Description:

TECHNICAL FIELD
[0001] The present disclosure, in general, relates to rotary electric machines. In particular, the present invention relates to a test fixture which can be used to simulate the actual condition of assembly of material for rotor winding at manufacturing plant and operation of the Turbo generator rotor at site under themal and mechanical stress.
BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention.
[0003] The Turbo Generator (TG) is a rotating electromechanical equipment which converts mechanical energy to electrical energy in an electrical power generating station. Normally, in a coal based thermal power plant, the TGs are coupled to steam turbines as a driver and source of mechanical energy. The TG rotor carries several turns of copper conductors arranged in helical manner with one conductor over the other and strips of inter turn insulation in between two layers of conductors, thus forming the rotor winding. The TG rotor carries DC current to act like an electromagnet during the operation of the generator.
[0004] The interturn insulation in the rotor winding consist of hard glass fibre laminates with one side B–stage(semicured)epoxy adhesives. During manufacturing stages, this B-stage material gets thermally cured and adheres to one side of the rotor conductor. During operation of TG at power plant, the rotor conductors expand and contract depending upon the load current/excitation current carried by the rotor winding. Due to adherence of the interturn insulation to the copper conductor and thermal resilience of the glass fibre and adhesive material, necessary interturn insulation property is ensured thus interturn faults are avoided.
[0005] Technical problem of the existing solutions is that the material used is normally manufactured and marketed by very limited manufacturers in European countries in line with their own specification. As such, no prior information is available with respect to the long term method of evaluation and suitability of the material except for testing the electrical stress withandability,i.e (i) Break down voltage ( BDV) and (ii) adhesion test at room temperature of the cured insulation (RT). In view of the above, there are instances of delayering of cured interturn insulation during operation of TGs at elevated temperature resulting in interturn faults and leading to earth faults in the TG rotor.
[0006] Accordingly, there is a need for a fixture or a model that can simulate the actual conditions of assembly of material in which several rotor conductors along with interturn insulation are assembled and cured at predetermined temperature and pressure.
OBJECTS OF THE DISCLOSURE
[0007] Some of the objects of the present disclosure, which at least one embodiment herein satisfy, are listed hereinbelow.
[0008] It is a general object of the present disclosure is to provide a SLOT model in which several rotor conductors along with inter turn insulation are assembled and cured at predetermined temperature and pressure.
[0009] It is another object of the present disclosure is to expose the model to a thermal stability test and cyclic temperature test.
[0010] It is another object of the present disclosure is to help in establishing of new as well as Indegenous sources to save spending foreign currency and cost to the end user.
[0011] 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
[0012] This summary is provided to introduce concepts related to a test fixture to simulate the actual condition of assembly of material for Turbo-generator rotor winding. The concepts are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
[0013] In an embodiment, the present disclosure relates to a test fixture to simulate the actual condition of assembly of material for Turbo generator rotor winding comprising a U-shaped channel, a plurality of wedges inserted in the space left between the slot model and the U-shaped channel. A plurality of flanges of the U-shaped channel and the plurality of wedges are fixed together. The slot model comprises a plurality of copper strips and a plurality of inter turn insulation wherein each of the copper strip from the plurality of copper strips is separated by the each of the inter turn insulation from the plurality of inter turn insulation. The plurality of copper strips and a plurality of inter turn insulation are held together and tightened by the help of top and bottom HGL (Hardened Glass laminate) strips.
[0014] In an aspect, the U-shaped channel has a plurality of flanges protruding out of its ends.
[0015] In an aspect, the plurality of flanges of the U-shaped channel and the plurality of wedges are fixed together by means of a nut and bolt.
[0016] In an aspect, a plurality of washers are fastened between the nut and the bolt.
[0017] In an aspect, the test fixture is subjected to (i) Thermal stability test and (ii) Cyclic temperature test.
[0018] In aspect, the plurality of inter turn insulation is preferably glassoflex and Flexible HGL with one side B- stage adhesive.
[0019] In an aspect, the test fixture is subjected to a double frequency (100 Hz) vibration test to simulate the condition of machine operation.
[0020] In an aspect, the test fixture is subjected to a dielectric test and adherence test on an indigenous and imported material.
[0021] In an aspect, a plurality of side packers is provided between the walls of the U shaped channel and slot model.
[0022] 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.
[0023] 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.
[0024] 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 DRAWINGS
[0025] The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described, by way of example only, and with reference to the accompanying figures, in which:
[0026] FIG. 1 illustrates a U-shaped channel pf the present subject matter;
