Multiple current-limiting circuit breaker with electrodynamic repulsion

A multipole circuit breaker having a movable contact for each pole, the movable contact being biased by a spirally-wound spring including a feeler part which slides on a bearing surface of the movable contact to modify the application point of a pressure force P in a second active repulsion position, resulting in a decrease of the restoring torque before operation of the mechanism. The movable contact is forked-shaped and is articulated on an eccentric spindle parallel to the rotation axis of the bar. The spirally-wound spring is mounted to float in the recess of the bar, and comprises two helicoidal wire windings.

BACKGROUND OF THE INVENTION 
The invention relates to a multipole current-limiting circuit breaker with 
molded insulating case, housing: 
a current interrupting device having per pole contact elements separable by 
electrodynamic repulsion, and at least one arc extinguishing chamber, 
an operating mechanism having a toggle associated with a connecting spring, 
and with a trip device, 
a switching bar made of insulating material acting as support for the 
movable contacts of all the poles, said bar being mechanically coupled to 
the toggle to be moved by the mechanism between the closed position and 
the open position of the contacts, 
a handle coupled to the mechanism and passing through an aperture in the 
front panel of the case, 
the movable contact of each pole being formed by a contact arm articulated 
on a spindle securedly united to the bar, said movable contact being able 
to be moved by electrodynamic repulsion from a first rest position to a 
second active position, and the spindle of the movable contact being 
eccentric with respect to the rotation axis of the bar, 
and flexible means comprising a spring housed in a recess of the bar to 
provide the contact pressure and to slow down the drop-back of the movable 
contact to the first rest position, the spring sliding on a bearing 
surface of the movable contact to modify the application point of the 
pressure force P in the course of the opening travel. 
In this first type of current-limiting circuit breaker, the occurrence of a 
short-circuit causes in a first phase high-speed opening, by 
electrodynamic repulsion, of the contacts of the faulty pole, and in a 
second phase tripping of the mechanism controlled by the tripping means. 
Rotation of the switching bar for final opening of the contacts takes 
place only during the second phase after the trip lever has been unlocked 
by the latch. 
The arm remains immobile during the first electrodynamic repulsion phase. 
Only the contact arm of the faulty pole opens, the contacts of the other 
poles remaining closed during this first phase. It is essential that 
rotation of the bar for confirmation of opening of the circuit breaker 
take place before the contact arm drops back to the closed position. The 
coordination defect between the two phases is mainly due to the bar being 
held in the closed position during the first repulsion phase and may cause 
contact chatter and premature wear of the circuit breaker. 
According to U.S. Pat. No. 4,480,242, the movable contact is subjected to a 
variation of the contact pressure spring restoring torque, said torque 
being increasing up to an intermediate position of the opening travel, 
then decreasing up to the open position. 
The document FR-A-2,553,930 filed by the applicant belongs to a second type 
of current-limiting circuit breaker having a reversible mechanism, in 
which the rotation spindle of the bar coincides with the articulation 
point of each contact arm. The drag spring is anchored between the movable 
contact and the bar. 
The contact arm of each pole cooperates with the toggle device to drive the 
switching bar in rotation in the opening direction after the 
electrodynamic repulsion means of the faulty pole have come into action so 
as to enable separation of the contacts of all the poles before the trip 
lever is unlocked by the latch. 
The reversibility of the mechanism by rotation of the bar during the first 
electrodynamic opening phase speeds up the tripping time to confirm final 
opening of the circuit breaker. Rotation of the bar before operation of 
the trip device is rendered possible due to the deformation of the toggle, 
the rods there having an offset angle between 10 and 20 degrees on the 
closed position. 
SUMMARY OF THE INVENTION 
The invention relates to the first type of current-limiting circuit 
breaker, and its object is to improve the drop-back prevention system of 
the movable contact at the end of repulsion travel. 
The circuit breaker according to the invention is characterized in that: 
the movable contact is shaped as a fork having a common body supporting two 
contact arms, and a securing shank articulated on the spindle and that the 
spirally-wound spring is mounted floating in the recess of the bar and 
comprises a feeler part cooperating with two balancing slots of the 
bearing surface securedly united to the body to distribute the contact 
pressure on the two contact arms. 
The spirally-wound spring comprises two helicoidal windings made of wire 
arranged coaxially in the recess and interconnected in the center zone by 
a protruding flexible link forming said feeler, and comprising two end 
strands pressing against a wall of the bar. 
