US533930A - Armature-winding - Google Patents

Description

2 Sheets-Sheet 1.

(No Model.)

D. P. THOMSON. ARMATURE WINDING.

No. 533,930. Patented Feb. 12, 1895.

wrrgcsscs UNITED STATES PATENT OFFICE.

DAVID P. THOMSON, OF SOHENEOTAD Y, NEIV YORK, ASSIGNOR TO THE GENERAL ELECTRIC COMPANY, OF BOSTON, MASSACHUSETTS.

ARMAT-URE-WINDING.

SPECIFICATION forming part of Letters .Patent No. 533,930, dated February 12, 1895. Application filed August 4:, 1'8 94. Serial No. 519A96. (No model.)

To all whom it may concern:

Be it known that I, DAVID P. THOMSON, a

, citizen of the-United States, residing at Schenfor dynamo-electric machines, and more specifically to the connections between the coils and the segments of the commutator in direct current machinery; and has for its object to provide a method of and means for cross-com necting the windings, as it is commonly called, so as to reduce the potential and reduce the number of volts per bar in the commutator.

In cases Where the maximum number of commutator bars permissible by the winding have been tapped 0E, and the number is yet not enough to reduce the volts per bar to a working value, it is usual to interpolate barsbetween those connected to the winding and to divide the lead from each coil so that it will deliver to two bars at corresponding points on the commutator, thus dividing the potential of adjacent bars to one half and giving double the number of com mutator segments.

In the construction of certain types of dynamo-electric armatures, it is found imperative to limit the number of volts per bar delivered to the commutator so as to avoid sparking at the brushes. This effectually removes the trouble experienced from sparking due to too high voltage per bar. In doing this it introduces a new difiiculty in that, as commonly connected, the leads to the commutator bars from the coils are of diiterent lengths, and thus, as the resistance and selfinduction of the two paths are different, the electro-motive force delivered to each of two different bars in a pair is also different. In armatures developing large currents, the difficulty presented by these differences of lead may become avery serious one, and it is this particular difficulty which my invention aims to overcome. To accomplish this purpose I make the leads to the two segments of equal or approximately equal length; and this I accomplish by taking the lead from the coil or bar of. the armature first to a point equidistant from the two segments of the commu tator to which it is to be connected, and at this point branching the lead and carrying one-half of it to each segment, thus affording a perfect remedy for the particular difficulty pointed out above.

The accompanying drawings show illustrations of my invention, Figures 1 and 2 being end views of armatures and commutators, as herein described, Fig. 1 showing my invention applied to an eight-pole machine and Fig. 2 as applied to one of six poles. Fig. 3 is a view of the particular connector which I have devised to carry out the purpose of my invention, and Fig. 4 is a modification thereof.

Referring to Fig. 1, A is the armature. B is the commutator. O, O, 0 O are the commutator brushes. D, D, &c.,are the poles of the machine which, as already pointed out, is an eight-pole machine of common type. The field-magnet windings are not shown, but may be of any desired type. E, F, G, H, I, K, L show respectively groups of armature bars each of which may be taken as a type of a coil of any kind desired by the engineer, my improved connection being applicable either to coil windings or bars. M, N, O, P are the junction or branching points of the leads, as already herein pointed out. The individual armature bars are lettered with the small letters corresponding to the large letter designating the group, as e, 6', 6 (be. I have not illustrated the negative brushes upon the commutator because the nuinberof lines required for their connections would confuse the drawing unnecessarily. The dotted lines in the drawings show the connections upon the back or pulley end of the armature. It will be sufficient in illustrating my invention to point out the connections for two sets of armature bars, for which purpose I have selected those lettered e andf respectively. The branching pointfor the connections of these bars is at M. The arrows show the direction of the current. \Vith the individual connections are shown lines of difierent character, as will be readily understood from the drawings, the heavy lines showing the connections to the coils which are being commutated. Starting from the barf, the current passes to the j unction point m, and thence by the heavy lines to the sections 5, 5, upon the commutator, part of the path to the junction point on being in common and the paths from thejunction point on to the commutator being of equal or approximately equal length. Similarly, starting from the bar f" the junction point m is reached by a common lead and thence by divided leads to the commutator bars 3, 3. It will be unnecessary to trace the connections further, as they are all made in the same way.

Referring to Fig. 2, I illustrate the same system of connections as applied to a six-pole machine, and its application will be apparent from the description of Fig.1 without further explanation.

In Fig. 3, Q represents the connection from the armature bars to the common junction point (as at M), and Q, represents a similar connector to the two commutator bars with which the coils are to be joined.

Fig. 4 shows a modification of the connection which I have devised, being substantially similar except that the connections to the commutator segments are of different lengths, but of the same resistance, which I accomplish by making the shorter arm Of of the connection of a higher resistance metal than the arm Q. This modification however is not preferred, inasmuch as the inductance of the parts Q and Q would be different and would give rise in some degree to the objections already pointed out, although they would be materially lessened by this construction.

The arrangement of leads which I have described has what I denominate a cushioning effect, inasmuch as the resistance of the leads is very much higher than that of the coils which they connect to the commutator segments, and this tends to the equal distribution of current and adds to the efficiency of the windin In series windings the difficulty of distribution of current among a number of different commutator segments connected to the same armature coil has been a great objection to the method of interpolating segments as a means of reducing the potential per bar; and so far as I have been aware, in the endeavor to keep the resistance of the armature at a minimum, the leads have also been made of low resistance and generally of unequal length, giving rise to the troubles which I have heretofore pointed out, which are particularly great in case the load is thrown suddenly off the machine, the sparking which follows in such cases often resulting in serious damage to the commutator. The method which I have devised, therefore, of making these leads of a higher resistance than the armature coils, and also of making them of substantially equal resistance and inductance, has to a great extent obviated these objections to a series wound armature generat ing large currents; and it is this method of distributing the current between the armature bars which I have devised and which I seek to protect especially.

What I claim as new, and desire to secure by Letters Patent of the United States, is-

1. The method of distributing current between a number of segments connected to a common coil in a series armature winding, which consists in making the leads from the coil to such segments of a higher resistance than the coil, and of substantially equal resistance.

2. The method of distributing current between a number of commutator segments connected to a common coil in a series armature winding, which consists in making the leads from such segments to the coil of higher resistance than the coil and of substantially equal resistance and inductance.

3. In a dynamo-electric machine, cross-connections for the commutator-segments,such cross-connections consisting of a lead from the armature coil to a point equidistant from the commutator segments to be connected thereto, and additional leads from such points to the commutator segments, substantially as set out herein.

4. In combination, in a dynamo-electric machine, armature coils and commutator segments, the segments cross-connected to the coils by leads of equal lengths, as herein set out.

5. In combination, in a dynamo-electric machine, armature coils, a commutator having a plurality of segments for each armature coil, and leads of equal lengths from the commutator-segments to the coil, substantially as described.

6. In a series wound dynamo-electric machine, armature coils, a commutator having a plurality of segments for each armature coil, a lead from each armature coil to a point equidistant from the segments to which it is to be connected, and leads from such point to the several commutator-segments, thus forming from each armature coil to its appropriate commutator-segments leads of substantially equal resistance and self-induction, as herein set out.

In witness whereof I have hereunto set my hand this 18th day of July, 189i.

.DAVID P. THOMSON.

'Witnesses:

B. B. HULL, A. F. DIACDONALD.

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