WO1999031787A1

WO1999031787A1 - Direct current motor with a slotted stator core

Info

Publication number: WO1999031787A1
Application number: PCT/YU1998/000004
Authority: WO
Inventors: Dragan Bojković
Original assignee: Bojkovic Dragan
Priority date: 1997-12-18
Filing date: 1998-02-06
Publication date: 1999-06-24
Also published as: AU5736198A; YU49097A; RS49861B

Abstract

The invention relates to direct current motor with a slotted stator core in which the laminated stator (G) is constructed in a toroidal form and which is provided with the active ampere-conductors, connected in concentrically distributed coils (p1, p2, p3, p4 and p5) in relation to the (f'-f'')-axis of the brushes. The exciting coil sections (t), placed on the pole-necks of the laminated iron - rotor (R), produce the transversal field of excitation in relation to the axis of the brushes, according to ampere-conductors of the stator. When these ampere-conductors are exposed to the exciting field of the rotor (R), produced as the result of contacting effect of the brushes (f), across commutator (k), to the currents in coil sections (t) which commutate and by means of the lateral connections of the other rotor sections, it is produced the main electromagnetic torque in the stator, producing with just reactively the rotating of the rotor, cause due to the immovability of the stator (G).

Description

Direct Current Motor with a Slotted Stator Core

This invention belongs at the field of electrical machines, first of all, of direct current. According to international classification, it is assigned to the sections H ( electrotechnics ) and marked with the class symbol H 02K 23/40 and in the same manner as H 02K 23/26.

The problems which are solved with this technical solution of the motor can be presented in the next:

The simplicity in the constructive sense.

The reduction of volume in a certain extent.

The broadening of regulating ( of operating ) possibilities of this motor.

A reduced request for maintenance of sliding contacting surfaces, respectively, the useful life of usage, especially of commutator and of rotor is increased.

Today, it can be deduced a conclusion, that all standard and the other types of special machines of direct current, including here and universal motors, in its base of construction, have a common likeness.

This likeness is seen in construction of magnetic circuits. All these electrical machines, are built in the principle as machines with the salient poles ( regardless of their number and upon the role ), which in its base have the same function, and it is, for making of excitation in magnetic circuit.

Having in mind the state of technics in this field, and which is well - known to those which are occupied thereby, the object of this invention was and avoidance of certain shortages in existing construction with a new constructive access.

Without intention, to dispute the all good characteristics, in this part of text, are mentioned only shortages in existing construction of direct current machines which are characterizing the present state of technics in this field.

The complexity of construction, and with it the higher price of direct current motor which possess the means for suppression of harmful reaction of the rotor.

The impossibility, that the motor constructed as a two - pole machine ( conditionally ) convert in work as a four - pole machine and the contrary.

The role of the stator is passive ( only for making of exciting of electromagnetic field ).

It is well known, that the flowing of the great currents, across sliding surfaces of the commutator, presents one of the great problems. It is too known that by the motors of direct current with the greater powers, the current of the rotor attains a few tenth time the higher value of the same at the stator. It is so, at least concerning in the parallel and in the motors with the separately exciting stator. Of course, it is understood that the great current in the rotor produced the great current on the commutator.

With the use of toroidal stator with the slotted stator core, it enabled that the main electromagnetic torque is produced in its ampere - conductors while under action of the rotor field, what is contrary with the former practice in the construction of direct current motors. The rotor field is produced with a suitable coiling ( what will be seen in a detailed description later ) and with a determinate position of axis brushes on the commutator. Till now, the existing motors produced the rotating torque with an action of the stator field to ampere - conductors of the rotor.

With this stator, by especially coiling and by specific disposition of coils per stator and rotor slots, considerably is reduced the great current of the rotor and thereby, the all harmful consequences, which are made withal.

Too, by this constructive access, it produced the possibility of very easy crossing of this motor, from a two - pole in a four - pole one and the contrary, not decreasing of efficiency withal.

