Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . t circuit will nearly always be found by examina-tion, as the trouble usually happens very close to thecommutator connections in the case of an open circuitand may very often be found between the commutatorbars themselves, in the case of a short circuit. If thetrouble is not at these places it will usually be in thewindings, in which case the only remedy is to have itre-wound. Temporary repairs may be made in the caseof an open circuit by short circuiting the commutatorbars around the open circuit
Twentieth century hand-book for steam engineers and electricians, with questions and answers .. . t circuit will nearly always be found by examina-tion, as the trouble usually happens very close to thecommutator connections in the case of an open circuitand may very often be found between the commutatorbars themselves, in the case of a short circuit. If thetrouble is not at these places it will usually be in thewindings, in which case the only remedy is to have itre-wound. Temporary repairs may be made in the caseof an open circuit by short circuiting the commutatorbars around the open circuit, but this method shouldonly be used in emergency, as the sparking will in timedestroy the commutator. With many dynamos, especially of older types, it isnecessary to shift the brushes with every change ofload. The current produced by the armature makes amagnet out of it and the magnetism of the armature ELECTRICITY EOR ENGINEERS 63 opposes that of the fields. In Fig. 35 the armature isworking with a very light load and the lines of forceof the field magnets are only slightly opposed by those. FIGURE 35. of the armature. In Fig. 36 we assume a heavy loadon the dynamo and consequently the magnetism of thearmature opposes that of the fields. This changes thelocation of the neutral point (when the coils under thebrush generate no current) and it becomes necessary to
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