Description:‘A ROTOR SYSTEM FOR ARRESTING INDUCED STRESSES UNDER HIGH SHOCK AND VIBRATION CONDITION OF ELECTRICAL INDUCTION MACHINE’

FIELD OF THE INVENTION:

[001] The present invention generally relates to a novel and safe method to arrest the induced stresses in short circuiting ring and rotor damper bar of rotating electric induction machines due to high shock condition generated from motor foundation, by special design of short circuit, alteration of the orientation of damper bar for brazing with short circuiting ring and support for short circuiting rings which restrict and support delectation of short circuit ring under induced stresses. In this present invention placement of design components like short circuiting ring, damper bar and support for short circuiting ring are also important.

[002] In particular, this invention is directed to a rotor system for arresting induced stresses of electrical induction machine.

BACKGROUND OF THE INVENTION:

[003] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[004] The shock is a wave pulse contains an impulsive wave front, that undergoes an initial dynamic acceleration followed by deceleration at different time period. These acceleration and deceleration phenomena in electrical induction machine induce stresses which is generated through foundation of machine, to machine feet, and from machine feet through machine body to End shield. Since the interface of stator and rotor is connected by bearings, thus shock pulses get transferred from bearings to rotor of the electrical induction machines. The sudden induced stresses of shorter time period wave forms results in deflection of components which can generate operational damage in the rotor system of induction machines. In full rotor system of electrical induction machines the weakest link is short circuiting ring and rotor damper bars. Thus, the short circuiting ring and rotor damper bars must be capable enough to sustain the induced stresses of rotor system. Hence, Design of short circuiting ring & its accessories & rotor damper bars and placement of these components become profoundly important to arrest the induced stresses due to shock load, getting propagated from foundation of electrical machines in all x, Y and Z direction.

[005] The prevalent prior art is a standard practice for AC Induction machines, in which damper bars are directly brazed to cylindrical groove of short circuiting ring. The same practice is suitable for vibration and shock load up to 2-3g for 5-6 msec. (milli second). In case of high vibration and shock (i.e. higher than 2-3 g), the prior art fails to arrest high induced stress generated by greater than 2-3g shock value.

OBJECTS OF THE INVENTION:

[006] It is therefore an object of the invention, to propose a rotor system for arresting induced stresses of electrical induction machine, which is exposed in very high shock load conditions.

[007] Another object of the invention is to propose a rotor system for arresting induced stresses of electrical induction machine, which is simple in construction.

[008] Yet another object of the invention is to propose a rotor system for arresting induced stresses of electrical induction machine, which works efficiently.

[009] These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION:

[0010] One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

[0011] According to the invention, the designed rotor system has capability to withstand/arrest the shock load. The shock load pulse wave front is undergone an initial dynamic acceleration followed by deceleration with different time period, generates stresses from machine foundation to stator system and subsequently it propagates to the rotor system. The stator part can be strengthened by addition of material or change of material. The limitation occurs with rotor systems. The weakest link in the rotor system is rotor damper bars and short circuit ring. To counter induced stresses, design of short circuit ring and orientation of rotor damper bar for brazing with short circuit ring and in addition to that an indexed support arrangement has been envisaged for short circuit ring inner diameter. The short circuit ring inner diameter has also to be indexed and matched with support ring. The support ring also restricts the radial movement of the short circuit ring and also gives locking to the axial movement of short circuit ring. Moreover, in the teethed structure of short circuit ring the rotor damper bar is bent by 90 degrees and brazed with short circuit ring. With this arrangement, the transferred stresses get mitigated and also the weakest area is protected to avoid operational failure.

[0012] Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.
[0013] It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

[0014] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:

[0015] The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

FIG-1 shows: a typical short circuit ring, wherein inner diameter is indexed and the outer diameter has teethed structure in accordance with the invention.
FIG-2 shows: support ring for short circuit ring according to the present invention.
FIG-3 shows: complete assembly in which rotor damper bars are to be brazed with short circuit ring, wherein the assembly is locked axially and radially.
FIG-4 shows: FEM model stress pattern while excitation under shock load.
FIG-5 shows: Actual rotor system suitable for shock load application.

[0016] The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:

[0017] While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

[0018] Under high external vibration and shock load condition which is excited from the foundation of machines, travels through motor stator frame to end shield and from End Shield to Shaft, and from shaft to the damper bar and short circuiting ring. This induced stresses which originate from foundation, travel all along the motor body and affect the area where weak links are involved. Thus the area of damper bars and short circuiting ring need to be redesigned to cater induced stresses caused by high vibration and shock condition of 40-50g for 10msec.

[0019] With this new invention for high shock and vibration condition application i.e. 40- 50g for 11msec., it is possible to deliver the induction motor to the customer, which the applicant used to refuse for design and manufacturing of such induction motors.

