U.S. patent application number 14/828694 was filed with the patent office on 2016-03-17 for squirrel-cage rotor.
The applicant listed for this patent is WIELAND-WERKE AG. Invention is credited to Gerhard THUMM, Volker VOGGESER.
Application Number | 20160079837 14/828694 |
Document ID | / |
Family ID | 54007449 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160079837 |
Kind Code |
A1 |
THUMM; Gerhard ; et
al. |
March 17, 2016 |
SQUIRREL-CAGE ROTOR
Abstract
The invention relates to a squirrel-cage rotor for an
asynchronous machine, said squirrel-cage rotor having at least one
laminated rotor core that comprises a plurality of grooves and said
squirrel-cage rotor having at least one rotor cage comprising
electrically conductive rotor bars that are embedded in the grooves
of the laminated rotor core in such a manner that the rotor bars
comprise at their two end regions an overlap beyond the laminated
rotor core, and said rotor cage comprising short-circuit rings that
are attached at the end face to the laminated rotor core and
comprise a plurality of slots that are arranged in the region of
their outer periphery and the end regions of the rotor bars
protrude into said slots. The short-circuit rings comprise in each
case at least two metal composite discs that comprise at least a
first metal disc and a second metal disc that is connected in a
planar manner to said first metal disc and is embodied from a
different material thereto. Adjacent metal composite discs are
arranged at least in part in such a manner that the first metal
discs are facing one another. The rotor bars are bonded to the
first metal discs in the region of the slots.
Inventors: |
THUMM; Gerhard; (Erbach,
DE) ; VOGGESER; Volker; (Senden, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
WIELAND-WERKE AG |
Ulm |
|
DE |
|
|
Family ID: |
54007449 |
Appl. No.: |
14/828694 |
Filed: |
August 18, 2015 |
Current U.S.
Class: |
310/211 |
Current CPC
Class: |
H02K 3/02 20130101; H02K
15/0012 20130101; H02K 2213/03 20130101; H02K 17/165 20130101 |
International
Class: |
H02K 17/16 20060101
H02K017/16; H02K 3/02 20060101 H02K003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2014 |
DE |
10 2014 013 684.1 |
Claims
1. Squirrel-cage rotor for an asynchronous machine, said
squirrel-cage rotor having at least one laminated rotor core that
comprises a plurality of grooves and said squirrel-cage rotor
having at least one rotor cage comprising electrically conductive
rotor bars that are embedded in the grooves of the laminated rotor
core in such a manner that the rotor bars comprise at their two end
regions an overlap beyond the laminated rotor core, and said rotor
cage comprising short-circuit rings that are attached at the end
face to the laminated rotor core and comprise a plurality of slots
that are arranged in the region of their outer periphery and the
end regions of the rotor bars protrude into said slots,
characterized in that the short-circuit rings comprise in each case
at least two metal composite discs that comprise at least a first
metal disc and a second metal disc that is connected in a planar
manner to said first metal disc and is embodied from a different
material thereto, that adjacent metal composite discs are arranged
at least in part in such a manner that the first metal discs are
facing one another and that the rotor bars are bonded to the first
metal discs in the region of the slots.
2. Squirrel-cage rotor according to claim 1, characterized in that
the rotor bars are embodied at least in part from a material that
can be easily welded to the material of the first metal disc.
3. Squirrel-cage rotor according to claim 2, characterized in that
the rotor bars are embodied at least in part from a material whose
base material is identical to the base material of the first metal
discs.
4. Squirrel-cage rotor according to claim 1, characterized in that
the first and second metal discs are connected one to the other in
a planar manner by means of a plating process.
5. Squirrel-cage rotor according to claim 1, characterized in that
the first metal discs comprise on their outer periphery at least
one bevel.
6. Squirrel-cage rotor according to claim 1, characterized in that
the first metal discs are embodied from aluminum or an aluminum
alloy.
7. Squirrel-cage rotor according to claim 6, characterized in that
the thickness s.sub.1 of the first metal discs is at least 60% of
the thickness s of the metal composite discs.
8. Squirrel-cage rotor according to claim 1, characterized in that
the first metal discs are embodied from copper or a copper alloy.