[0027] FIG. 2 illustrates a front view of a test fixture to simulate the actual condition of assembly of material for Turbo-generator rotor winding;
[0028] FIG. 3 illustrates top view without bolts of the present subject matter;
[0029] FIG. 4 illustrates an exploded and side view of the present subject matter;
[0030] FIG. 5 illustrate an isometric view of the present subject matter; and
[0031] FIG. 6 illustrates an assembly of 6 test fixtures.
[0032] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative systems embodying the principles of the present subject matter.
DETAILED DESCRIPTION
[0033] The detailed description of various exemplary embodiments of the disclosure is described herein with reference to the accompanying drawings. It should be noted that the embodiments are described herein in such details as to clearly communicate the disclosure. However, the amount of details provided herein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.
[0034] It is also to be understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and embodiments of the present disclosure, as well as specific examples, are intended to encompass equivalents thereof.
[0035] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a",” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.
[0036] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0037] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
[0038] FIG. 1, 4, and 5 illustrates a test fixture (100) to simulate the actual condition of assembly of material for Turbo-generator rotor winding. It comprises of a U-shaped channel (101) to intake a slot model from the top. This U-shaped channel (101) has a plurality of flanges protruding out of its ends. The U-shaped channel (101) has a cavity to intake a Slot model (102) from the top. The Slot model (102) is slided into the cavity part of the U-shaped channel (101).
[0039] A plurality of wedges (107) are inserted in between the space left while the slot model (102) is inserted in the U-shaped channel (101). The wedge on each side has an L-shape to easily fit in the space. One portion of the L-shaped wedge is affixed to provide support to the U-shaped channel (101) and the other is affixed to the Slot model (102). The wedge is fixed to the flange by means of nut (109) and bolt (110). A plurality of washers (111) are provided between the nut (109) and bolt (110) to distribute the pressure of the nut evenly over the surface, so that the surface isn't damaged.
[0040] The slot model (102) comprises of a plurality of copper strips (104) and a plurality of inter turn insulation (105). The plurality of copper strips (104) and plurality of inter turn insulation (105) are placed alternatively to each other where each of the copper strip from the plurality of copper strips (104) is separated by the each of the inter turn insulation from the plurality of inter turn insulation (105). The plurality of copper strips (104) and plurality of inter turn insulation (105) are tightened by the help of HGL strips to fill any space left in between. The top HGL strip (103) and bottom HGL strip (106) are provided at the top and bottom of the slot model (102) to keep the plurality of copper strips (104) and plurality of inter turn insulation (105) in place.
[0041] A hex screw (108) is present at the top of the test fixture (100) to support it as a whole. The hex screw (108) is tightened in the middle and hence a downward force is exerted which pushes the plurality of wedges (107) to the slot model (102) so that the whole test fixture (100) is sturdy and no unnecessary space is left in between to cause any limitation. The side packers (112) also serve the similar purpose, where the side packers (112) are inserted between the U-shaped channel (101) and the slot model (102). The arrangement thus is to simulate the actual assembly of Turbo generator winding with several vertically assembled rotor copper winding with interturn glasoflex insulation.
[0042] Fig. 6 discloses an assembly of test fixtures (100) where six of the test fixtures are shown in an assembly. Fig. 2 is a part of Fig. 6, where multiple test fixtures (100) are assembled together for evaluation purposes.
[0043] The Slot models (102) are cured in an oven at predetermined elevated temperature (In the current case at 160°C for 16 hours for Class-F Epoxy adhesive system). The cured Slot models (102) are subjected to (i) Thermal stability test at 160°C for 12 weeks (one week in each cycle) and (ii) Cyclic temperature test (50 cycles at 160°C -14 Hours in each cycle of temperature rise and cooling to room temperature). The purpose of the above two tests is to simulate the condition of thermomechanical stresses on the insulation of the Turbo Generator rotor winding during sustained full load and cyclic loading of the Turbo Generators at site. During the above two tests the cured slot models are subjected to double frequency (100 Hz as the normal operating frequency of generators are 50 Hz) vibration to simulate the condition of machine operation. Following the above cycles, the dielectric test of the insulation (i.e Break down voltage-BDV test) and adherence test carried out on both imported and indegenously developed material with (4+2) Slot Models each for comparison of range of values for a comprehensive decision.
[0044] The below table provides that there are Six Slot models made with actual TG rotor winding Copper strips with interturn insulation in between. The dimentions are furnished below. Three each for evaluation of Imported and Newly developed Indegenous materials.
S.No Test No. of Moulds
Indigenous Imported
1 Thremal Stability Test at 1600 C for
1 Week
2 Week
3 Week
.
.
12 Week 3 3
2 Cyclic Temerature at 1800 C 14 Hrs for
1 Cycle
2 Cycle
3 Cycle
5 Cycle
12 Cycle
25 Cycle
50 Cycle 3 3

