DE3931484A1 - Reluctance motor with magnetic pole rotor - has alternating layers of magnetisable and non-magnetisable material - Google Patents

Abstract

The rotor (1) has at least one pair of magnetic poles (P,P'), exhibiting a layer structure transverse to the radial plane of the rotor with layers (3,4) of a magnetisable and a non-magnetisable material in alternation between two opposing poles (P,P'). The stator has a series of stator windings (Wa,Wb,Wc) corresponding to the stator of a three-phase motor for providing a magnetic field enclosing the rotor. Pref. the magnetisable layers (3) are made of a foil or sheet material, or by adjacent wire sections, the alternating non-magnetisable layers (4) pref. comprising a partially electrically conductive material, e.g. Al. ADVANTAGE - Provides max. output torque.

Description

The invention relates to a reluctance motor formed electric motor with at least one pole pair sending rotor with directional magnetic Conductivity, the size of which is in the direction of a the poles of a pair of poles leading a maximum owns, as well as with a stator to generate a the changeable magnetic field penetrating the rotor.

With a reluctance motor, the fact is used that that a body with directional magnetic Conductance, e.g. a body made of soft magnetic material with a non-circular cross-section, within a magnetic field seeks a preferred position in which the direction, in which the body has its maximum magnetic conductance  has, with the direction of the magnetic field Right. Here are soft magnetic bodies two layers rotated by 180 ° to each other in the same way possible because the polarity of the magnetic field relative to soft magnetic body is irrelevant.

Deviates the position of the soft magnetic body relative to Magnetic field from the two possible preferred positions, so exerted a torque on the body, which from the Orientation of the body depends on the magnetic field and in an unstable middle position of the body between the mentioned preferred positions assumes a vanishing size.

In the case of a reluctance motor, a generally soft magma now forms netic body with directional magnetic conductance the rotor, which is then energized when the windings of the A magnetic field and - depending on the orientation of the magnetic field relative to the rotor - a corresponding rotation moment is exercised.

Depending on the position of the rotor, the reactance changes (blind resistance) which is energized to generate the magnetic field Winding. The so-called longitudinal reactance (maximum value the reactance) when the direction of the maximum magnetic Conductivity of the soft magnetic rotor with the direction of the magnetic field generated by the winding in or on the rotor agrees. The so-called cross-reactance (minimum value of the dance) is when the direction of the maximum magnetic Conductivity of the rotor is transverse to the magnetic field of the winding.  

The maximum torque that can be generated by a reluctance motor depends among other things on the relationship between longitudinal reactance and cross-reactance and is mainly from the Structure of the rotor and in particular the magnetized cash part or the magnetizable parts of the same dependent.

A principal advantage of reluctance motors is in that for a given electrical power consumption comparatively high torques are generated by the motor can. For this reason, reluctance motors are fundamental well suited as a servo or actuator.

From the imprint of P.J. Lawrenson "design and Performance of Switched Reluctance Drives with High Performance DC Drive Characteristics "in PCIM 1989, Munich, a reluctance motor is known, the rotor of which has two pairs of poles owns that as radial extensions on the outer circumference of a soft magnetic ring part are arranged. That rotor interacts with a three-phase stator, which ins a total of three pole pairs, each diametrically opposed to each other overlying poles designed in the manner of pole shoes owns. Becomes a phase of the stator with electrical current is applied between the poles of the Pole pair generates a magnetic field, with the result that the poles of the closest pole pair of the rotor try to approximate the stator poles mentioned.

The rotor of this reluctance motor interacts with sensors, which represent the respective rotor position. So that can the phases of the stator using an appropriate food circuit controlled depending on the rotor position  be so that a magnetic field with the desired Orientation can be generated to in the respective Position of the rotor a torque in one or to effect another direction.

Because the stator of this well-known reluctance motor is pronounced Pole and the phases of the stator in succession are energized, there are strong fluctuations in the Torque curve over the angle of rotation. Consequently can not freeze, especially at low speeds running smoothness can be achieved.

