Electrical transmission or interconnection systems – Switching systems
Reexamination Certificate
2002-07-16
2003-05-13
Sircus, Brian (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
C307S125000, C361S160000, C385S100000
Reexamination Certificate
active
06563236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a feed line switching circuit for switching a feed line by energizing relays by feed current control, and more particularly to a feed line switching circuit suitable for a branching unit constituting an optical submarine cable system.
2. Description of Related Art
FIG. 7
is a circuit diagram showing a configuration of a conventional feed line switching circuit disclosed in Japanese patent application publication No. 7-34550/1995, for example. In
FIG. 7
, reference numerals
1
a
-
1
c
each designate a feed line for feeding repeaters and the like with a current;
2
a
-
2
c
each designate a power supply such as a DC constant current source; and the reference numeral
3
designates a ground.
The reference numeral
4
designates a feed line switching circuit for switching the feeding from the feeding across the feed lines
1
a
and
1
b
to the feeding across the feed lines
1
a
and
1
c
or vice versa by feed current control. In the feed line switching circuit
4
, reference numerals
5
a
-
5
c
designate terminals connected to the feed lines
1
a
-
1
c.
The reference symbol K
1
designates a relay connected between the feed lines
1
a
and
1
b;
K
2
designates a relay connected between the feed lines
1
a
and
1
c;
reference numerals K
3
and K
4
designates relays connected in series across the feed lines
1
b
and
1
c.
The relays K
1
-K
4
each consist of a vacuum relay or the like that operates in response to a feed current. The reference symbol k
1
-
1
designates a contact set of the relay K
1
; k
2
-
1
designates a contact set of the relay K
2
; reference symbols k
3
-
1
and k
3
-
2
each designate a contact set of the relay K
3
; and k
4
-
1
and k
4
-
2
each designate a contact set of the relay K
4
.
Next, the operation of the conventional feed line switching circuit will be described.
First, to achieve the feeding across the feed lines
1
a
and
1
b,
the power supplies
2
a
and
2
b
are driven so that the feed current flows from the power supply
2
a
to the power supply
2
b
through the feed line
1
a,
terminal
5
a,
relay K
1
, contact k
4
-
2
, contact set k
2
-
1
, terminal
5
b
and feed line
1
b.
As a result, repeaters (not shown) connected to the feed lines
1
a
and
1
b
are supplied by double-end feed. In this state, when the feed current reaches the working current of the relay K
1
, the relay K
1
actuates its contact set k
1
-
1
to open the connection across the feed lines
1
a
and
1
c,
and to close the connection between the relay K
3
and the feed line
1
c.
Furthermore, the power supply
2
c
is driven to pass the feed current through the ground
3
, relay K
3
, contact set k
1
-
1
, terminal
5
c,
feed line
1
c
and power supply
2
c.
As a result, the repeaters connected to the feed line
1
c
are supplied by single-end feed. When the feed current reaches the working current of the relay K
3
, the relay K
3
closes its contact k
3
-
1
and opens its contact k
3
-
2
, thereby self-holding the connection between the relay K
3
and the feed line
1
c.
Likewise, to achieve the feeding across the feed lines
1
a
and
1
c,
the power supplies
2
a
and
2
c
are driven so that the feed current flows from the power supply
2
a
to the power supply
2
c
through the feed line
1
a,
terminal
5
a,
relay K
2
, contact k
3
-
2
, contact set k
1
-
1
, terminal
5
c
and feed line
1
c.
As a result, the repeaters connected to the feed lines
1
a
and
1
c
are supplied by double-end feed. In this state, when the feed current reaches the working current of the relay K
2
, the relay K
2
actuates its contact set k
2
-
1
to open the connection across the feed lines
1
a
and
1
b,
and to close the connection between the relay K
4
and the feed line
1
b.
Furthermore, the power supply
2
b
is driven to pass the feed current through the ground
3
, relay K
4
, contact set k
1
-
1
, terminal
5
b,
feed line
1
b
and power supply
2
b.
As a result, the repeaters connected to the feed line
1
b
are supplied by single-end feed. When the feed current reaches the working current of the relay K
4
, the relay K
4
closes its contact k
4
-
1
and opens its contact k
4
-
2
, thereby self-holding the connection between the relay K
4
and the feed line
1
b.
In the conventional feed line switching circuit with the foregoing configuration, the impedance of the feed passage can sometimes vary because of the operation of the contacts, thereby varying the feed current flowing through the feed line switching circuit
4
.
For example, assume that the feeding across the feed lines
1
a
and
1
b
is carried out by the feed current control when a breaking of the optical submarine cable on the side of the feed line
1
c
takes place, and a shunt fault occurs in which the end of the optical submarine cable on the side of the feed line
1
c
is grounded by seawater. In this case, the feed current passes not only through the passage of the power supply
2
a
—relay K
1
—power supply
2
b,
but also through the shunt fault point—relay K
2
—relay K
1
—power supply
2
b
transiently. When the sum of the two feed currents reach the working current of the relay K
1
, the relay K
1
opens the contact set k
1
-
1
, thereby disconnecting the shunt fault point. Thus, at the time when the contact set k
1
-
1
activates, the impedance of the feed passage seen from the feed line
1
b
to the feed line switching circuit
4
increases, so that the feed current flowing through the feed line switching circuit
4
is reduced transiently.
Thus, the feed current flowing through the feed line switching circuit
4
is reduced when the feed current reaches the working current of the relay K
1
and the contact set k
1
-
1
is opened. As a result, the feed current flowing through the relay K
1
is reduced at the same time, and hence the relay K
1
can return to unenergized state again. In such a case, the relay K
1
will repeat the energized state and unenergized state (chattering), presenting a problem of disabling the switching of the feed line.
SUMMARY OF THE INVENTION
The present invention is implemented to solve the foregoing problem. It is therefore an object of the present invention to provide a feed line switching circuit and branching unit capable of positively switching the feed line with preventing the current reduction in the relay after it is energized, and hence capable of preventing its chattering.
According to a first aspect of the present invention, there is provided a feed line switching circuit for switching feeding by feed current control between feeding across a first feed line and a second feed line and feeding across the first feed line and a third feed line, the feed line switching circuit comprising: a relay that is connected between the first feed line and the second feed line, and operates in response to a feed current flowing through the relay; a first contact of the relay that closes when the relay is unenergized and opens when the relay is energized;, and a resistor that constitutes a series circuit with the first contact, which series circuit is connected in parallel with the relay, wherein a resistance r of the relay and a resistance R of the resistor are set to satisfy a relationship of
(
R
/(
r+R
))×
Ia<Ib
where Ia is a current value flowing through the second feed line immediately before operation of the relay, and Ib is a current value flowing through the second feed line immediately after the operation of the relay.
Here, the relay may further comprise a second contact that is connected between the first feed line and the third feed line, and that closes when the relay is unenergized and opens when the relay is energized.
Besides, each of the resistors may consist of any one of a single resistor, a combination of a plurality of resistors and an assemblage of other elements that provides resistance in its entirety.
According to a second aspect of the present invention, there is provided a feed line switching circuit for switching feeding b
Asakawa Kenichi
Kumayasu Satoshi
Nakagawa Eiichi
Sato Kazunori
Mitsubishi Denki & Kabushiki Kaisha
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rodriguez Calixto
Sircus Brian
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