US1670581A - Continuous-current variable-speed machine - Google Patents

Description

May 22, 1928.

1,670,581 F. KESSELRING CONTINUOUS CURRENT VARIABLE SPEED MACHINE Filed April 6, 1927 2 Sheets-Sheet l May 22, 1928.

F. KESSELRING CONTINUOUS CURRENT VARIABLE SPEED MACHINE Am An A14 Ata W5 III III Filed Apr'l e, 1927 Am WM 2 She cs-Sheet 2 litz / O 'n-nO WQ' 15 4+ Fig.3

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.7/1 Van/or Patented May 22, 1928.

UNITED STATES PATENT oF cs.

FRITZ KESSELRING, OF FURTH, GERMANY.

' CONTINUOUS-CURRENT VARIABLE-SPEED MACHINE.

Application filed April 6,1927, Serial No. 181,562, and. in Germany April 15, 1926.

For certain purposes, especially for power vehicles, electric current 4 generating plants are required,the dynamo engines of which deliver, in spite of great variations in the ,number of revolutions, a nearly invariable voltage or output, at any rate a voltage or output that is by far less variable than the number of revolutions.

Several proposals have already been made to solve the problem and there has been designed, in fact, a ,machine that has been widely usedand which comprises the exciting windings which are connected up to a main brush and to an auxiliary brush arranged between the main brushes.

This dynamo machine that has become known under the name three-brush ma chine is distinguished by its great simplicity and reliability of service, but, onthe other hand, it suffers from certain drawbacks enumerated hereinafter: (1) The uniformity of the output or of the current produced leaves much to be de sired, in that at average speed the average output is greatly surpassed, whereas with high numbers of revolution the current curve sinks nearly to 0. a I

(2) The output at a lowest number of revolutions is comparatively small so that a correspondingly heavy machine is necessary in order to obtain a certain definite amount of current at a certain small number of revolutions. g Adjusting the machine to a certain definite output is difiicult since slight shitting of the auxiliary brush causes a large variation of the output. I

l) The commutation. conditions are very unfavorable with high numbers of revolution because then the commutating field is nearly zero or even negative. 7

It has been endeavored to improve the three-brush engine by making use, in additionto the exciting coils connected up to the auxiliary brush, of another set of coils of by far thinner wire connected up to the two mai brushes; but however this contrivance has notbeen able to render the machine perfect. I

The object of the present invention is to improve the three-brush machine in such a degree that actually all drawbacks inherent in the original construction are obviated, ,aud thefinvention aims further at attaining this'result without any increase of the costprice of the machine. The invention is based on the discovery that if a certain suitable proportion between the main poles and the auxiliary poles is chosen the decrease of the resulting flux is, owing to the saturation and the stray, by far smaller than the increase of the number of revolutions so that the re sulting flux characteristic resembles approximately an equilateral hyperbola. Practically, the invention consists in designing most of the poles existing in the machine as main poles, the exciting coils of which are connected up to the main brushes, whereas thev remaining poles are designed as auxiliary poles, the exciting coils of which are connected up to the auxiliary brush and to one of the main brushes; besides, the armature has serieswinding and all exciting coils consist of wire of normal section.

'The invent-ion is illustrated diagrammatically and by way of example on the accompaying drawings, on which Figure 1 is a diagrammatic view of a four-pole continuous current machine designed according to this invention; Figure 2 is a similar representation showing a six-pole machine; Figure 3 is a represent-ation'of the ampere-windings and the magnetic fluxes existing and acting at various numbers of revolutions; and Figure & is a representation of the current curve of an existing and running inachine designed strictly according to the present invention.

I 1, 2 and 3 (Fig. 1) are the main poles, 4

is the auxiliary pole, 5 and 6 are the main brushes, and 7 is the auxiliary brush. The exciting coils of the main poles and of the auxiliary poles are connected with the brushes in such a manner that if the armature 8 with the commutator 9 rotates in the direction indicated by the arrow the magnetic fluxes N1 and N3 are directed radially inwards and the magnetic fluxes N2 and Ne of the mainpole 2 and of the auxiliary pole 4 are directed radially outwards, themain brush 5 constituting the positive pole ofthe machine and the auxiliary brush constituting the negative pole thereof. The auxiliary brush 7 has positive polarity with respect to the main brush 6 as long as the number of revolutionsflof the armature is small, but' when the number of revolutions increases more and more, the polarity of the brush 7 becomes negative and With'this re- N 1 is reversed.

