US2857449A - Arc welder transformer cabinet - Google Patents

Description

Patented Oct. 21, 1958 2,857,449 ARC WELDER TRANSFORMER CABINET Clifford M. Akins, Minneapolis, Minn.,

quette lvlanufacturing Co., a corporation of Minnesota Application April 13, 1954, Serial No. 422,749 2 Claims. (Cl. 174-16) assignor to Mar- Inc., Minneapolis, Minn.,

This invention relates generally to improvements in alternating current arc welders and more particularly to improvements in the cabinets or housings in which certain components thereof are enclosed.

The ordinary welder of this type includes a transformer by which the usual commercially available source of alternating current potential is transformed into the proper voltage and amperage welding potential, and from which there leads the usual conductors to the welding rod holder and ground connection by which the welding circuit is completed to the work. The transformer for this use must have certain characteristics among which is the ability to furnish the necessary heavy currents and a relationship between primary and secondary such that there is a comparatively heavy flux leakage. Both of such characteristics are affected and influenced by the nature of the cabinet within which the transformer and associated components are housed and heretofore it has been the general practice to make such cabinet of steel, i. e., a ferrous and magnetic material. As a result high eddy currents and hysteresis effects are created in the cabinet, it becomes very hot during operation of the welder and the efficiency of the transformer as well as its usable output is materially reduced.

Obviously a cabinet is necessary for protective purposes and to carry the taps by which the connections are made to the transformer and, equally obviously, such cabinet must be very strong and sturdy in order to stand up under hard service to which these welders are often subjected. As stated supra, these requirements have been met by using steel to construct the cabinet but it has also been proposed to make the cabinets of relatively non-magnetic metals, or metals having high electrical resistance in the effort to provide strength while reducing losses from hysteresis and eddy currents. Aluminum as an example while not magnetic is a conductor and thus there would remain a current flow to cause losses, in addition to which the metal is relatively quite expensive. Stainless steel, Monel, manganese steel and like materials have somewhat similar characteristics, and while their use may offer some slight help it falls far short of solving the problem.

It is the primary object of my present invention to make the cabinet of a truly non-magnetic material which is in addition an insulator or non-conductor of electrical currents and thus to completely solve the problems of losses from eddy currents and hysteresis, so that the cabinet will remain much cooler and the transformer efliciency will be increased to the point that either a smaller transformer may be used for a given output, or alternatively, a welder using the same size of transformer may carry a higher rating.

In accordance with my invention the cabinet is made up from suitable panels and moldings of plastic reinforced with the well known and now widely used product known as Fiberglas, this being the trade-mark name for the fibers of glass used in making an increasing number of products heretofore made of metal. The resulting cabinet is not only very strong but is relatively inexpensive and has all of the desirable electrical characteristics. In particular the cabinet material is a non-conductor thus not only removing the cabinet itself from any eddy current and hysteresis effects upon the transformer but making it possible to mount the secondary taps or jacks and other connections directly in the cabinet material without requiring use of separate insulating panels and inserts as is now necessary in all metal cabinets. Furthermore, since the cabinet is not even a conductor of the loss inducing currents, it heats much less and the only heat comes from the ambient temperatures within the casing, and this is minimized by properly ventilating the cabinet to permit this internal heat to escape.

These and other more detailed and specific objects will be disclosed in the course of the following specification reference being had to the accompanying drawings, in which Fig. l is a frontal elevation of an electric arc welder with a cabinet according to my invention.

Fig. 2 is a side view, a part of the cabinet being broken away to disclose interior details.

Fig. 3 is a vertical sectional view through the cabinet alone, substantially along the line 3-3 in Fig. 1.

Fig. 4 is a graph with curves illustrating the improvements in efiiciency and output welding current with my cabinet as compared to the ordinary steel cabinet.

Fig. 5 is a horizontal cross section through the cabinet alone, taken at about the level of the line 55 in Fig. 1.

Fig. 6 is a horizontal sectional view through an arc welder cabinet of circular shape and showing also the transformer mounted therein.

