Design of Electrical Machinery Volume 3; A Manual for the Use, Primarily, of Students in Electrical Engineering Courses - Couverture souple
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1912 Excerpt: ...the hardened steel ball is caught at the lowest point between the race and the end of the shaft. As the 602771 armature revolves, the ball is carried upward, and the spring compressed. The reaction of the spring forces the shaft away and the ball falls back to its normal position. Thus, a periodic longitudinal motion, of a frequency determined by the natural period of the motor, is imparted to Fig. 82.--Stator of 3000 K.W., Six-phase Rotary Converter (Westinghouse). the armature as it revolves and uniform wear of commutator and collector rings is assured. Overspeeds.--As a safeguard against overspeeds in rotary converters, a safety device consisting of a spring-closed knife switch actuated by a centrifugal tripping mechanism is attached to the same end of the shaft as the oscillator. The knife switch is held open by a pivoted latch so arranged that when the simple centrifugal governor attached to the shaft operates at a predetermined speed, it trips the latch and releases the spring, thus insuring a quick and positive closing of the switch. This switch is contained in a metal box attached to the bearing housing and completes an auxiliary circuit through the tripping coils of the directcurrent circuit-breakers. Field Break Switch.--If a rotary is started from the alternating current side, it should be provided with a doublethrow field switch so that during starting the field may be opened in several places, so as to reduce the strain on the insulation that might otherwise result from the high voltage induced in the field coils. When the alternating-current switches are closed on a self-starting rotary, the rotary is virtually a transformer, the armature winding acting as the primary, and the field winding as the secondary. This transformer action becomes les...
Les informations fournies dans la section « Synopsis » peuvent faire référence à une autre édition de ce titre.
