Low-voltage circuit breaker including a current transformer

A low-voltage circuit breaker comprises a current transformer which at least partly encloses a first connecting bar and is supported by a stationary carrier independently of a second connecting bar. In the region opposite this support, the current transformer is disposed between an L-shaped carrier (angled-off), of the contact arrangements of the circuit breaker and an insulating piece inserted between the connecting bars. In this arrangement, the current transformer can be exchanged with a relatively small amount of labor, while at the same time, adequate strength of the connecting bars against forces is achieved which are introduced into the connecting bars by the continuing current bars.

BACKGROUND OF THE INVENTION 
The present invention relates to a low-voltage circuit breaker having a 
carrier for a contact arrangement and connecting bars, as well as having a 
current transformer surrounding one of the connecting bars and wherein the 
carrier is designed angled-off for accommodating the current transformer. 
A circuit breaker of this type has become known from U.S. Pat. No. 
3,584,170. Due to the angled-off shape (L-shape) of the carrier, the 
connecting bars of the circuit breaker on the back side have unequal 
lengths. At the longer connecting bar which is surrounded by the current 
transformer, the forces applied at the connecting points therefore are 
applied with a longer lever arm. This can lead to a large stress of the 
connecting bars and the carrier of the contact arrangements, especially if 
the circuit breaker is permanently installed in a switching system. 
This difficulty could be corrected by increasing the strength of the 
circuit breaker in the vicinity of the connecting bars in such a manner 
that the current transformer is embedded in the material of the carrier of 
the contact arrangements and thereby, the free length of the connecting 
bar enclosed by the current transformer is substantially shortened. Then, 
the current transformer could, of course, no longer be exchanged as is 
demanded in practice for unconditional employment of the circuit breakers. 
SUMMARY OF THE INVENTION 
Starting from the known arrangement, it is an object of the invention to 
provide an accommodation of the current transformer in the circuit breaker 
which on the one hand permits a replacement with justifiable effort, but 
on the other hand provides great strength in the vicinity of the 
connecting bars. 
The above and other objects of the present invention are achieved by the 
provision that the current transformer is supported on a stationary part 
of the circuit breaker independently of the connecting bar assigned to the 
current transformer, as well as by an insulating piece which is inserted 
between the connecting bars and contains tapped holes for clamping screws 
of the connecting bars. The insulating piece stiffens the connecting bars 
such that they can take up, without the danger of damage, substantially 
large forces which stem from the continued bus bars. If the current 
transformer is to be replaced, it is substantially sufficient to remove 
this insulating piece in order to make the current transformer accessible. 
Because the current transformer is supported independently of the 
connecting bar, it is particularly easy to remove the transformer from the 
circuit breaker and to insert it into the latter. In this connection it 
turns out to be advantageous to support the current transformer standing 
on the mentioned stationary part of the circuit breaker and to make the 
arrangement so that the insulating piece, together with the carrier of the 
contact arrangements, forms a pocket for receiving the part disposed 
opposite the part of the current transformer which is supported 
stationary. This substantially formed-locking mounting of the current 
transformer in the circuit breaker turns out to be sufficient although the 
current transformers are relatively heavy components due to the iron core 
and the windings disposed thereon and are subjected to not inconsiderable 
mechanical stresses due to the switching shocks of the circuit breaker. 
A cross piece connecting the side walls of the circuit breaker can serve as 
the stationary part for supporting the current transformer. Since such a 
cross piece is generally part of the customary circuit breakers, it is 
sufficient for a present purpose to adapt the dimensions of fastening 
elements of the current transformer to the position of such a cross piece, 
or to attach the cross piece in such a manner as is advantageous for 
supporting the current transformer without jeopardizing its other 
functions. The current transformer may comprise two coil forms which are 
intended to be slipped on a rectangular iron core and which are provided 
in a symmetrical arrangement with mounting points for base parts. This has 
the advantage that the coil form for two windings of the current 
transformer can be composed of form sections of half the size, the shape 
of which is simplified by the fact that the complete base parts are 
omitted. The latter can be made more simply as small individual parts 
which are attached at the mounting points of the coil forms. It is 
advisable in this connection to provide the mounting points of the coil 
forms and the base parts with mating projections and undercuts. 
Due to the described location of the current transformer which is gripped 
with its region opposite the base parts between the carrier and the 
contact arrangements and the insulating piece inserted between the 
connecting bars, a relatively simply detachable fastening arrangement in 
the region of the base part is sufficient. This fastening arrangement may 
consist in that the stationary part of the circuit breaker, and in 
particular the mentioned cross piece, has holes, accessible from below, 
for fastening elements engaging the current transformer, for instance, one 
screw for each base part. 
As already mentioned, a substantial stiffening of the connecting bars is 
obtained already by the mere insertion of the insulating piece. Additional 
stiffening can be achieved by fastening the insulating piece detachably to 
a stationary part of the circuit breaker with freely accessible fastening 
elements. This can be accomplished by bolting the insulating piece to 
mounting locations of the side walls for the circuit breaker provided for 
this purpose, or by providing the carrier of the contact arrangement with 
tapped holes in order to fasten the insulating piece to the carrier.