In the publication "Electrical Drive Technology" by Fritz Kümmel, VDE-Verlag GmbH, Berlin and Offenbach, 1986 , a cross section of a rotor with two pole pairs for a reluctance motor is shown on page 304 . This rotor consists of a large number of sheets arranged in radial planes of the rotor, with special sheet metal cuts with cutouts and slots which act as barriers to the magnetic flux ensure that the ratio between the longitudinal and transverse reactance has a value of approximately 3. However, this does not achieve satisfactory torques in relation to the electrical power consumption of the motor.

The object of the invention is now a reluctance motor to create one that is characterized by a greatly increased reactance ratio or with given performance recording particularly high torques allowed to generate. This object is achieved in that each pole pair of the rotor has a layered structure each extending from pole to pole and transverse to one  Radial plane of the rotor extending layers alternately magnetizable and non-magnetizable Owns material.

The magnetically conductive - usually soft magnetic - According to the invention, material is therefore in an axial view of the rotor at least approximately arranged as the course the field lines of a pole to pole of a pair of poles Corresponds to the rotor's extended magnetic field.

Because of this structure of the rotor it is achieved that the magnetic flux in the direction from pole to pole one Pole pair of the rotor through paths from magnetized available material, i.e. in this direction becomes a very high magnetic conductance (or a very low magnetic resistance). Against that the magnetic flux on one across the layers trending path from a large variety of layers Push through non-magnetizable material. this has an extremely low magnetic conductance (or one very high magnetic resistance). Dement speaking, the reluctance according to the invention is distinguished motor by a large value of the ratio between Longitudinal and transverse reactance and compared to the electrical Power consumption high torques.

To achieve high torques, it is advantageous if the layers of the rotor radial planes of the rotor are arranged vertically penetrating.

Furthermore are for high torques as well as good effects just the motor rotors with non-magnetizable layers made of electrically insulating material advantageous.  

In contrast, if it is crucial to good damping and So that the engine runs smoothly, it is advantageous, the non-magnetizable layers electrically conductive material, for example aluminum, to manufacture.

Otherwise, the smoothness - regardless of the material of the non-magnetizable layers - this also increases be that the layers obliquely to radial planes of the Rotor are arranged.

If a rotor with several pole pairs is required, are the layers of each pole pair with respect to the axis of the rotor arranged curved, the concave side the curvature faces away from the rotor axis.

The magnetizable layers usually consist of Foils or sheets. However, it is also possible, in particular the magnetizable layers in each Layer level arranged side by side, from pole to pole of the each pair of poles running wire pieces.

To manufacture a rotor with several pole pairs with in Above-mentioned curved layers can form a wrap with a double layer spiraling to the winding axis magnetisable and non-magnetisable material and then broken down into sectors or sector sections which form the pole pairs.

It is also possible to use the pole pairs Sectors or sector sections of a multi-layer coil with several tubular, concentric to each other  layers of non-magnetizable material and screw on the outer circumferences of the tubular layers shaped wires made of magnetizable material to manufacture.

The magnetizable layers usually consist of soft magnetic material as mentioned above.

However, in principle it is also possible to use permanent magneti arranged layers.

Otherwise, the preferred features of Invention on the claims and the following explanations tion of particularly useful embodiments based on the Drawing referenced.

It shows

Fig. 1 is a radial section of a rotor according to the invention having a pole pair in three charakeristi rule layers within a magnetic field,

Fig. 2 is a schematic sectional view of a modern fiction, with the reluctance motor rotor according to Fig. 1,

Fig. 3 is a schematic representation of a stator winding of this motor,

Fig. 4 is a perspective view of a rotor with four pole pairs, wherein the magnetizable layers are formed by metal plates,

Fig. 5 is a perspective view of a rotor with four pole pairs, wherein the magnetizable layers are formed by wires or pieces of wire,

Fig. 6 a of Fig. 2 corresponding sectional view of a reluctance motor, the rotor has two pole pairs, and

Fig. 7 is a block diagram for torque control of the reluctance motor according to the invention.