Referring now more particularly and by reference characters to the drawing A designates generally the cabinet or casing of an alternating current electric arc welder, said welder being, in the present instance, shown as mounted upon wheels B carried by an axle C so that it may be readily moved about from place to place, the operator for this purpose grasping the handles D at the top of the welder and tilting it so that the stand or rest E clears the floor surface F. Where this movability is not necessary, of course, the wheels may be dispensed with and any suitable stand or mounting employed. In accordance with the conventional construction the welder includes a heavy duty transformer G including a laminated core H upon opposed legs of which the usual primary and secondary windings I and J are placed and this transformer is secured to the generally rectangular base frame K of the cabinet A in any suitable manner. The secondary of the transformer is provided with a number of taps indicated herein at L, actually a series of jacks into any one of which a plug (not shown) may be inserated and from which the usual flexible wire runs to the welding rod holder. These taps permit the operator to select various welding amperages according to need, of course. In addition another tap or jack M, located like the taps L in the front of the cabinet, provides for connection to a ground lead (not shown) and the on-off control switch N is conveniently located in the upper front of the cabinet.

As thus far described the welder may be regarded as entirely conventional in general construction and operation, and while there are some additional components they are not herein shown or described since they are not necessary to an understanding of my present invention. It has been the custom heretofore to make the cabinet A of steel which material is, of course, both magnetic and an electrical conductor. The characteristics of the transformer used in these welders are such that there occurs a'quite heavy flux leakage between the primary and secondary windings and since the cabinet surrounds and is in the field of the transformer there results very considerable hysteresis effects and eddy current losses in the cabinet. As a result the cabinet heats to a high degree, actually becoming uncomfortable to the touch While the transformer core itself is still quite cool and this cabinet heating obviously is very undesirable. For one thing the cabinet heat is objectionable to the operator of the welder and, more important, since the heat represents a loss in usable output from the transformer it requires either that a larger transformer be used for a given maximum welding current, or that the welder carry a lower than should be necessary rating because of the loss in efficiency.

It has, to my knowledge, been proposed to solve this problem by the use of a metal cabinet made of some metal which is relatively non-magnetic. For example stainless steel, aluminum, Monel metal and the like might be used but even the use of such metals has been found to only partially alleviate the undesirable hysteresis and eddy current effects, and this partial solution is accomplished usually at an added manufacturing expense as compared to the cheaper steel cabinets.

In accordance with my invention I make the cabinet A if not entirely, at least in large part of a material which is completely non-magnetic in nature and non-conductive of electricity. Such a cabinet, of course, will completely solve the problem of losses and heating due to hysteresis and eddy currents flowing in the cabinet-and as a result the transformer efficiency is greatly increased and the usable welding current output for a transformer of a given rating in the ordinary metal cabinet is substantially increased. Attention is called in this regard to the graph in Fig. 4 in which the curves and 11 show the difference in transformer efficiency as between a transformer in the cabinet of my invention and one of equal size but enclosed in a steel cabinet. Or considered in another way, i. e., usable welding current output in-amperes for a transformer in a cabinet according to my invention and one of equal capacity in a steel cabinetthe curves 12 and 13 graphically depict the improvement. These curves are plotted from actual test runs of welders with the different cabinets.

The material I employ is a fiber glass reinforced plastic or some suitable polyester resins, this combination of materials being one now finding many uses heretofore served by metals of various kinds. The fiber glass when suitably bonded with the plastic material forms a structural product which is light, durable and inexpensive as well as non-magnetic and a fine insulator, electrically speaking. And such material may be readily molded and formed into shape for its various uses.

Considered in more detail, the cabinet A is generally rectangular in shape and is made up of a front 14, back 15 and connecting sides 1617, which parts are suitably secured to the base frame K and are held together by screws 18 (Figs. 3 and 5) for convenient assembly and disassembly. Thus these four parts form anopen box which surrounds the transformer G, and although they are directly in the field of the transformer the nature of the material as used according to my invention substantially eliminates any hysteresis or eddy current losses in the cabinet. Actual tests prove that the fiber glass and plastic cabinet remains cool except for the heating from ambient temperatures about the transformer, while a steel cabinet quickly becomes so hot as to be uncomfortable to the touch before the transformer itself becomes barely warm, thus proving that it is the electrical losses in the cabinet causing the heating.

The cabinet is also fitted with a removable cover 19 fitted down over the upper edges of the front, back and sides 14-17 and held in place by screws 20 (Fig. 3) to suitable brackets 21 in accordance with usual practice, it'being to this cover that the aforesaid handles D are secured. This cover may be made up from metal with little effect on the transformer output, or may be made from the same material as the remainder of the cabinet according to choice. Upper edges of the cabinet parts 1417 are offset inwardly or lowered as indicated at 22 so that Warm air may escape from beneath the edges of 4 the cover 19 and since the bottom of the cabinet is open there is adequate ventilation to dissipate the normal transformer heat from within the cabinet.

