US993359A - Alternate-current motor. - Google Patents

Description

MV .A.PYNN. ALTERNATE CURRENT MOTOR.

APPLIUATION FILED MAR. 2, 1903. v 993,359. I I I Patented May 30,1911.

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WITNESSES 07%: M)

V. A. FYNN.

ALTERNATE CURRENT MOTOR.

APPLICATION 111.111) MAE. 2, 190a.

993,359. 1 Patented May 30,1911,

'! SHEETS-SHEET 2.

Fig. 3a,.

v. A. FYNN. ALTERNATE CURRENT MOTOR.

APPLIUATION FILED KAR. 2, 190B.

Patented May so, 1911..

'I SHEETS-SHBET 3.

RE ULAT/MG .DEVI CE INVLWTOR w/msssts V. A. FYN N.

ALTERNATE CURRENT MOTOR.

'APPLIOATION FILED MAR. 2, 190a.

993,359, I Patented May 30, 1911.

7 SHEBTS-SHEET 4.

EGUAAT/NG paw/c V. A. FYNN.

ALTERNATE CURRENT MOTOR.

APPLICATION FILED MAE. 2, 1908.

993 Patented May 30; 1911.

SHEETS-SHEET 5.

mmv ro/av. PYNN. ALTERNATE GURRENT MOTOR. APPLICATION FILED MAR, 2, 1908.

Patnted May 30, 1911.

7 SHEETS-SHEET 6.

WITNESSES.-

, V. A. PYNN.

ALTERNATE CURRENT MOTOR.

APPLICATION FILED MAB. 1908.

Patented May 30, 1911.

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INVENTOR 1 Wal /re [3y Attomeys, Q

WITNESSES:

l" mm sTA'rEs PATENT OFFICE.

HtALIERE ALFRED FYNN, OF BLACKHEATH, ENGLAND.

amnmwrn-cunnnn'r moron Specification of Letters Patent.

Patented Ma Bo, 1911.

' Application filed March 2, 1908.. Serial 11o. 418,873.

. To all whom it may concern: I

applicable. to single-phase generators and such machines may also be temporarily used in continuous current circuits acting either as motors or generators.

It is more particularly my object 1(1) to compensate. such single-phase motors 2'. e.

to-improve their power factor (2) to increase their torque ampere, (3) to obtain a maximum torque. greater than has hitherto been possible in the said type of motor (4:) to improve their commutation both at the moment of starting and Whenrunning, and (5) to generally improve the operation of such machines. Generally speaking the said objects are achievedfin a neutralized singlephase series conduction motor in which the normal m'otor field is excited bya winding at least partly disposed on the rotor, by pro-' viding an auxiliary alternating field which is not coaxial with the said normal motor field, the said auxiliary field being produced .by a winding placed on thestator, on the rotor or on both, and the phase magnitude and direction of said auxiliary field being suitably chosen. This auxiliary field is preferably produced along the axis of the neutralizing Winding 2'. 6. along the armature axis, but it can be producedalong any other axis as long as its own axis does not coincide with that of the normal. motor field. The phase of this auxiliary field can be the same as the phase of the motorfield or it' can differ from it. 1 a I l he first object of this invention is achieved byso choosing the phase,.magni- .tude and direction of the auxiliary field that a compensating EPM. F. of proper phase, magnitude and direction may be generated at the brushes conveying thefield current and by rotation in. said auxiliary field'of I those rotor conductors which conveythe field current.

The second andthird objects are achieved by so choosing the phase, magnitude and direction of the auxiliary field that an additional or auxiliary torque is produced between'said auxiliary field and at least part of the rotor conductor carrying theexcit-v ing current. The se ond and third objects are also partly achieve by so adjusting the magnetizing current f the series transformer sometimes used between armature and field Winding so as to bring armature current and motor field into closer phase coincidence. I

Tlie fourth object is achieved by so choosing the phase, magnitude and direction of the auxiliary field in respect of the phase,

magnitude and direction of the motor field and taking the prevailing speed into consideration, that the vector sumof the various E. M. F..s which are present in the coils undergoing commutation may become as small 7t;

as possible. The said auxilia f field not 1 only allows the resultant E. F. to be reduced, but also allows if required thephase of that resultant to be so chosen that it can then conveniently be annulled by some of the known means for improving the commutation, such for instance as commutatingi poles.

It will be understood that all that; im-

provements or their modifications need not $5 necessarily be used simultaneously or all on the same machine.

In order that my invention, its scope and the possible modificationsmay be more fully understood, I propose to shortly state the theory which led me to discover these improvements and although I believe this theory to be substantially correct yet I wish it .to be understood that I do not bind myself to this or an other theory. My invention will be better understood by reference to the drawings, in which Figure 1 shows a neutralized single-phase conduction motor in which the field winding is disposed on the stator and wherein a transformer is interposed between the arma ture and field circuit.v Figs. 1 1, 1, 1*, are explanatory vector diagrams illustrating the mode of opera ion of the known motors shown in Figs. land 2. Fig. 2 shows a known modification 0 Fig. 1 where the field winding is disposed on the rotor. -Fig. 3

shows one way of a plying the invention, the auxiliary field being excited in parallel from the mains. Figs. 3 to 3" illustrate the mode of operation of the improved motor shown in Fig. 3. Fig. 4 shows another way of applying the invention, the auxillaryfield being excited from the armature brushes. Fig. 5 shows a way of applying the invention where the auxiliary field is excited n parallel from the mains, part of the neutralizing windin being made use of for this purpose. windings, one of them doing duty as armature and the-other as field winding. Fig. 6 shows a way of applying this invention while only making use of one set of brushes per pole pair or their equivalent. Fig. 6 illustrates certain commutating conditions of Fig. 6. Fig. 6 shows a rotor Winding by means of which a similar efiect is obtained as that secured by displacing the brushes as shown in Fig. 6. Fig. 7 shows one way of disposing the field winding partlyv on the rotor and partly on the stator. Figs. 8 and 9 show an arrangement of stator windings permitting of the reversal of the direction of rotation of Fig. 6 without displacing the brushes. Fig. 10 shows a way of applying the invention, in which the auxiliary field is excited by means of shunt and series transformers. Fig. 11 shows means for exciting the auxiliary field in series with the mains. Fig. 12 shows an arrangement in which the auxiliary winding is not disposed'in the armature axis and may be excited from an outside source. Fig. 13 shows a modified disposition of the field brushes.. Fig. 14: shows :a modified disposition' of the armature and field brushes. Fig. 15 shows an arrangement of circuits and brushes by means of which part of the single rotor winding is made use of as armature and part as field winding, the armature current being derived from series transformers.

