GB131590A - - Google Patents

Abstract

131,590. Akt.-Ges. Brown, Boveri, et Cie. Aug. 17, 1918, [Convention date]. Resistances.-An adjustable resistance comprises two or more liquid resistances having different characteristics, their movable and fixed electrodes each being connected mechanically and electrically, and one resistance at least being of the tubular type, i.e. with a column of liquid variable in length. The resistances may be brought into circuit successively. In one arrangement, movable electrodes 18, 19, Fig. 2, are carried by a cross-piece 11 guided vertically and linked to an arm 9 on an operating shaft 10. They are connected by flexible conductors 21 to a terminal 22. One movable electrode 19, which first enters the liquid, co-operates with an annular electrode 6. This, with upper and lower tubes 4, 5 of earthenware or cement, forms a passage a little larger than the electrode 19 and situated so as to allow free circulation of liquid. The other electrodes 18, 23 consist of plates, the fixed one being situated at the bottom of an insulating tube 7. Instead of plates, there may be used grids made up of sloping bars, or of separate roof-like or conical parts; another arrangement is shown in Fig. 5. The two resistances may be in eeparate vessels or in separate compartments of the same vessel; instead of the liquids being at different levels, they may be at the same level. the electrodes being arranged accordingly. The upper electrodes may be hung from different crankarms, which are moved during different ranges of motion of the operating shaft 10. The electrode may be extended over the whole length of the lower tube 5, or an additional electrode may be provided at the bottom of the tube. Fig. 7 shows an alternative construction with one movable electrode 18 over the other 19, one fixed electrode being represented by a flange on the other fixed tubular electrode. A combination of two resist. auces may have a characteristic curve as shown at c or e, Fig. 1, in which the abscissµ represent movement of electrodes and the ordinates the resistance. The point of flexure II corresponds to the immersion of the second movable electrode. Curve d represents a combination of three resist. ances. Curve a is that of a simple plate resist. ance, and b that of a simple " tubular " resistance. The combined resistances are useful for starting and controlling motors. Three such sets may be used for three-phase motors.