To a better understanding of the very nature of this invention, which will be detailed in the following description, it used the accompanying drawings.

Fig. 1 shows the view of a vertical central sections of the motor.

Fig. 2 and Fig. 3 show a shaped view of the stator and rotor lamina of the motor sequentially.

Fig. 4 presents a unfolded scheme of stator winding.

Fig. 5 g . ives a scheme the suitable use in the practice for connection by changing of operation from two - pole in four - pole motor and the contrary.

Fig. 6 under a presents a unfolded scheme of the rotor and the same Fig. under b also a unfolded scheme of the rotor in partial section.

Fig. 7 under a and b presents a detail of instant, when the brushes cover only per one slice on the commutator.

Fig. 8 presents a lateral chiefly schematic view of the motor, with all details which are essential to a understanding of description.

Fig. 9 presents a simplified drawing of slightly modified motor from Fig. 8, where is under a as a two - pole and under b as a four - pole one.

In this solution of the motor which is detailed in the following text, the very resultant of rotating torque is a consequence of the sum of two rotating torques. Of a main and of an auxiliary one. Both of them support the rotation in the same course. The main torque arises as the result of action of the rotor field to all ampere - conductors of the stator which are arranged per its slots. But, since the stator is fixed and one can not to move, it will according to law of action and reaction, the produced electromagnetic forces act on the rotor to revolve in the contrary course of that in which it would be revolved the stator. And the auxiliary torque appears as reaction of the stator field to tho.se ampere - conductors of the rotor which are placed in no much large surroundings about axis of the brushes. Only these ampere - conductors about above mentioned axis are exempted of mutual annulment of fields in the rotor slots, what it will be with something more details exposed in the following text. This appearance occurs because of the contacting action of the brushes on the commutator. There are always per two active uncompensated packs of ampere - conductors per each of brushes.

Acting in the direction of the axis brushes, it is seen that the flux of the stator reaction acts here usefully, producing by that the auxiliary rotating torque ( holding up the movement of the rotor ).

Practically observing, the resulting flux, as solely existential at the magnetic circuit of the motor, exactly no passes by through the axis of direction of the brushes, already its axis is something displaced for the some angle in the contrary course of rotation of the motor. This angle depends of load current in the rotor and in the stator.

In other words, the part of the auxiliary' torque will be decreased when the rotor current increases what shifts the resulting flux further of -axis brushes in which are found uncompensated ampere - conductors of the rotor. Respectively, when is the part of auxiliary torque upper ( by upper intensity of stator current ) the motor will aspire to similar features of behaviour as in a classical direct current motor.

Nevertheless, this movement of the resulting flux or the slipping of magnetic lines is little less expressively here ( due to an existence of slots as in the rotor so and in the stator, respectively because of the discontinuity in such an air gap ) then by the classical machines which have not the means for suppression of the rotor reaction. This circumstance has for the result the greater uniformity in this distribution of the density of magnetic flux at the air gap around.

Figure 1 shows the view of a vertical central section of the motor. The rotor R and the stator G are presented as the blocks of compressed cores with its windings, built up each of them separately of shaped slim sheets mutually insulated, produced of electrical steel. The commutator k and the brushes / with the brush - holders h makes composition of the motor as is shown in Fig. 1. The rotor R with the shaft o has the rests in the bearings placed in the enclosure e of the motor.

Figure 8 shows a detailed axial or lateral schematic view of the motor wherein the invention was practically realised.

The core of the rotor R of this motor has the form of a toothed cylinder wherein each of teeth on its pole - neck is provided with a concentrical coil . The ends of these coils are brought out and binded for the slices d of the commutator k. The aim which is wanted achieve with this coiling is, the formation of magnetising field in such a way as is seen from Fig. 8. As already briefly noted in the introductory part, thus the obtained polarisation is in essence a direct result of produced effect in the zone of the brushes and lateral parts of rotor coil sections ( see Fig. 6 ) what it will be seen afterwards better.

