US2702876A

US2702876A - Protective means for electrical devices

Info

Publication number: US2702876A
Application number: US116794A
Authority: US
Inventors: Arthur E Moog
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1949-09-20
Filing date: 1949-09-20
Publication date: 1955-02-22
Anticipated expiration: 1972-02-22

Description

Feb. 22, 1955 A. E. MOOG 2,702,876

PROTECTIVE MEANS FOR ELECTRICAL DEVICES Filed Sept. 20, 1949 FIG. 1

l .J INVENTOR.

/ ARTHUR E. M006 F) rra /vf y United States Patent '0 PROTECTIVE MEANS FOR ELECTRICAL DEVICES Arthur E. Moog, Caldwell, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application September 20, 1949, Serial No. 116,794

2 Claims. (Cl. 317-45) The invention relates to electrical devices, and more particularly to protective means therefor, and to the absorption or eummation of products of combustion when the devices overheat.

An overheated electrical device, such as a transformer, generates steam, ODIIOXIOUS rumes and smoke irritating to the nose and throat. if the housing enclosing the device is sealed, the steam pressure may become so great as to rupture the housing, and permit the fumes and smoke to escape therefrom.

When such a device 18 used in aircraft, the pilot and passengers are seriously alarmed by the fumes and smoke which permeate the caom of the craft. 'lhe pilot is often prompted to make an emergency landing with all its hazards rather than risk remaining airborne with the uncertainty of a ma or failure, whereas only a minor piece or equipment may have overheated without meeting safe operation of the craft.

it is common practice to use a fuse in circuit with an electrical device to open the circuit during overheating, but the device cannot readily be fused so that the circuit is opened before fumes and gas escape from the device.

One object of the present invention is to absorb prodnets of combustion when an electrical device overheats so that the fumes and smoke do not escape therefrom.

Another object is to provide an electrical device, having a sealed housing and a fuse, with a substance to absorb moisture and other products of combustion when the device overheats, so that steam pressure within the housing is maintained sufficiently low until the circuit is opened by the fuse and while the device cools, to prevent rupture of the casing.

Another object is to embed the fuse in the windings of the coils or other wiring so that the fuse responds readily to overheating of the device.

The invention contemplates an odor absorbing substance associated with an electrical device subject to overheating to avoid odors when the device overheats. The substance preferably absorbs moisture also so that when the housing of the device is sealed, pressure within the housing due to steam is reduced to prevent rupture of the housing. The invention contemplates protecting the device by a fuse embedded in the wiring and highly responsive to overheating of the device so that the steam generated during overheating is a minimum.

The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawing wherein one embodiment of the invention is illustrated. It is to be expressly understood, however, that the drawing is for illustration and description only, and is not to be construed as defining the limits of the invention.

In the drawing, Figure 1 is a front view of a transformer constructed according to the invention, with a portion of the front wall cut away to better show the construction.

Figure 2 is a schematic wiring diagram showing the circuit arrangement of the transformer.

Figures 3 and 4 are perspectives of the transformer windings showing details of construction.

In Figure 1, a three-phase transformer constructed according to the invention has a hermetically sealed housing 1 adapted to withstand pressure of approximately pounds per square inch. The housing has a front wall 3, a rear wall 5,

side walls

7, 9, a top wall 11, and a bottom wall 13. A laminated core 15 is secured within housing 1 by brackets 17. Core 15 has outer legs 19 and an inner leg 21. An outer phase winding 23 is wrapped on each outer leg 19, and an inner phase winding 25 is wrapped on inner leg 21. The windings are connected by leads 27 to taps 29 on top wall 11.

Each outer phase winding 23 (see Figures 2 and 3) comprises an inner primary coil 31 and an outer secondary coil 33 separated by suitable interwinding insulation. A fuse 35 is positioned between the primary and secondary coils in the insulation and is connected in series with the primary coil.

Inner phase winding 25 includes successively wound

secondary coils

37, 39, 41, and a tapped primary coil 43. Suitable interwinding insulation is provided between each coil. A fuse 45 is positioned between

secondary coils

37, 39, in the associated interwinding insulation, and a fuse 47 is positioned between secondary coil 41 and primary coil 43 in the associated interwinding insulation. The

fuses

45 and 47 are connected in series with primary coil 43, as shown in Figure 2. With the arrangement described, the fuses are intimately associated with the respective phase windings, and a rise in temperature in the windings will be readily detected by the fuses.

Before housing 1 is hermetically sealed, the entire air space within the housing is filled with activated alumina 49, preferably of 8 to 14 mesh, which substantially surrounds core 15 and

windings

23, 25.

When one or more of the windings in the transformer overheats, the fuse associated with the overheated winding melts and opens the circuit in which the overheated winding is connected. Before the circuit opens, the insulation and varnish on the overheated winding may give off products of combustion, including moisture, smoke and obnoxious fumes comprising distillation products. The moisture, smoke and odors are absorbed by the activated alumina, and any pressure that might otherwise be generated within the housing, by moisture being converted to steam, is avoided so that the housing ordinarily will not rupture. However, should the housing rupture before the transformer cools, then the activated alumina serves as a filter and absorbs the smoke and fumes so that the gases emitted from the housing after rupture are without odor.

Other substances, such as barium oxide, having the absorbing qualities of activated alumina, may be used, but it is preferred to use a substance which is nonconductive so that should excessive moisture be absorbed by the substance, it will not short circuit the transformer windings.

Although but one embodiment of the invention has been illustrated and described in detail as embodied in a transformer, it is to be expressly understood that the invention is not limited thereto and is applicable to motors, generators, amplifiers or to any other electrical equipment subject to overheating. Various changes can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. An electrical device having a sealed housing, electrical components in said housing subject to overheating, a fuse in said housing connected in circuit with said components to open the circuit when the device overheats, there being activated alumina filling substantially the entire air space in said housing to absorb products of combustion and to relieve pressure in said housing to preillent rupture of the housing before said components coo 2. In a transformer, a sealed housing, primary and secondary windings in said housing, a fuse subject to the temperature of said windings and connected in circuit with at least one of said windings and adapted to open the circuit when said windings overheat, there being activated alumina in said housing to absorb products of combustion when said windings overheat to relieve pressure and prevent rupture of the housing before said components cool.

(References on following page) UNITED STATES PATENTS Hunter Nov. 6, 1894 Ferrell Aug. 1, 1916 Greenwood Oct. 11, 1932 Hill Feb. 13, 1934 Ford Oct. 9, 1934 Brunner Dec. 15, 1936 Hill Oct. 10, 1939 Kater Mar. 26, 1940 Nowak et a1. July 30, 1940 Anderson Oct. 10, 1944 Schaefer Feb. 20, 1945 FOREIGN PATENTS Great Britain Aug. 15, 1929 Great Britain Dec. 9, 1929 Great Britain Feb. 27, 1933? OTHER REFERENCES Related Materials, Gregory.