Distribution of the contact pressure with the spirally-wound spring is 
achieved by means of two balancing slots provided on the bearing surface 
of the body of the fork-shaped movable contact. Each slot is provided with 
latching surfaces to temporarily block the movable contact in the second 
active position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, a multipole circuit breaker 10 with molded insulating case 12 
comprises a breaking module 14 per pole, formed by a monoblock cartridge 
16 made of molded plastic material, and having the shape of a 
parallelepiped rectangle. The cartridge 16 comprises a front panel 18 
having an orifice 20 for passage of the movable contact 22 therethrough, 
and the breaking module 14 comprises an electrodynamic contact repulsion 
device. 
Inside the cartridge 16 there are located two stationary contacts 24, 26 
respectively connected by connecting conductors 28, 30 to a first contact 
strip 32 of a connection terminal 34, and to a second contact strip 36 
designed to be connected by a screw 38 to a third contact strip 40 of a 
trip device 42. 
The trip device 42 comprises a magnetothermal trip device 44 equipped 
opposite from the contact strip 40 with a fourth contact strip 46 forming 
part of the other connection terminal 48 of the pole. The trip device 44 
is electrically connected in series in the pole with the contacts 22, 24, 
26 of the breaking module 14. 
The trip device 42 comprises in addition a trip bar 50 mounted with limited 
rotation between a charged position and a tripped position according to 
the position of the actuating element of the trip device 44, for example 
the bimetal strip 52 or blade 54. The rotary bar 50 is moved to the 
tripped position as soon as the current flowing in the pole exceeds a 
preset threshold. The trip bar 50 moreover cooperates with a latch 56 of 
an operating mechanism 58 with toggle 60 and handle 62. 
The mechanism 58 is common to all the poles, and is housed inside the case 
12, only the handle 62 being accessible from outside passing through an 
aperture 64 arranged in the front panel of the case 12, for manual 
operation of the circuit breaker 10. 
The lower rod 66 of the toggle 60 is coupled to a protuberance 68 of a 
switching bar 70 acting as support for the movable contacts 22 of all the 
poles. The switching bar 70 is made of insulating material and extends 
parallel to the trip bar 50 in the transverse direction of the poles. 
An unlocking action of the trip bar 50 on the latch 56 releases the 
mechanism 58, which is discharged due to the expansion action of a 
connecting spring 72, resulting in movement by pivoting of the toggle 60, 
and rotation of the bar 70 to the open position of the contacts 22, 24, 26 
of all the poles. The unlocking order of the latch 56 can come from the 
magnetothermal trip module 44, or from an auxiliary trip device, notably 
an undervoltage release MN, shunt release MX, differential trip device, 
etc. 
Each breaking module 14 houses two arc extinguishing chambers, only one 74 
of which is represented in FIG. 1, each chamber being in communication 
with an opening or channel 76 for the breaking gases to escape to the 
outside of the cartridge 16. Each arc extinguishing chamber 74 is formed 
by stacking of the deionization plates with V-shaped notches facing the 
movable contact 22. 
In FIGS. 2 and 3, the switching bar 70 of a three-pole circuit breaker is 
equipped with three identical movable contacts 22, located at regular 
intervals along the transverse direction of the bar 70. Each movable 
contact 22 is in the shape of a fork with two parallel contact arms 22a, 
22b cooperating in the closed position with the two stationary contacts 
24, 26. 
The inside of the cartridge 16 of each breaking module 14 is subdivided by 
an intermediate insulating wall into two adjacent compartments, into which 
the two arms 22a, 22b of the fork-shaped movable contact 22 penetrate 
through the orifice 20, the movable contact 22 being positioned astride 
the wall when pivoting thereof takes place between the closed and open 
positions. The bar 70 is guided in rotation by bearings (not represented) 
provided in the cartridge 16 of the different breaking modules 14. 
Referring to FIGS. 4 to 6, each fork-shaped movable contact 22 comprises a 
common base 80 supporting the two vertical contact arms 22a, 22b, so as to 
form a reversed U-shape. The straight base 80 extends in the transverse 
direction of the bar 70, and is equipped in the center zone with a 
securing shank 82 whose free end is articulated on a horizontal spindle 84 
securedly united to the bar 70. The shank 82 is situated in the mid-plane 
of symmetry with a reverse orientation with respect to the two elementary 
contact arms 22a, 22b. 
The spindle 84 of each movable contact 22 is housed with clearance in two 
aligned bearings 86, 88 arranged on the upper face of the bar 70. The 
contact spindle 84 is parallel and eccentric with respect to the rotation 
axis of the bar 70. 
Each movable contact 22 cooperates with a spirally-wound spring 90 located 
in a recess 92 bounded by a rectangular frame 93 of the bar 70 to provide 
the contact pressure in the closed position. The spring 90 comprises two 
coaxial helicoidal windings 90a, 90b, made of wire and interconnected by a 
flexible intermediate link 94, through which the shank 82 passes bearing 
on the base of the movable contact 22. The flexible link 94 of the spring 
90 comprises two strands of wire, shaped as a half-turn acting as feeler, 
and having an upwardly-curved protruding part 94a. 