[0020] Now, reference may be made to the figures 1-5 illustrating various parts of rotor system of instant invention. The rotor system of the invention for electrical induction machine helps to braze short circuiting ring (4) and rotor damper bars (3) differently from existing practice and affirm the configuration in the high vibration and shock condition. The fig 1. shows the teethed structured of the Short Circuiting Ring. The design of short circuit ring involves length and width of the groove, thickness of Short circuit ring, inner diameter indexing etc. The short circuit ring (4) inner circumference is indexed and matched with indexed support ring (5). The outer circumference of the short circuit ring (4) is having teethed structure.
[0021] As shown in the figure 2, the support ring (5) for short circuit ring restricts and provides rigidity to the short circuit ring (4) under induced stress condition. The support ring (5) for short circuit ring (4) is mounted on the rotor shaft (1). The rotor shaft (1) is mounted on rotor hub (2). The indexed outer part of support for short circuiting ring has also to be matched with indexed inner diameter of short circuit ring. The support for short circuit ring also provides locking axially and radially to the short circuit ring.

[0022] Referring to the fig. 3 regarding assembly of rotor system where all components are assembled so as to work in a combination. The brazing process and selection of brazing alloys are important requirements for such rotor system.

Brazing is a metal joining process in which two or more metal items are joined together by application of controlled heating via torch, furnace, induction, dipped, or resistance as heat sources occurring at a temperature above 450°C .In this process melting and flowing a filler metal which is called brazing alloy into the joint, with the filler metal having a lower melting point than the adjoining metal… Brazing differs from welding in that it does not involve melting the work pieces. Brazing differs from soldering through the use of a higher temperature and much more closely fitted parts than when soldering. During the brazing process, the filler metal flows into the gap between close-fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal is cooled to join the work pieces together with considerable strength.

[0023] As illustrated in the figure 3, in the teethed structure of short circuit ring (4) the rotor damper bar (3) is bent by 90 degrees and brazed with short circuit ring. With this arrangement, the transferred stresses get mitigated and also the weakest area is protected to avoid operational failure.

[0024] The rotor damper bars (3) are bent 90 degree inward in the groove /teethed structure and brazed suitably with short circuiting ring (4). The matched indexed support ring (5) for short circuit ring is placed in the indexed inner diameter of the short circuit ring for axial and radial locking of short circuit ring.

[0025] In prior art the rotor damper bar is directly brazed in the grooves of short circuit ring. Moreover, no such arrangement for the support of short circuit ring exists. This prior arrangement is also not suitable for shock load application.

ADVANTAGES OF INVENTION:
- Mitigation of the transferred stresses;
- Protection of the weakest area to avoid operational failure;
- Capability to withstand/arrest the shock load by rotor system;
- Simple in construction;
- User friendly.

TEST RESULT :
[0026] The figure 4 exhibits the FEM model analysis of distribution of stresses under vibration and shock condition. This shows that stresses are well within the acceptable range. The figure 5 shows the actual manufactured rotor for high vibration and shock load conditions.

WORKING OF INVENTION :

[0027] In all electrical induction motor have rotor system which mainly comprises of rotor shaft, Damper bars and Short Circuiting Rings. As per basic theory of Induction motor the rotor system particularly Damper bars and Short Circuiting Rings, which are brazed with both sides of damper bars, feel high current and thus rotor of motor starts energizing. In industrial induction electrical machines, no such extra stresses induced in the rotor system as system does not undergo any heavy shock and vibration conditions. When machine is subjected under high shock and vibration condition, the stresses induced from motor foundation feet to rotor system and thus finally reach to the weakest part of the chain which has been strengthened by introducing change in the design of Short Circuiting rings, brazing pattern and Support for Short Circuiting Ring.

[0028] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0029] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

[0030] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[0031] The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

[0033] The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

[0034] While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:WE CLAIM:

1. A rotor system for arresting induced stresses under high shock and vibration condition of electrical induction machine comprises of short circuit ring (4), wherein rotor damper bar (3) is bent, in which support ring (5) for the short circuit ring (4) is mounted on rotor shaft (1) and the rotor shaft (1) is mounted on rotor hub (2).

2. The rotor system as claimed in claim 1, wherein said rotor damper bar (3) is bent by 90 degrees and brazed with the short circuit ring (4).

3. The rotor system as claimed in claims 1-2, wherein the short circuit ring (4) inner circumference is indexed and matched with the indexed support ring (5).

4. The rotor system as claimed in claims 1-3, wherein the outer circumference of the short circuit ring (4) is having teethed structure.

5. The rotor system as claimed in claims 1-4, wherein the Brazing is a metal-joining process in which at least two metals are joined together by application of controlled heating via torch, furnace, induction, dipped/resistance as heat sources occurring at a temperature above 450°C, wherein in this process melting and flowing a filler metal which is called brazing alloy into the joint, with the filler metal having a lower melting point than the adjoining metal.