As regards of production of core of the stator G, it is in a toroidal form with the slots in which are placed windings ( pl, p2, p3, p4, p5 ) mutually connected with the linear conductors ( j, h, I, k ). This stator winding observed in a complete, as a matter of fact, is distributed in the several little less windings which are concentrically arranged, so that the active parts of these are located in the field of rotor action from both side of axis - ( / ' -/ " ) of the brushes. The binding posts of the rotor and of the stator in the scheme are marked with A, B and , K, sequentially. Sticking to one's opinion that the motor operates according to principle which is forward brought out, the idea was that the rotor get in the some way the part of excitation and that is the stator more active, producing in the indirect way ( reactively ) with its ampere - conductors the rotating torque of the rotor. What is an advantage of this way, it has already said.

In Fig. 2 is shown a view of the stator design of the lamina which reminds to the stator form of a standard induction motor.

The design of the rotor lamina ( see Fig. 3 ) have not difference in comparison with the till now known view of classical rotor lamina of direct current machines. But just coiling of winding as is seen from Fig. 6 and from Fig. 8 on the rotor has a considerable difference in comparison with habitual coiling. Only this form and this coils span, provide the full correctness in working of this motor. Also, solely this way of coiling is possible for working of the same motor either as two - pole or as four - pole. Thus an applied coil span ( or coil step ) of one coil section of the rotor windings is equal as distance of two neighbouring slots, wherein the several turns of conductors are surrounded by determinate insulation, forming such a coil section or the most common said a coil. The connecting of all coil sections of the rotor winding mutually and with commutator k is seen too from Fig. 6 and Fig. 8. Consistently, all these coil sections are connected in series across the commutator from both sides of axis of the brushes, forming so on the very brushes the parallel connection of two identical current - branches.

Figure 4 gives a clearly presentation of unfolded winding of the stator from Figure 8. The applied winding parts or winding sections are arranged concentrically per inside of circumference of the slotted stator core, but so, that the axes of all these fields, of above mentioned sections, are coincide. Therefore, as is seen from Fig. 4 the winding here is not cylindrically grouped around the poles, already, discretely arranged per circumference of the stator, but so, that its active parts by the following of the current through them, and under action of the rotor field, produce the electromagnetic forces, and these, the main rotating torque of the motor. In such a designed machine when the stator is loaded, in the rotor will appear a so low direct electromotive force ( emf. ) when we begin to revolve this rotor. It is so little because the span ( step ) of coil sections on the rotor is very little. This emf. by this motor in operation is in essence the contra emf. which reaches the high value, approximately to applied voltage on the brushes, but lesser of this for the drop of Ohmic voltage in the rotor circuit.

In the following exposition, first of all it will be given a comment in reference to Fig. 6 and Fig. 7.

Figure 6b presents a cross section of the rotor winding per the slots, with indicated courses of currents in all coil sections, for a given position of the brushes. From the same figure it is seen that each of slots there are per two identical active parts of winding or of coil sections, mutually insulated and with different courses of the currents. The intensity of magnetic field, as a sum of all ampere - conductors of this two - layer, longitudinally in the slot, is zero. An annulment of magnetic field, on the active parts of the rotor conductors of one slot, is caused due to the existence of the currents with inverse courses in both coil sections. Only in slots 1, 2 and 7, 8 ( see Fig. 6a ) for the shown position of the brushes there is no annulment of magnetic flux. It is seen better from Fig. 6b which presents the unfolded scheme of the rotor in a partial cat if it is observed from commutator side and for the right course of coiling of the coil sections. From the mentioned Fig. 6b when each of brushes covers the equal surfaces of two neighbouring slices ( or commutator copper bars ), it is very easily remarked, that there is no current through the conductors of the coil sections which are in short circuit of the very brushes on commutator ( the case when it is had the linear commutation ). With an ejection of these coil sections out of current circuit, and owing to described effects of the brushes, the state which have arisen in the slots with the currents, looks as in Fig. 6b. Taking in regard and lateral connections of the rotor coil sections, are built up the conditions for keeping of continuous exciting field in the rotor.

