FIELD OF THE INVENTION
00001. The present invention relates to a bandage tape for securing the
magnets in rotor of electrical machines against flying off due to centrifugal force,
which is prepared by poly-glass bandaging tape impregnated with polyester resin
system.
BACKGROUND OF THE INVENTION
2. Recently there has been a trend towards permanent magnet machines due to certain inherent advantages associated with PM machines such as high efficiency, high power density and simple variable frequency control. Though PM machines suffer from the disadvantages of high magnet cost, sensitivity of magnet towards temperature and demagnetization, their advantages far outweigh the disadvantages and hence their demand is on increase. Keeping pace with development of the permanent magnet machines BHEL has developed its own technology for these machines. In permanent magnet machines magnets are inserted into rotor slots which have to be secured against getting dislodged from slots due to centrifugal force. World over many techniques have been used to secure magnets in the slots. BHEL has adopted a specially designed technique for such application which is being covered through this patent.
3. Generally, two types of topologies are used for placing magnets in the rotor.

1) Surface mounted PM rotor
2) Interior mounted PM rotor

4. The background research shows that different manufacturers of permanent magnet machines have their own methodology of securing magnets in rotor slots which varies from bonding the magnets to magnetic steel or using a retaining sleeve for high speeds.
5. Hence, there is always a need to innovate a technology for bandaging the magnet in rotor of high speed electrical machines, which provides higher efficacy.
6. The present invention meets the long felt need.
OBJECTS OF THE INVENTION
7. It is therefore the primary object of the present invention to provide a methodology to bandage the magnets in rotor by using poly-glass tape bonded and impregnated with thermosetting polyester resin system.
8. Another object of the present invention is to provide a methodology to bandage the magnets in the rotor to securely placing of magnet against the impending centrifugal force resulting due to rotation of the rotor.
9. Yet another object of the present invention is to provide a bandage tape to the rotor, which is rigid with a hard smooth resin rich surface and having improved heat dissipation factor.
10. Further object of the present invention is to provide a bandage tape, which having good tensile strength, resistant to humidity and saline water.

000011. Another object of the present invention is to provide a bandage tape to
the rotor, which has a temperature index of at least 180 and can fight against
the environmental intrusion such as moisture.
SUMMARY OF THE INVENTION
12. One or more drawbacks of conventional systems for bandaging magnets in rotor of electrical machines are overcome, and additional advantages are provided through the composition 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 details herein and are considered to be part of the claimed disclosure.
13. A component for bandaging magnets in rotor of electrical machines is a poly-glass banding tape, which impregnated with specially formulated fully catalyzed thermosetting polyester resin named RE009 solventless class 200 Deg. C Varnish. (Quantity - 5 Litres approx.).
14. Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments.
15. 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.
16. 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.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
17. While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way 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.
18. It is to be noted that a person skilled in the art would be motivated from the present disclosure to arrive at a method for securing the magnets in rotor of high speed electrical machines. However, such modifications should be construed within the scope of the disclosure.
19. As used in the description herein and throughout the claims that follow, the meaning of "a", "an", and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.
20. The terms "comprises", "comprising", or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusion, such that a method, magnet, high speed, electrical machine that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such method, or assembly, or method. In other words, one or more elements in a system or device proceeded
by "comprises a "does not, without more constraints, preclude the existence
of other elements or additional elements in the system, apparatus or device.

21. The present invention provides a method for securing the magnets in rotor of high speed electrical machines with the help of poly-glass banding tape in order to check flying off due to centrifugal force.
22. This innovative technology is particularly suitable for high speed machines i.e. machines with 3000 rpm synchronous speed.
23. However, this technology may also be applied to other speed machines.
24. The method of bandaging the magnets in rotor comprises the steps of:
i) calculation of the centrifugal force which depends on the size and structure
of the rotor, speed, number of magnets and their size; ii) insertion of the magnets into the slots made on the surface of the rotor
hub with the help of end plates; iii) preheating the rotor to a temperature of 90 to 120°C;
iv) impregnation of high strength, moisture resistant and unidirectional poly-glass banding tape and subsequent bonding with a specially formulated fully catalyzed high temperature thermosetting polyester resin system; v) application of said poly-glass tape in transverse motion with half overlap
throughout the length of rotor with a tension of 100 N/mm width; vi) sealing or fusing the end of tape so that the tape does not slip back and
the bandaging remains in full tension; vii) application of a layer of 2 mm thick epoxy glass laminate over the
bandaging, which may be removed after the curing process; viii) curing of the bandaging tape to get the final homogenous mass.
000025. The centrifugal force acting on the magnets is calculated which
depends on the size and structure of the rotor, speed, number of magnets and
their size. Based on the force acting on the magnets the thickness of the
bandaging to be applied is calculated to generate the required resistive force to
balance out the centrifugal force acting on the magnets.

