. Practical wireless telegraphy; a complete text book for students of radio communication . with motor generator sets are very effective inneutralizing induced potentials. Troubles of this sort are now infrequent. An induced current of high voltage may, for instance, burn the insulation of the con-ductors in a motor generator and place one of the wires in direct contact with the an earth connection exists at any other point in the power system, a complete short-circuitmay occur. It should be kept in mind at this point that the frame of the motor generator inmodern Marconi sets is conn
. Practical wireless telegraphy; a complete text book for students of radio communication . with motor generator sets are very effective inneutralizing induced potentials. Troubles of this sort are now infrequent. An induced current of high voltage may, for instance, burn the insulation of the con-ductors in a motor generator and place one of the wires in direct contact with the an earth connection exists at any other point in the power system, a complete short-circuitmay occur. It should be kept in mind at this point that the frame of the motor generator inmodern Marconi sets is connected directly to earth and therefore electric contact betweenthe armature or field winding and the frame, -under this circumstance, would be more seriousthan in systems which are not earthed. (a) Testing for Grounds.—Fig. 328 shows how a grounded wire can be traced a 110-volt source of current and an incandescent lamp, of the circuit is con-nected to the frame of the motor generator and the other to the commutator or to one of the 314 PRACTICAL WIRELESS TELEGRAPHY. TEST^LAMP Fig. 328—Locating Grounds in a Motor. URMATURE COIL terminals of the field winding. If the lamp lights to partial or full brilliancy, the insulation of the armature or field circuits is broken down at some point. The circuit in which the ground exists can be determined by taking the brushes off the commutator and applying the foregoing test to the armature and field coils separately. By disconnecting the wires joining the field poles, the test can be applied to each coil individually until the troublesome one is found. It is comparatively easy for an inex-perienced man to rewind a defective field coil, but replacing a burned-out armature coil requires the services of a skilled repairman. This is a painstaking job which requires careful workmanship. (6) Locating Troubles in the Arma-ture.—If the insulation between an arma-ture coil and the iron is supposedly at fault, and furthermo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
