. Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise. in opposition to thefield, thus weakening the latter. The dots and crosses in inductor sections, have theirusual significance in defining the direction of current, representing respectively the headsand tails of arrows. Ques. Explain how the field becomes weakened byarmature reaction. Ans. In all armatures there is more or less inductancewhich causes the cu
. Hawkins electrical guide. Questions, answers & illustrations; a progressive course of study for engineers, electricians, students and those desiring to acquire a working knowledge of electricity and its applications; a practical treatise. in opposition to thefield, thus weakening the latter. The dots and crosses in inductor sections, have theirusual significance in defining the direction of current, representing respectively the headsand tails of arrows. Ques. Explain how the field becomes weakened byarmature reaction. Ans. In all armatures there is more or less inductancewhich causes the current to lag behind the pressure a cor-responding amount. Accordingly, the current does not stop flow-ing at the same instant that the pressure becomes zero, therefore,when the coil is in the position of zero pressure, as in fig. 1,413, 1,162 HAWKIXS ELECTRICITY the current is still flowing and sets up a magnetic field whichopposes the main field as indicated by the dotted arrows, thusweakening the main field. Ques. In what kind of arm iture is this effect especiallypronounced ? Ans. In slotted armatures provided with coils of a largenumber of turns. CURRENT COMETO REST REVESTED ■ CURRENT IN !■--■:: _j -: FIELDH EETH. Fig. —Section of armature and field showing strengthening effect of armature reaction whenthe current leads the pressure. If the circuit contain an excess of capacity the current willlead the pressure, so that when the coil is in the position of zero induction, as shown,the current will have come to rest and reversed. Accordingly, lines of force (indicated bythe dotted lines) are set up by the current flowing through the coil and which are in thesame direction as the lines of force of the field, thus strengthening the latter. Ques. What would be the effect if the current leadthe pressure? Ans. It would tend to strengthen the field as shown infig. 1,414. The value of the armature ampere turns which tend to distort andto diminish or augment t
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