Fig. 16 shows a similar arrangement, but.

where thefield current is derived from series transformers. Fig. 17 shows an arrangement by. which only a part of the rotor winding is utilized, that part doing duty both as armature and as field winding. Fig. 18 shows one means of limiting the speed of such motors by converting them into self excited shunt conduction motors. Figs. 19 and 20 are diagrams which are explained hereinafter.

In Fig. 1 is shown an ordinary neutralized series conduction [motor in which N is the neutralizing Winding, aa the armature brushes, \LA. the rotor or armature, F the field winding disposed on the stator and fed by way of example through a series transformer T the primary of which is included in the armature circuit. The potential difference at the motor terminals is supposed to be .P. Assume the motor to be locked in any given position and a current I flowing through N, A and T. Assume that the transformation ratio of T is unity and that This figure also shows two rotorooasse and of F respectively where a2,:m',+m",'

and as, w,; the two-latter being respectively the reactances of A and N. Let N and be so chosen that the fields due to the% two windings and which thread both windings are entirely neutralized. Under these conditions Fig. 1- shows an approximately correct phase diagram at the terminals of A-l-N. It will be understood that 12,, is the sum of the leakage fields around A and N thus l' i, and by assumption Q: 1 Since closes almost entirely through air it has been shown in phase with I; this is approximately correct. It is seen that E is the E. M. F. required to drive I through A-l-N.

Fig. 1 shows the approximate phase diagram at the terminals of F and at the ter minals ofthe machine. The field winding is of course not neutralized and consequently its reactance 17 is large, a small component of this reactance which lags about 90 behind 2' has been purposely omitted as being generally very small. Seeing that the motor field I -closes--almost entirely through iron it will lag appreciably behind i as shown at (o. It is seen that E is the E. M. F. required at the terminals of F in order to drive a through F. In view of the assumptions made E: may be taken to be equal in all but sign to the E. M. F. at the primary termiillads of T. Now P must be the resultant of E and E: as shown in Fig. 1 and therefore 41., is the phase difi'erencebetween the current taken by the motor and its terminal voltage.

What happens when the motor shown in Fig. 1 is allowed to run up and. reaches a speed s is shown in Fig. 1 where s is supposed to be about one half of 'the synchronoue speed. In this figure the two previous diagrams have been superposed and the parallelogram of E. M. F.s constructed in .a diflerent but well known manner, 0-3 is the E. M. F. which has to be equalled and opposed by P when the motor is standing still whereas 0-4 must be equalled and opposed at the speed a if the same torque is still to be given by the motor, in other words if I is to remain coiistant. The con dition that I shouldremain constant is by no means essential, yet it greatly facilitates the comparison of the various diagrams and has been adopted for this reason. Now it is seen that although P has to be increased to P at the speed 8 yet 45., is reduced to t in other words the power factor of the motor llt in Fig. 1 increases with the speed- This fact that the back E. M. F. appearing at the armature-brushes and generated by rotation of the armature conductors in 1 is not, in phase with the working E. M. ,F. impressedv on the armature and is sodirected as to partly counteract the various reactance volt ages which lower-the power factor. This back E. M. F. is shown at 0 and is here, owing to the direction of rotation, 'of op.- posite phase to 9 It should be noted that if the load is increased, the terminal voltage being kept constant, the power factor will drop very rapidly in a motor such as shown in Fig. l for e cannot increase as fast as for instance t'w if at all, for the latter is directly proportional to the current only whereas the former is directly proportional to P (therefore-to the current) but also inversely proportional to the speed which must decrease with decreasing load if P is kept constant.

In Fig. 1 the series transformer T is not essential but it'becomes of importance to use T if F is discarded and the armature winding itself is made use ofas field winding by applying to thecommutator brushes 1, f, displaced preferably by with respect to the brushes a a as shown in Fig. 2. The number of poles is throughout designated by n. If T in Fig. 2 were 9 The character of the motor remains exactly discarded. it would be necessary to connect say a with f" and the current distribution through the armature would not be'so satisfactory. Itis preferable in case T is discarded to provide two independent windings on the rotor. The mere fact of transferring F fro1n the stator, as in Fig. 1, to the rotor, as in Fig. 2, makes very little difie'rence indeed if any, to the operation of the known motors under discussion. There is now but one other E. M. F. to consider, which is very small and has been shown in Fig. 3 at (2 it is not to scale, otherwise it could hardly have been seen in the diagram. In the parallelogram of E. M. F.s it is shown at 45.

This M. F, is generated at the brushes f by rotation in the leakage field I the same whether the field winding is disposed on the stator, as in Fig 1, or on the rotor, as in Fig. 2.

