some one of the
contacts 9, l9 and I2 opens the resistance l4
passes enough current to maintain the relay l3
in its contact closing position after it has been
25 operated to this position. The circuit of the
control relay 5 is from. one side of the bus CB
through the conductor IS, the operating coil 23
of relay 5, the contacts 20 of the auxiliary relay
l3, and the contacts I‘! of the time limit relay
30 IE to the other side of the bus CB. The energiza
tion of the control relay 5 effects the closing of
the contacts 24 ofthis relay to complete the cir~
cuit of the closing coil 4 of the circuit breaker as
follows: From one side’ of the bus CB through
the conductor 19, the closing coil 4 and the con
tacts 24 of the control relay 5 to the other side of
the bus CB, whereby to effect the closing of the
circuit breaker 3. The time limit relay It will
open its contacts I‘! a predetermined time after
40 the circuit breaker 3 is closed to de-energize the
operating coil 23 of the control relay 5 and the
operating coil l5 of the auxiliary relay I3, These
relays therefore open their contacts 24, 20 and
21. The opening of the contacts 2| de-energizes
45 the operating coil I8 of the time limit relay i6,
which returns to its normal condition to close its
contacts after a predetermined time.
This com~
pletes the synchronizing operation with the ap
6 and H are set to respond, these relays operate.
Thus it will be assumed that the relays 6 and II
have their contacts closed when OM reaches the
position Om preceding phase coincidence by an
angle 0, where, assuming a substantially constant
frequency difference, 6 is an angle corresponding
to the phase change of the voltage OM during the
time required for the operation of the auxiliary
relay 13 after its operating coil I5 is energized
and until its contacts 2d are closed; the time re
quired for the operation of the control relay 5
after its operating coil 23 is energized by the clos
ing of the auxiliary relay contacts 20 until the
contacts 24 are closed; and also the time required
by the circuit breaker 3 after its closing coil 4
is energized and until its contacts are closed.
This angle 9 may be called the operating phase
difference angle. In other words, at the phase
10
angle position Om the synchronizing relays 6
and H have their contacts 9, It, and I2 closed 20
to short-circuit the portion 22 of the resistance
l4 whereby to energize fully the operating coil
l5 of the auxiliary relay [3. Although the time
required until the operating coil l 5 is fully ener
gized after a portion 22 of the resistance 14 is
short-circuited has been omitted in the con
sideration of the phase angle 6, this angle can be
made larger to correspond to such added time, if
necessary. In other words, the operating phase
difference angle 0 can be so selected by adjust 30
ment of the relays that when OM has reached
the position Om, both synchronizing relays will
have their contacts closed to short-circuit the
portion 22 of the resistance M whereby to ener
gize the operating coil 15 of the auxiliary relay
l3, and as OM proceeds from the position Om
toward OE, the auxiliary relay l3 and the control
relay 5 will successively operate, and then the
operating mechanism of the circuit breaker 3 will
start the closing movement so that when OM has
turned far enough to coincide with OE, the oper
ating mechanism of the circuit breaker will com
plete its motion and close the contacts.
While synchronizing apparatus such as de
scribed is similar to that heretofore known to the
art, it has disadvantages when used in connec
tion with alternating current circuits subject to
rapid frequency changes and in high-voltage
paratus so far described.
_ large-capacity alternating current circuits. Sim
The circuit breaker 3 does not close it con
ilar disadvantages arise in synchronizing ar
tacts immediately upon energization of its clos
rangements which are dependent in part on the
ing coil but an appreciable time thereafter, which skill of the operator. For example, assuming that
may be in case of large circuit breakers, a sec
the alternating current circuits l and 2 are high
ond or more. Thus as shown in Fig. 3, when the voltage large-capacity circuits, then the circuit
55 closing coil is energized, the operating mechanism
breaker 3 used for connecting these circuits must
of the circuit breaker will start its closing motion also be of high voltage and large capacity. This
after an interval of time t. After another inter
means in general that a considerable length of
val of time T, the contacts of the circuit breaker time is required by such a circuit breaker for
50
engage. Likewise, the relay 5, even though it is
60 of the so-called instantaneous type, will not in
stantly close its contacts when its operating coil
is energized but will require some time to close
its contacts.
