Compressed gas, high tension circuit breaker, with operating energy assisted by the thermal effect of the arc

The invention relates to a compressed gas high tension circuit breaker in which the energy required for operation is assisted by the thermal effect of the arc, the circuit breaker comprising fixed main contacts and fixed arcing contacts, a moving assembly comprising moving main contacts and moving arcing contacts, a blast nozzle, and a thermal volume in which the gas pressure increases under the effect of heating due to the arc which extends between the arcing contacts when the separate, the circuit breaker including the improvement of means for responding to the pressure existing in said thermal volume (3, 35) to exert a greater force on the moving assembly (9) than the forces exerted thereon due to its resistance to movement, said means including a differential piston arrangement.

The present invention relates to a compressed gas high tension circuit 
breaker in which the operating energy is assisted by the thermal effect of 
the arc. 
BREAKER OF THE INVENTION 
Circuit breakers of this type are already known in which a thermal volume 
is provided whose temperature, and consequently whose pressure, increases 
considerably under the effect of the arc which is established at the 
moment the arcing contacts are separated. 
On the zero crossing of the current to be interrupted the gas in the 
thermal volume expands and blasts the arc. 
The gas blast of thermal origin is generally combined with a gas blast of 
mechanical origin which is obtained by virtue of the moving parts of the 
circuit breaker causing a piston to move relative to a cylinder. 
The pressure generated by the arc in the thermal volume opposes 
displacement of the moving parts of the circuit breaker. In other words, 
although the arc is energetically and effectively blasted, this result is 
obtained at the expense of an additional energy requirement for moving the 
circuit breaker components when breaking a circuit. 
Preferred embodiments of the invention provide a thermal blast circuit 
breaker requiring as little operating energy as possible. 
German published patent specification No. 2 847 221 describes a circuit 
breaker having a compression chamber in which the gases heated by the arc 
are directed into the space lying between the outer casing of the circuit 
breaker and the compression chamber and are caused to exert a force on a 
ring which is fixed to the moving equipment. 
This arangement reduces the energy required to operate the circuit breaker 
to some extent. However, the expansion volume available to the gases is 
relatively large and the pressure which can be exerted on the ring is 
relatively small. 
Further, there is a danger in conveying hot gases to the vicinity of the 
outer envelope of a circuit breaker in that unwanted arcing may be 
provided. 
Preferred circuit breakers in accordance with the invention avoid these 
drawbacks. The hot gas used to assist the opening operation remains 
confined within a relatively small volume and within components which are 
at the same potential. 
SUMMARY OF THE INVENTION 
The present invention provides a compressed gas high tension circuit 
breaker in which the operating energy is assisted by the thermal effect of 
the arc, the circuit breaker comprising fixed main contacts, fixed arcing 
contacts, a moving assembly comprising moving main contacts and moving 
arcing contacts, a gas blast nozzle, and a thermal volume in which the gas 
pressure increases under the heating effect of the arc which is 
established on separation of the arcing contacts, the circuit breaker 
including the improvement of a volume delimited by first and second fixed 
pistons, first and second cylinders belonging to said moving assembly, and 
an end plate which is common to both cylinders, said volume delimited by 
said pistons and said second cylinder being in communication with said 
thermal volume, and said first cylinder being maintained at the pressure 
extending within the remainder of the circuit breaker.

MORE DETAILED DESCRIPTION 
In FIG. 1, reference 1 designates an envelope of electrically insulating 
material which encloses the active portions of a circuit breaker which is 
cylindrically symmetrical about a longitudinal axis XX. 
The inside of the envelope is filled with a dielectric gas having a high 
arc-quenching power, e.g. sulfur hexafluoride, at a pressure of a few 
bars. Reference 2 designates the volume between the envelope 1 and the 
active portions of the circuit breaker, and reference 3 designates a 
volume surrounding the axis XX. 
The circuit breaker comprises a fixed assembly 4 comprising fixed main 
contact fingers 5 and a tubular fixed arcing contact 6. The end of the 
tube has a portion 6A made of material which withstands arcing (e.g. 
tungsten). The fized assembly includes bores 6B and 7 for putting the 
volume 3 into communication with the volume 2 in order to evacuate and 
diffuse hot gas after an arc has been interrupted. 
Reference 8 designates the annular volume lying between the fixed main 
contacts 5 and the fixed arcing contact 6. 
