ES334502A1 - Liquid resistor apparatus - Google Patents

Abstract

In a variable liquid resistor of the type in which the resistance varies according to the depth of the conducting liquid between the electrodes, the depth of this liquid is controlled by the pressure of the vapour produced by the current flowing through and heating it. The resistor has two chambers 1 and 2 (Fig. 1) interconnected by ducts 4, 5 and 6, and filled with a conducting liquid such as caustic potash solution. Electrodes 13b and 14b in the reservoir chamber 1 connect with a further pair 13c and 14c (Fig. 4) in the chamber 2 and their narrow projections 13d and 14d. The whole assembly is closed by a plate 15. Current flowing between electrodes 13c and 14c heats the liquid thus forming vapour which forces the level of the liquid down in chamber 2, the displaced liquid passing up through duct 4 into chamber 1. Thus the submerged area of electrodes in chamber 2 decreases and the resistance increases, a sudden step increase occurring when the level falls below the bottom edge of the main area of electrodes 13c and 14c, leaving only projections 13d and 14d submerged. The liquid level can drop to the level of the bottom of tube 4 after which the pressure of the vapour is such that it opens valve 7 and escapes through 11 to condense in the liquid of chamber 1, defining a maximum resistance value. Piston 9 working- in cylinder 10 forms a dashpot to show the valve movement, which, if required, can be controlled from outside the resistor by the use of an electromagnet (18), Fig. 10 (not shown). Duct 5 acts as a by-pass for excess vapour. The resistances of chamber 1 and chamber 2 are in parallel, and if chamber 1 is made without electrodes a fixed resistor is connected in circuit to simulate their effect. The complete device can be used as a starter resistor for an asynchronous motor or, in the case where the operation of valve 7 is controlled electromagnetically externally, as an amplifier. Apparatus for three-phase current is described.