Resistance body

Application filed September 29, 1931, Serial No. 565,782, and in Germany September 29, 1930.

Electrostatic charges arising in high tension apparatus of electric power stations are frequently led to ground by way of a conductor in the form of a water jet, the resistβ ance offered by the latter serving to prevent said apparatus against being immediately connected to ground. Resistances in the form of water are further used for cooling the anodes of generating apparatus for short 10 electric waves in which case an immediate connection between the anode and the ground is avoided on account of the resistance of the water. It had been proposed to construct water resistances of the aforementioned kind ¹⁵ in the form of bodies of ceramic material with channels provided therein and water had either been filled into or passed through said channels to form the resistance material proper within said channels.

According to this invention resistance bodies of this kind are made in such a manner that a liquid is filled into a pipe or hose which consists of ceramic material treated by a process of baking. A pipe or hose of this ²⁹ kind may, for instance, be made by pressing a ceramic material through an orifice with a central mandrel, for instance, in a manner similar to making hollow tiles. This pipe ₃θ may be wound in still plastic condition into a coil of any desired conformation, preferably with the several, turns side by side or one on top of the. other. This form-of Coil is of especial advantage on account of the 35 fact that it requires a relatively small space.

The resistance coils of ceramic material which form part of this invention are distinguished from heating coils in that the several turns of the resistance coils are wound 40 in immediate contact with each other, while heating coils are made up by turns which are necessarily spaced from each other, because heating coils, in contra-distinction to resistances, are destined to radiate towards the 45 outside and evidently an immediate contact between the several turns must be avoided.

Instead of winding up the pipe of ceramic material in a plurality of turns, it may also be subdivided into several sections which are ⁶⁰ connected with each other at their ends in a manner to provide a coherent channel passing through said several sections.

The aforementioned pipe of ceramic material which is wound into a coil may be either of circular or of square or approxi- 66 mately square cross-section, preferably rounded at the edges to avoid fractures on the latter during baking. However, other cross-sections may likewise be used for the pipe or hose, for instance of the form of a ⁸⁰more or less oblong quadrangle containing two or more channels. In a resistance body of this kind the resistances in the several channels may be connected with each other either in parallel or in series and, in case the pipe ^e5is wound into a coil prior to baking, the resistances in the several channels may also be connected in opposition to each other, thus presenting a bifilar path to the electric current passing through said resistances. Pref- ⁷⁰erably the water which forms the resistance proper is not permanently kept within the channels of the resistance body but passed in a stream therethrough, especially if the resistance body is destined to be used for 75 cooling electric apparatus under tension, because as a rule water or other resistor liquids will be decomposed or heated by electric current passing through the same. The pipe of ceramic material which forms part of ⁸⁹the present resistance body is further provided with an extension and with tightening fixtures on the latter permitting said pipe to be tightly connected with inlet and outlet conduits for the resistor liquid. ⁸⁸

As has above been mentioned, the preferred construction of the resistance body is such that the pipe of ceramic material which is destined to serve as a receptacle for the resistor liquid is of the form permitting the ⁸⁰placement of the turns which are produced during passage of the pipe through the orifice of the press immediately side by side or one on top of the other, so that the entire body of the pipe may be given the form of a cylinder, prism or pyramid. If it is desired to give the coiled pipe a circular form, preferably a press may be used with an orifice which is not of straight but of slightly curved conformation. 10(

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A number of constructions of the resistance constructed according to this invention are shown in the accompanying drawings.

Figs. 1, 3, 5, 6, 8, 13' 14, 15, 16 and 17 are perspective views of various modifications of my invention;

Figs. 2, 4 and 7 are cross-sectional views of the coils of Figs. 1, 3 and 8, respectively;

Figs. 9,10 and 11 are cross-sectional views of coils embodying a plurality of passages therethrough;

Fig. 12 is a cross-sectional view of a further modification of my invention;

Fig. 18 is an elevational view, partly in section, of a combined resistor terminal and liquid feed used in conjunction with my resistor; and

Fig. 19 is a cross-sectional view of an extrusion tip used in the manufacture of my resistor.

According to Fig. 1 the pipe 1 of ceramic material which forms the receptacle for the resistor liquid is made in the form of a coil having a number of adjacent turns positioned in a plane, a channel 2 passing through the several turns. A base-plate 3 is provided as a support for said coil thus formed by the pipe. Both ends 4 and 5 of the coil are bent upward to permit convenient supply and discharge of the resistor liquid to and from the coil. The coiled pipe shown in Fig. 1 is of square cross-section as indicated more clearly in Fig. 2.