Now according to ni y invention and in that manner of carrying it into practice which is shown in Fig.3, I, in order to imtain disadvantages are: met with.

prove the power factor produce preferably in the armature axis, and preferably by induction from the stator, an auxiliary alternating field such at Q If the direction of rotation is such that the E. M. F. generatedalong the armature axis by rotation in the motor field is of opposite phase to the motor field then the E. M. F. generated along the field axis byrotation in an auxiliary field disposed along the armature axis will be in phase with this auxiliary field and vice versa. Thus in this case-e generated at the field brushes f, ft will be in phase with 4 This adds the component 5-6 to the parallelogram of E. M. F.s in Fig. 3%, reduces P to P. and reduces b. to for the same speed s. i

The diagram Fig. 3"" corresponds to the manner of carrying out my invention which is shown in Fig. 3 where Ois the auxiliary winding fedby way of example from the supply by way ofthe shunt transformer T In this arrangement 1 will always be prac tically in quadrature with Pas shown in Fig. 3*, whether it is to be shown in the diagram as leading P or lagging behind it depends on the position of the reversing switch S It will be seen from the diagram that the power factor will be either improved or reduced. accordin to the direction of Q It will also be seen om'Fig. 3? that the direction of rotation can \be reversed either by reversing the current,through the armature or through the field inding. A reversing switch S is shown f r the latter purpose. When the direction of rotation is reversed in 'of the Variable ratio type and capable of being regulated at K and K. The diagram Fig. 3 however reveals, further facts which I will deal with before showing other ways of carrying out my invention.

It will be noted that power factor unity can be easily obtained by increasing '-I and without raising the speed, therefore as long as the motor revolves at all, and as long 'the former manner then I must also be re-" versed. Both T and T are shown as being as 1 .of suitable phase and magnitude is available "itis theoretically possible to ob tain unity power factor. The question 'of magnetic densities willhowever determine the lowest speed at which unity power factor can be secured with a given torque. That speed will obviously be far below the synchronous so that unity power factor can be secured over the whole practical range of speed. It is also clear from Fig. 3 that as far as the improvement of the powerfactor is concerned it is better for e to lead I by less than 90 rather than by more. If the lead is less than 90 then not only can the power factor be improved but P. can also be reduced... It will be seen later however that if this lead is less than 90, then cer- 5 assess Designating. the phase difierence between I and by y we can say that, for either direction of rotation, the power factor will be improved for any values of y for which one component of D leads I by 90, it being assumed that 1 is resolved into two components oneof which is parallel to I and the other perpendicular to it. In other words the power factor will be improved for all values of 7 above zero but below 180. When =90 then the compensating efieet of D, is a maximum.

The torque conditions are of importance; it is seen from Figs. 3 and 3 that the current I in the armature axis will produce a torque with the field E in the-motor field axis. This is shown in the usual way in Fig. 3 But the field current in the motor field aXis and the auxiliary field 1 in'the armature axis will also yield a torque as shown in Fig. 3. The direction of these torques can be found by ascertaining for any given instant the sign of the various vectors involved and then plotting the results for instance in, the manner shown in Figs. 3 and 3 The assumption underlying these two last figures are that from top to bottom and from left to right of the paper he considered positive and that the current distribution on the periphery of the rotor be such as to tend to create a field coinciding in direction with the arrow giving the direction of the current vector in Figs. 3 and 3 Proceeding it is seen that at any given instant, andfor the conditions chosen in Fig. 3 the torque proportional to IX D, is the greater as shown in Fig. 3", it will therefore determine the direction of rotation, and may be referred to as the main and positive torque. The auxiliary torque proportional to i I is much smaller as shown-in Fig. 3 but is in this instance also positive. In ascertainingthe' directions of these torques only those. components of the one or the other factors should be taken into account which are of the same or opposite phase as the corresponding factor. Thus in Fig. 3

. it is only the component, I of the factor 1 whichis to be considered for that purpose; it is ofcourse also the only component of- I which does give a. torque in conjunction with the corresponding factor 6.

A study of Fig. 3 at once shows that, for the particular direction of rotation chosen,

the torque i l is zero when 1:90 When '65 phase of 1 as referred to the phase of I no longer holds good as far as the direction of the auxiliary torque is concerned. In order to define the direction of the latter independently of any phase difference between I and 2', the phase of 1 must be referred to that of 2'. We may then say that the auxiliary torque will be positive, for the direction of rotation assumed in Fig. 5) 6. when 2' and I are of about the same direction), as.long as D, leads 2' by at least 90. If the direction of rotation is reversed, for instance by reversing i 6. when in Fig. 3 2' is of about opposite direction to I), then the auxiliary torque will be positive as long as a, does not lag behind 11 by more than 90. In either case 7 must be less than 180 if 5, is to help to compensate the motor. The main torque would be increased if D, were in phase with I. The angle a) by which l lags behind 2' depends, as is known, on the iron losses and may assume very appreciable dimensions when the densities are high or the iron quality poor. One of my improve ments consists in eliminating this phase difference. I achieve this by interposing a series transformer between armature and field circuit, as shown in Fig. 9. or 3 and by so choosing the magnitude of the magnetizing current of that transformer that, in Fig. 3 for instance, 2' shall lead I by that same angle a). Une more point is of importance, when 1 is due to P as in Figs. 3 and 3, then it is obvious that I will always lag behind I? by practically 90. Now the very presence of alters the phase relation between P and I or 2'. At the moment of starting and as will be seen from Fig. 1 there is a large phase difierence between P and I or i, and y will therefore be largerthan 90 in other words the torque i will be large and in this manner yet another object of my in vent-ion will be achieved for the motor will now st-artlike a machine with two very effective armature and two very efiective field aXes per pole pair. As the speed increases the conditions in Fig.- 3 will ob tain and with a still higher speed Pg, may easily come to lag behind I or i, in other words the machine will take a leading current,-when y will become less than 90 and this would determine a negative torque.