Figure 7 under a and b shows the courses of currents in the slots about axis of the brushes in a moment when the brushes come into the contact only with one slice. Also, and in these cases, it is disturbed the balance of mutual annulment of fields in the presented slots ( see Fig. 7 under a .and b ), wherein are made again the similar conditions for an attainment of the rotor field. As is seen, thus described process of formation of the rotor field, is independent of position of the brushes on the slices. This motor in a form which is shown in Fig. 9 ( simplified drawing ) can from a motor with one pair poles very easy change at the motor with two pairs poles. It is all achieved by the active use of the whole stator winding per its circumference in both of cases ( see Fig. 9 under a and b ). By this changing in four - pole, it is needed to adjust as following: An additional pair of the brushes B^f - B" ( see Fig. 9 ) is necessarily dropped down on the commutator and so makes a new disposition of the polarity, shown at the Fig. 9b. Besides, it is had that the current with its course in the serial connection of divided stator winding, flows so, that in a half of stator winding remains the same and that in other half of the same winding changes the course. Therefore, with the convenient reconnection of winding /' - K" from Fig. 9a in two identical semi - windings /' - JT and /" - K" ( see Fig. 9b ), the stator is arranged for operation in four - pole motor.

Thus, it is from a two - pole motor, very simply changed the work in a four - pole one, with a new mechanical characteristic ( torque - speed ) and that it was without changing of efficiency.

It ought to remark, that is in this case, the coiling and connection of rotor coil carried out entirely the same, as in Fig. 8 and Fig. 6. Referring to this case, it is very essentially to keep in mind that there is the limited capacity of this motor, defined from the side of the rated values, as these are: The density of magnetic flux ( which ought to remain unchanged ) and applied voltage, respectively the current in the rotor. These requirements have to be satisfied by the crossing of this motor from two - pole in four - pole motor and the contrary.

This access of reconnection in this way may be applied only here, just thanks to otherwise production of the stator, in comparison with the till - now known stator with the salient poles. Too, and so the little span of coil sections in the rotor, this access makes very efficient for this possibility.

Figure 5 gives a sketch explaining the suitable use in the practice for connection by the changing of operation from a two - pole in a four - pole motor and the contrary.

To state of the switcher So in position 1 the machine does as two - pole and by the position 2 as four - pole motor. Withal, it is still necessarily, with a simple mechanical device in the position 2, put down the brushes B' - B" on the commutator, as is shown in the scheme. The semi - windings of the stator ' - K' and J" - K" are coiled in the same courses.

Intelligibly, this motor may without of any changes or of some appendices to operate as well and in an alternating current, what only increases the breadth of its usage.

Too and here, as in the known direct current motors, the windings of the rotor and of the stator can be interconnected in series, in parallel ( shuntly ) and independently. It is well known that the use of uniformly slotted stator per interior of its circumference is nothing newly in the machines which are supplied with alternating currents ( as for example: the induction motors, synchronous motors and the like ). But the use of above mentioned stator in the like form ( nonsalient - pole ) and in the composition of any direct current motor, sto functionally thought - out ( as in this way ), it may give a certain progress and some of new possibilities in an exploitation of the electromotive power - plants for direct current which are not till - now were possible and known.

As already in the some way noted, the very usage of the sliding contact of all kinds, with the flowing of load currents through them, generally is unwonted. But when we can not to avoid them, it is naturally, at least aspire to the reduction of these contact currents as much as possible.

It can be remarked, that this way of the disposition of the rotor and of the stator with its distinctions, reminds to their exchanged roles, in comparison with the existing direct current motors. And really, now it is had that an excitation is settled on the rotor and that the current of load flows at the stator. Just it is wished, that the lower current, in this case an exciting current, flows across the sliding contacts of the commutator and that the strong current, flows through the firm connections of the stator.

With this, especially is decreased the deterioration of the commutator, which is expressed in the classical direct current motors.

