The Diseases Of Electrical Machinery

ELECTRICAL MACHINERY. M no harm, since this high voltage is only required for a comparatively short time. One should on no account try to get any more out of the machine. A reduction of the current has not much effect, since with such heavy excitation the influence of the load on the shunt current is very small, so that the heating of the coils and armature iron does not depend upon the load but upon the voltage. The Bearings.—Modern bearings are always fitted with ring lubrication. Several firms employ self-align- ing bearings with spherical seatings, even with motors of i horse-power only. If the motors are carefully put in order when starting up for the first time, the bear- ings will very rarely run hot, in spite of the high journal speed. When a hot bearing does occur, it is always due to neglect. The bearings of new machines must always be washed out with paraffin oil until the oil flowing away remains clear. In many cases small and medium machines are kept a good time in stock, so that it is impossible to prevent some little oil finding its way into the oil chamber. If a machine be started up without this cleaning out, the bearing may run hot, and the journal may bind in the bearing or the babbit- metal bushing be melted out. The use of a good and not too heavy oil for filling the oil box goes without saying. If the oil is too thick, the oil rings will not run round. The oil box should not be filled too full, as then the oil ring is