This negative torque may be made use of to limit the speed of the motor even at no load. If it is desired to avoid this negative torque then I must not be allowed to lag appreciably behind I or 2'; this can be prevented for instance by reducing I which at starting and at low speed is advantageously chosen large. Or a negative torque can be avoided and even a positive torque secured while allowing P to lag behind I and i by changing the phase of the E. M. F. impressed on C (Fig. 3) or generally by changing the phase of 1 as the speed increases; this can for instance be achieved by impressing more than one E. M. .F. on C, these E. M. F.s being of difiering phase, and by changing their relative magnitudes, or directions of both. A glance at Fig. 1 will show that such E. F.s of difiering phase are available in the motor itself; thus E at the terminals of A-N in Fig. 3, also. E. at the brushes f f in Fig. 3 or at the primary or secondary termi-' nals of T in Fig. 3 and finally P, the difference of potential of the mains. The E'. M. F.s at the terminals of A-and N respectively are also available for the said purpose. They are the componentsof E; the- E. M. F. at the termlnals A-N they are not shown in Fig. 1 and may be designated by E. and E respectively. These components of E are however shown in Figs. 3 and 3 for the case illustrated in Fig. 3 the effect of I on A and N has been taken into account in Figs. 3 and 3. These figures will be referred to in greater detail a. little later. Any one or more of these E. M. F.s may be.made use of in order to excite 49 if one such E. M. F. only is used it is obvious from Fig. l andifrom what has been said that E and P are generally more suitable than E. if phase compensation is principally aimed at. 1 These F .s may be derived directly from the various points mentioned or through transformers embodied in the motor. itself or separate therefrom. It will be understood that an E M.

F. or E. M. F.s of suitable phase andderived from any other or external source can.

,be used with-equal success; although this is not necessary itmay be sometimes convenient or desirable. Such an external source may be apolyphase supply or a phase converter, either rotary or static or the like. Any phase splitting device may also be used for the purpose. V e The magnitude of the auxiliary field 1 should, as'has been explained, vary withthe speed it the power factor is to be kept con stant, decreasing with increasing speed; it should also vary with the current-taken by the motor, increasing as the current increases. The phase which I should occupy relatively to the phase of I or i if a negative auxiliary torque is to be avoided and phase compensation secured has already been fully defined. The considerations which determine the mannerin which themagnitude and if required also the phase of should be re lated are therefore now known. This regulation can be carried out -by-hand or electromagnetically, by means of known devices, or'by means ofocentri-fus gal on other automati'cdevices; or by a combination of'all or any ofthe said means. At this stage yet another factor must be wint10ducedWlZ1ich so far has beenleftout' of consideration in order to not unduly complicate the diagrams. 'This factor is .the

effect produced by- I on the armature winding and on the neutralizing winding N. .If it is assumed that the number of turns of N and their inductive relation to I be so chosen that the E. M. F. (en) inducedin N by 15, is of the same .magnitude as the E. M. F. (ea) induced in Aalong the axis a a then Figs. 3 and 3 will show the actual phase and value of E.,, E and E when G in Fig. 3 is made use of. Under the con.- ditions named en equals and opposes ea since N and A are in series and in opposition and that is why this factor has not so 'far beenconsidered. It .is of course not necessary that en shall be equal to ea and the effect of adifference between these two E. M. F.s is easily seen from Figs. 3 and 3 In most casesit will be preferable to so dimension N and A that the motor is as fully neutralized as possible; under these condi-.

tions cn and eawill-be nearly if not quite equal and opposed.

we have in the rotor winding, and appearing at the brushes a a, the E. F.s Im' Ir and e a. These must be equaled and opposed at the brushes a a by the E. M. F. E shown in Fig. 3 The rotorA and the stator winding N being connected in series relation, an E. M. F. E must be present at the terminals of A plus N which equals and opposes the vectorial sum of E -FE". if 'the' current I is to flow through the combi nation.

It should be pointed out that the magnetizing chrrent required by O in order to produce I could very much reduce the overalthough the power factor at the terminals of the motor, and not includingthe C Wind ing,- might -be'high. In order to avoid this drawback in all cases, the exciting winding is not only disposed on the rotor butalso on the stator and preferably along the motor field axis. If these two parts of theexciting winding are now connected in opposition then a high overall cos (1) can be maintained with a much smaller I whereas .the current 2' for a given .magnitudeo 'must now be chosen greater than before thus securing a larger auxiliary torque. v

The conditions of commutation "will now be considered.

. All commutation all power factor particularly at slow speeds i diagrams are drawn to.

a much larger scale than any of the others induced or generated .by I2, have been so as to make them clearer; all-the E.'M. F.s Y

are the respective currents in the right and left halves and ifrot-ation is counter clockwise, then the current in the coil undergoing commutation must be reversed from l l a within the time 2f during which the coil undergoing commutation is short circuited by the brush a. The motor field 1 will induce 6 in the shortcircuited coil and that E. M. F. will cause a current i to flow therein. The phase of with respect to 6 can be determined in-the usual way if w is the ohmic resistance and 00.. the reactance of each coil. The brush contact resistance (whether varying or not) as well as the brush resistance are assumed to be included in w. The shortcircuited current z' may be greatly in excess of the working current I; it will cause local heating and when the rotor begins to rotate, then the interruption of this current each time a segment leaves the brush, .will cause sparking. The permissible sparking during the first few revolutions sets the limit for the magnitude of 39 at the moment of starting and therefore determines the maximum startingtorque. The same diagram also holds good for the brushes act of the new motor shown in Fig. 3 as long as the rotor is at rest. A similar diagram holds good for the brushes f f of that last motor when at rest. I has however inductive eflect on the coils shortcircuited by the brushes f f whereas is fully effective. The E. M. F. induced in these oils is a, the shortcircuited current is i e E. M. F. 0 corresponds to c of Fig. 1 and i correl sponds to i of that figure.

Suppose now that the known motor shown in Fig. 1 is allowed to reach that same speed s' which was taken as a basis for Fig. 1;

while the current taken by the motor is kept the same as at starting. which assumption was also made for Fig. 1, then and there'- I fore 6 and a; must remain unaltered in the coil undergoing commutation so that Fig.

