GB1588386A

GB1588386A - Traction motor transformer

Info

Publication number: GB1588386A
Application number: GB10918/78A
Authority: GB
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1977-03-24
Filing date: 1978-03-20
Publication date: 1981-04-23
Also published as: DE2811935A1; JPS53131430A; CH627874A5; FR2385200A1; SE7803358L

Abstract

This transformer (20) has a magnetic core (22), which is provided with a winding (24), and is mounted in a transformer tank (26). The latter is closed by a cover (30) by means of which a housing (32), which is connected to the tank (26), is firmly connected to an air cell (40) as an expansion chamber for a dielectric transformer fluid. The air cell (40) compensates for the thermal volume changes of the transformer fluid. This arrangement of the housing (32) prevents a conductive connection between the tank (26) and the housing (32) and in consequence results in a small structural volume. <IMAGE>

Description

(54) TRACTION MOTOR TRANSFORMER (71) We, GENERAL ELECTRIC COM PANY, a corporatíon organized and existing under the laws of the State of New York, United States of America, of 1 River Road, Schenectady 12345, State of New York, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to traction motor transformers, and is particularly useful for such transformers which contain a thermally expandable dielectric liquid of the type that readily absorbs moisture, oxygen and/or other atmospheric contaminants, such as transformers for use in a self-propelled, electrically powered transit car having limited mounting space for the transformer.

One extremely basic electrical power transformer comprises a magnetic core and winding assembly housed in a suitable enclosure and having electrically conductive means for connecting said winding to an external Dower source, and to an external load. The winding is immersed in a fluid dielectric whose type is primarily determined by the power transformer's voltages, winding size and enclosure size. An air space is provided within the transformer enclosure immediately above the liquid dielectric for thermal expansion of said liquid dielectric.

In locations where fire would very likely cause serious personal injuries, liquid dielectrics such as askarels are utilized; askarel being the generic name for chlorinated diphenyls. Dielectric materials of the askarel type have a relatively high flammability temperature and therefore present a much lower fire risk than, for example, mineral oil which is used in most standard liquid dielectric transformer apnlications.

In recent years there has been a definite trend away from the use of askarel filled transformers because of the conviction by some that these materials are harmful to man and his environment. Because of this development several materials have been tested to see if they can be substituted for askarels and, at the present time, silicone oil or polydimethylsiloxane (PDMS) is being utilized by some transformer manufacturers for such a substitution. A significant disadvantage of PDMS or silicone oil over liquid dielectrics such as an askarel or mineral oil, is that it readily absorbs moisture, oxygen and other atmospheric contaminants which substantially degrade its electrical insulating qualities. Another disadvantage of silicone oil is that its coefficient of thermal expansion is far greater than that of either an askarel or mineral oil.

In order to make effective use of silicone oil as a liquid dielectric a system must be provided that will isolate such a liquid from the contaminants in its immediate environment and enable said liquid to change volume over its entire thermal loading cycle. We market such an oil preservation system under our trademark Atmoseal. This particular system is used with very large, stationary. power transformers. In this system, which constitutes a relatively large structure, an expansion chamber incorporating a collapsible air cell is housed in an enclosure that is separate and apart from that of the transformer.

The air cell enclosure is positioned above and is normally supported by its associated transformer. Conduit is provided between the transformer and expansion chamber enclosures so that a liquid dielectric can freely flow between these enclosures. In addition to needing conduit between the transformer and expansion chamber enclosures for liquid dielectric flow and substantial suppdrt structure for the expansion chamber enclosure, this particular oil preservation system requires a relatively large ainout of space which is not available in a self-propelled, electrically powered transit car.

The present invention provides a traction motor transformer includirig a magnetic core mounted internal of and in a fixed relation with respect to a container, a winding on said magnetic core having means for connecting same to an external electrical circuit, a cover distinct from said container and incorporating an expansion chamber, said cover being in sealing relationship with said container to form a liquid-tight enclosure with the interior of the expansion chamber in freely communicating relationship with the interior of the container, an expandable air cell being located within the expansion chamber, the air cell being open to the atmesphere through a liquid-tight opening in the wall of the expansion chamber, and a liquid dielectric filling the container and the space between the air cell and the remainder of the expansion chamber.

