DE102006021419B4 - Electric motor - Google Patents

Abstract

Electric motor with rotor, comprising a squirrel cage,
wherein the short-circuit cage comprises bars (1, 2, ...24) and rings which have electrical connection points at least at their axially front and rear end regions
wherein the pattern of all electrical connections (120) between each two connection points has a discrete rotational symmetry around the rotor axis, the number of which is smaller than the number of bars (1, 2, ...24),
where at least two connection points are not connected to each other.
wherein the connection points are arranged on three circles which are designed as rings, wherein the connections (120), in particular those assigned to the connection points or connected to the connection points, are also only arranged within these circles, in particular not between circles of different diameters,
wherein the connected rods can be combined into groups which are arranged in the circumferential direction,
the rings are arranged concentrically and are each designed without interruption,
wherein at each connection (120) of a connection point a respective ring and a respective rod are electrically connected,
characterized in that
the first ring connects bars 1, 2, 7, 8, 13, 14, 19 and 20, the second ring connects bars 3, 4, 9, 10, 15, 16, 21 and 22 and the third ring connects bars 5, 6, 11, 12, 17, 18, 23 and 24.

Description

The invention relates to an electric motor, in particular comprising at least one winding which can be excited by induction in the secondary part, preferably a rotor cage.

In asynchronous motors, squirrel cages are known that are connected to the rotor of the electric motor. It is known to construct the cage in such a way that an axially front ring and an axially rear ring are connected with bars.

The winding of the stator is very complex and is also called a three-phase winding.

From the US6,359,355 B1 A simple stator winding for an electric motor is known that can be implemented with single-tooth winding. However, this winding cannot currently be used with secondary parts whose excitation is caused by induction, because the superficial fields caused by a single-tooth winding lead to undesirable excitation fields with negative effects on noise and vibrations.

From the WO 2005/027308 A1 is an electrical machine with an induction rotor.

From the US 5 955 811 A is an electromagnetic rotary machine with magnetic bearings.

From the US 3 987 324 A The closest state of the art is a highly efficient induction motor.

From the US 2 808 552 A An induction motor is known.

The invention is therefore based on the object of developing an electric motor in a cost-effective and simple manner.

According to the invention, the object is achieved in the electric motor according to the features specified in claim 1.

Important features of the electric motor are that the electric motor is designed with a rotor comprising a squirrel cage,
wherein the short-circuit cage comprises bars having electrical connection points at least at their axially front and rear end regions
where the pattern of all electrical connections between any two connection points has a discrete rotational symmetry around the rotor axis, the number of which is smaller than the number of rods.

The electric motor comprises at least one winding in the secondary part that can be excited by induction, preferably a rotor cage, which is also referred to here as a squirrel cage.

The connections can be implemented on a ring, for example on a thick-walled hollow cylinder that is axially shorter than radially extended, by providing corresponding interruptions in the circumferential direction. Alternatively, the connections can also be provided using different rings. Instead of rings, however, parts with different geometric shapes can also be used for this purpose. In particular, the rods can also be arranged on a single diameter and the connections can be made with crossovers.

The advantage here is that single-tooth winding can be used, i.e. each individual pole can be wound. The winding technology can now be used on asynchronous machines, while still achieving smooth, even rotation. Other advantages of this winding are that it is cost-effective to manufacture because winding the teeth is easier and quicker than pulling the wires into slots, which would otherwise be necessary. A high level of efficiency can also be achieved because the winding head is very short. In addition, a compact design can be achieved because the winding head can be made very short. Simple insulation can also be provided because there is no phase separation. Another advantage is that the spectrum of the magnetic rotating field waves generated is very homogeneous. So in this spectrum there is essentially only one main rotating field wave. Other waves with different numbers of pole pairs and directions of rotation have a negligible amplitude.

Thus, the excitation of the rotor from the stator fields leads to mainly a rotor field and therefore to a smooth running of the asynchronous motor, even though single-tooth winding has been implemented.

The main advantage is that by creating a discrete symmetry of the current loops occurring in the squirrel cage, the rotating field waves that correspond to the desired number of poles of the rotor are filtered out from the many possible rotating field waves generated by the stator.

In an advantageous embodiment, the number of poles corresponds to the number of poles, in particular of the rotor and/or the stator. The advantage here is that the number of poles can be realized in a simple manner, namely by a symmetry of the connections and connection points. It is not the number of bars within the electrical machine that is decisive. dend, but this symmetry of the pattern of connections and junctions.

At least two connection points are not connected to each other. The advantage here is that not all rods are connected to all rods. This saves connections and also improves the engine.