' P will still correctly represent the commutating conditions for the speeds, a't least equal to zero.

toward the end of the commutating'time t. The commutating conditions shown in 1 are obviously had, at the instant considered, 2} should be equal to both in phase and magnitude, whereas it leads the latter considerably and is very much greater. If the current I diminishes as the speed increases then the commutation will improve, for then e 6 and i will all diminish and '5 will lag farther behind 6 on account of the increased frequency of commutation. Indeed as the commutation frequency increases the shortcircuited current will not be able, within the time t, to reach that value which corresponds to 6 therefore z' will with increasing speed approachboth in phase and magnitude. With the help of the contact resistance commutation may become quite good but only at the speeds considerably abovethe synchronous. These remarks will also ."show what phase and magnitude an auxiliary commutating E. M. impressed on the coil in question should have in order to secure a good commutation at somewhat lower speeds; its phase and magnitude cannot very well be constant.

Fig. 3* refers to the conditions under the brush a of the new motor shown in Fig. 3 when running with the same current I and at the same speed S. In this motor ther aretwo E. M. F .s in the short circuited coil. (2 induced by r. and (2' enerated by rotation in 1%. Their resultant UR the true commutating E. ill. F. and happens to be of nearly the correct phase and magnitude. Although the ohmic drop '5 w and the re actance voltage i m are shown in all the diagrams these vectors are not always lettered. Fig. 3* shows that commutation can always be made sufiiciently good by altering in one of two ways. Either choose therefore 6'5" so that 2' equals LOLH in phase and magnitude, or choose it so that c equals and opposes 8 when QR will be In the first case the contact resistance will only be called upon to rectify the unavoidable little irregularities which will occur during commutation; in the second, the oommutation will bedue to contact resistance only. But the motor shown in Fig. 3 has another set of brushes ff and the commutation under these must also be considered. Fig. 3 shows the condition under brush f for the same assumptions as underlie Fig. 3*. Here a is induced by E;

and e, generated by rotation in D The resultant OR, happens to be a little too largebut is nearly of the correct phase for i nearly coincides With --as it should. It isseen that if 1 is'so chosen that OR under the brush ais of quite correct phase andmagnitude to insure good commutation, then OR under the brush f will in some cases be of nearly, in others of quite, correct phase and magnitude. But if OR is reduced to zero under a, it will also, at the same time, be reduced to zero under 7. This last condition is satisfied when Q I whentheir phase difference is nearly 90 and when the motor speed is near to or A study-of the e ual 'to the synchronous. diagrams shown in Figs. 3* and 3 will disclose all the other possible combinations which will 'conduce to the improvement of the commutation under the one or the other set of brushes or under both simultaneously.

In both axes the values of e 2 and e can be varied to some extent by locally concentrating or strengthening or locally weakening the fields by rotation in which these E. M F.s are generated or by superimposing on these fields auxiliary fields of the same or nearly the same 'phase and direction and produced in any known or suitable manner and with the help of special commutating polesor with the help of one or more sta tor teeth situated in the neighborhood of or in the .commutating zone itself. These poles or teeth may be excited by means of a shunt or series transformers win any equivalent manner.

In all cases it is at starting that the greatest commutating difliculty generally occurs; now my improved motor has this advantage over the one shown in Figs. 1 or 2 for instance, that it. can be started with two effective armature and field axes per pole pair. Since there are two torque producing fields v in my motor, then, assuming the same current to flow through both motors, it is only necessary, in order to get the same torque in both cases, that the sum of the effective components of the said two fields in my motor be equal to the effective field component inthe known motor. Obviously then each individual field in my motor, 2'. 6. 1 and .9 will be smaller than the motor field required 1n the known motor, thus in lfig. 3 6 will be much smaller than c, of Fig. 1 and c of shown in Fig. 3 for instance, willbe considerably smaller torque'for torque and hence It is' Fig. 3. will be much smaller than e ofFig. 1. At starting therefore the individual short circuit'current under the brushes, in that. form of my improved (motor which is the commutation will be much better.

' with the. help hardly necessary to call attention to the many, other deductions to be drawn from the diagrams given; those skilled in the art should easily see all the remaining points.

Having thus fully stated the theory upon which this invention is based and explained carrying the nvention into practice particularly in connection with the example shown in Fig. 3, it will not be necessary to describe and other modifications which are not described or-illustrated should be easily recognized by those skilled in the art with the It is to be understood that modification shown inconnection with one examplemay be used with an of the other examples as far as they app y. All the drawings show well applicable to motors with any number of pole pairs. The stationary member may be of the stator type or it may have more or carry any suitable type of winding although a concentrated win in has been shown throughout for the sa e of convenience. The revolving member may carryany suit able winding such as used in this type of machine; such windingwill be connected to consists in varying the number of turns of C.

.andis excited from the mains mature winding, the other on which bear the brushes f f and which does duty as field windin. I? InF g. 6, one set of. brushes only and one brushes from the neutral position coincidin with the axis of the neutralizing winding and shifting them forward dr -1n the direction of the intended rotation indicated by the arrow D.. In'that case that portion of the rotor winding which is shown in heavy shown in thin lines act as field winding. This manner of carrying out my'invention has the advantage among others that the arthe further examples given in great detail' help of this description and the diagrams.

two pole motors but the invention is equally,

a commutator in the usual way. In the fig method of regulating I which is shownthrough T while the rotor carries two inde-" .pendent windings the one on which bear the brushes ana and which does duty as ar-' lines acts as armature winding whereas that mature winding can be neutralized much I x I f I of that theory some way of less defined polar projections and it may In Fig. 5, .a part of N is inade use of as G winding rotor winding only are used, and the latter does duty as, armature and as field winding. This is brought about by displacing the more effectively by means of'N, which is then preferably distributed on the stator so as to correspond as closely as possible with that part of the rotor winding which acts as armature winding. By way of example U is excited directly from-the mains.