These intervals of time required for the actions
65 of the circuit breaker and the relay are considered
in the vector diagram of Fig. 4 wherein OE and
OM respectively represent the Voltage vectors of
the alternating current circuits l and 2. It will
be assumed that one of these, OE, is still, while
70 the other, OM, is rotating in the direction indi
cated by the arrow a; that is, approaching OE and
reducing the phase difference. When the phase
and frequency differences between the electro
motive forces become less than the predeter~
75 mined values for which the synchronizing relays
closing the circuit; that is, the time interval 1?
plus T covering the period after the closing coil 60
is energized until its contact is closed. In other
words, when using a circuit breaker for high
voltage large-capacity circuits the operating
phase difference angle 6 of the synchronizing re
lays has to be selected relatively large. Conse
quently, the possibility of the occurrence of the
following dif?culties is greater. Thus after the
synchronizing relays have operated the fre~
quency difference and phase difference between
the electromotive forces of the circuits l and 2 70
may change. In other words, after OM has
passed the position of Om, the angular velocity of
OM may change and its direction of rotation may
even reverse. Nevertheless, the circuit breaker
closing operation has been started and the oper
75
2,115,595
ation will procede as intended to result in ?nally
closing the breaker at an instant when OM does
not coincide with OE. That is, the circuits are
not in synchronism. The consequences are not
only a shock to the two systems to which the two
circuits belong but also to the circuit breaker
itself. It will be obvious therefore that practical
di?iculties arise in the application of synchro
nizing apparatus as described to circuits wherein
the frequency is subject to rapid changes and
10 particularly
in connection with circuits requiring
large relatively slowly closing circuit breakers
and in synchronizing arrangements dependent on
the skill of the operator.
ing operation of the circuit breaker will continue
until OM reaches the inphase position OE when
the contacts of the circuit breaker will close.
On the other hand, if the frequency difference
between the electromotive forces of the circuits
I and 2 has changed, either in magnitude or di
rection, after the synchronizing relays 6 and II
have operated and the action for closing the cir
cuit breaker has been started; that is, after OM
has passed the position of Om, the operation will 10
be as follows: When the closing operation of the
circuit breaker mechanism has arrived at the
1.5 In view of the foregoing, I propose, in accord
ance with my invention, to provide improved syn~
chronizing apparatus embodying a switch for
connecting two alternating current circuits and
frequency dependent synchronizing devices used
20
3
in the control of such switch so that the closing
operation of the switch may be started without
the probability of danger to circuits subject to
frequency changes and also with high-voltage
large-capacity circuit breakers. In accordance
25 with my invention, I provide means dependent
on the relative frequencies of the electromotive
forces of vthe circuits I and 2 for interrupting
the closing operation of the connecting means 3
when the difference between the frequencies so
point A, indicated in Fig. 3, the auxiliary switch
28 will be closed. At this instant, if OM is in the
position OP or past it, the trip coil 21 of the cir 15
cuit breaker 3 will not be energized, because the
contact 28 of the relay 25 is open and the clos
ing operation of the circuit breaker may be com
pleted. But if at this instant OM has not reached
the position OP, the trip coil 21 of the circuit 20
breaker 3 will be energized because the contact
28 of the relay 25 is still closed. The circuit of
the trip coil 21 is from one side of the control
bus CB, the circuit breaker auxiliary switch 26,
the trip coil 21, the contacts 28 of the relay 25, 25
the contacts 20 of the relay I3, and the contacts
I‘! of the relay I6 to the other side of the bus
CB.
Consequently, the closing operation of the
an auxiliary switch 26 on the circuit breaker 3
and suitable tripping means such as a trip coil
circuit breaker mechanism will be interrupted or
checked by tripping at an intermediate point of 30
its travel. This supervising action continues
throughout the closing motion of the mechanism.