The connected rods can be combined into groups that are arranged in a circumferential direction. The advantage of this is that a high level of efficiency can be achieved, in particular a high torque with low losses. In particular, very high-pole arrangements can also be implemented with such advantages.

The connection points are arranged on three circles, whereby the connections, in particular those assigned to the connection points or connected to the connection points, are also only arranged within these circles, in particular not between circles of different diameters. The advantage here is that no crossing or overlapping of the connections with each other is necessary.

In an advantageous embodiment, the circles are provided in a first axial region and/or at a first axial location. The advantage here is that one or more rings can be used to produce the connections, which are designed with or without interruptions, and thus a simple and cost-effective method of connection can be used despite the sophisticated patterns according to the invention.

In an advantageous embodiment, not all bars are electrically connected to one another. The advantage here is that a number of poles and thus a number of poles can be produced that is lower than the number of bars.

In an advantageous embodiment, the number of poles of the rotor is 2, 4, 6 or 8. The advantage here is that even such low and medium-high numbers of poles can be achieved in a simple manner.

In an advantageous embodiment, the stator and/or its stator laminated core comprises individually wound teeth. The advantage here is that the stator can be manufactured in such a simple, quick and cost-effective manner. This is because the manufacture of individually wound stator poles can be carried out with high quality, particularly in comparison to the complicated process of pulling a three-phase or multi-phase current winding into the stator laminated core, because during this pulling in the winding wires are exposed to forces directed in different directions.

In an advantageous embodiment, the number of poles of the rotor and the number of teeth of the stator do not have a common prime factor, with at least one of the numbers having at least two prime factors. The advantage here is that pole notches, slot notches and losses can be reduced.

In an advantageous embodiment, the motor is an asynchronous motor or comprises at least one electrical machine part that operates according to the asynchronous motor principle. The advantage here is that generators can also be designed according to the invention or motors whose rotor partially comprises permanent magnets to form a partial motor according to the synchronous principle or material recesses to form a partial motor according to the reluctance principle.

In an advantageous embodiment, the motor is an internal rotor or an external rotor. In particular, the motor is designed as a rotary or linear motor. The advantage here is that the invention applies to a wide variety of types of motors that include at least one electrical sub-machine that operates according to the asynchronous motor.

Further advantages arise from the subclaims.

In the invention, the term “motor” always also refers to an electrical machine, i.e. also a generator or the like.

• Die 2a, 2b zeigen Ausführungsbeispiele gemäß der Erfindung. Die Ausführungsbeispiele nach 1a, 1b sind nicht Teil der Erfindung und dienen nur der Erläuterung.

The invention will now be explained in more detail with the aid of illustrations:

• The 2a , 2 B show embodiments according to the invention. The embodiments according to 1a , 1b are not part of the invention and are for illustration purposes only.

The electric motor is designed as an asynchronous motor with an internal rotor design. The rotor rotates with the squirrel cage inside the stator. The associated stator laminated core is designed with inward-facing teeth, with each tooth being wound individually.

In the 1a A first variant of the rotor's squirrel cage is shown schematically in a developed view. The rotor shaft is also shown schematically to clarify the viewing direction.

The cage comprises 24 axially aligned rods, which are arranged in 4 modules and are electrically connected to one another. This means that the six rods of the first module, i.e. the rods with the numbers 1 to 6, are electrically connected to one another.

The other three modules are also made up of six electrically connected rods. The modules are not electrically connected to each other.

In the invention, the axially front and rear ring is made up of four ring segments each. The front and rear rings could also be described as rings with four interruptions.

In another embodiment, the rods do not run parallel to the axial direction, but at a skew angle. This means that even less unrest can be generated than with rotary motion.

In a further embodiment, the electrical connection 120 is preferably made by means of a welded connection. Alternatively, the connection is made with a material bond and/or is already provided during manufacture. Each module can be manufactured by means of die casting or another casting process, so that the module can be produced in one piece. Metals such as aluminum or copper, as well as alloys that contain at least portions of such metals, are suitable materials.

Instead of a motor designed as an internal rotor, an advantageous design also includes a correspondingly designed variant as an external rotor.

In another embodiment, as in 1b shown, in contrast to 1a a certain number of bars are omitted from the modules. In this variant, too, the main rotating field carries out the main excitation of the rotor squirrel cage. Of the multitude of magnetic stator rotating fields of the single-pole winding, only the desired rotating field causes excitation of the rotor with cage. This makes it possible to combine the simple and cost-effective production of the stator winding using single-tooth winding with a rotor with cage that is also simple and cost-effective to produce.

This is achieved by interrupting the two short-circuit rings provided axially at the front and rear in a suitable manner. In this way, preferred poles can be formed in the rotor winding.