The diagram Fig. 6 illustrates the com mutation conditions toward the end of the time t in the coil under brush a of the mo- 10 tor in Fig. 6 on the assumption that the machine is running at a speed s and taking a current I. These assumptions are therefore the same as those underlying all other commutating diagrams. In this case there 1 are four'E. M. F.s which are unavoidably present in the short circuited coil. The m0- tor field induces (2 and 6' is generated by rotation in the auxiliary field induces c and e is generated by rotation in 1 The resultant OR is again the true commutating E. M. F. For the conditions chosen it is nearly of the correct phase but of too great a magnitude. Fig. 6 together with'what has already been said on this subject of commutation will show what steps must be taken in order to improve the commutation. One new factor must however be considered in this case and that is the angular displace ment 0. of the brush line from the axis-0f the v neutralizing winding N. When ac? nearly coincides with N, then e and e' are at a maximum whereas 6 and e" are nearly zero.

W hen a0 is nearly at right angles to N, then 6 and 6' are nearly zero and c and e at a maximum. This gives an additional and simple means of adjusting the phase and magnitude of OR. At synchronism UR becomes zero for all values of the current ta ken by the motor if a. is chosen equal to 4:59, the phase dilference between and 1 is about 90, about equals e and the fluxes are still proportional to the E. 'M. F.s.

Instead of using an ordinary continuous current winding on the rotor and displacing the brushes in the manner shown in Fig. 6, the rotor winding may be suitably altered so as to achieve the same purpose without however having to displace the brushes or to use more than one set of them per pole pair. Such a winding is shown for a two-pole machine in Fig. 6 where each coil of the rotor winding consists of two turns 1-2-8- and 5-6-'?-8, these two turns are disposed in two planes preferably displaced by 180/11, degrees F with respect to each other. When the axis of N is parallel to the plane of the turn 1-2-3-4- then this turn acts as field winding and the other turn then acts as armature winding. The current in the first produces 1 and yields a torque with the current in the second yields a torque with 1 and is neutralized by N. Each coil of this winding may consist of more than two turns and they may be equally divided between the two planes or not; if they are, then the arrangeeoaase ment corresponds to a displacement of 45 of the brushes in the example shown in Fig.

56 where an ordinary rotor winding is made use of.

The proportion of field to armature turns in Fig. 6 is fixed as long as the brushes remain in a fixed position. It is generally preferable not to displace the brushes while operating the machine although this can of course be done. l Vhen it is nevertheless desired to vary the motor field strength inde pendently of the armature current some such arrangement can be used as is shown in Fig.

7 where by way of example the winding F is disposed on the stator and in the motor field axis and so arranged that the number of its turns can be varied as for instance at .K, also that it can be reversed as at S and be thus made to produce a magnetization in the same or in the opposite direction to that produced by that part of the rotor winding which does duty as field winding. This method of varying i is not only applicable to the example shown in Fig. 6 but to any one of the other examples. It is easier to improve the power factor of the motor as a whole when that portion of the field winding which is disposed on the stator is con nected in opposition to that portion of the field winding which is disposedon the .rotor. The auxiliary winding 0 is here connected by way of example across the armature and across part of the field winding, some known andR suitable regulatingmeans being inserted at The direction of rotation can be changed in the example shown in Fig. Gfby moving the brushes beyond the neutral position or that coinciding with the axis of N. Or it can be changed by providing two sets of brushes these sets being positioned on opposite sides of the neutral position, the one set being used for one direction of rotation and the other for the other. According to another modification two sets of windings N G and N 0 can be disposed on either side of the brush axis (m when the one or the other set of windings may be used according to the direction of rotation re quired. It is not necessary although preferable that a be the same for both directions of rotation. According to a fourth modification a is chosen equal to say 45 and the two sets of stator windings are placed at right angles to each other. If N and C are used for operating'in one direction then N or C or N +C can at the same time 'do duty as F winding (see Fig f7) for the purpose of regulating the motor field and vice versa. A fifth modification which is illustrated for both directions of rotation in Figs. 8 and 9 consists in separating each winding N and G into two independent units N, and N and C, so arranged that the current through at least one unit of each set of units can be reversed. The necessary connections .rent into such windings.

' In Fig. 10 is given one example in which the resultant E. M. F. impressed on the auxiliary winding, C is derived from two sources, means being provided by way of example for regulating both components at K and K and for reversing one of them at S. One component is derived from the mains through the transformer T and the other from the series transformer T feeding the field circuit. That transformer is shown by way of example. as having two secondaries.

In all the examples sofar considered the auxiliary winding 0 has been fed by a shunt or a shunt anda series transformer; it will be understood that more than one of such transformers may be used simultaneously. Fig. 11 shows a further modification in whlch C is fed from'a series transformer only. This manner of feeding C has by way of example, bination with that disposition of the brushes which is shown in Figs. 6, 7, 8 and 9; it can of course and as has already been stated, he used in combination with any of the other examples shown or described. The magnetization produced by C can be regulated by means of K as shown in Fig. 11. Y

A further modification, which is not illustrated, consists in exciting C directly by means of the current passing through the motor and without the interposition of a serles transformer. In this last modification the motor can work very Well on a continuous current circuit and without a chan e of connections. I Al the examples described show the auxillary winding disposed on the stationary member and intheaxis of the neutralizing winding. Although this arrangement is.

generally preferred it is not necessary that the auxiliary winding C should be disposed in thatparticular axis; it may be disposed in any other axis making an anglejB. with N as longas the axis of C does not coincide with the axis of the motor field I Such anarrangement' is shown in Fig. 12 where 'Cis by way of example supposed to be connected to some external source with an E. M. F. (D.) -j

been shown in com- The auxiliary winding 0 can at least in part be disposed on the-rotor; this either necessitates an additional set ofbrushes and an additional rotor winding or that part of the rotor winding can be made use of for the purpose which does duty as armature winding. The auxiliary E. M. F., wherever derived from, can then be applied to the brushes aa? thus entirely dispensing .with a stator winding C. This is shown in Fig. 19.