Description
[0001] The invention relates to a squirrel-cage rotor for an
asynchronous machine, said squirrel-cage rotor having at least one
laminated rotor core that comprises a plurality of grooves and said
squirrel-cage rotor having at least one rotor cage comprising
electrically conductive rotor bars that are embedded in the grooves
of the laminated rotor core in such a manner that the rotor bars
comprise at their two end regions an overlap beyond the laminated
rotor core, and said rotor cage comprising short-circuit rings that
are attached at the end face to the laminated rotor core and
comprise a plurality of slots that are arranged in the region of
their outer periphery and the end regions of the rotor bars
protrude into said slots.
[0002] The fundamental construction of squirrel-cage rotors for
asynchronous machines is generally known from the prior art.
Various methods are known for producing the rotor cage. In some
cases, the entire rotor cage is cast in one piece. As a deviation
from this, embodiments are known where the rotor bars are produced
from a semi-finished product and are embedded in the grooves of the
laminated rotor core. The short-circuit rings are subsequently cast
on. A further variant provides in contrast to this to produce the
short-circuit rings from correspondingly formed metal sheets. The
metal sheets must have good electrically conductive characteristics
and must be connected in a reliable manner to the rotor bars. This
connection is formed in many cases by means of a soldering process,
such as for example can be found in the document DE 34 21 537
A1.
[0003] Furthermore, squirrel-cage rotors are known from DE 195 42
962 C1, wherein the short-circuit rings are constructed from copper
metal sheets and steel metal sheets that are positioned in an
alternating manner with respect to one another. As a consequence,
the mechanical stability of the short-circuit rings is to be
improved and the in-laid steel metal plates are to limit the extent
to which the short-circuit ring can expand even in the case of
higher rotational speeds. The steel metal sheets are soldered to
the copper metal sheets and the conductor bars.
[0004] It is proposed in the document DE 697 34 839 T2 to produce
the short-circuit rings of a cage rotor from a bimetal metal sheet,
in particular a steel-copper metal sheet. Bimetal short-circuit
rings that are produced in this manner are then positioned with
their steel face towards with the laminated rotor core, so that
subsequently the short-circuit ring can be welded to the laminated
rotor core.
[0005] The object of the invention is to provide an improved
squirrel-cage rotor for an asynchronous machine. The improvement
relates to the construction of the short-circuit rings and their
connection to the rotor bars.
[0006] The invention is characterized by means of the features of
claim 1. The other related claims relate to advantageous
embodiments and further developments of the invention.
[0007] The invention includes a squirrel-cage rotor for an
asynchronous machine, said squirrel-cage rotor having at least one
laminated rotor core and having at least one rotor cage comprising
electrically conductive rotor bars and short-circuit rings. The
laminated rotor core comprises a plurality of grooves. The grooves
can be embodied as grooves that are open in the radial direction
towards the exterior. The rotor bars are embedded in the grooves of
the laminated rotor core in such a manner that they comprise at
their two end regions an overlap beyond the laminated rotor core.
Short-circuit rings that comprise a plurality of slots that are
arranged in the region of their outer periphery are provided on the
end faces of the laminated rotor core and the end regions of the
rotor bars protrude into said slots. The slots can be embodied as
through-going openings that are open in the radial direction
towards the exterior or are closed. In accordance with the
invention, the short-circuit rings comprise in each case at least
two metal composite discs that for their part comprise at least one
first metal disc and a second metal disc that is connected in a
planar manner to said first metal disc and is embodied from a
different material thereto. Adjacent metal composite discs are
arranged at least in part in such a manner that first metal discs
of these metal composite discs are facing one another. The rotor
rods are bonded, preferably welded, to the first metal discs in the
region of the slots.