The moving assembly 9 of the circuit breaker comprises a tubular moving 
main contact 10 and arcing contact fingers 11. These contacts are fixed to 
a cylindrical structure comprising a plurality of concentric tubular parts 
12, 13, 14 and 15. 
The tube 15 has the finger 11 fixed to one end thereof and has its other 
end connected to operating means (not shown). The tubes 13, 14, and 15 are 
interconnected and closed by an end plate 16, whereas the tubes 12 and 13 
are interconnected by an end plate 17 which leaves an annular passage 
around the tube 15. A nozzle of insulating material 18 is fixed to the end 
plate 16 and has a throat-delimiting portion 18A, and when the circuit 
breaker is closed it comes into contact with the fixed arcing contact. 
Ducts 20 made inside the nozzle, and bores through the tube 13 put the 
volume 3 into communication with an annular volume 22 between the tubes 12 
and 13 when the tube 6 has left the nozzle. 
Finally, the circuit breaker includes two fixed annular pistons 24 and 25 
which are engaged respectively in the volume 26 lying between the tubes 13 
and 14 and the volume 27 lying between the tubes 14 and 15. 
The piston 24 is fixed to rods such as the rod 28, while the piston 26 is 
fixed to a tubular rod 29 which extends along the annular passage between 
the end plate 17 and the tube 15. The rods 28 and 29 are fixed to a common 
metal block 30 which is itself connected to an electricity connection 
point (not shown). A sealing ring 29B seals the volume 32 lying between 
the pistons and the end plate 17. 
The volumes 22 and 32 communicate with each other via bores 13A through the 
tube 13. 
The rods 28 have longitudinal channels 28A and transverse orifices 28B and 
28C therethrough in order to put the volume 26 into communication with the 
volume 2. 
Sliding electrical contacts 33 provide electrical contact between the end 
plate 17 and the tube 29. 
The end plate 17 has a non-return valve 34 whose function is explained 
below. 
Let the cross-sectional area of the annular volume 27 be designated by S1 
and the cross-sectional area of the annular volume 32 be designated by S2. 
Wide orifices 16A put the volume 27 into communication with the volume 35 
lying between the nozzle and the moving arcing contacts. 
The volume 3 is reduced by a disk-shaped part 15A which is fixed to the 
tube 15. Holes 15B provide communication between the volume 3 and the 
volume 2. 
Finally, holes 14A through the tube 14 allow equilibrium to be established 
between the pressures in the volumes 26 and 27 when the circuit breaker is 
engaged. 
The circuit breaker operates as follows: 
in its closed position, as shown in FIG. 1, current passes through the 
contacts 5 and 10, the tubes 12 and 13, the end plate 17, the contacts 33, 
the tube 29, and the block 30; 
the circuit breaker is opened by displacing the moving assembly comprising 
the contacts 10 and 11, the nozzle 18, and the tubes 12 to 15 to the right 
(as shown in the drawing). 
When the main contacts separate, and before the arcing contacts 6 and 11 
separate, electric current passes through the arcing contacts 6 and 11, 
the end plate 16, the tubes 12 and 13, the end plate 17, the contacts 33, 
the tube 29, and the block 30. The calibrated valve 34 opens to allow the 
volume 32 to fill without slowing down the movement. When the arcing 
contacts 6 and 11 separate, as shown in FIG. 2, an arc 40 is struck 
between said contacts. 
The gas in the volume 35 is compressed firstly by the mechanical effect of 
the piston 25 and secondly because of the temperature rise due to the arc. 
The increased pressure established in this manner in the volume 35 is 
conveyed via the ducts 20 and 22 to the volume 32. 
This pressure acts on the area S2 of the volume 32, which area is larger 
than the area S1 of the volume 27. The valve 24 closes. By virtue of the 
ducts 28A and the holes 28B and 28C the pressure in the volume 26 remains 
constant and equal to the pressure in volume 2. 
As a result, the force exerted on the end plate 17 by the gas in the volume 
32 is greater than the resistance to motion produced by the gas in the 
volume 27. In other words, the greater the energy of the arc, the greater 
the increase in pressure and the greater the operating energy applied to 
the moving assembly. This results in quicker arc extinction since the 
moving assembly is accelerated by the arc instead of being slowed down by 
the arc. After the arc has been extinguished, the hot gases escape via the 
holes 6B and 15B and the space 41 which opens between the nozzle 18 and 
the contact 6. 