It isfurther not necessary that when two' sets of brushes are used as for instance in Fig. 3, that these should be displaced by exactly degrees although this particular spacing is as a rule preferred. The brushes f, f can for instance be displaced somewhat as shown in Fig. 13. In this example C is shown connected to the primary terminals of the series transformer T. The ampereturns due to the exciting or field current passing through the brushes f f do not) all act as field turns in this case. Similarly to Fig. 6 one part of these ampere-turns does duty as field the rest as armature ampereturns. The latter may, according to the direct-ion in which the field brushes have been displaced from the axis of the motor field and relatively to the direction of vrotation of the motor, act with or against the armature ampere-turns due to the armature current passing through the brushes a, a The armature brushes can also be displaced from the armature axis-similarly to the manner in which the field brushes have been displaced in Fig. 13. By way of example a variable ratio transformer T has been interposed in this case between the motor and' the mains; it is well understood that such a transformer can be used whenever convenient.

Fig. 14 shows one modification in which both sets of brushes have'by way of example been displaced by about 45 from the axis of N. In this case C is being fed by way of example from that part F of the motor field winding which is disposed on the stator. It will be understood that in this case the result obtained is a diflerential one.

In Fig. 3, for instance, the armature winding, between the brushes (1, a, is distributed over the pole pitch and this is also the case with the field winding between the brushes 1, such a space distribution is poor, and magnetic saturation is easily set up in some portions .of the polar\'embrace, In order to avoid these drawbacks the disposition of the brushes on the 'rotor may be modified. as.-

shown in Figs. 15 and 16.

The so-called. winding coeflicient forv In Fig. 15 it is only that part of the rotor v I winding which is shown in heavy lines order to make such a current distribution possible, I, according to one modification, feed those parts of the rotor winding which are to do duty as armature winding, through series transformers T and T and connect these to the brushes a, a and a. a}, respectively, and in such a manner that no current will tend to pass from a to a or from a to a or vice versa. This is achieved by connecting the secondaries of these transform ers in opposition with reference to those portions of the rotor winding which lie between the brushes a, a and a and a. In order to send a current through the rotor Winding lying between the brushes (r (4 and a a, I send it in at the center point 1 of the secondary of T and out at the center point 2 of the secondary of T rent traverses each half of these secondaries in opposite directions, these secondaries will be non-inductive as far as the field current is concerned. This field current must of course flow from a to a and from a to a or vice versa. The rest of the connections are by way of example similar to those shown in Fig. 11.

According to a further modification shown in Fig. 16 it is the field current which is derived from the transformers T? and T whereas the armature current is led through their secondaries non-inductively. In any case T and T may have the same iron core and any suitable regulating devices may be introduced.

A further modification is shown in Fig. 17; the two sets of brushes are preferably disposed as shown, the one set aa coaxially with N, the other f displaced by 180/74, degrees with respect to the first. A transformer T the primary of which is connected in series with N carries by way of example two independent secondaries t and t the first is connected to the brushes a, P, the second to f, a and in such a manner that t and t are in opposition with respect to those portions of the rotor winding which are comprised between the brushes a, f, and-a f The current flowing between the brushesa, f and f, a acts partly as an armature and partly as a field current. In order to reverse the direction of rotation it is necessary either to c'onnect t to a and t to a, which corresponds to a reversal of the armature current, or to connect t to f and t to f, which corresponds to a reversal of the field current. In the first instance the current through N, in the second that through C should be reversed.

By shon'tcircuiting the brushes f, 7 which carry the field current the motor can at any time be converted into a self-excited machine as described in my previous U. S. ap-

Since this field cur-.

plications Nos. 348,659 and 348,907. By self-excited machine is meant one whic generates its own exciting E. M. F. or current when rotating.

If at the time of the conversion the auxiliary field is excited by a varying current, say in series relation to the mains, then the speed .of the motor will also vary and its speed characteristic will be similar to that of a series machine after the brushes 7, f have been shortcircuited. If the auxiliary field is however then excited by a constant E. M. F. or current, say in parallel to the mains, then the machine will assume a shunt characteristic as soon as the brushes 7, f are shortcircuited and this may be useful in some cases. Means for carrying out this conversion are by way of example shown in Fig. 18 where the switch 'M is provided for the purpose of shortcircuiting the 'field brushes 7, Another switch M is also provided by means of which the primary of T may also be shortcireuited if desired.

Fig. 20 shows a neutralized series conduction motor in which the field winding is partly disposed on the rotor, being the rotor winding itself between the brushes f and f and partly disposed on the stator at F. These two parts of the field winding are connected in series with each other and in series relation with the working circuit by means of Y the transformer T. The stator field windingF can be regulated at K and the direction of the current through F can be reversed at S-. The working circuit comprises the neutralizing winding N, the primary of T and the revolving member A connected in series with N and in opposition theret by way of the brushes a, a The auxilia ywinding C is disposed on the stator and in the axis of N it is connected in parallel to the supply by way of the variable ratio shunt transformer T Motors constituted as described in this specification can of course be made use of as generators or as brakes for instance when employed for traction or similar work. The speed of these motors can be varied for a given current by varyin the terminal voltage or the magnitude 0 the motor field or by varying the magnitude or phase of the auxiliary eld. These motors can when required be operated with continuous current for instance when a car or a train equipped with such machines passes from an alternating on to a continuous current system. The alterations in the connections sometimes required at the moment of such a transition will be understood without further explanation. It must be noted that although 1 sometimes .loses much of its importance when motors constituted as here described are operated on continuous current, yet this auxiliary field can often be used with ad combination with a stationary member pro-' vided wltli a neutralizing winding and a revolving member .carrying a conductively "the stator field winding.

said exciting current vantage'and will always increase the torque 'whether C is connected in series or in parallel to the supply.