As Fig. 3 shows, the several turns of the coiled pipe are placed one on top of the other to form a cylindrical body, a base-plate 3 being again used, the same as in the construction shown in Fig. 1. Both ends 4 and 5 of the coiled pipe are preferably bent out of the cylindrical coil, the inlet 4 being lient in upward and the outlet 5 in downward direction. The cross-section of the several turns of the coil is shown as being circular as indicated in Fig. 4. During the winding of the coil the cross-section of the several turns will be more or less flattened, because the ceramic mass is still plastic when being wound into a coil. This flattened cross-section of the turns is more clearly shown in Fig. 5. The form of cross-section shown in Fig. 5 is possessed of the advantage that the surface resistance, measured in the direction of the axis of the cylinder, is essentially increased as compared with the surface resistance of a coil having a smooth cylindrical form.

According to Fig. 6 the several turns of the coil are of square cross-section and placed one on top of the other to form a coil of prismatic form.

As Fig. 7 shows, the cross-section of the several turns of which the coil is composed may also be of quadrangular conformation having rounded edges which, as had above been mentioned, will prevent tearing at the edges during baking. A wound resistance body having turns of the cross-section shown in Fig. 7 is represented in Fig. 8. The coil wound according to Fig. 8 is again mounted on a base-plate 3 and in addition provided with a cover-plate 3'. The cross-section of 70 the several turns of the coil as shown in Fig. .8 may also be of the forms shown in Figs. 9, 10 or 11. According to Figs. 9 and 10 two channels are provided within the coiled pipe, which channels may either be placed side by 75 side as shown in Fig. 10 or one on top of the other as shown in Fig. 9. Also, a cross-section may be adopted having three channels as shown in Fig. 11.

Irregular cross-section may eventually also 80 be chosen for the turns of the coiled pipe of ceramic material, for instance the form shown in Fig. 12. According to Fig. 12 the several turns are placed one on top of the other in a manner to produce a coil of the 85 form of a cone enlarging in diameter from the bottom towards the top. A coiled pipe of this form is also shown in Fig. 14. As shown in Fig. 12 the cross-section of the several turns may l>e of such conformation that co the under edge 7 of each upper turn projects somewhat beyond the upper edge of the adjacent under turn. The cross-section of the turns as shown in Fig. 12 will have the effect of providing underneath each turn a dry 05 space which prevents formation of a coherent conductive film or layei· of liquid on the outside of the coil, at the same time providing a possibility for any drops of liquid which may be formed at the under edges of the turns to ioo immediately fall off said edges without coining in contact with the (inter surface of the turn positioned underneath.

The coiled pipes of ceramic material shown in Figs. 13 and 14 are likewise composed of ios turns of square cross-section in the form of a cone. More particularly, the coil shown in Fig. 13 is of the form of a cone tapering towards the top, while the coil shown in Fig. 14 is of the form of a cone tapering towards 110 the bottom.

It is not necessary to wind-up the coiled pipes into helical form, such as is the case in the constructions so far described, as it is also possible to build-up the coils on a base- 115 plate 3 from a pipe having its turns arranged in the form of waves as shown in Fig. 15.

This form of the turns will have the effect of decreasing the self-induction of the resistance body. 120

As has been mentioned above, the pipe of ceramic material may also be provided with two or more channels which may be connected either in parallel or in series, or also in opposition to each other, a bifilar path Ϊ25 for the current being thus provided which will likewise have the effect of decreasing the self-induction of the resistance body.

A decrease of the self-induction of the resistance body may also be attained by wind- ¹³⁹

1,917,331 ing two or more pipes into a coil. Examples of a construction of this kind are shown in Figs. 16 and 17, Fig. 16 resembling in principle the form of pipes shown in Fig. 15 and Fig. 17 the form of the turns shown in Fig. 16, the several turns being wound up as shown in Fig. 3. In either case two pipes 1 and 1' are wound up side by side into a coil or serpentine.

Fig. 18 shows an example of a construction of the resistance body permitting connection of the coiled pipe with conduits for the supply and discharge of resistor liquid to and from said pipe. According to Fig. 18 the end of the pipe 1 with the channel 2 therein is equipped with an extension 8, a metal ring 9 being fixed to said extension by means of putty 10. The metal ring 9 is provided with an outer thread for the reception of a threaded cap 11. The latter serves for securing the tubular leading-in electrode 12 by means of a metal disc 13 which is shrunk onto said electrode and tightened by solder as indicated at 14. Tightening against the extension 8 of the pipe 1 is effected by a disc-shaped packing 15. The tubular structure of the electrode 12 permits the resistor liquid to be supplied to and discharged from the pipe 1.

Fig. 19 shows the orifice of a forming press which may serve for making the pipes of ceramic material. According to Fig. 19 this orifice is provided with a mandrel 16 positioned in the longitudinal axis of the orifice, the mandrel 16 as well as the interior. 17 of the orifice being somewhat curved. By so arranging the orifice of the forming press the pipe of ceramic material will be given an initial curvature, which facilitates winding of the pipes into coils of the several forms described herein and shown in the drawings.