A thin portion 29A of the tube 29 which comes level with the hole 15 at the 
end of circuit breaker opening, provides additional flow volume which is 
sufficient for the required gas flow. 
FIG. 3 shows a variant in which the volume 35 is no longer connected to the 
volume 22 via a passage through the nozzle, but rather via a non-return 
valve 50 made of insulating material and capable of sliding in an annular 
cavity 51 made in the nozzle and resiliently biased by springs such as 52. 
When the pressure in the volume 35 reaches a suitable value, the valve 50 
opens and thereby puts the volume 32 under pressure. 
When the pressure falls, after the arc has been extinguished, the springs 
close the valve. The hole 51A at the bottom of the cavity serves to reduce 
the pressure behind the valve. 
In the variant shown in FIG. 4, the volume 22 has been omitted. Pressure is 
conveyed to the volume 32 from the volume 3 via holes 15B, the volume 60 
lying between the tubes 29 and 15 (with the gap between these tubes being 
increased in this case), and holes 29D made through the tube 29 close to 
the piston 25. 
The tube 29 is thickened at 29C in order to limit the pressure losses of 
volume 60. 
Bleed holes 13B serve to return the volume 32 to the internal pressure of 
the circuit breaker after the arc has been extinguished. 
FIG. 5 shows a variant embodiment in which the circuit breaker includes a 
semi-moving assembly 100 which is resiliently biased by a spring 101 which 
is fixed to a fixed assembly referenced 70. 
The fixed assembly is connected to an electricity connection point (not 
shown) and comprises a tube 71 fixed to a ring 103 against which the 
spring 101 is pressed. The end of the tube 71 has arcing contact fingers 
72. The fixed assembly further comprises concentric tubes 73, 74, and 75. 
The tube 74 is extended by a portion 74A which serves as the main fixed 
contact. The tubes 74, 75, and 71 share a common end plate 76 having a 
nozzle 78 fixed thereto. The tube 73 has an end plate 79. Reference 81 
designates the volume lying between the tubes 74 and 75, reference 82 
designates the volume lying between the tubes 75 and 71, and reference 83 
designates the volume lying between the nozzle 78 and contacts 72. 
The moving assembly comprises contact fingers 90 which are protected by 
tube 91, together with a tubular arcing contact 92 which is terminated by 
a portion 92A made of material which withstands the effects of arcing. The 
tube 92 is connected to a circuit breaker electrical contact point (not 
shown) and also to a circuit breaker operating member (likewise not 
shown). 
The tube 92, the fingers 90 and the tube 91 are connected by an annular 
portion 93 having large orifices 93A therethrough in order to put the 
volume 94 lying between the moving contacts 90 and 92 into communication 
with the volume 2 lying outside the moving assembly. 
A disk 92B connected to the tube 92 and a disk 71B fixed to the tube 71 
limit the extent of the volume 3 close to the axis of the circuit breaker. 
The semi-moving assembly comprises two tubes 101 and 102 interconnected by 
an end plate 103. The tube 101 which is terminated by insulating portion 
101A slides around the tube 73. The tube 102 slides around the tube 71, 
and bears a piston 105 having two portions of different cross-section, one 
of which slides between the tubes 74 and 75 and the other of which slides 
between the tubes 75 and 71. 
The volume lying between the piston 105 and the end plate 79 is designated 
by 107. It communicates via the volume 80 between the tubes 73 and 74, via 
holes 74B and 74C and via at least one duct 78A through the nozzle with 
the region in which the arc will be formed. 
The piston has channels 105A passing therethrough which put the volume 81 
to the pressure existing outside the active portions of the circuit 
breaker via the space lying between the tubes 102 and 71, and via the 
holes 71A through the tube 71. 
A sealing ring 79A provides sealing between the tube 102 and the end plate 
79. The holes 103A through the end plate 103 allow free relative 
displacement between the moving assembly and the semi-moving assembly. 
The end plate 79 has a non-return valve 79B arranged so that it does not 
open unless the pressure in the volume 107 is less than the pressure in 
the volume 2. 
This circuit breaker operates in a manner similar to those described above. 
When breaking an arc, the pressure increase in the arcing zone is 
transmitted to the chamber 107, thereby displacing the semi-moving 
assembly which is already being urged by the spring 101, and thus causes 
an energetic gas blast to occur in the volume 82. 
When breaking a low intensity current, the energy supplied by the spring is 
sufficient to displace the semi-moving assembly.