. Practical wireless telegraphy; a complete text book for students of radio communication . tions per minute, current at afrequency of 60 cycles per second would be obtained from its armature. Remembering theformula given for determining the frequency we see that in a complete revolution of thearmature any point passes through four fields which would set up four reversals of current. If the armature revolves at the rate of1800 revolutions per minute, correspondingto 30 revolutions per second, there willbe 4 X 30 or 120 reversals of current,or a frequency of 60 cycles. If the gener^tor had 32 f
. Practical wireless telegraphy; a complete text book for students of radio communication . tions per minute, current at afrequency of 60 cycles per second would be obtained from its armature. Remembering theformula given for determining the frequency we see that in a complete revolution of thearmature any point passes through four fields which would set up four reversals of current. If the armature revolves at the rate of1800 revolutions per minute, correspondingto 30 revolutions per second, there willbe 4 X 30 or 120 reversals of current,or a frequency of 60 cycles. If the gener^tor had 32 field poles, the frequency willbe 32 X 30 or 960 alternations correspond-ing to 480 cycles. The student should understand that theforegoing description and drawing simplyshow in an elementary way the construc-tion and functioning of a generator. Thediagram is merely intended to indicate theconnections of the machine, the directionof the magnetic lines of force and themethod by which the voltage generated byFig. 24.—Showing tke Function of 3 Simple Commutator, the armature is ELECTROMAGNETIC INDUCTION. 27 36. Direct Current Dynamo.—Direct current is obtained from dynamo coilsby a commutator, which, is placed on one end of the armature driving shaft. Insimple form it consists of a split brass or copper ring of two parts, C, D, whichis thoroughly insulated from the armature shaft (shown in Fig. 24). The circuitfrom the loop A, B is completed through the contact brushes E and F throughan external load as at R. The function of the commutator should be clear from the following explanation: As-sume the coil A, B to be in rotation in the direction of the arrow; then in the particularposition shown in Fig. 24, the segment D will be a (+) pole and segment E a (—) current will therefore flow in the external circuit from brush F to brush E. WhenA, B turns completely over so that side B goes under the south pole and side E under thenorth pole, the current will flow
Size: 1734px × 1440px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjecttelegra, bookyear1917