DETAILED DESCRIPTION 
With reference now to the drawings, the low-voltage circuit breaker 1 of 
FIG. 1 is shown simplified in a cross section through a pole and the 
control cam. The circuit breaker 1 has, as supporting parts, two side 
walls 2 and 3, of which one side wall 2 is visible in FIG. 1, while both 
side walls 2 and 3 are shown in FIG. 2. Between the side walls 2 and 3 
extends an insulating carrier 4 for three adjacent contact arrangements. 
The current path of each pole comprises, starting from an upper, forked 
connecting bar 5 with bar sections 6 and 7, a stationary contact 10, a 
movable switching lever 11, a flexible current ribbon 12 as well as a 
lower connecting bar 13 which is likewise composed of bar sections 14 and 
15. The contact lever 11 is movably supported at a contact carrier 16 
which can pivot about a stationary pivot 17. The contact carrier 16 is 
engaged with the interposition of a coupling rod 20 by a control shaft 21 
supported in the side walls 2 and 3. The connecting joint 22 between the 
control shaft 21 or a lever 23 mounted thereon and the coupling rod 20 is 
engaged by a toggle switch arrangement of three movably linked toggle 
levers 24, 25 and 26 which is supported in the "on" position of the 
circuit breakers by a support lever 27 and a ratchet lever 30 at a 
half-shaft 31. Rotation of the half-shaft 31 by a tripping device not 
shown or by hand through a push button 32 cancels the support of the 
toggle lever system and causes the latter to buckle. The contact carrier 
16 and the contact lever 11 then assume the "off" position under the 
influence of a compression spring 33. 
The energy required for switching on is stored in a manner not shown in 
detail, by cocking one or several coil compression springs 38 which are 
braced with their one end against a cross piece 34 connecting the side 
walls 2 and 3 and which act with their other end on the lower toggle lever 
26. The cocked compression spring 38 can be locked in a manner known per 
se, and a further push button 35 is provided for releasing thereby this 
latch and therefore, for switching on the circuit breaker. 
As is further shown in FIG. 1, the carrier 4 consisting of insulating 
material is designed angled-off, the one leg 36 of the coil form having 
fastening means for securing the connecting bars 5 and 13 on the switch 
side. The further leg 37 of the carrier 4 is designed so that it 
corresponds approximately to the dimension of a current transformer 40 in 
the longitudinal direction of the connecting bars. The current transformer 
has an iron core 41 which supports a coil form consisting of two form 
sections 32. 
The current transformer 40 surrounds the lower connecting bar 13 of the 
circuit breaker 1 with spacing and is supported independently of this 
connecting bar. As shown in FIG. 2, three like current transformers 40 are 
provided, corresponding to the three-pole design of the circuit breaker 1. 
The lower coil form section 42 of each of these current transformers is 
provided with base parts 43. With these, the current transformers rest on 
the cross piece 34, in which there are through-holes, not shown, for 
fastening screws 44, for each base part 43. The cross piece 34 is designed 
such that there is unimpeded access to the fastening screws 44 from below, 
as is shown particularly by FIGS. 1 and 3. 
The current transformer 40 is further secured at its part opposite the base 
parts, 43, i.e., in the vicinity of the upper coil body section 42. This 
purpose is served by an insulating piece 46 which is inserted between the 
connecting bars 5 and 13. The insulating part 46 is shown partly in cross 
section in FIG. 1 in order to make the clamping screws 47 engaging the 
insulating piece visible, which are provided for connecting continuing 
current bars 50 to the connecting bars 5 and 13. In FIG. 1, the connecting 
bars 50 are shown broken off and the bar sections 6, 7 and 14, 15 
respectively, extend beyond them. As will be seen, the insulating piece 46 
forms a strong stiffening of the connecting bars 5 and 13. At the same 
time it fixes the current transformer 40 with little tolerance. 
In the example according to FIG. 1, spacing will be recognized between the 
insulating piece 46 and the upper leg 37 of the carrier 4. The reason for 
this is that the insulating piece 46 is not connected directly to the 
carrier 4, but is bolted at its ends to abutments of the side walls 2 and 
3, as is shown in the left part of FIG. 2. As shown, a support bent out of 
the one side wall is designated with 51, and a connecting screw with 52. 
This arrangement is similarly provided at both side walls 2 and 3. 
As a further possibility for fastening an insulating piece, the connection 
to the carrier 4 is shown in the right part of FIG. 2. To this end, the 
insulating piece 48 is fastened to the leg 37 with screws 49. This leg is 
provided with tapped holes, not shown, for instance, one in the center of 
each pole. In this case the space, shown in FIG. 1 and already mentioned, 
between the leg 37 and the insulating piece 46 is omitted. The distance 
between the insulating piece 48 and the leg 36 of the carrier 4 is 
designed, however, according to the dimensions of the current transformer 
40. 
As already mentioned, the current transformer 40 contains an iron core 41 
as well as two coil form sections 42. According to FIG. 3, these are 
provided as mounting points 55 for the base parts 43 and thus can be 
employed selectably as the upper or lower coil form section, the one 
mounting point remaining unused. The mounting points 55 are provided with 
undercuts 60 which correspond to projections 61 of the base parts 43. In 
this manner, the base parts 43 can be anchored to the coil forms in a 
form-locking manner. 
In the foregoing specification, the invention has been described with 
reference to specific exemplary embodiments thereof. It will, however, be 
evident that various modifications and changes may be thereunto without 
departing from the broader spirit and scope of the invention as set forth 
in the appended claims. The specification and drawing are, accordingly, to 
be regarded in an illustrative rather than in a restrictive sense.