WO2008087068A1

WO2008087068A1 - Electrical machine, in particular synchronous motor with electrical commutation

Info

Publication number: WO2008087068A1
Application number: PCT/EP2008/050122
Authority: WO
Inventors: Wolfgang Krauth; Eckhart Nipp
Original assignee: Robert Bosch Gmbh
Priority date: 2007-01-17
Filing date: 2008-01-08
Publication date: 2008-07-24
Also published as: DE102007002443A1

Abstract

The invention relates to an electrical machine, in particular an EC synchronous motor with permant excitation in the armature (20), and multiphase winding (18) in a claw pole system (19) of the stator (16), and three connections for a three-phase rectifier. For a stator which is compact and simple to produce, it is proposed to construct the winding (18) from two adjacent annular coils (29, 30) connected in series, the connection of which and the beginnings of which each form one of the three connections. It is also proposed to arrange annular pole plates (25 to 28) on the outer and inner faces of the two annular coils (29, 30), from each of which in alternating sequence a claw pole (31, 32, 33) extends along the working air gap (24) beyond at least one of the two annular coils.

Description

description

title

Electrical machine, in particular synchronous motor with electrical commutation

State of the art

For variable-speed electric drives are now increasingly used electronically commutated synchronous motors with permanent magnetic excitation. In this case, the permanent magnets are located in the rotor, which can be designed both as an internal and external rotor. The magnet systems are constructed as axial flow or transversal flow systems. In the stator of the machines single or multi-phase windings are arranged. If low-cost small drives with electronic commutation, so-called EC motors are required, as for example in motor vehicle construction, single-phase machines are frequently used for this, if only one direction of rotation is required, as for example with fans and pumps. Such machines can be produced particularly cost-effectively and easily with a stator in claw-pole design and toroidal coils. In multi-phase machines, as required for a reversing operation, the stator windings are energized by means of an electronic circuit, an inverter. Preferably, the classic three-phase bridge circuit according to FIG. 1 is used. The three phase windings of the motor can then be used in both star and

Triangle be interconnected.

In order to combine the advantages of multi-phase machines, such as low pendulum moments and reversing, with the manufacturing advantages of Klauenpolausführung and annular coil of the stator, usually as many identical Klauenpolsysteme as phases are desired, axially juxtaposed and rotated by the phase shift angle to each other and arranged with a three-phase Inverter bridge circuit energized. Such a known electric machine shows the US 6765321 B2. Obviously the invention

The present solution seeks to produce a multi-phase electronically commutated synchronous motor on the one hand as cost effective and compact and on the other hand to be able to power with the usual inverter in three-phase bridge circuit.

In such EC synchronous motors an annular coil is omitted together with the claw poles due to the characterizing features of claim 1 compared to a motor with three-phase stator. The thus modified Klauenpolanordnung the electromagnetic conditions are largely maintained. This has the advantage of a considerable cost savings in the manufacture of the machine. In addition, the previously required Klauenpolpaare for each coil of a multi-strand machine are superfluous by the common magnet system for both coils. Another advantage is that in the now two-strand machine, a significantly shorter stator is used, resulting in a compact design of the machine result. The machine can also work as usual via a three-phase inverter in reversing mode.

The measures listed in the dependent claims, advantageous embodiments and developments of the features specified in the main claim arise.

A particularly easy to manufacture and compact design of the Klauenpol- magnet system is achieved in that between the two toroidal coils two adjacent pole plates are arranged, each having opposite to each other to form a claw pole angled claws. In a synchronous motor with axial working air gap to achieve a compact design, the two toroidal coils are arranged axially adjacent to one another and the pole plates attached to the end faces of the coils, so that the claw poles protrude axially over both annular coils. The toroidal coils are the same design and can thus be manufactured by winding machines in high numbers. A high efficiency of the machine is achieved by the fact that the claw poles are guided over the entire length of the working air gap. For cost-effective production of the magnet system, the pole disks are expediently punched with their claw poles of sheets and formed by deep drawing. Expediently, the width and thickness of the claw poles remain the same over their entire length. This results in a magnetically uniform sequence of three claw poles along the circumference at the working air gap. This leads to a rotating field with 60 ° or 120 ° electrically shifted clocks with a corresponding phase shift of the output from the inverter three-phase voltages. The concept of an EC synchronous motor with a two-stator winding can be realized both with a two-pole and with a multi-pole rotor, that is, with one or more distributed over the circumference of the rotor magnetic pole pairs. Equally variable is the number of claw poles respectively formed on the pole discs. To achieve small rotational steps and low pendulum moments, it is therefore advantageous to use in an at least two-pole, preferably four-pole rotor pole pieces, which are each provided with at least two, preferably four claw poles. In an EC synchronous motor with external rotor can be arranged with the toroidal coils on a magnetically conductive axis in an advantageous manner, in which case the pole disks of Klauenpolsystems are attached to the magnetic yoke on the axis, the free end has a bearing point for a cup-shaped external rotor ,

Short description of the drawing

The invention will be explained in more detail below by way of example with reference to FIGS. Show it:

1 shows a circuit arrangement for a three-phase EC motor according to the

State of the art,

2 shows a longitudinal section through a two-strand EC motor according to the invention in external rotor design,

FIG. 3 shows the stator of the machine with the claw pole system in an enlarged spatial representation,

FIG. 4 shows the stator from FIG. 3 in exploded view,

FIG. 5 shows the circuit arrangement of the EC motor according to FIG. 2 with a three-phase converter,

6 shows a diagram with the voltage and current profiles of the three phases on the two coils of the EC motor and FIGS. 7a to 7c each show a development of the claw pole system and the permanent magnets of FIG

Runner with the phase-dependent changing polarities of the claw poles.