The series Winding of the armature is indicated by that winding -e1ement-wvhi ch is located between the commutator lamellse 10 and 11 that-ware just being sh0rt-circuited by the auxiliary brush 7. 12, 13, let, 15 and 16 area-rinature conductors. These conductorsare connected with each other in series-on the rear-side ofthe armatureby lamellae 10 and. 11 by the 'wires 21 and'22.

WVi'th the six-pole jmachine shown in Fig. 2the numerals 23, 24,25 and 26"denote the mainpo'les, 27 and 28 the auxiliary P0165, and Sand-G the main brushes, 7 denotes the auxiliary brush, '8 the armature, and 9 the commutator. The exciting coils'of the poles areconnected up to the brushes-in such a manner-that when the armature rotates in the direction indicated jbythe arrow in the centre, the magnetic fiuxes' in the main poles 23 and 26 and'in the auxiliary pole 27 are di-' rected' radially inwards, and in the main poles '24'and and in the auxiliary pole 28 radially outwards, thus forming the main brush 5 the positive pole and the main brush '6 the negative pole of the machine,'an'd the auxiliary brush 7 has positive polarity'wi'th respect to themain brush 6 as long a'sthe 3 number ofre-volutions of the armature 1s sm-a'l-l. With a high number of revolutions the polarity of the auxiliary brush is refor 120 and 240- 'versed,-as'is also the directionof the magnetic flux in the auxiliary poles 27'-and 28. The exciting coils of the two 'auxiliaijy poles are connected in s'eriesbythe wires 29 and 30.

Also in Fig. '2 v the series winding of the armature-is iiidica'ted by the winding 'e'lement'located between the commutator lamellae 10 and 11 which are just'being short-circuited by the auxiliary brush-7, j c

"As the 'armat ures have series windings, the main brushes-in F igfil-can be shifted on the circumference of the "commutator by 180. The auxil iary'brush 7 can assume, besides the position shown in the drawing, three other positions by being shifted by 90 and nd to the left relatively to the positio n'show'n in=the drawing.

:With the six-pole machine shown in Fig. 2 the main brushes and (Sean be shifted without a change of their polarity. The auxiliary brush 7 can assume 5 other positions besides that shown in the drawing, the-several positions being separated from one another by 60".

Also the six-pole machine might be designed with only one auxiliary pole. If two auxiliary poles are employed, they need not lie accurately opposite each other, as in Fig.

aaccordin-g toin Fig; 1.

2 his arrangement is advantageous because the magnetic attractionsexertedupon the armature by all polesbalance'each other in pairs. 1

Fig. 3 showsthe. magneto-motive and the magnetic"forcesactive in a machine designed The numerals 1, 2 and 3 indicate the main and N2, are the. magnetic fluxes of these poles, the direction of which is indicated by arrows, A63 andAtet, as well'a's A61 and Afi2, are the magneto-motive "the fluxes mentioned are produced; The fluxes N3 and N1 enter into'the armature 8 where then; a division takes place, in that a part 'turnsto one of the adjacentpoles and forces by which the other part turns to the other of these poles. Thus, the flux N1 is divided into the parts NZl/l and N 3/4, 'N 4/1 and N1/2 form the magnetic circle prop'er'anduare produced bythe total of the ampere-windings which'encompass them;

It may be supposed in what follows that the ampere-windings and thefluxes are positive when they have the direction indicated by the arrowsin Figs. 1 and 3, whereas they are negative in the oppositedirection. 'N3/4: is produced by At? and Ant, Na rby A6 1 and Azf1,"and so on. For the sake of simplicpoles and 4 indicates the auxiliary pole. N3-a'nd Ng as well as N1 ity it is assumed in this example that with a i'ninimum number of revolutionsfit=n0 all magneto-motive forces and all"fiuxe s are equally strong and positive, that is to say: AZ3=At4=AZ/l=AZ2 and i i 'N2/3=N3/et=N4/1=Nl/2. And there may be assumed furthermore, that the saturation, as well as the stray, exert no influence. i'valu'es are stated in the form of-re'ct'angles which, being positive, lie all'above the ab scissa axis OO. As has already been said in one of the preceding paragraphs, the