[0008] The invention is based on the consideration that the
short-circuit rings of the rotor cage comprise in each case a
plurality of metal composite discs. The metal composite discs
comprise at least two metal discs that are embodied from different
materials and are connected one to the other in a planar and
electrically conductive manner. The materials of the metal discs
differ from one another with respect to their density, electrically
conductive characteristics, strength characteristics and their
costs. Consequently the metal composite discs offer, in contrast to
mono-metal discs, more freedom with regard to optimizing the
short-circuit rings with respect to the electrical conductance
value, weight, strength and costs. The choice of the mutually
combined materials and the thickness ratio of the individual metal
discs plays an important role. The metal composite discs must be
connected to the rotor bars at their end regions in an efficient
electrically conductive manner. The connection must be reliable and
must not fail during the entire serviceable life of the machine
even under the influence of forces such as during the operation of
rapidly rotating components. Therefore, the connection between the
rotor bars and the metal composite discs is a bonded connection, by
way of example by means of a soldering process or preferably by
means of a welding process. Since it is difficult to bond different
metal materials to each other, the technique used to connect the
rotor bars and short-shirt rings is selected such that essentially
only the metal disc of a metal composite disc whose material can be
best connected to the material of the rotor bars is connected to
the rotor bars. Within the scope of this invention, this metal disc
is described as the `first metal disc` whereas a metal disc that is
embodied from a different material thereto is described as the
`second metal disc`. The current is transferred from the rotor bars
to a metal composite disc by way of the bonded connections
initially to the first metal disc. The planar bond between the
metal discs renders it possible to transport the current within the
metal composite disc with a minimum amount of electrical
resistance. In accordance with the invention, the metal composite
discs of the short-circuit rings are arranged at least in part in
such a manner that the first metal discs of adjacent metal
composite discs are facing one another. As a consequence, first
metal discs, which are embodied from an identical material, of
adjacent metal composite discs are positioned directly next to one
another. This is achieved in the case of metal composite discs that
comprise two metal discs by virtue of the fact that adjacent metal
composite discs are arranged in a mirror-inverted manner with
respect to one another with regard to their disc arrangement.
Alternatively, solutions using multi-layer metal composite discs
are possible.
[0009] The particular advantage of this type of construction of
short-circuit rings resides in the fact that two adjacent metal
composite discs can be connected to a rotor bar by means of a
single connection process, by way of example by means of a single
welding procedure. Consequently, outlay and costs for connecting
the short-circuit rings to the rotor bars can be almost halved.
Furthermore, it is possible to produce a reliable connection
between two adjacent metal composite discs without additional
outlay. This improves the electrical conductivity of the
short-circuit rings and increases the mechanical stability.
[0010] In a preferred embodiment of the invention, the rotor bars
can be embodied at least in part from a material that can be easily
welded to the material of the first metal discs. It is possible to
produce particularly reliable connections by means of a welding
process. Suitable connection methods are by way of example laser
welding or electron beam welding. The two materials that are welded
one to the other preferably have melt temperatures or rather melt
regions that are close to one another and also similar thermally
conductive characteristics. The difference in melt temperatures or
rather weld regions is preferably a maximum 20 K.
[0011] In a particularly preferred embodiment of the invention, the
rotor bars can be embodied at least in part from a material whose
base material is identical to the base material of the first metal
discs. The two materials that are to be welded one to the other can
therefore be different alloys of the identical base material. The
two alloys can in many cases be easily welded as a result of the
identical base material. In particular, the conductivity and the
strength of a material can be purposefully influenced by means of
suitable alloying elements. It is thus possible by way of example
to manufacture the rotor bars preferably from an alloy that has a
particularly high strength, whereas an alloy that has particularly
good conductivity characteristics is used for the first metal discs
of the short-circuit rings.
[0012] In an advantageous embodiment of the invention, the metal
discs that are embodied from a different material and are part of
the metal composite disc are connected one to the other in a planar
manner using a plating technique. The plating technique is a
particularly suitable method of connecting different metal
materials in a planar manner one to the other, said materials being
available in a strip or sheet metal form. A particularly suitable
method for this purpose is the laser roll plating technique. The
plating method renders it possible to produce in a favorable manner
semi-finished products that are embodied from metal composites, by
way of example bimetal strips. Semi-finished goods of this type can
be metal composite discs that have been produced by means of a
suitable separating method, by way of example stamping or laser
cutting, and that are required in order to construct a
short-circuit rotor in accordance with the invention.
[0013] In the case of an advantageous embodiment of the invention,
the first metal discs can comprise at least one bevel on their
outer periphery. It is preferred that this bevel extends in the
radial direction at least as far as the slots. A bevel of this type
provides the first metal disc with a geometry that is favorable for
connecting to the conductor bars. The bevel produces a type of
circumferential groove by means of which it is possible to access
the connection site between the first metal disc and the conductor
bar. If a soldering process is used, the solder material can be
introduced into the groove and thus directed to the connection
site. If a welding process is used, energy can be introduced into
the weld site by means of the groove by way of example using a
flame or a laser beam or electron beam.
[0014] In an advantageous embodiment of the invention, the first
metal discs, in other words the metal discs that are bonded to the
conductor bars, can be embodied from aluminum or an aluminum alloy.