Embodiments of the invention

Starting from a known circuit arrangement of an EC synchronous motor with three-phase converter according to Figure 1, the invention with an embodiment of Figure 2 to 5 and the operation with the aid of Figures 6 and 7a to 7c is explained in more detail.

The designated 10 in Figure 1 circuit arrangement shows a known three-phase EC synchronous motor 11 with permanently magnetically excited rotor I Ia, whose - A -

three stator windings 1 Ib are usually supplied by the three phase outputs R, S, T of an inverter 12 in bridge circuit via electronically controllable semiconductor switch 13. The inverter 12 is connected on the input side to a DC power source 14. About the semiconductor switch 13 can be speed and direction of rotation and the rest position of the runner control.

With the solution according to the invention, these functions can now be realized by a two-stranded version of the synchronous motor, whereby a coil is saved together with its magnet system in the stator. Figure 2 shows the schematic structure of such a synchronous motor 15 in longitudinal section in an external rotor design. Its stator 16 is mounted on a rigid shaft 17 and consists of a multi-phase winding 18, which is bordered by a claw pole 19. Its cup-shaped rotor 20 made of soft magnetic material is fixed with its hub on a drive shaft 21 of the machine, which is aligned with the axis 17 of the stator. The free end 17 a of the attached to a bracket 17 b axis 17 is formed as a bearing point 22 for the cup-shaped rotor 20.

On the inner circumference of the cup-shaped rotor eight radially magnetized permanent magnets 23 are arranged distributed uniformly with alternating polarity over the circumference. Stator 16 and rotor 20 act together via an axial working air gap 24. The winding 18 consists of two toroidal coils 29, 30th

With reference to Figures 3 and 4, the structure of the stator 16 according to the invention will be explained in more detail. The claw pole system 19 of the stator 16 consists of four annular pole plates 25 to 28, each of which surrounds one of two axially juxtaposed ring coils 29 and 30 in pairs. Of the front-side outer two pole plates 25 and 26 claw poles 31 and 32 are bent at right angles axially at each outer periphery. Between the two

Ring coils 29 and 30, the two adjacent pole plates 27 and 28 are arranged. They each have two mutually oppositely axially angled claws 33a, 33b to form a claw pole 33. At the two outer pole plates 25 and 26 and at the inner pole plates 27, 28 between the toroidal coils 29, 30, four claw poles 31, 32 and 33 are formed, the uniformly distributed over the circumference in alternating sequence engage each other and thereby along the working air gap 24 protrude axially over both annular coils 29 and 30. It can be seen from FIG. 2 that the claw poles are guided over the entire length of the working air gap 24 predetermined by the permanent magnets 28 of the rotor. The pole plates 25 to 28 are punched with their claw poles 31 to 33 in a simple manner from soft magnetic sheets and formed by deep drawing. Thickness and width of the claw poles 31 to 33 remain constant over their entire axial length. The pole plates 25 to 28 are joined together axially with the two annular coils 29 and 30 and on the axis 17 made of soft magnetic material, so that the axis 17 forms the magnetic yoke for the claw pole system of the stator 16.

FIG. 5 shows the circuit arrangement for supplying the two-phase EC synchronous motor 15 according to FIG. 2. It can be seen that the two ring coils 29, 30 arranged next to one another are connected in series, their connection 34 and their coil starts each one of the three phase connections R, S, T form. These connections are connected in the same way as in FIG. 1 to the outputs of a three-bridge converter 12.

The operation of the synchronous motor 15 will now be explained with the aid of Figures 6 and 7a to 7c. Usually, the ring coils 29, 30 are cyclically energized via the inverter 12 in six cycles as in machines with three coils according to the prior art. In the following, however, an energizing cycle of three cycles is chosen for the simplified representation of the mode of action.