A compact transit car transformer, for example, may thus be provided which incorporates a system for isolating the liquid dielectric within such a transformer from atmospheric contaminants in its immediate environment and thereby preserving the dielectric strength of said liquid dielectric. The system includes an expandable air cell whose interior space freely communicates with the external atmosphere through a liquid-tight opening in the transit car transformer's housing. Transit car transformer compactness is achieved by locating this liquid dielectric preservation system within an expansion chamber incorporated directly in the cover of said transit car transformer, container or tank.

In order that the invention may be clearly understood, a preferred embodiment thereof will now be described by way of example only with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a compact transit car transformer incorporating a liquid dielectric preservation system in a cover thereof, that is constructed in accordance with the embodiment of the present invention.

FIG. 2 is a partial cross sectional view taken on the line 2-2 in FIG. 1.

FIG. 2A is a partial cross sectional and exploded view taken on the line 2-2 in FIG.

1 showing the cover and dielectric fluid removed from the compact transit car transformer tank.

Referring now to the drawings and specifically to FTG. 1 which is a perspective view of compact transit car transformer 20 constructed in accordance with a preferred embodiment of the present invention. Transformer 20 includes magnetic core 22 having its core-legs lying in a horizontal plane and having winding 24 positioned around one leg of said core 22 in a fixed position with respect to said core 22. Core 22 is mounted within and is in a fixed position with respect to a container in the form of transformer tank 26. Electrical power enters and exits from transformer 20 by means of electrical bushings such as bushing 28, on transformer tank 26. These bushings are electrically connected, by suitable means, to winding 24 of said transformer 20.Additional bushings (!lot shown) are similarly mounted on another wall of said transformer tank 26 for the same purpose.

Transformer tank 26 has a cover 30 which incorporates dielectric liquid expansion chamber 32. Chamber 32 forms a part of said cover 30. The structural details of cover 30, chamber 32 and apparatus that is in or connected to said cover 30 and chamber 32 can be more clearly seen and its operation more clearly understood by referring to FIG. 2.

In FIG. 2, which is a partial cross sectional view taken on the line 2-2 in FIG.

cover 30 of transformer tank 26 incorporating chamber 32, is depicted.

Flanged port 34 having protective cap 36 extends through wall 38 of chamber 32 and the exterior surface of said flanged port 34 is in a liquid-tight relationship with said wall 38 of said chamber 32.

Protective cap 36 prevents water, debris, etc. from entering flanged port 34 while at the same time permits ambient air to freely pass through said flanged port 34.

Air cell 40, which is constructed of a fabric reinforced elastomer, has a single opening 42 therein through which ambient air can readily pass. The flanged portion of flanged port 34 extends into opening 42 of air cell 40 and is in a liquid-tight relationship with said air cell 40.

Cover 30, which includes chamber 32, is welded to transformer tank 26 to provide a liquid-tight seal between said transformer tank 26 and said cover 30. Ports 44A and 44B in cover 30 enable a liquid dielectric within transformer 20 to pass between transformer tank 26 and chamber 32 of cover 30. Valves 46A and 46B open when the pressure in chamber 32 exceeds a predetermined value. Liquid-tight access panel 48 permits the installation and/or removal of air cell 40 in chamber 32.

Silicone oil 50, the liquid dielectric in this the preferred embodiment of the invention, is introduced into transformer tank 26 and chamber 32 of cover 30 through valve 52 and completely covers the exterior surface of air cell 40 that is within chamber 32. The oil 50 is pumped into transformer tank 26 and chamber 32 until they are filled and air cell 40 is in the fully collapsed state. A volume of silicone oil 50, equivalent to the volume of air desired within air cell 40, is then decanted through valve 52.

The thermal expansion of silicone oil 50 in transformer tank 26 forces said oil into chamber 32 through ports 44A and 44B in cover 30. As silicone oil 50 enters chamber 32 it compresses air cell 40 forcing air out of said air cell 40 through opening 42 and flanged port 34. With this arrangement silicone oil 50 can thermally expand against the ambient air without being contaminated by contaminants in said air.

When silicone oil 50 cools and its volume is reduced, said silicone oil 50 flows from chamber 32 into tank 26 through ports 44A and 44B in cover 30 allowing air cell 40 to expand under the pressure of the ambient air that freely enters said air cell 40 through flanged port 34, and opening 42.

As previously indicated, cover 30 is welded to transformer tank 26 forming a liquid-tight relationship between these two members. Cover 30 may, as an alternative, be bolted to transformer tank 26 if suitable liquid-seal forming gasket material is provided between these members.