In other words, the relay 25 will re-examine the
synchronous condition of the alternating current
circuits I and 2 in the course of the closing op 35
eration of the circuit breaker 3 after some point,
such as A, has been passed, and if the phase dif
2'1‘ for the circuit breaker 3. The auxiliary switch
28 is open when the circuit breaker is open and
difference, angle 0 and also smaller than a pre
30. varies as substantially to change the time before
the inphase condition occurs. Thus, as shown in
Fig. 1, I provide a relay 25 responsive to the phase
relation between the electromotive forces of the
circuits ! and 2 and thus dependent on the rela
35 tive frequencies of these electromotive forces,
40 so associated with the circuit breaker as to close
when. the closing mechanism of the circuit breaker
has started its closing operation or when the clos
ing operation has advanced to some predeter
mined extent, such, for example, as indicated
by the point A in Fig. 3. The phase difference re
lay 25 which is also illustrated as of the sum and
difference type disclosed in the patents referred
to, is connected to he energized from the poten—
tial transformers l and 8, and has normally closed
50 contacts 28 which may be arranged directly in
the circuit of the trip coil 21. The relay 25 is to
be so set that under safe synchronizing condi
tions, it will open its contact 28 when OM reaches
some position OP between Om and 0Q, where
(‘A Car. 0Q corresponds to the position of OM when the
circuit breaker mechanism has traveled to the
extent indicated by the point A in Fig. 3 and the
auxiliary switch 26 is closed.
Thus, in accordance with my invention, after
60 the synchronizing relay 6 and the auxiliary syn
chronizing relay I I have operated and the switch
closing operation has been started, if OM has
passed the position Om and the frequency dif
ference between the electromotive forces of the
l) circuits has not changed; that is, the speed and
direction of OM have not varied, the following
operations will occur: When OM reaches the
position OP, the relay 25 will open its contacts
2%; and when the closing movement of the circuit
70 breaker has progresed to the point A of Fig. 3,
OM will have reached the position OQ and the
auxiliary switch 26 of the circuit breaker 3 will
be closed. However, as the contact 28 of the relay
25 has already opened, the trip coil 21 of the cir
cuit breaker 3 will not be energized, and the clos
is
ference angle is smaller than the operating phase
determined angle on, it will permit the closing 4.0
operation to continue, but if not, it will inter- '
rupt the closing operation and regardless of the
energization of the closing coil 4, the circuit
breaker 3 is tripped. Obviously, it is essential that
the circuit breaker 3 be so arranged that it is 45
either electrically or mechanically trip-free.
the embodiment of my invention shown in Fig. 2,
a normally open circuit-closing time limit relay
29 is connected to be energized in parallel with
the operating coil 23 of the control relay 5. The 50
circuit closing time limit action of this relay is ' ~
so chosen that it will close its contacts 30 when
the closing mechanism of the circuit breaker has
started its closing motion or the closing motion
has advanced to a predetermined point, for ex 55
ample, as indicated by the point A in Fig. 3. In
this embodiment of my invention, tripping of the
circuit breaker will be effected if at the given point
in the circuit breaker closing operation OM has
not reached the position OP because the contacts to
28 of the relay 25 will be closed, and the time
limit relay will close its contacts 30. The trip
ping circuit is from one side of the control bus
CB through the trip coil 21, the contacts 30 of
the time limit relay 29, the contacts 28 of the .65
relay 25, the contacts 20 of the relay I3, and the
contacts I‘! of the relay I6 to the other side of
the bus CB.
Obviously, a certain time is required from the
energization of the trip coil 2'! of the circuit 70
breaker until the circuit breaker is fully tripped.
If this time corresponds to T’ shown in Fig. 3,
then the tripping will be effected after the cir
cuit breaker has been closed. Under certain con
ditions, it may be considered that even though
2,115,595
the frequency and phase differences were to be
come larger, the differences would not be great.
Accordingly, there might be cases where it would
be more convenient not to have the tripping of
. the circuit breaker after the point B.