It is accordingly advantageous if the conductor bars are embodied
at least in part from aluminum or an aluminum alloy. As a result of
their density and their relatively good electrically conductive
characteristics, aluminum and aluminum alloys are preferred
materials for conductor bars and short circuit rings of a cage
rotor. In order in this advantageous embodiment to improve the
electric conductance of the short-circuit rings, the second metal
discs of the metal composite discs are preferably embodied from
copper or a copper alloy. As a consequence, a favorable compromise
between electric conductance and weight is achieved. In a
particularly advantageous embodiment of the invention, the
thickness s.sub.1 of the first metal discs is at least 60% of the
thickness s of the metal composite discs. The first metal discs are
embodied from aluminum or an aluminum alloy. In comparison to other
metal materials, aluminum is characterized by virtue of a very low
density and a favorable price in relation to its volume. If at
least 60% of the metal composite discs are embodied from aluminum
or an aluminum alloy, then they are characterized by means of a low
weight and low costs.
[0015] In the case of an alternative advantageous embodiment of the
invention, the first metal discs, in other words the metal discs
that are bonded to the conductor bars, are embodied from copper or
a copper alloy. It is accordingly advantageous if the conductor
bars are embodied at least in part from copper or a copper alloy.
As a result of their high electrically conductive characteristics,
copper and copper alloys are preferred materials for conductor bars
and short-circuit rings of a squirrel cage rotor. In order in the
case of this advantageous embodiment of the invention to reduce the
weight and the costs of the short-circuit rings, the second metal
discs of the metal composite discs can be embodied preferably in
aluminum or an aluminum alloy. As a consequence, a favorable
compromise is achieved between electric conductance, weight and
cost.
[0016] The invention is further explained with reference to the
following exemplary embodiments and with reference to the schematic
drawings, in which:
[0017] FIG. 1 illustrates a sectional view of a squirrel-cage
rotor,
[0018] FIG. 2 illustrates an enlarged view of the view in FIG. 1 in
the region of the connection between the rotor bar and a
short-circuit ring,
[0019] FIG. 3 illustrates an enlarged view of a further embodiment
of a squirrel-cage rotor in accordance with the invention in the
region of the connection between the rotor bar and a short-circuit
ring.
[0020] Mutually corresponding parts are provided with the same
reference numeral in all figures.
[0021] FIG. 1 illustrates a sectional view of a squirrel-cage rotor
1 in accordance with the invention. The squirrel-cage rotor 1 has
an essentially cylindrical shape with an axis A and a centrally
arranged bore hole 4 for receiving a shaft, not illustrated. Said
squirrel-cage rotor comprises a laminated rotor core 11 that is
constructed in a manner known per se from individual metal sheets.
The laminated rotor core 11 comprises a plurality of grooves 12,
two of which are visible in the sectional view. Furthermore, the
squirrel-cage rotor 1 comprises a plurality of electrically
conductive rotor bars 2, two of which are visible in the sectional
view, and also two short-circuit rings 3. The rotor bars 2 and the
short-circuit rings 3 together essentially form the squirrel cage.
The rotor bars 2 are embedded in the grooves 12 of the laminated
rotor core 11 in such a manner that they comprise at their two end
regions 21 an overlap beyond the laminated rotor core 11.
Generally, the rotor bars 2 are not arranged in parallel to the
axis A of the cage rotor 1 but rather are arranged inclined by a
defined angle of twist with respect to the axis A. However, for
reasons of clarity, this feature is not shown in the schematic
illustrate in FIG. 1. The rotor bars 2 are embodied in the
illustrated exemplary embodiment as solid mono-metal bars. However,
it is also possible to use bi-metal bars and/or hollow bars. The
short-circuit rings 3 are attached to the end faces of the
laminated rotor core 11. The short-circuit rings 3 comprise in the
region of their outer periphery a plurality of slots 31. The number
and position of the slots 31 are to be selected such that said
slots can be brought into alignment with the grooves 12 of the
laminated rotor core 11. The end regions 21 of the rotor bars 2
protrude into the slots 31 of the short-circuit rings 3.
