Claims:WE CLAIM:
1. A hotel winding arrangement for a locomotive transformer, the winding arrangement comprising at least two coils of a predetermined power capacity arranged axially one above the other on a secondary side of the locomotive transformer wherein each of the coil serves an electrical load.

2. The hotel winding arrangement as claimed in claim 1, wherein the coils are separated by at least one winding block.

3. The hotel winding arrangement as claimed in claim 1, wherein each of the coil comprises plurality of disc, each disc having a predetermined number of turns.

4. The hotel winding arrangement as claimed in claim 1, wherein the locomotive transformer is a core type transformer.

5. The hotel winding arrangement as claimed in claim 1, wherein each of the coil serves a load generated by a pantry and a load generated by a coach of a locomotive.

6. The hotel winding arrangement as claimed in claim 1, comprising at least one winding bushing to electrically connect the coils to the load.

7. The hotel winding arrangement as claimed in claim 1, wherein a designated percentage impedance value is achieved between primary windings and each of the coils.

8. The hotel winding arrangement as claimed in claim 1, wherein a designated total allowable copper loss value is maintained between primary windings and each of the coils.
, Description:FIELD OF THE INVENTION
[001] The invention relates to a winding arrangement for a transformer, more particularly to a hotel winding arrangement for a locomotive transformer to cater to loads generated by pantry and coaches of a locomotive.

BACKGROUND OF THE INVENTION
[002] Locomotive Transformers form an integral part of Electric Loco Unit and serve as source of power supply to cater to varied running loads generated in an electrical locomotive. Figure 1 is a line diagram of winding arrangement for a conventional locomotive transformer 100 with two wound limbs wherein the transformer is supplied with a single phase power of designated capacity to the primary windings 110.
[003] As shown, the locomotive transformer is commonly constituted of secondary windings – traction windings 130, 132, 134 and 136, filter windings 140, auxiliary windings 150 and hotel load winding 120 with each winding provided with a designated power capacity and voltage as required to cater to specific load generated in the locomotive viz. the traction load, load on account of pantry and coaches and other auxiliary loads due to HVAC, lighting, fan etc. Such power capacity of each of the winding is generally fixed and may not be altered without carrying out necessary modification or changes in the existing windings.
[004] With continuous upgradation in respect of locomotive design based on ergonomical considerations and increased passenger load, improvements in existing utilities/parts/components of the locomotive cause the load and the power consumption requirement to be increased accordingly. Accordingly, the locomotive transformer capacity has to be upgraded to keep up with the increasing loads.
[005] Earlier, the complete loads of the locomotive were catered by separate generator units. However, the combined weight of these generator units increased bulkiness, occupied space and affected the overall locomotive efficiency. In wake of this, one generator unit was proposed to be replaced and the requisite locomotive load was supposed to be catered by a hotel load winding that catered to the load of pantry and coaches. But the present hotel load winding of the conventional locomotive transformer is not suitable to cater to the increased loads of pantry and coaches.
[006] Alternatively, redesigning locomotive transformer with increased power capacity exceeding the existing dimensional constraints of the conventional locomotive transformer may not be a viable option (especially with an increased height) owing to limited space available in the locomotive. Such a design consideration would only add to the weight and energy consumption of the locomotive with additional running and maintenance costs. Moreover, to accommodate such redesigned transformer with new dimensions will require redesigning of the storage space.
[007] Therefore, there is a need to have a locomotive transformer which may cater to the increased load generated by pantry and coaches within the existing dimensional constraints of a conventional locomotive transformer thereby keeping the performance and reliability of the Loco Unit intact.

SUMMARY OF THE INVENTION
[008] Accordingly, the present invention in one aspect provides a hotel winding arrangement for a locomotive transformer, the winding arrangement comprising at least two coils of a predetermined power capacity arranged axially one above the other on a secondary side of the locomotive transformer wherein each of the coil serves an electrical load. Each of the coil serves a load generated by a pantry and a load generated by a coach of a locomotive vehicle.
[009] In an embodiment of the present invention, the coils of the winding arrangement are separated by at least one winding block.
[010] In another embodiment of the present invention, each of the coils has a plurality of disc and each disc has a predetermined number of turns.
[011] In another embodiment of the present invention, the locomotive transformer is a core type transformer and has at least one winding bushing to electrically connect the coils to the load.