In such
cases, the auxiliary switch 25 of Fig. 1 or the time
limit relay 25 would be arranged to close at some
point between A and B such that the time be
fore closure would be greater than the time T’.
10
It will be obvious that in accordance with my
invention I provide means for redetermining the
synchronous condition in connection with the use
of heretofore known synchronizing apparatus so
that in the course of the closing operation of the
circuit breaker, the phase difference of the elec
tromotive forces of the circuits to be synchronized
may be determined and if its value is found not
less than the predetermined value at which the
synchronizing apparatus is to operate, the clos20 ing operation of the circuit breaker may be im
mediately checked as if the operating phase dif
ference angle were diminished from 6 to a.
Therefore, synchronizing devices embodying my
invention can be used without worry in circuits
having large frequency variations, in high-power
high-voltage alternating current circuits and in
synchronizing arrangements depending at least
in part on the skill of the operator.
While I have shown and described my inven
tion in considerable detail, I do not desire to be
limited to the exact arrangements shown, but
seek to cover in the appended claims all those
modi?cations that fall within the true spirit and
scope of my invention.
What I claim as new and desire to secure by
Letters Patent of the United States is:
1. In combination, two alternating current cir
cuits, means for connecting said circuits, means
for actuating said connecting means, synchroniz
ing means dependent on the relative frequencies
of the electromotive forces of the circuits for ini
tiating the operation of said actuating means be
fore the inphase condition by a time substantially
equal to the time of the closing operation of said
45
connecting means, and means dependent on the
relative frequencies of the electromotive forces
of said circuits for preventing the actuating
means from completing an initiated closing op
eration of said connecting means when the rela
tion between the frequencies differs in a prede
55
termined manner substantially to change the time
before the inphase condition occurs.
2. In combination, two alternating current cir
cuits, means for connecting said circuits includ
ing a circuit breaker having a trip-free operat
ing mechanism, means dependent on the relative
frequencies of the electromotive forces of the cir
cuits for starting a closing operation of said
mechanism before the inphase condition by a time
substantially equal to the time of the closing op
eration, and means dependent on the relative fre
quencies of the electromotive forces of said cir
cuits for tripping said mechanism when the re
lation between the frequencies differs in a pre
determined manner substantially to change the
time before the inphase condition occurs.
3. In combination, two alternating current cir
cuits, means for connecting said circuits, means
for actuating said connecting means, synchro~
nizing means for initiating the operation of said
actuating means when the phase difference and
frequency difference between the electromotive
forces of said circuits are below predetermined
Values, and means for preventing the actuating
means from completing an initiated closing op
eration of said connecting means when the fre
quency difference between the electromotive
forces of the circuits differs in a predetermined
manner from said predetermined value during
the closing operation of said connecting means.
4. In combination, two alternating current cir
cuits, means for connecting said circuits includ
ing a circuit breaker having a tripping mecha
nism, means for starting a closing operation of
said circuit breaker when the phase difference
and the frequency difference between the elec-'
tromotive forces of said circuits are below pre
determined values, and means for tripping said
mechanism prior to the closing of the contacts of
the circuit breaker when the frequency difference 15
between the electromotive forces of the circuits
differs in a predetermined manner from said pre
determined value at a different predetermined
phase difference.
5. In combination, two alternating current
circuits, means for connecting said circuits,
means for actuating said connecting means, syn
chronizing means for initiating the operation of
said actuating means at a predetermined phase
difference between the electromotive forces of the
circuits when the frequency difference of said
electromotive forces has a predetermined value,
and means for preventing the actuating means
from completing an initiated closing operation
of said connecting means when the frequency dif
ference between the electromotive forces differs in
a predetermined manner from said predetermined
value at a smaller predetermined phase differ
ence.
6. In combination, two alternating current cir
cuits, a trip-free circuit breaker for connecting
said circuits, means for starting a closing opera
tion of said circuit breaker when the phase dif
ference and the frequency difference between
the electromotive forces of said circuits are be
low predetermined values, and means for tripping
said circuit breaker prior to the closing of the
contacts thereof when the frequency difference
between the electromotive forces of the circuits
differs in a predetermined manner from said pre
determined value at a smaller phase difference
than that at‘ which the closing operation was
started.