The motors here'described can be operatedon the series parallel or any other system of grouping.

What I claim and desire to secure by Let ters Patent is g I 1. In an alternate current motor the combination with a stationary member provided with 1, a neutralizing winding and a field winding displaced from said neutralizing winding and connected in series relation therewith, of a revolving member connected in series relation with the neutralizing winding along one axis and in series relation with the field winding along another axis, and means for producing an alternating flux along an axis approximately coinciding with that of the neutralizing winding.

2. In an alternating current motor, the combination with a stationary member provided with, a neutralizing winding and a field winding displaced from said neutralizing winding, of a revolving member pro-. vided with a commuted Winding connected in -series relation with the neutralizing winding, means infseries relation with the neutralizing winding for conveying an exciting current through said stator field winding and through said revolving memher along an axis displaced from that of the neutralizing winding, and means for producing. an' auxiliary flux through the motor along an axis displaced 3. In an alternating current motor, the combination with a stationary -member provided with a neutralizing winding and a field winding displaced from the neutraliz-. ing winding, of a revolving member carrying a conductively sup-plied working current along an axis approximately coinciding with that of the neutralizing winding, and a conductively supplied exciting current along another axis said exciting current being in series relation with the working current, and means for producing an auxiliary field through the motoralong an axis displaced from that of the exciting current.

4. In an alternating current motor, the

field winding displaced from the neutralizing winding, of means for varying the number of turns in said stator field winding, a

supplied working current along an axis approximately coinciding with that of the neutralizing winding, and a conductively supplied exciting current along another axis 7 being'in 'series rela tion with the working current, and means for producing an auxiliary flux through the from that of motor along. an axis displaced from that of the exciting current.

5. In an alternating current motor, the combination of a stationary member provided with a neutralizing winding, a'field winding displaced by about 180/71. degrees with respect to the neutralizing winding, and an auxiliary. winding disposed along an axis approximately coinciding with that of said neutralizing winding, a revolving member provided with a commuted winding connected in series relation with said neutralizing winding along an axis apspect to that of the neutralizing winding.

6. In an alternating current motor, the combination of a stationary winding member provided with a neutralizing winding and an auxiliary winding connected in parallel with the circuit containing said neutralizing winding, and disposed along an axis approximately coinciding with that of the neutralizing winding, a revolving member provided with a commuted winding connected in series relation with said neutralizing winding along an axis approxi mately coinciding with that of the neutralizing winding and an exciting circuit on .the revolving member connected in series relation with said neutralizing winding along an axis displaced with respect to that of the neutralizing winding.

7. In combina n of a stationary member provided with a neutralizing winding, a field winding displaced with respect to the neutralizing winding, and an auxiliary winding connected in parallel to the mains and disposed along an axis approximately coinciding with that of the neutralizing wind-' ing, a revolving member provided with a commuted'winding connected in series relation with said neutralizingwinding along an axis approximately coinciding with that of'the neutralizing winding and an exciting circuit on the revolving member connected in series relation with said neutralizing winding and said stator field windin along an axis displaced with respect to that .of the neutralizing winding:

8. In an alternating current motor, the combination of a stationary member'provided with a neutralizing winding, a field winding displaced from the neutralizing. winding,

and an auxiliary winding disposed along an axis approximately coinciding with that of said neutrahzlng winding,

a series transformer, a revolving member provided with a winding connected to a commutator, a set of n alternating current motor, the

working brushes on said commutator approximately in line with and connected 1n series relation with the neutralizing winding, a set of exciting brushes on said commutator displaced with respect to the working brushes and connected by way of said transformer in series relation with the neutralizing and the stator field winding.

9. In an. alternating current motor, the combinationwith a stationary member provided with a; neutralizing winding, of a revolving member connected in series relation with the neutralizing winding along two axes, and means for producing an alterriat ing flux along an axis approximately coinciding with that of the neutralizingwinding but differing in phase from the flux produced by said neutralizing winding.

10. In an alternating current motor, the combination with a stationary member provided with a neutralizing winding, of a revolving member provided with a commuted winding connected in series relation with the neutralizing winding along an axis approximately coinciding with the axis of said neutralizing winding, means connected in series relation with the neutralizing winding for conveying an exciting current through the revolving member along an axis displaced from that of the neutralizing winding,- and means for producing an auxiliary flux threading both members of the motor along an axis displaced from the axis along which the exciting current is conveyed through the revolving member, said auxiliary flux differing in phase from the flux produced by the neutralizing winding.

11. In an alternating current motor, the

combination with a stationary member provided with 'a neutralizing winding, of a revolving member provided with a commuted winding connected in series relation with the neutrallzin winding along two axes one of which is dlsplaced by about 180/n degrees from the axis of the neutralizing winding, and means for producing an alternating flux along an axis approximately coinciding with that of the neutralizin winding but diifering in phase from the ux produced by said neutralizing winding.

12. In an alternating current motor, the combination with a stationary member provided with a neutralizing winding and an auxiliary winding connected to'produce a flux differing in phase from the' flux produced by .the neutralizing winding, said auxiliary winding being disposed along an axis approximately coinciding with that of the neutralizing winding, a series transformer, a revolving member provided with a winding connected to a commutator, a set of working brushes on said commutator approximately in line with and connected in series relation with the neutralizing winding,a set of exciting brushes on said commutator displaced with respect to the working brushes and connected in series relation with the neutralizing winding by way of said series transformer.

In witness whereof, I have hereunto signed my name in the presence of two subscribing witnesses.

, VALERE ALFRED FYNN.

Witnesses:

ROBERT MILTON SrEAnPomr, HERBERT D. JAMnsoN.

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