[0045] Working of the present subject matter:
[0046] The process of evaluation of the material is done for relaible operation of Turbo Generator Rotor in electrical Power Generating Stations with long life. The test fixture are subjected to (i) Thermal stability test at 160°C for 12 weeks (one week in each cycle) and (ii) Cyclic temperature test (50 cycles at 160°C for 14 Hours in each cycle of temperature rise and cooling to room temperature). The purpose of the above two tests is to simulate the condition of thermomechanical stresses on the insulation of the Turbo generator rotor winding during sustained full load and cyclic loading of the Turbo Generators at site.
[0047] During the above two tests the cured test fixtures (100) are subjected to double frequency (100 Hz) vibration to simulate the condition of machine operation. Following the above cycles, the dielectric test of the insulation ( i.e Break down voltage- BDV test) and adherence test carried out on both imported and indegenously developed material with (4+2) test fixtures each for comparison of range of values for a comprehensive decision. This will ensure reliable operation of Turbo Generator rotor in electrical power generating stations with a long life. The entire exercise will also facilitate development of indegenous/ alternate sources of this material deciding the reliability of Turbo Generator operation.
[0048] With the present test fixture, the following technical advantages are obtained.
[0049] The invention facilitates complete evaluation of inter turn insulation suitable for Turbo Generator rotor application.
[0050] The invention also helps in establishing new as well as Indegenous sources and helps in saving of foreign currency and cost to the end user.
[0051] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

Claims:We claim:
1. A test fixture (100) to simulate the actual condition of assembly of material for Turbo-generator rotor winding. It comprising:
a U-shaped channel (101) to intake a slot model from the top;
the (longitudinal) Slot model (102) slidably inserted into the U-shaped channel (101) and fixed together. It comprises of,
a plurality of copper strips (104) and a plurality of inter turn insulation (105) mounted in vertical direction inside the Slot model (102), wherein each of the copper strip from the plurality of copper strips (104) is separated by the each of the inter turn insulation from the plurality of inter turn insulation (105);
a top HGL strip (103) and a bottom HGL strip (106) inserted at the top and bottom of the Slot model (102);
a plurality of wedges (107) inserted in the space left between the slot model (102) and the U-shaped channel (101); and
a hex screw (108) fastened in the middle of the test fixture to affix the plurality of wedges (107) to the Slot model (102).

2. The test fixture as claimed in claim 1, wherein the U-shaped channel (101) has a plurality of flanges protruding out of its ends.

3. The test fixture as claimed in claim 1 or 3, wherein the plurality of flanges of the U-shaped channel (101) and the plurality of wedges (107) are fixed together by means of a nut (109) and bolt (110).

4. The test fixture as claimed in claim 3, wherein a plurality of washers (111) are fastened between the nut (109) and the bolt (110).

5. The test fixture as claimed in claim 1, wherein the plurality of inter turn insulation (105) is preferably glassoflex.

6. The test fixture as claimed in claim 1, wherein the test fixture (100) is subjected to (i) Thermal stability test and (ii) Cyclic temperature test.

7. The test fixture as claimed in claim 1, wherein the test fixture (100) is subjected to a double frequency (100 Hz) vibration test to simulate the condition of machine operation.

8. The test fixture as claimed in claim 1, wherein the test fixture (100) is subjected to a dielectric test and adherence test on an indigenous and imported material.

9. The test fixture as claimed in claim 1, wherein a plurality of side packers (112) are provided between the walls of the U shaped channel (101) and slot model (102).