7. In combination, two alternating current cir
cuits, a trip-free circuit breaker for connecting
said circuits, means for starting a closing opera
tion of said circuit breaker when the phase dif
ference and the frequency difference between the
electromotive forces of said circuits are below
predetermined values, and co-operating means
for tripping said circuit breaker prior to the clos
ing of the contacts thereof when the frequency
difference between the electromotive forces of
the circuits differs in a predetermined manner
from said predetermined value at a smaller phase
difference than that at which the closing opera
tion was started including a circuit breaker aux
iliary switch closeable at an intermediate point
in the closing operation of the circuit breaker
and a synchronizing relay connected to be ener 65
gized from said circuits.
8. In combination, two alternating current cir
cuits, a trip-free circuit breaker for connecting
said circuits, means for starting a closing
operation of said circuit breaker when the
phase difference and the frequency difference
between the electromotive forces of said circuits
are below predetermined values, and co-operating
means for tripping said circuit breaker prior to
the closing of the contacts thereof, when the fre
2,115,595
quency difference between the electromotive
forces of the circuits differs in a predetermined
manner from said predetermined value at a
smaller phase difference than that at which the
closing operation was started including a trip
circuit and means for controlling said tripping
circuit including a synchronizing relay connect
ed to be energized from said circuits and a time
limit relay operative to complete a circuit con
10 trolling operation at an intermediate point in the
closing operation of the circuit breaker.
9. In combination, two alternating current cir
cuits, means for connecting said circuits, means
for actuating said connecting means, synchroniz
15 ing means for initiating the operation of said
actuating means, and means dependent on the
phase relation of the electromotive forces of said
circuits for preventing the actuating means from
completing an initiated .closing operation of said
20 connecting means prior to‘ actual closure.
10. In combination, two alternating current
circuits, means for connecting said circuits,
means for actuating said connecting means, syn
chronizing means for initiating the operation of
25 said connecting means when the phase difference
and the frequency difference between the elec
tromotive forces of the circuits are less than pre
determined values, means for preventing the
actuating means from completing an initiated
closing operation of said connecting means a pre
determined time before actual closure, and means
dependent on the phase relation of the electro
motive forces of the circuits operative under pre
determined circuit conditions to permit the com
35 pletion of an initiated closing operation of said
connecting means.
11. In combination, two alternating current
circuits, means for connecting said circuits,
means for actuating said connecting means, syn
40 chronizing means for initiating the operation
5
of said actuating means, means for preventing
the actuatingv means from completing an in
itiated closing operation of‘ said connecting
means a predetermined time before actual clo
sure, and means responsive to the phase relation
between the electromotive forces of the circuits
operative at a predetermined phase difference to
permit the completion of an initiated closing op
eration of said connecting means when said phase
difference occurs prior to said predetermined 1O
time.
12. In combination, two alternating current
circuits, means for connecting said circuits,
means for actuating said connecting means, syn
chronizing means for initiating the operation of
said actuating means, and means dependent on
the phase relation of the electromotive forces of
said circuits for preventing the actuating means
from completing an initiated closing operation of
said connecting means when the phase difference
between the electromotive forces exceeds a pre
determined value at a predetermined intermedi
ate point in the closing operation of said con
necting means.
13. In combination, two alternating current
circuits, a trip-free circuit breaker for connecting
said circuits, means for starting a closing opera
tion of said circuit breaker when the phase dif
ference and the frequency difference between the 30
electromotive forces of said circuits are below
predetermined values, and means dependent on
the phase relation of the electromotive forces of
said circuits for interrupting the closing opera
tion of said circuit breaker when the phase dif 35
ference between the electromotive forces exceeds
a predetermined value at a predetermined point
in the closing travel of the circuit breaker mecha
nism.
SEIICHI TANIAI.
40
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