The rotor shown in FIG. 1 1, which is mounted rotatably about an axis perpendicular to the plane of the drawing central axis 2, has a layer structure consisting of alternating with each other layers 3, 4 of magnetizable within its effective for generating the driving power of a reluctance motor range or non-magnetizable material. These layers 3 and 4 are arranged in the illustrated example in parallel to the axis 2 uncurved planes, so that a rotor-side pole pair P, P 'is formed. Accordingly, the rotor 1 along a pole from one pole to the other of the pole pair P, P 'leading path has a very high magnetic conductance and along a layer 3 and 4 traversing path an extremely low magnetic conductance.

The rotor 1 may now be located within a magnetic field, the field lines H of which are oriented transversely to the rotor axis 2 . Otherwise, magnetizable layers 3 made of soft magnetic material are assumed. Accordingly, the magnetizable layers 3 have no or all if only a negligible permanent magnetization, so that the polarity of the magnetic field is irrelevant for further consideration. Therefore, the field lines H of the magnetic field in Fig. 1 are symbolized by a double arrow.

Because of the very different values of the magnetic conductance in the direction of the layers 3 , 4 or in a direction transverse thereto, the rotor 1 has a distinctly stable position, which is shown on the left in FIG. 1.

In this stable position, the layers 3 and 4 of the rotor 1 are parallel to the direction of the field lines H of the magnetic field. If the rotor 1 is deflected from the stable position, it seeks to return to the stable position shown.

If the rotor 1 , as shown in FIG. 1 in the middle, is in a position in which the layers 3 and 4 lie transversely to the direction of the field lines H of the magnetic field, the rotor is in an unstable position, in that no torque is effective. However, if the rotor 1 is deflected somewhat in one direction or the other from this unstable position, it will continue to rotate in the respective direction of rotation in order to assume the stable position described above.

In the right part of Fig. 1, the rotor 1 takes a position between its stable position and the unstable position, such that the direction of the field lines H of the magnetic field passes through the planes of the layers 3 and 4 at an angle of approximately 45 °. In this position of the rotor 1 , a maximum torque in the direction of the arrow M is exerted thereon. If the rotor 1 is rotated by about 90 ° to the position shown on the right in FIG. 1, a corresponding maximum torque becomes effective in the opposite direction.

A reluctance motor is now shown schematically in section in FIG. 2, the rotor 1 having the same structure as in FIG. 1.

The rotor 1 of this motor is surrounded in the usual manner by a stator 5 , which is designed as in conventional three-phase motors and has three windings W _a , W _b and W _c .

The windings W _a , W _b and W _c are arranged in slots on the inside of the stator 5 , each of the windings mentioned being distributed over a plurality of slots. A winding W _a , W _b or W _c therefore includes wires diametrically opposite each other with respect to the rotor axis, which are interconnected in a winding head, not shown.

In Fig. 3 is now one of the windings, W _a , exemplified in schematic form with the stator 5 omitted Darge. If this winding is energized with an electric current i _a in the direction shown, a magnetic field is generated whose field lines H have the direction shown within the winding. If the winding is energized in the opposite direction, the magnetic field is correspondingly opposite oriented.

The ends of the windings W _a , W _b and W _c can, as is shown schematically in FIG. 3, each be led out separately in order to be able to excite each of the windings separately from the other windings.

However, since separate excitation of individual windings is generally not necessary, the three windings W _a , W _b and W _{c can} also be connected in a star.

A uniformly rotating magnetic field passing through the rotor can best be achieved by energizing the windings W _a , W _b and W _c with sinusoidal currents which have a phase shift of 120 ° relative to one another. One such rotating magnetic field then searches the rotor 1 "entrain", ie the rotor 1 can be driven in rotation in one direction or the other.

Incidentally, when the rotor 1 is at a standstill, by de-energizing the windings W _a , W _b or W _c with the motor shown in FIG. 2, an effective torque can be generated in one direction or the other.

The layer structure of the rotor 1 shown in FIGS. 1 and 2 can be produced in virtually any manner. For example, the magnetizable layers 3 can consist of appropriately large sheets or foils of generally soft magnetic material, for example iron, while the layers 4 are formed of sheets or foils of non-magnetizable material, for example aluminum or plastic. The foils or sheets can be connected to one another in any way, for example by gluing or riveting, but the rivets should consist of non-magnetizable material in order to keep the value of the magnetic conductivity in the layers transversely penetrating directions as low as possible.