The material now used for the cabinet being nonconduc'tive to electricity further permits me to mount the taps'L and M directly in the front 14 of the cabinet and eliminates the need for a separate insulating panel for the taps as now required. Since the repeated insertion and removal of the current selector plug (not shown), by which connection is made to the taps, puts some stress on the cabinet front the same is made heavier or thicker over its center portion 23 and is also recessed at 24 for added stiffness through this area, as will be readily appreciated.

While the cabinet heretofore described is rectangular in shape,it'is very possible that I may prefer to make the cabinet of circular configuration, as viewed in plan or horizontal section and as seen in Fig. 6. In such case the cabinet will have a circular wall 25 attached to a suitable base frame 26 whereon the transformer G is mounted and supported. It is to be noted that this type of cabinet will actually take up less space and even though the circular configuration places the wall 25 of the cabinet in more intimate relationship to the field of the transformer G, the use of the insulating or nonmagnetic material, according to my invention, will permit this without inducing losses by heating in the cabinet due to hysteresis and eddy current effects. In fact, the use of such material for the cabinet will make it possible to reduce the size thereof in comparison with the physical size of the transformer and associated components so that a very minimum of floor space is required for the Welder.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

1. An improved cabinet for containing an arc welder transformer having primary and secondary windings and of the type inducing hysteresis and eddy current losses in the surrounding metallic cabinet commonly used, and wherein said are welder transformer is positioned centrally of the cabinet to permit free flow of air around the transformer and in contact with the Walls of the cabinet, the said improved cabinet being made of a prod uct commercially known as fiber glass which is both nonmagnetic and electrically non-conductive to thereby elim inate such hysteresis and eddy current losses, said cabinet being open over the entire area of its bottom for the free ingress of air to flow over the arc Welder transformer and over the inner surfaces of the walls of the cabinet and a cover secured to the upper end of the cabinet with an air outlet passage extending substantially completely around the cabinet between the upper end thereof and the marginal edge of the cover to dissipate heat from the entire area within the cabinet.

2. A cabinet as in claim 1 wherein the upper ends of the walls of the cabinet extend inwardly of the marginal edge of the cover to provide said air outlet passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,138,754 Andrus et al Nov. 29, 1938 2,143,811 Wickersham Ian. 10, 1939 2,158,868 Stacy May 16, 1939 2,327,774 Dickinson Aug. 24, 1943 2,644,135 Schnoll June 30, 1953 2,816,947 Leightner et al Dec. 17, 1957 FOREIGN PATENTS 429,684 France Sept. 28, 1911 58,760 Switzerland 'Feb. 22, 1912 28,957 Denmark Dec. 12, 1921

Claims (1)

1. AN IMPROVED CABINET FOR CONTAINING AN ARC WELDER TRANSFORMER HAVING PRIMARY AND ECONDARY WINDINGS AND OF THE TYPE INDUCING HYSTERESIS AND EDDY CURRENT LOSSES IN THE SURROUNDING METALLIC CABINET COMMONLY USED, AND WHEREIN SAID ARC WELDER TRANSFORMER IS PSITIONED CENTRALLY OF THE CABINET TO PERMIT FREE FLOW OF AIR AROUND THE TRANSFORMER AND IN CONTACT WITH THE WALLS OF THE CABINET, THE SAID IMPROVED CABINET BEING MADE OF A PRODUCT COMMERCIALLY KNOWN AS FIBER GLASS WHICH IS BOTH NONMAGNETIC AND ELECTRICALLY NON-CONDUCTIVE TO THEREBY ELIMMATE SUCH HYSTERESIS AND EDDY CURRENT LOSSES, SAID CABINET BEING OPEN OVER THE ENTIRE AREA OF ITS BOTTOM FOR THE FREE INGRESS OF AIR TO FLOW OVER THE ARC WELDER TRANSFORMER AND OVER THE INNER SURFACE OF THE WALLS OF THE CABINET AND A COVER SECURED TO THE UPPER END OF THE CABINET WITH AN AIR OUTLET PASSAGE EXTENDING SUBSTANTIALLY COMPLETELY

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