The feeler of the flexible link 94 is positioned in two V-shaped slots 96, 
98 provided on the bearing surface 80a of the base 80 to ensure that the 
contact pressure is balanced in the closed position of the contacts 22, 
24, 26. The two slots 96, 98 are symmetrical with respect to the mid-plane 
passing through the shank 82, and the two end strands 100, 102 of the two 
windings 90a, 90b are permanently pressed against the internal upper 
surface of the frame 93. 
The spring 90 is mounted floating in the recess 92 with respect to the axis 
of the rotary bar 70. Cooperation of the spring 90 with the base 80 of the 
fork-shaped movable contact 22 constitutes a device for temporary holding 
of the contact at the end of the electrodynamic repulsion travel. 
Operation of a pole of the circuit breaker 10 with electrodynamic repulsion 
is as follows: 
In the closed position represented in FIG. 1, the fork-shaped movable 
contact 22 is in a stable position bearing against the corresponding 
stationary contacts 24, 26. The symmetrical reaction of the two strands 
100, 102 of the spirally-wound spring 90 on the frame 93 of the bar 70 
ensures balancing of the contact pressure on the two arms 90a, 90b due to 
the distributed thrust action of the intermediate link 94 or feeler on the 
body 80. FIG. 4 shows the pressure force P which is exerted on the movable 
contact 22 when the latter is in a first rest position. The line of action 
of the force P is appreciably perpendicular to the intermediate link 94 of 
the spring 90, and urges the movable contact 22 counterclockwise to exert 
the contact pressure. 
The handle 62 of the mechanism 58 is in the closed position, pressing up 
against the left-hand end of the aperture 64. The mechanism 58 with the 
spring 72 is charged, and the trip device 44 is inactive. The application 
point 103 of the force P is on the edge of the body 80. 
In FIG. 7, the occurrence of a short-circuit current in the pole causes an 
electrodynamic repulsion effect of the contacts, with high-speed movement 
of the movable contact 22, which pivots around its spindle 84, in the 
clockwise direction. The electrodynamic repulsion ensures high-speed 
opening of the contacts of the faulty pole, before mechanical operation of 
the operating mechanism 58. The spring 72 and toggle 60 remain immobile, 
as does the switching bar 70, whose position corresponds to that of FIG. 
1. The arc remains anchored between the movable contact 22 and the 
stationary arcing horn 104, and is propelled in the direction of the 
deionization plates of the arc extinguishing chamber 74. 
At the end of opening travel on repulsion (FIG. 8), the movable contact 22 
is fully open and presses up against the wall of the cartridge 16. The arc 
is cooled by the plates of the chamber 74, and the trip device 44 begins 
controlling the tripping phase of the mechanism 58 (see arrows). 
After tripping of the mechanism 58 (not represented in the figures), the 
latch 56 releases the toggle 60 causing expansion of the spring 72 and 
clockwise rotation of the bar 70, so as to confirm opening of the movable 
contact 22. 
During the electrodynamic repulsion phases represented in FIGS. 7 and 8, it 
is imperative that the movable contact 22 does not reclose before 
operation of the bar 70 following tripping of the mechanism 58. The delay 
in drop-back of the movable contact 22 is obtained by means of the 
displacement of the application point 103 of the force P exerted on the 
body 80 when repulsion takes place. 
In the repulsion position of FIG. 6, sliding of the flexible link 94 to the 
inside of the balancing slots 96, 98 modifies the location of the 
application point 103 of the force P exerted by the spring 90. The line of 
action of the force P passes close to the pivoting spindle 84 of the 
movable contact 22, which appreciably decreases the restoring torque to 
the closed position. This decrease of the restoring torque enables the 
drop-back of the movable contact 22 to be delayed before the bar 70 
performs its operation. 
The slots 96, 98 advantageously comprise latching surfaces shaped to 
temporarily block the movable contact 22 in the maximum repulsion 
position. 
FIG. 9 shows a manual opening phase of the circuit breaker 10 by actuation 
of the handle 62 in the direction of the arrow. The mechanism 58 remains 
charged, and rotation of the bar 70 causes movement of the movable contact 
22 to the open position as soon as the handle 62 has passed the 
intermediate opening dead-point position. 
There is no electrodynamic repulsion of the contacts, and the application 
point 103 of the force P of the spring 90 corresponds to that of FIG. 4. 
It is clear that the spirally-wound spring 90 can be replaced by any other 
type of spring.