BRIEF DESCRIPTION OF THE DRAWINGS
[012] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 is a line diagram of winding arrangement for a conventional locomotive transformer.
Figure 2 is a line diagram of winding arrangement for a locomotive transformer in accordance with an embodiment of the present invention.
Figure 3 is a schematic representation of winding arrangement for a locomotive transformer in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[013] The present invention is directed towards a hotel winding arrangement to cater the load requirements of pantry and coaches of a locomotive.
[014] Figure 2 shows a line diagram of winding arrangement for a locomotive transformer 200 in accordance with an embodiment of the present invention. In an embodiment of the invention, the transformer is a single phase core type transformer with two wound limbs. As shown in figure 2, the locomotive transformer is constituted of different windings – primary windings 210, traction windings 230, 232, 234 and 236, filter windings 240, BUR or auxiliary windings 250 and hotel load windings 220,222 with each winding provided with a designated power capacity and voltage as required to cater to specific load generated in the locomotive .
[015] The windings are designed with sandwich type construction on both limbs such that the windings are axially symmetrical on each of the limbs. Furthermore, all the windings in the locomotive transformer are designed with disc type winding construction and each disc has a predetermined number of turns. Number of turns per winding and number of discs per winding are designed based on the power and voltage requirement of each winding. Accordingly, the design is made based on the principle of axial symmetrical windings on each limb.
[016] Figure 3 is a schematic representation of winding arrangement for a locomotive transformer 300 in accordance with an embodiment of the present invention. As shown, each limb consists of 3 primary windings 210 (denoted by HT in figure 3) located at the top and bottom side of the each limbs. The primary windings are adapted to receive an input voltage at a designated capacity to cater to varied loads of the locomotive.
[017] Also, 2 traction windings 230,232,234 and 236 (denoted by TR in the figure 3) are located at the top and bottom side of the each limbs. Further, BUR winding 250 (as shown in the figure 3) is placed at the center position of the limb 1 and similarly the hotel windings 220,222 (denoted by HL in figure 3) are placed at the center position of the limb 2.
[018] Furthermore, the filter windings 240 (denote by Fi as shown in figure 3) are placed between the primary and traction windings, and connected together in series and parallel configuration to meet the technical requirements of the windings. Further, the interconnections made between the pairs of primary windings and between the pairs of traction windings in series and parallel configuration also meet the technical requirements of each of the windings.
[019] In this regard, the traction windings cater to the traction load of the locomotive by providing the designated power and voltage to the traction motors of the locomotive. Further, the filter windings aid to filter the undesired harmonic currents generated during the electrical supply. Furthermore, the BUR windings or the auxiliary windings cater to the auxiliary load generated in the locomotive on account of oil pumps, compressors, lights, blowers, battery charging etc. An auxiliary convertor unit typically of IGBT (Insulated- Gate Bipolar Transistor) based configuration is fed from the BUR windings to cater to the auxiliary loads. Additionally, the hotel load windings cater to the load generated by pantry and coaches of the locomotive.
[020] In this regard, the winding arrangement of the hotel load windings as described hereinbefore comprises at least two coils of a predetermined power capacity arranged axially one above the other on a second limb of the locomotive transformer wherein each of the coil serves an electrical load. Each of the coil thus provides a separate output voltage point/connection to supply to the pantry and the coaches thereby serving the load generated by the pantry and the load generated by the coach of the locomotive. In an embodiment of the present invention, each of the coil has a plurality of disc and each disc has a predetermined number of turns. Number of turns per coil and number of discs per coil determine the power capacity of the hotel winding.
[021] Further, the coils of the hotel load winding arrangement are separated by at least one winding block and at least one winding bushing is provided to electrically connect the coils to the load.
[022] Further based on the specific requirements of power and voltage supply to the locomotive, the locomotive transformer can be designed accordingly to cater to the varied loads generated. For example, in a locomotive transformer of power rating 7775 kVA, the primary winding is designed to 7775 kVA and the secondary windings are designed to their respective kVAs (4 traction windings of 1449 kVA, filter windings of 400kVA, BUR winding of 334 kVA, 2 hotel load windings of 622.5 kVA) such that sum of all these secondary windings is 7775 kVA.
[023] In the above example of locomotive transformer with power capacity of 7775 kVA, each of the two hotel load winding has a capacity of 622.5 kVA /960 Volts from which two separate voltage outputs can be drawn. The two separate output voltages can be electrically connected to external electrical load with the help of bushings provided on the locomotive transformer. Further, the hotel load windings are made of continuously transposed copper (CTC) wound in a disk type fashion especially continuous double disc winding with 6 discs wherein each discs has 9 turns. Furthermore, the winding arrangement/ construction with the two hotel load windings has 50 turns per winding. Such winding arrangement advantageously aids to accommodate the two hotel load windings without altering the existing dimensions (axial height: 126 mm; radial built: 217 mm) of the conventional locomotive transformer.
[024] Advantageously, the winding arrangement with the hotel load windings described hereinbefore is able to meet the designated percentage impedance of 15% between the primary windings and each hotel load winding as applicable for conventional locomotive transformer with single hotel load winding.
[025] Advantageously, the winding arrangement with the hotel load windings described hereinbefore maintains copper loss between the primary windings and the hotel load windings within the designated value of 16 KW as applicable for conventional locomotive transformer with single hotel load winding.
[026] Advantageously, the locomotive transformer described hereinbefore can be mounted under slung on under frame. Moreover, provision of such winding arrangement does away with the use of existing generator car in the locomotive/Loco Unit.
[027] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.