The three ends from the inner ends of the coils are joined together permanently at a, while the three outer ends f are carried through the shaft to the commutator. Ity this wind ing the highest differences of potential are found only upon the outside wires, tne result being greatly in favor of retention of insulation under all conditions. The position of the coils Hien) the armature is such that they follow each other in shnilar electrical sequence at 120 of a revolution apart, an arrangement which gives, with the small nunilier of generat ing Iieuees, nn emit innit N. of effect. The three free ends are carried out through the shaft, and kept well insulated while passing to their connections nt the counnutntor near t he end of the shaft The commutator consists of a copper ring, slit into three segments of I'20' nearly. These segments are independently mounted npon a metal frame, which gives the segment its posi tion. The three metal frames (Figs. 32 and 33), for the support of the segments, are mounted in two metal llantfes trot thoroughly insuhtted from them. The flanges .1.1 are themselves borne upon the shaft and covered with n layer of vale:mite. The segments are readily detachable by removal of screws passing thnnigh lateral ears extending from each side of a segment, K. The wires from the shaft connect to each framework G G respectively, and consequently there is one wire electrically connected to each segment.
Fig. 34 shows diagrammatically the winding of the armature and also the manner of applying the brushes to con duct the current to the circuit. There are usually two pairs of brushes. formed of comb-like copper springs, the brush es of each pair being diametrically op posite, and the two brushes that are positive or negative set so as to bear upon the commutator at points about 60° apart, as shown. The figure also shows at CC the relation of the field coils to the rest of the circuit L L L.
The commutator-brushes are, how ever, made movable, those diametrically opposite being mounted upon yokes in insulated holders, so as to be capable of movement around the commutator-shaft. The purpose of this arrangement is to permit the automatic setting of the brushes to maintain a stand ard current, irrespective of changes of speed and of resistance in the circuit.
The brush-holder yokes are connected to a lever and connecting rods L, Fig. 33, so that the brushes receive a move ment backward 3,} times as great as that imparted to SS forward during regula tion. This movement is effected by an attachment to the connecting arm A from the motor magnet lever X, Fig. 36. The motor-regulator magnet is constructed of a stout [-shaped iron frame, to the center of which is bolted a bar of iron, surrounded by a magnetizing coil. K, of low resistance. The polar extremity of this P. is a projection having an approximately paraboloi dal form, and its armature, A. is provided with a circular open ing, the edges of which are rounded so as to move over the pole without contact. The armature is swung upon pivots at U, be tween the legs of the The construction is such that the ends of the armature move at equal distances relatively from the frame at each end, leaving the pivots l' without strain. A dash-pot, I), is provided, to prevent too sudden movements. The attraction exerted by such a magnet, when a constant current flows through its coils, is practically constant in all positions of the armature within its prescribed range. It is seldom, however, sufficiently sensitive to current fluctuations to serve alone as a means of regulation. It is therefore put under the control of a shunting con
tact, operated by what is termed a current-controller magnet. The controller-magnet (Fig. 31) is constructed of two helices C C, placed side by side and serving as solenoids attracting into their interior a donble-core B, the parts of which are yoked together and suspended by an adjustable spring, S, from the support above, The yoke carries a contact-point on its un der side, and a stationary contact-point, 0, is mounted immediately thereunder. When these contact-points are touching each other they complete a shunt-circuit of practically no resist ance around the coil li of the regulator-motor magnet (Fig. 36). To avoid sparks at the con tacts, a permanent shunt of carbon coils, inclosed in glass tubes, is connected around the contacts. The connections are exhibited in Fig. 38, where K is the commutator, C C the wag net-coils, A the motor-regulator, R the controller, B the contact-points, E the carbon resist ance. Every slight fluctuation of the line-current is felt by the controller-magnet, and the result is that when set for normal current a tremor of the contact-surfaces is constantly taking place, so that the magnet A (Fig. 38) is maintained at such a state of excitation as will curse it to move and maintain the brushes at those positions corresponding to a predetermined current under variations of speed and of resistance, even down to a short circuit. The regu lation is effected so promptly that a machine may have all its lights shunted at once without damage. Unsteady power 'does not practically injure the steadiness and uniformity of the lights or current.
One of the novel features of the machine is the air-blast attachment to the commutator. It was invented fur the purpose of permitting the use of electromotive forces up to 2,1100 volts and over, while a free oiling of the commutator-surfaces is still permissible for diminishing wear, a single commutator being used, and that containing but three segments. It is based upon the discovery by Prof. Thomson that a strong jet of air of small moonlit can effectually break any conducting line of particles tending to bridge the commutator-slots, and cause the local discharge termed Small nozzles ate mounted directly opposite the tips of the foremost positive and negative commutator-brush. At the moment the slot in the com mutator passes the tips of the brush, it puff of air is sent through the slot and repeated at every slot. These small puffs are furnished at the proper instant by a small rotary, positive blast mechanism (Fig. 30), which is mounted upon the journal-box at the commutator side of the machine, and within which are carried by a slotted hub 11 (rotated by the shaft S) a set of three hard-rubber wings loosely placed in the slots in the hub at R R R. 120° apart. An inclosing case of interior elliptical ()Milne is divided by the hub 11 into two hue or crescent shaped chambers, into which the rubber wings are thrown by centrifu gal force during rotation. Inlet openings arc provided at 11, covered with fine wire gauze to exclude particles. The outlets are at J .1, and communicate with the nozzles over the commutator-slots. By this con struction, when the parts are correctly set, six puffs of air are obtained at every rotation, three from each nozzle, alternating in succession from the nozzles, and corresponding to the times of passage of the commuta tor divisions or slots past the ends of the forward brushes. The ad vantages obtained by the use of the air-blast for high electromotive-force currents are great.