The Diseases Of Electrical Machinery

 ELECTRICAL MACHINERY. 59 of consideration the unusual heating—by the voltages being no longer equal. The position of the fault can easily be found by means of a galvanoscope or incandescent lamp, or by an electric beil. Wrong Connection. in the Stator Winding.— It does not often happen that the stator coils are wrongly connected, still it will do no harm to refer here to one or two points connected therewith. If a single coil is wrongly connected, it can only be that the beginning and end of the coil have been changed one with another. The coils are always connected one after another, the end of the first with the begin- ning of the second, and the end of the second with the beginning of the third, and so on. If, therefore, one of the coils is wrongly joined up, it will act against the others, and so tend to reduce the total voltage of the separate phase by twice the voltage of the par- ticular coil. It is, however, also quite possible that a complete phase is wrongly connected with the others. It may happen that the beginning and end of one phase of a three-phase machine have got mixed, so that instead of the beginning being connected to the terminal and the end to the neutral point, the reverse has taken place (Fig. 31). A machine connected in such a way certainly gives three-phase currents. The currents, however, are not relatively displaced 1200, but only 60° [The author has described this fault previously in connection with the winding of three- phase motors, in his Handbuch der Elektrotechnik^ vol. 9, 2nd part, pp. 60, 91, 92.]