The edges of the layers 3 and 4 forming the peripheral surface of the rotor 1 can be machined by material removal so that the peripheral surface has the shape of a circular cylinder surface.

In principle, however, it is also possible for the layers 3 and 4 to form steps on the circumference of the rotor 1 , which are enclosed by a circular cylindrical envelope surface. The latter embodiment only allows the generation of somewhat reduced torques, since the air gap between the outer circumference of the rotor 1 and the inner circumference of the stator 5 is somewhat larger on average than in the embodiment in which the circumferential surface of the rotor 1 largely corresponds exactly to a circular cylinder. However, the somewhat reduced torque is offset by less expensive production.

Furthermore, it is possible to design the rotor 1 such that an enveloping surface surrounding it has a non-circular cross section. For example, each half of a pole lying in a direction of rotation can have a larger and the other half a smaller diameter with respect to the rotor axis 2 . This results in a correspondingly non-uniform air gap between rotor 1 and stator 5 , with the result that a torque direction of the rotor is distinguished from the other. In this distinguished direction, even greater torques in the opposite direction can be achieved with a corresponding current supply to the stator windings than in an embodiment with a constant wide air gap.

The same effect can also be achieved in that the inner circumference of the stator 5 has a non-circular cross-section, the inner diameter of the stator 5 inside a winding W _a , W _b or W _c increasing somewhat when rotating in one direction.

Reluctance motors with such asymmetrical air gaps are particularly useful for drives with a preferred Torque direction, e.g. B. drives for hoists, cranes, Elevators and the like

If the non-magnetizable layers 4 consist of electrically insulating material, for example plastic, particularly high efficiencies can be achieved. If, on the other hand, electrically conductive materials, for example aluminum, are used for the non-magnetizable layers, the efficiency is reduced, but the motor is particularly quiet.

In addition, the smoothness can also be increased in that the layers 3 and 4 are not aligned exactly perpendicular to the radial planes of the rotor 1 , but penetrate the radial planes more or less obliquely.

Since the layer structure of the rotor 1 can be designed as a practically monolithic block, the mounting of the rotor 1 does not pose any structural difficulties. At the axial ends of the layer structure, circular flanges can be attached, for example with screws, pins and the like. It must only be noted that the flanges adjacent to layers 3 and 4 and the screws, pins and the like protruding into the layer structure. Like. Should consist of non-magnetizable material to ensure a high magnetic resistance of the rotor 1 in a direction perpendicular to the layers.

If necessary, the flanges mentioned can also be "bell-like", such that a cylindrical ring web is arranged on the flange and somewhat overlaps the outer circumference of the layer structure.

Centric bearing journals for the rotary mounting of the rotor 1 are then arranged on the flanges in bearing parts fixed to the stator.

Fig. 4 shows an example of a rotor 1 with four poles P ₁ , P ' ₁ , P ₂ and P' ₂ , ie with two pole pairs. Here, the magnetizable and non-magnetizable layers 3 and 4 extend in the direction of the rotor axis 2 , curved planes, the convex side of these planes facing the rotor axis 2 .

As can be seen from the sectional view of the corresponding reluctance motor shown in FIG. 6, the associated stator 5 is in principle constructed in the same way as was explained with reference to FIGS . 2 and 3 for a rotor 1 with a pair of poles. Only the number of windings is doubled, ie in addition to the windings W _a , W _b and W _c , the stator 5 has the windings W ' _a , W' _b and W ' _c . The windings W _a and W ' _a , W _b and W' _b and W _c and W ' _c are each electrically connected to each other in such a way that they are energized together and in phase, but with opposite directions of rotation with respect to the winding axis.