polarity of the auxiliary brush decreases, with respect to the'niain brush '6, with the increase of the number of revolutionsfbe comes finally Zero, and changes thereafter its direction if the number of -revolutions increases still more. Owing thereto, with "a number of revolutions n=nl, AL-+l will be 0; with a. higher number of revolutions 72/ 712, the ampere-windings of the auxiliary pole will be -Att. In the case of vz n3, they will, become 2At l; in the case of n=n h they willbeeome 3At4, and so on. These at cases are also graphically represented in Fig. '3. The fluxes N2/3 and N 1/2 are the same for "all numbers of revolution; the fluxes N 3/4. and N 4/1 become smallerfand smaller with the increase of the numbers of revolution, become then Zero, and with still higher numbers of revolutions, finally negative. As with 72 71 1 and At l tl, A 51 and A253 remain however, unchangech'Nii/l and Na/l beconie only one half of what they "ice Below the poles'the would be as with n=n0, and as with n=a2, A64 is as great, but reversely directed than with 010, NEE/4 and N l/'1 become zero. Furthermore, as with n=1z3, At4 is twice as great and inversely directed than with 220, NEE/4 and N4/l will become only half so great and be directed inversely as with n0. And as, finally, with 'n=n4, A64 is three times as greatas with 710, and inversely directed, Nil/4 and N4/1 will be equally great, but inversely directed than with NO. It the resulting flux at H2110 amounts, for instance, to 400,000 lines of force, it is diminished at a l to 300,000, at 2:2 to 200,000, at 123 to 100,000, and at 224 to 0. is in reality, with suitable dimensions, neither the stray, nor the saturation must be neglected, the picture changes in reality about as indicated in dotted lines for 11 21: and 11:024, that is to say, the negative fluxes are smaller than those that have been theoretically ascertained. The resulting fluxes decrease in reality nearly like an equilateral lyperbola so that, in fact, the output of the machine remains constant even at very large variations of the number of revolutions.

The output at a minimum number of revolutions is, with the present improved machine, greater than with a three-brush machine, from the reason, as with the improved machine the excitation need not, as with said. other machines, be weak in comparison to the armautre ampere-windings. The output of the machine depends, therefore, solely upon the admissible heating.

hen a machine of the improved construct-ion has been adjusted for a certain definite output the adjustment is by far less liable to an alteration than is the case with the three-brush machine, because the auxiliary brush can be located in more nearly the middle than with other machines.

The commutation conditions are, with higher numbers of revolution more favor able from the reason, that with the highest number thereof most poles are excited constantly so that it is easily possible to obtain a favorable commutation field by a. suitable shape of the pole shoes.

Fig. 4 shows a current-curve of an existing machine designed and used for motor-car lighting. This machine has been connected up in parallel with a 12-volt battery. The numbers of revolution have been inscribed on the abscissa, and the current strengths on the ordinate. J denotes the current generated by the machine; it is apparent that it remains nearly constant from 1400 up to 4000 revolutions per minute. 21 62 23 is the constant exciting current of the main poles 1, 2 and 3. i4 denotes the exciting current of the auxiliary pole 4.

This pole is positive at 650' revolutions, becomes smaller when the number of revolutions increases, becomes Zero at n 1400, reverses its direction and increases when the number of revolutions increases, as already described. The theoretical representation in Fig. 3 has been confirmed fully by the built machine that has been tested in every respect.

I claim:

1. A continuous current machine adapted to run with variable numbers of revolutions and with approximately invariable voltage and comprising a field magnet system com posed of main poles and of auxiliary poles, main brushes and a third brush, the exciting coils of said main poles being branched from said main brushes, and the exciting coils of said auxiliary poles being branched from one of the main brushes and said third brush, the armature having a series winding, and the number of the said auxiliary poles being smaller than that of the said main poles, substantially as described.

2. A continuous current machine adapted to run with variable numbers of revolutions and with approximately. invariable voltage and comprising a field magnet system composed of main poles and of auxiliary poles, all poles together amounting to six; main brushes and a third brush, the exciting coils of said main poles being branched from said main brushes, and the exciting coils of said auxiliary poles being branched from one of the main brushes and said third brush, the armature having a series winding, the number of the said auxiliary poles being smaller than that of the said main poles and two of the auxiliary poles being arranged diametrically opposite to one another, substantially as described.

FRITZ KESSELRING.

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