In the simple embodiment according to 1a or 1b The poles are formed by forming a number of groups of bars corresponding to the number of pole pairs of the stator, which are electrically connected to one another. In the embodiment according to 1b In addition, individual rods in the middle of the pole are not formed, which also reduces the moment of inertia.

Like in the 2a Schematically shown as a developed front view, three rotor cages are formed, arranged in tiers, each connected to different bars. The first interrupted ring is arranged on a smaller diameter, the second on a medium diameter and the third on a larger diameter. The first ring connects bars 1 and 4. It also connects bars 7 and 10. The other connection points are also shown in the 2a marked dark. The wave is also indicated to show the direction of view.

Thus, two bars of the first module, which includes bars 1 to 6, are electrically connected.

Like in the 2 B shown schematically, other connection systems can also be used to advantage and also only excite the desired four-pole fundamental wave. The first, second and third rings are as in 2a concentrically arranged, but without interruption. The electrical connections 120 are marked dark. For example, the first ring connects bars 1, 2, 7, 8, 13, 14, 19 and 20. The non-connections 121 are marked lighter. In these areas there are only overlaps without electrical contact or significant electrical contact.

In another embodiment, no rings are used, but rather types of connection technology are chosen.

The 1a , 1b , 2a , 2 B The connections shown have a pattern in the circumferential direction such that the connection pattern repeats every 90°. In other words, a rotation of 90° converts the squirrel cage into itself.

According to 1a and 1b The bars are divided into groups, the number of which corresponds to the number of poles. There are therefore four groups. The groups follow one another in the circumferential direction.

Both 1a , 1b , 2a , 2 B the number of poles is 4.

After 2a and 2 B the rings are offset from each other in the circumferential direction. In the latter arrangement, a rotation of 360° / 24 transfers the first ring into the second and the second into the third ring.

The important feature in any case is that the pattern of the connection points between the rod and the ring or the number of rings has a symmetry corresponding to the number of poles. In the figures, the number of poles is four and the symmetry is therefore fourfold. If the number of poles on the rotor squirrel cage is different, the symmetry is correspondingly different.

Thus, the symmetry of the squirrel cage filters out, so to speak, the corresponding rotating field wave from the multitude of rotating field waves generated by the stator with single-pole winding, which corresponds to the number of symmetry.

List of reference symbols

1, 2, ...24

Rod

120

electrical connection

121

no electrical connection

Claims (10)

Electric motor with a rotor, comprising a squirrel cage, wherein the squirrel cage comprises bars (1, 2, ...24) and rings which have electrical connection points at least at their axially front and rear end regions, wherein the pattern of all electrical connections (120) between each two connection points has a discrete rotational symmetry around the rotor axis, the number of which is smaller than the number of bars (1, 2, ...24), wherein at least two connection points are not connected to one another. wherein the connection points are arranged on three circles which are designed as rings, wherein the connections (120), in particular those assigned to the connection points or connected to the connection points, are also only arranged within these circles, in particular not between circles of different diameters, wherein the connected rods can each be combined into groups which are arranged so as to penetrate in the circumferential direction, wherein the rings are arranged concentrically and are each designed without interruption, wherein at each connection (120) of a connection point a respective ring and a respective rod are electrically connected, characterized in that the first ring connects the rods 1, 2, 7, 8, 13, 14, 19 and 20, the second ring connects the rods 3, 4, 9, 10, 15, 16, 21 and 22 and the third ring connects the rods 5, 6, 11, 12, 17, 18, 23 and 24. Electric motor according to Claim 1 , characterized in that the number of poles corresponds to the number of poles, in particular of the rotor and/or the stator. Electric motor according to at least one of the preceding claims, characterized in that the circles are provided in a first axial region and/or at a first axial location. Electric motor according to at least one of the preceding claims, characterized in that not all bars are electrically connected to one another. Electric motor according to at least one of the preceding claims, characterized in that the number of poles of the rotor is 2, 4, 6 or 8. Electric motor according to at least one of the preceding claims, characterized in that the stator and/or its stator laminated core comprises individually wound teeth. Electric motor according to at least one of the preceding claims, characterized in that the number of poles of the rotor and the number of teeth of the stator do not have a common prime factor, wherein at least one of the numbers has at least two prime factors. Electric motor according to at least one of the preceding claims, characterized in that the motor is an asynchronous motor or at least comprises an electrical machine part which operates according to the asynchronous motor principle. Electric motor according to at least one of the preceding claims, characterized in that the motor is an internal rotor or an external rotor. Electric motor according to at least one of the preceding claims, characterized in that the motor is a rotary motor.

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