The curved layers 3 and 4 of the rotor shown in FIG. 4 can be produced, for example, by spirally winding a double layer consisting of a sheet made of magnetizable material and a film made of non-magnetizable material. From the winding thus formed, segments or sectors can then be cut out, each of which represents a portion of the rotor 1 shown in FIG. 4 and accordingly only in the orientation shown in FIG. 4 relative to one another - in principle in any way - must be joined together . The central region 6 of the rotor 1 can be cast with plastic or be formed by a correspondingly shaped plastic part. If necessary, a shaft can also be arranged within the central region 6 , which takes over the rotary mounting of the rotor 1 . Within the rotor 1 , the shaft can have a non-circular cross-section in order to ensure a rotationally fixed connection between the shaft and the rotor 1 by positive locking.

The rotor 1 shown in FIG. 5 is similar to that of FIG. 4. However, the magnetizable layers 4 are each formed by wire pieces lying side by side in one plane.

To manufacture such a rotor 1 , a multi-layer coil can first be produced by helically winding a wire made of magnetizable material onto a cylinder part made of non-magnetizable material to form a layer. This layer of magnetizable wire is then coated with a layer of non-magnetizable material. Then this cylindrical sheath of non-magnetizable material is wrapped with magnetizable wire to produce the next magnetizable layer, etc.

In this way, a multi-layer coil with several concentric layers of magnetizable wire as well several intermediate layers of non-magnetic Formable material.

This coil can now be broken down into sectors or sector sections, which in turn form sections of the rotor 1 shown in FIG. 5 and accordingly only have to be mounted with their convex sides facing one another.

Fig. 7 now shows how a reluctance motor 7 is appropriately controlled.

The rotor of this motor 7 interacts with a rotary position sensor 8 , the signals of which represent the respective rotational position of the rotor relative to the stator or other stationary parts of the motor 7 .

These signals are passed on to the input of a microprocessor 9 .

This microprocessor 9 receives, via a second input 11, further signals which indicate the desired direction of rotation of the motor and the value of the respectively desired torque. These signals depend, for example, on what position or what state a machine element driven by motor 7 is in.

The microprocessor 9 then generates, depending on the position of the rotor signals from the rotary encoder 8 and depending on the signals present at the input 11 , which represent the desired direction of rotation and the desired torque, setpoint _signals i _1soll , i _2soll and i _3soll , which represent the desired energization of the stator windings of a three-phase stator, as shown for example in FIGS . 3 and 6. These signals i _1soll , i _2soll and i _3soll control a _{feed circuit} 10 which feeds the windings of the stator of the motor 7 as a function of the signals mentioned. The supply _currents i _1ist , i _2ist and i _3ist actually supplied to the stator windings are _regulated with respect to the current intensity and / or other parameters as a function of the setpoint _signals i _1set , i _2set and i _3set , that is to say the _{feed circuit} 10 has its own control with transducers 12 to carry out a target-actual value comparison.

In this way, a magnetic field oriented in such a way can be generated within the stator of the motor 7 that the field strength is such that the rotor tries to turn in the desired direction with the desired torque.

This rotor position-dependent energization of the stator windings is particularly expedient when the motor 7 is used as a feed or positioning drive.

The desired torque can be changed the current forms and / or by changing the peak values of the currents as well as by switching individual on or off Windings of the stator can be changed, at the same time  to take into account that the size of the torque also by the size of the angle between each Position of the rotor and the respective position or direction of the magnetic field generated on the stator side, i.e. through the Location and direction of the stator current vector is influenced.

In principle, the microprocessor 9 causes magnetic fields with controllable field strength and controllable orientation to be generated within the stator of the motor 7 , depending on the respective position of the rotor, so that a torque of the desired strength and direction is exerted on the rotor , in fact in dependence on corresponding signals fed to the microprocessor 9 .