000026. When the poly-glass tape is applied on the length of rotor, the number
of layers to be applied will depend upon the total thickness of bandaging as
decided in as per the size and structure of the rotor, speed, number of magnets
and their size. While deciding the number of layers to be applied, due care shall
be taken to account for reduction in tape thickness from uncured to cured stage.
27. The epoxy glass laminate can be secured in its position (so that it firmly presses the bandaging) with help of two layers of poly-glass tape over the glass laminate. This is done in order to obtain a smooth surface over bandaging after the curing. It is very important to provide non-magnetic protection layer as the magnetic material may not be suitable due to presence of magnets below the bandaging.
28. The curing process of the bandaging tape comprises the steps of:
i) keeping the rotor inside the oven at either 140 ± 3°C for six hours or 150 ± 3°C for 5 hours along with extra duration of 3 hours to bring the body of rotor from ambient to curing temperature; ii) checking the hardness of band, which is to be yellowish or lemon colour and with shore hardness more than 88 on the scale.
000029. The fully cured band is rigid with a hard smooth resin rich surface,
which is void free. This mass greatly improves heat dissipation factor. During
the curing cycle, the resin contained in tape not only flows and forms the bands
into homogeneous structure but the resin also penetrates between opening in
core and magnets assisting in anchoring the magnets against side movement
thus adding to the overall stability under all conditions. The tape when cured
has good tensile strength, resistance to humidity and saline water and a
temperature index of at least 180.

30. Semi cured tape in stage-B is used in the form of a soft, well balanced flat ribbon ensuring that each yarn strand bears an equal share of the load. In B-stage, the specially formulated resin insulates each glass yarn. During curing the resin flows, filling the voids and the air spaces to provide a homogenous laminate.
31. In accordance with another embodiment of the present invention, there is provided a poly-glass tape for securing the magnets in rotors of electrical machines, which is high strength, moisture resistant unidirectional and specially formulated fully catalyzed high temperature thermosetting polyester resin system. The continuous twisted fibre glass yarns of electrical grade having high tensile strength are laid parallel to form a thin flat ribbon with exceptional strength. The tape is soft and pliable.

32. The fully cured band is rigid with a hard smooth resin, rich surface, which is void free and greatly improves the heat dissipation factor.
33. The poly-glass tape is prepared to fight against the environmental intrusion such as moisture etc.
34. 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.
35. 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.
000036. The present disclosure provides a method for bandaging magnets in
rotor of electrical machines
Equivalents:
37. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.
38. 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 particular 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, eve it 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).
39. 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.
40. 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.
41. 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.

000042. 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.

WE CLAIM :
1. A component for bandaging magnets in rotor of electrical machines is a poly-glass banding tape, which impregnated with specially formulated fully catalyzed thermosetting polyester resin.
2. The component for bandaging magnets in rotor as claimed in claim 1, wherein the polyester resin is RE009 solventless class 200 Deg. C Varnish.
3. A method of bandaging the magnets in rotors of electrical machines comprises:
i) calculation of the centrifugal force which depends on the size and structure of the rotor, speed, number of magnets and their size.
ii) insertion of the magnets into the slots made on the surface of the rotor
hub with the help of end plates; iii) preheating the rotor to a suitable temperature;
iv) impregnation of high strength, moisture resistant and unidirectional poly-glass banding tape and subsequent bonding with a specially formulated fully catalyzed high temperature thermosetting polyester resin system; v) application of said poly-glass tape in transverse motion with half overlap
throughout the length of rotor; i) sealing or fusing of end of tape so that the tape does not slip back and the bandaging remains in full tension; vii) application of a layer of epoxy glass laminate over the
bandaging, which may be removed after the curing process; viii) curing of the bandaging tape to get the final homogenous mass.
4. The method of bandaging the magnets in rotors as claimed in claim 2, wherein
the rotor is preheated at a said temperature of 90 to 120°C.

5. The method of bandaging the magnets in rotors as claimed in claim 2, wherein the poly-glass tape is applied throughout the length of 100 N/mm width.
6. The method of bandaging the magnets in rotors as claimed in claim 2, wherein the epoxy glass laminate is of 2 mm thick.
7. The method of bandaging the magnets in rotors as claimed in claim 2, wherein the epoxy glass laminate is placed with help of two layer of poly-glass tape.
8. The method of bandaging the magnets in rotors as claimed in claim 2, wherein the curing of the tape comprises the steps of:
i) keeping the rotor inside the oven at either 140 ± 3°C for six hours or 150 ± 3°C for 5 hours alongwith extra duration of 3 hours to bring the body of rotor from ambient to curing temperature;
ii) checking the hardness of band, which is to be yellowish or lemon colour and with shore hardness more than 88 on the scale.
9. The method of bandaging the magnets in rotors as claimed in claim 2, wherein
the fully cured band is lemon or yellowish in colour and hardness is more than
88.
Dated this 30th day of January, 2019