Although in use cover 30 is in sealing relationship with tank 26, constructionally the cover 30 is distinct from transformer tank 26 as shown in FIG. 2A which is a partial cross sectional and exploded view taken on the line 2-2 in FIG. 1 with the cover 30 and silicone oil 50 removed.

When cover 30 is removed from transformer tank 26, the expansion chamber 32 and air cell 40 contained in said chamber are removed with said cover. No additional expansion chamber appartus is provided or needed for transformer 20. Having the expansion chamber as part of cover 30 of transformer 20 makes it unnecessary to provide a separate expansion chamber unit for said transformer 20. This is one feature of the present invention that results in a considerable savings in space. The close proximity of chamber 32 to transformer tank 26 makes it unnecessary to provide additional means for channeling thermally expanding or contracting silicone 50 oil flowing between these two spaces.

WHAT WE CLAIM IS: 1. A traction motor transformer including a magnetic core mounted internal of and in a fixed relation with respect to a container, a winding on said magnetic core having means for connecting same to an external electrical circuit, a cover distinct from said container and incorporating an expansion chamber, said cover being in sealing relationship with said container to form a liquid-tight enclosure with the interior of the expansion chamber in freely communicating relationship with the interior of the container, an expandable air cell being located within the expansion chamber, the air cell being open to the atmosphere through a liquid-tight opening in the wall of the expansion chamber, and a liquid dielectric filling the container and the space between the air cell and the remainder of the expansion chamber.

2. A traction motor transformer according to claim 1, wherein said liquid dielectric is polydimethylsiloxane.

3. A traction motor transformer according to claim 2, wherein said polydimethylsiloxane is silicone oil.

4. A traction motor transformer according to any one of claims 1 to 3, wherein said container is a transformer tank.

5. A traction motor transformer according to any one of the preceding claims, wherein sealing relationship between said container and said cover is formed by welding these members together.

6. A traction motor transformer according to any one of claims 1 to 4, wherein the sealing relationship between said container and said cover is formed by a gasket that is interposed between these two members and bolt means that hold said members together.

7. A traction motor transformer substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. The thermal expansion of silicone oil 50 in transformer tank 26 forces said oil into chamber 32 through ports 44A and 44B in cover 30. As silicone oil 50 enters chamber 32 it compresses air cell 40 forcing air out of said air cell 40 through opening 42 and flanged port 34. With this arrangement silicone oil 50 can thermally expand against the ambient air without being contaminated by contaminants in said air. When silicone oil 50 cools and its volume is reduced, said silicone oil 50 flows from chamber 32 into tank 26 through ports 44A and 44B in cover 30 allowing air cell 40 to expand under the pressure of the ambient air that freely enters said air cell 40 through flanged port 34, and opening 42. As previously indicated, cover 30 is welded to transformer tank 26 forming a liquid-tight relationship between these two members. Cover 30 may, as an alternative, be bolted to transformer tank 26 if suitable liquid-seal forming gasket material is provided between these members. Although in use cover 30 is in sealing relationship with tank 26, constructionally the cover 30 is distinct from transformer tank 26 as shown in FIG. 2A which is a partial cross sectional and exploded view taken on the line 2-2 in FIG. 1 with the cover 30 and silicone oil 50 removed. When cover 30 is removed from transformer tank 26, the expansion chamber 32 and air cell 40 contained in said chamber are removed with said cover. No additional expansion chamber appartus is provided or needed for transformer 20. Having the expansion chamber as part of cover 30 of transformer 20 makes it unnecessary to provide a separate expansion chamber unit for said transformer 20. This is one feature of the present invention that results in a considerable savings in space. The close proximity of chamber 32 to transformer tank 26 makes it unnecessary to provide additional means for channeling thermally expanding or contracting silicone 50 oil flowing between these two spaces. WHAT WE CLAIM IS:

1. A traction motor transformer including a magnetic core mounted internal of and in a fixed relation with respect to a container, a winding on said magnetic core having means for connecting same to an external electrical circuit, a cover distinct from said container and incorporating an expansion chamber, said cover being in sealing relationship with said container to form a liquid-tight enclosure with the interior of the expansion chamber in freely communicating relationship with the interior of the container, an expandable air cell being located within the expansion chamber, the air cell being open to the atmosphere through a liquid-tight opening in the wall of the expansion chamber, and a liquid dielectric filling the container and the space between the air cell and the remainder of the expansion chamber.