Claims (17)

1. An electric motor designed as a reluctance motor with at least one pole pair having a rotor with directionally dependent magnetic conductance, the size of which has a maximum in the direction of a path leading across the poles of a pole pair, and with a stator for generating a changeable magnetic field penetrating the rotor, thereby characterized in that each pole pair (P, P '; P ₁ , P'₁; P ₂ , P ' ₂ ) has a layered structure with layers ( 3 ) extending from pole to pole and extending transversely to a radial plane of the rotor ( 1 ) , 4 ) made of alternately magnetizable and non-magnetizable material. 2. Motor according to claim 1, characterized in that the magnetizable layers ( 3 ) consist of soft magnetic material. 3. Motor according to one of claims 1 or 2, characterized in that the layers ( 3 ) of the magnetizable material from foils, sheets or the like. 4. Motor according to one of claims 1 or 2, characterized in that the layers ( 3 ) of the magnetizable material from each other in the respective layer plane, opposite poles of a pole pair (P, P '; P ₁ , P'₁; P ₂ , P ' ₂ ) connecting pieces of wire exist. 5. Motor according to one of claims 1 to 4, characterized in that the non-magnetizable layers ( 4 ) at least partially made of electrically insulating material, for. B. plastic. 6. Motor according to one of claims 1 to 5, characterized in that the non-magnetizable layers ( 4 ) at least partially made of electrically conductive material, for. B. aluminum. 7. Motor according to one of claims 1 to 6, characterized in that the magnetizable layers ( 3 ) in a rotor ( 1 ) with a pair of poles (P, P ') are each arranged in flat or approximately flat planes. 8. Motor according to one of claims 1 to 6, characterized in that in a rotor ( 1 ) with a plurality of pole pairs (P ₁ , P '₁; P ₂ , P' ₂ ), the magnetizable layers ( 3 ) with respect to the axis ( 2 ) of the rotor ( 1 ) are curved, the concave side of the curved layers facing away from the rotor axis ( 2 ). 9. Motor according to claim 8, characterized in that the rotor ( 1 ) is composed in sections of sectors or sector sections of a winding with a spiral double layer to the winding axis made of magnetizable and non-magnetizable material. 10. Motor according to claim 8, characterized in that the rotor ( 1 ) sections from sectors or sector sections of a multi-layer coil with a plurality of tubular, concentrically arranged layers of non-magnetizable material and arranged on the outer circumference of these layers layers of helically wound wires magnetisable material is composed. 11. Motor according to one of claims 1 to 10, characterized in that radial planes of the rotor ( 1 ) of the layers ( 3 , 4 ) are penetrated perpendicularly. 12. Motor according to one of claims 1 to 10, characterized in that radial planes of the rotor ( 1 ) by the layers ( 3 , 4 ) are penetrated obliquely. 13. Motor according to one of claims 1 to 12, characterized records that between the outer rotor circumference and stator circumference an air gap with essentially the same Width is present. 14. Motor according to one of claims 1 to 12, characterized records that between the outer rotor circumference and stator circumference an air gap remains free, which has several sections with increasing width in one circumferential direction. 15. Motor according to one of claims 1 to 14, characterized in that the windings (W _a , W _b , W _c ; W ' _a , W' _b , W ' _c ) of the stator ( 5 ) designed in the manner of a three-phase motor are. 16. Motor according to one of claims 1 to 15, characterized in that the rotor ( 1 ) cooperates with a rotary encoder ( 8 ) and the stator ( 5 ) of the motor ( 7 ) or its windings depending on the position of the rotor ( 1 ) can be energized in such a way that a magnetic field penetrating the rotor with controllable orientation and / or field strength can be generated within the stator. 17. Motor according to claim 16, characterized in that the rotary position encoder ( 8 ) is connected to an input of a microprocessor ( 9 ), the other input ( 11 ) receives signals which indicate a desired position of the rotor ( 1 ), a desired direction of rotation or . Describe a desired torque or the like of the rotor ( 1 ) that the microprocessor ( 9 ) in dependence on the input signals mentioned setpoint signals (i _{1 set} , i _{2 set} , i _{3 set} ) for the electrical currents in the stator windings (W _a , W _b , W _c ) generated and forwarded to the input of a feed circuit ( 10 ) for the stator windings, and that the feed circuit ( 10 ) is associated with transducers ( 12 ) whose signals reflect the feed currents actually supplied to the stator windings and a regulation of the Enable supply circuit ( 10 ) by comparing the setpoint and actual value.