Note: Descriptions are shown in the official language in which they were submitted.
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C~SE 2958
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AXI~L LOCKING OF AMORTISSEUR BA~;
This invention relates to a method for the
axial locking of amortisseur bars, to a method of
assembling the bars into a rotor, and to apparatus
having such axially locked bars.
Background of the Invention
In the assembly of a rotor for a synchronous
motor, it has been common practice to assemble the
field windings on the rotor and subsequently to insert
the amortisseur bars. r~he amortisseur bars are then
locked against axial movement by brazirlg a ferrule to
at least the centre bar or centrally located bars of
each pole, adjacent the rotor, at each end of the
bar. When the bars are brazed to the amortisseur ring
lS or end ring on each side of the rotor, all the bars
are locked against axial movement.
Because the ferrules are closely adjacent to
the rotor, it is possible to damage the field windings
by the brazing which takes place in the immediate
vicinity.
Summary of the Invention
When a rotor is assembled according to the
invention, for each pole there is a ferrule brazed to
one end of one bar and to the other end of at least
one other bar before assembly~ r~he amortisseur bars
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are then lnserted and the bars having ferrules are
inserted Erorn opposite sides so that for each pole
there is at least one ferrule adjacent the rotor at
each side of the rotor. The end rings are
subsequently brazed to the ends of the amortisseur
bars which locks all bars against axial movernent.
It is therefore an object of the invention
to provide a method for axially locking amortisseur
bars without endangering winding insulation which
could occur when bra~ing ferrules to each end of bars
in situ.
It is another object of the invention to
provide an improved method for assembliny amortisseur
bars into a rotor of a d~namoelectric machine which
1~ provides axial lockiny of the bars.
Accordinyly there is provided in a
dynamvelectric machine haviny a rotor with a plurality
of poles, an imprvved method ~or assembling
amortisseur bars in said rotor to prevent axial
movement of said bars, cornprising the steps of
assembling a rotor core having first and second sides,
installing rotor windings on said core, selecting at
least two amortisseur bars for each pole of said
rotor, fixedly mounting on each selected bar a single
2S ferrule at a respective predetermined distance from
the end of the respective bar, said predetermined
distance being such that when one of said bars i9
inserted into said rotor from said first side to its
final position the ferrule will be adjacent said first
side of said rotor, and when the other of said bars is
inserted into said rotor from said second side to its
final position the ferrule will be adjacent said
second side of said rotor, inserting said amortissuer
bars into said rotor, and fastening the protruding
ends of said amortisseur bars on said first side to a
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first end ring and fastening the protruding ends of
said arnortisseur bars on said second side to a second
end ring.
There is also provided a dynamoelectric
S machine having a rotor with a plurality of poles and
rotor windings on said rotor, comprising a plurality
of amortisseur bars for each pole of said rotor, at
least two of said amortisseur bars per pole havilly a
respective single ferrule fixedly rnounted thereto
lU prior to assembly of said bars in said rotor, said
ferrules being a respective predetermined distance
from an end of said rotor whereby one of said at least
two amortisseur bars when inserted in said rotor has
the respective ferrule thereon adjacent one side of
said rotor and another of said at least two
amortisseur bars when inserted in said rotor has the
respective ferrule thereon adjacent the other side OL`
said rotor, and an end riny for each side of said
rotor fixedly rnounted to the protruding ends of said
amortisseur bars on the respective side of said rotor.
~rief_Description of the_Drawin~s
Figure 1 is an isometric view of a rotor
having amortisseur bars~
Figures 2 and 3 are schematic views looking
dvwn on the pole face of a rotor and showing two
arrangernents according to the invention,
Figures 4, 5 and 6 are partial sectional
views showing a section through an amortisseur bar and
end ring showing three different forms of ferrule, and
: 30 Figure 7 is a sectional view taken along
line l-7 of Figure 6.
Description of the Preferred Embodinents
Referring to Figure 1 there is showrl an
isometric drawing of a rotor 10 for a synchronous
; 35 motor havin~ a plurality of poles 11 with a plurality
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CASE 295
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of amortisseur bars 12 secured to an end ring 14. In
the assembly of rotor 10 in the past it has been the
practice to insert amortisseur bars 1~ which then
project on either side of the pole through which they
are mounted. A ferrule or ring, just slightly larger
than the amortisseur bar is then slipped on both ends
of each bar which has been designated to provide axial
locking and the ferrules placed adjacent the pole.
This places the ferrule in the vicinity of the rotor
windillgs 15. The ferrules are then brazed or welded
to the respective amortisseur bar. This brazing or
welding could subject the rotor windings to undue
héat. When the ferrules are fastened, the end
rings 14 are brazed or weldéd to the ends of the
lS amortisseur bars 12. The end rings are normally
spaced outwardly of the po~es and their windirlg~ and
conse~uently this braziny or weldiny operation iY
unlikely to damage the windings.
