Abstract: In a polyphase liquid rheostat cells for separately accommodating adjustable electrodes with the cells filled with an electrolyte, covered at the top and open at one end face, are formed from electrically nonconducting plastic sheets which are welded together in a liquid tight manner with the welds arranged, at least in the zones which are subject to voltage stresses, so that they are adjacent only to external spaces which are free of liquid thereby preventing an electrical short circuit between cells of different phases in the case of a leak in the welded seam.