[0022] In accordance with the invention, the short-circuit rings 3
comprise in each case four metal composite discs 32 that for their
part comprise in each case a first metal disc 33 and a second metal
disc 34 that is connected in a planar manner to said first metal
disc and is embodied from a different material thereto. In each
case, two adjacent metal composite discs 32 are arranged in such a
manner that the first metal disc 33 or second metal disc 34 that
are embodied from an identical material are facing one another. If
you count for each of the two short-circuit rings 3 the metal
composite discs 32 commencing at the front face of the laminated
rotor core, then in each case the second and the fourth metal
composite discs 32 are arranged in a mirror-inverted manner with
respect to the first and third metal composite disc 32. As a
consequence, in each case between the first and the second and also
between the third and the fourth metal composite disc 32, the first
metal discs 33 that are embodied from an identical material are
facing one another. Likewise, in each case between the second and
the third metal composite disc 32, the second metal discs 34 that
are embodied from an identical material are facing one another. In
the schematic illustration of FIG. 1, adjacent metal composite
discs 32 are illustrated for reasons of clarity in each case
slightly spaced apart from one another. In reality, the metal
composite discs 32 are generally positioned without a spacing with
respect to one another. Furthermore, it is possible that a spacing
is provided between the laminated rotor core 11 and the two metal
composite discs 32 that are positioned directly adjacent to the
laminated rotor core 11. The first metal discs 33 comprise on their
outer periphery a circumferential bevel 35 that extends in the
radial direction as far as the slots 31 of the short-circuit rings
3.
[0023] By virtue of the identical hatchings of the elements that
represent the rotor bars 2 or rather the first metal discs 33 in
FIGS. 1, 2 and 3, it is to be clarified that the rotor bars 2 and
the first metal discs 33 are preferably embodied from identical or
similar materials. It is particularly preferred that the rotor bars
2 and the first metal discs 33 are embodied from aluminum or an
aluminum alloy. As illustrated in FIG. 1, in this case the
thickness s.sub.1 of the first metal discs 33 is at least 60% of
the total thickness s of the metal composite disc 32. In the case
of an alternative embodiment, the rotor bars 2 and the first metal
discs 33 can be embodied from copper or a copper alloy.
[0024] The rotor bars 21 are bonded, preferably welded, to the
first metal discs 33 in the region of the slots 31. This is further
explained in connection with FIG. 2.
[0025] FIG. 2 illustrates an enlarged section from FIG. 1 in the
region of the connection between a rotor bar 2 and the first metal
discs 33 of a short-circuit ring. A bonded connection 36 is
produced in each case in the region of the slots 31 between the
first metal discs 33 and the end region 21 of the rotor bar 2,
illustrated in this case in a shortened manner. In the case of a
solder connection, the connection 36 can be a solder material that
fills a solder gap. In the case of a weld connection, the
connection 36 can be formed by means of a molten material of the
mutually connected partners or by means of a weld filler material.
The two metal discs 34 and the rotor bar 2 are not bonded together,
which is illustrated in FIG. 2 in each case by means of a gap
between these components.
[0026] FIG. 3 illustrates an enlarged section of a further
embodiment of a squirrel-cage rotor in accordance with the
invention 1 in the region of the connection between a rotor bar 2
and a short-circuit ring 3. In the case of this embodiment, the
short-circuit ring 3 comprises two metal composite discs 32 that
are arranged in a mirror-inverted manner with respect to one
another and comprise in each case a first metal disc 33 and a
second metal disc 34, and also metal composite discs 321 that are
positioned between said metal composite discs and comprise two
first metal discs 33 and a second metal disc 34 that is arranged
between two said first metal discs. In each case, a bonded
connection 36 is provided in the region of the slots 31 between the
first metal discs 33 of the metal composite discs 32 and 321 and
the end region 21 of the rotor bar 2, illustrated in this case in a
shortened manner. Although the outlay for producing metal composite
discs 321 that comprise more than two metal discs 33, 34 is greater
than when producing straightforward bi-metal discs, the outlay
involved in assembling the short-circuit ring 3 is considerably
reduced as a result of using this type of multi-layer metal
composite discs 321. The embodiment in accordance with FIG. 3 can
be modified to the extent that more than one metal composite disc
321 is used, said one metal composite disc comprising two first
metal discs 33 and a second metal disc 34 that is arranged between
the two first metal discs 33.
LIST OF REFERENCE NUMERALS
[0027] 1 Squirrel-cage rotor [0028] 11 Laminated rotor core [0029]
12 Groove [0030] 2 Rotor bar [0031] 21 End region [0032] 3
Short-circuit ring [0033] 31 Slot [0034] 32 Metal composite disc
[0035] 321 Metal composite disc [0036] 33 First metal disc [0037]
34 Second metal disc [0038] 35 Bevel [0039] 36 Connection [0040] 4
Bore hole [0041] A Axis [0042] s Thickness of a metal composite
disc [0043] s.sub.1 Thickness of the first metal disc
* * * * *