Figure 2 shows a view looking down OlltO a
pole face 16. Seven amortisseur bars 12A - 12~ exter~d
through the pole and are fastened to end rings 14
and 14A. Eerrules 17 and 18 are brazed or welde~ to a
respective amortisseur bar so that they are adjacent a
respective side 20 and 21 of pole 11 having pole
face 16 as designated, this is done before the
arnortisseur bars are inserted into the poles. Where
there are an odd number of amortisseur bars, this
arrangement is convenient. There may, of cour~e, be
more than two amortisseur bars which have a ferrule
attached.
~ uring the assembly of a rotor, after t}le
rotor windings are in place, ferrule 17 is brazed or
welded to amortisseur bar 12E in the position shown,
and ferrule 18 is brazed or welded to amortisseur
bar 12C in the position shown. This brazing or
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welding of the ferrules to the respective amortisseur
bars is done before the bars are inserted into their
pole so that there i5 no danger of the windings beiny
heated by the brazing or welding. The arnortisseur
bars are then inserted. The amortisseur bar 12E is
inserted from side 20, an~ the amortisseur bar 12C is
inserted from side 21. The bars 12~, 12B, 12D, 12F
and 12G may be inserted from either side 20 or side 21
as convenient. The amortisseur bars are subsequently
brazed or welded to end ring 14 and 14A. Once this is
done, all the amortisseur bars 12 are locked or
secured against axial movement.
Referring now to Figure 3, four amortissuer
bars 12H - 12K extend through a pole having a pole
face 16A. Amortisseur bars 12I and 12J have
Eerrules 17A and 18A brazed or welded thereto,
respectively. This arrangement illustrates an even
number of amortisseur bars per pole. There may, o~
course, be three or four of the amortisseur bars with
a respective ferrule.
During assembly, as before, ferrules 17A
and 18~ are brazed or welded to bars 12J and 12I,
respectively, before the amortisseur bars are inserted
into their pole. The bars are then inserted, bar 12J
from side 20 and bar 12I from side 21, until the
ferrules are adjacent the respective side of the
pole. The bars without a ferrule may be inserted from
either side. The ends of amortisseur bars 12~ - 12K
are subsequently brazed or welded to a respective end
ring 14 or 14A.
Figure 4 is a sectional view taken through
part of the rotor core 22 forming a pole with a pole
face 16. An amortisseur bar 23 has a ferrule 24
brazed or welded to it. Ferrule 24 is in the form of
a ring whose opening conEorms to the outside of bar 23
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and is slightly larger so that it will slip over
bar 23. It is preferable to do the brazing or welding
of the ferrule to the respective bar on the side that
will be remote from the side of the pole so that the
ferrule will butt flatly against the side of the pole
to prevent axial movement. The end of the bar 23 is
brazed or welded to end ring 14 after all the
amortisseur bars are installed.
Figure 5 is a sectional view taken through
part of a rotor core 22 and is similar to Figure 4
except that a different form of ferrule is used.
Ferrule 25 of Figure 5 has a hole 26 drilled through
the ferrule to provide a convenient passaye for
providiny an improved weld. The welding of t~le
ferrule to the bar is done in the region of hole 26.
If desired, more than two holes 26 could be used, or
alternately one hole 26 could be used. It has been
found that two opposed holes, as shown, provide a
satisfactory weld.
~eferring to Figures 6 and 7, yet another
form of fastener is shown. The fastener in Fiyures 6
and 7 is not in the forln of a ring, however, f~r
convenience it is referred to as a ferrule and it is
intended that "ferrule" will include this. The
ferrule of Figures 6 and 7 is a rectangular metal
piece 27 and 28 brazed or welded on opposite sides of
amortisseur bar 30 which has a generally oblong
cross-section. Some caution must be used when braziny
or welding the ferrule pieces 27 and 28 to bar 3~ to
avoid getting the brazing material or weldiny material
on the edges adjacent the pole side because axial
moveJnent of the bar might then cause sorne distortion
when the uneven material butts against the side of the
pole. The terminating edyes 31 of the pair o~
pieces 27 and 28 are direc-tly opposite one arlother,
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that is they are aligned with one another.
Various other forms of ferrule may be used,
but whatever form of ferrule is used it is brazed or
welded or otherwise fastened to an amortisseur bar at
a predetermined distance from one end of the bar so
that after the bar is inserted in a pole on the rotor
and is positioned in its final or operatiny position,
the ferrule will be closely adjacent a side of the
respective pole. It is preferable that for each pole
at least two amortisseur bars will have ferrules
fastened thereto, one per bar, at predetermined
distance from an end of the bar so that after the bars
are installed the ferrules will be adjacent op~osite
sides of the pole. When the bars are subsequently
brazed or welded or otherwise fastened to an end ring
at each end, the bars will all be secured against
axial movement. While it is preferable that at least
two bars per pole should have ferrules, the actual
number will depend on the size of the rotor and the
number of poles on the rotor. Preferably the bars
having a ferrule thereon are equally spaced on either
side of the pole center.
It is believed the description provided will
give a satisfactory understanding of the inventionO