This invention in its solution offers a few new and useful thinks of practical importance.

As the first: It is avoided that the strong current flows across sliding surface of brushes and slices, respectively, the exciting current is considerably reduced, what is the main advantage of this solution. Of course, it has the sense only when the motor functions with independently supplied excitation and at the parallel connection of the rotor and stator winding.

An omission or exclusion of the auxiliary poles and of compensating coils, does this motor more simplified for construction, what decreases its price. As the third, thus a constructed motor can very easily change the work, from a two - pole machine in a four - pole one and on the contrary. It is attained with an appendix of only one pair of movable brushes, as is seen in the previous text, and that in spite of all that, no come to the changing of efficiency of the same.

It is emphasised as especially, the very well continuity of speed regulation in the mechanical characteristic of this motor.

An example of invention, described in this way, is not limited only to specific construction herein shown, already, it understands all similar forms of direct currents machines, and which would arise from this type, wherein the construction and operation in its base would have an outline of given description and enclosed claims.

Claims

1. Direct current motor with a slotted stator core, characterized thereby, what the active ampere - conductors of the stator ( G ) with its contrary directions, are symmetrically distributed per slots in relation to the (/ ' -/ " ) - axis of the brushes and which are connected in concentrical sections of the coils (pl ), ( p2 ), (p3 ), (p4 ), (p5 ) and that the rotating rotor ( R ) on each of its pole - necks is provided with an exciting coil section ( t ), and all these together, connected across slices ( d ) of the commutator ( k ), makes a closed loop of the rotor winding.

2. Direct current motor according to request 1, characterized thereby, what the stator core is produced in a toroidal form with the slots per interior of circumference, for the placement of distributed stator winding in the form of concentrical sections.

3. Direct current motor according to request 1, in its modified form to operation either in two - pole or in four - pole, characterized thereby, what the stator winding is divided into two identical halves ( J ' - K ' ) and ( J " -K " \ always connected in series across selecting switcher ( So ), to reversal of current and voltage in the circuits of the stator and of the rotor, and that the rotor is supplied by that, across the commutator, with another pair of moving brushes ( B ' - B " ), placed at right angle according to already existing fixed pair ( A ' -A " ) of ones.

AMENDED CLAIMS

[received by the International Bureau on 29 September 1999 (29.09.99); original claims 1-3 replaced by new claims 1-3 (1 page)]

1. Direct current motor with a slotted stator core, characterized thereby, what the toroidal stator ( G ) is provided with the active ampere - conductors, wherein these with its contrary directions, are symmetrically and uniformly distributed per all slots of the stator in relation to the ( / ' -/ " ) - axis of the brushes, and which are connected in concentrical sections of the coils (/?! ), ( p2 ), (p3 ), (p4 ), ( ρ5 ), forming so herewith a single - layer structure in the slots of the stator, and that is the main excitation of above cited motor achieved on the rotating rotor ( R ), so what each of its pole - necks is provided with an exciting coil section ( ), and all these together, connected across slices ( d ) of the commutator ( k ), makes a closed loop of the exciting rotor winding.

2. Direct current motor according to request 1, in its some modified form as a universal pole - cl nging construction, to operation either in full two - pole or in full four - pole, characterized thereby, what the stator is provided with the winding which is divided into two identical halves ( / ' - K ' ) and ( J " - K " ), always connected in series across selecting switcher ( So ), to reversal of current direction in these available semi - windings of the stator, wherein the all active sides of ampere - conductors of these semi - windings, are placed towards the forming poles of the rotor, and where the commutator touches, only necessarily needed the number of the brushes.

3. Direct current motor according to request 2, characterized thereby, what is provided with the one pair of the mechanical moving brushes ( B ' - B " ), placed at right angle according to already existing fixed pair (A ' -A " ) of ones.

AMETOSHEET

"Statement under Article 19( 1 )"

"Claim 1. replaced by amended claim 1.; claim 2. cancelled; claim 3. subdivided into amended claims 2. and 3."