According to Figure 6, the DC voltage at the input of the inverter 12 is given by a clocked control of the semiconductor switch 13 in cyclic alternating sequence as rectangular pulses on the phase outputs R, S and T, to control the speed of the pulse length is variable. The first voltage pulse Ul then passes through the phase output R to the toroidal coil 29. As a result, a current flows via the upper semiconductor switch 13 of the left bridge via the connection R through the first ring coil 29 and there via the connection S and the lower semiconductor switch 13 of the middle Then, a second voltage pulse U2 occurs at the connection S, which is supplied via the connection 34 to both coils 29 and 30. This voltage now drives a current through the upper semiconductor switch 13 of the middle bridge and the

Terminal S in the reverse direction, that is from the coil ends forth simultaneously by both coils and 29 and 30 with closed lower semiconductor switches in the left and right bridge. Thereafter, a third voltage pulse U3 occurs at the terminal T of the left bridge, which now drives a current through the second coil 30 via the upper semiconductor switch 13 of the right bridge, via the terminal S and the lower semiconductor switch 13 of the middle bridge to the negative terminal of the DC power source 14 is performed. These voltage and current waveforms are shown in the diagram of Figure 6 and repeat in a temporally cyclic sequence. The polarities occurring at the claw poles 31 to 33 of the synchronous motor 15 cooperate with the permanent magnets 23 of the rotor 20 in such a way that it is driven in a direction of rotation predetermined by the pulse sequence. With the help of Figures 7a to 7c, this mode of action is explained in detail. They show the development of a Klauenpolfolge the stator 16 in cooperation with the permanent magnet 23 of the rotor 20th FIG. 7a shows the polarization of the claw poles of the synchronous motor 15 from FIG. 1 at the time a in the diagram according to FIG. Thereafter, in the first ring coil 29, a current flows in the forward direction, which forms a north pole N via the left pole plate 25 at the claw poles 31. Accordingly, a south pole S are formed by the same current flow in the coil 29 via the two inner pole plates 27 and 28 respectively on the claws 33a and 33b of the middle claw pole 33. Since the left annular coil 30 does not carry any current, a part of the magnetic flux of the right annular coil 29 also passes through the left coil and forms a further, weaker south pole (S) on the claw pole 32 via the left pole plate 26. In the case of the eight-pole rotor 20 and the twelve claw poles 31 to 33 according to FIG. 3, each pole pair of the rotor 20 is assigned a respective claw pole 31, 32 and 33 of the claw pole system 19. The polarity of the stator 16 produced by the current flow in the left-hand ring coil 39 results in the position of the rotor 20 shown in FIG. 7a at the time a, the south pole S of the rotor 20 facing the north pole of the claw pole 31. By contrast, the adjacent north pole N of the rotor 20 is each half opposite the south pole S of the middle claw pole 33 and the weaker south pole (S) of the left claw pole 32.

As soon as a further voltage pulse U2 is applied to the connection S by the converter 12, the current in the ring coils 29 and 30 is thus also switched over. It now flows through both annular coils 29 and 30, a current in the reverse direction and thereby, according to Figure 7b on the claw pole 31 of the left pole plate 25, the polarity is changed and formed a south pole S. In the same way, a south pole S is also formed by the current in the right annular coil 30 on the claw pole 32 of the right pole plate 26. The magnetic fluxes generated within the two toroidal coils 29 and 30 are now directed counter to form a north pole N via the two inner pole plates 27 and 28 at the middle claw pole 33. This will now be the

Rotor 20 is rotated from the position shown in Figure 7a in the direction of arrow 35 until finally at the time b (according to Figure 6), the position shown in Figure 7b is reached. Here now the permanent magnetic south pole S of the rotor 20 is opposite the north pole N of the middle claw pole 33 and the adjacent north pole N of the rotor 20 is half opposite a south pole S of the claw pole 32 and a south pole S of the claw pole 31.

As soon as another voltage pulse U3 occurs at the terminal T, the current flow in the left-hand coil 29 according to FIG. 6 is switched off and switched over in the right-hand annular coil 30 in the forward direction. As a result, a flow direction reversal takes place at this annular coil 30. According to FIG. 7c, this is done via the right-hand pole plate 26 on

Claw pole 32 a north pole N formed. About the two inner pole plates 27, 28 a south pole S is formed at the middle claw pole 33. In addition, part of the magnetic flux of the right annular coil 30 is directed through the left annular coil 29 to the left pole plate 25 and forms there at Klauenpol 31 a weaker south pole (S). As a result, the rotor 20 is further rotated out of the position according to FIG. 7b in the direction of the arrow 35 until it reaches the position shown in FIG. 7c at the time c (according to FIG. 6). Now stands the permanent magnetic south pole of the rotor 20 of the north pole N of the claw pole 32 to the right pole plate 26 and the adjacent north pole N of the rotor 22 is in each case half south pole S of the middle claw pole 33 and the weaker south pole (S) of the claw pole 31 at the left pole plate 25 opposite.

In the further cyclic continuation of the voltage pulses U1 to U3 in accordance with FIG. 6, the rotor 20 is now incrementally rotated further in the direction of the arrow 35.

The invention is not limited to the illustrated and described embodiment of an EC synchronous motor 15 with eight-pole external rotor. The number of pole pairs in Klauenpolsystem can, as is generally the case with Klauenpolanordnungen, largely freely chosen without additional effort. The items can be relatively easily assembled by axial joining to a compact stator, for Klauenpolsystem only two different laminations are required by the two outer pole plates are provided with long claw poles and the two inner pole plates with short jaws, the pairs one each form the middle claw pole. Likewise, this claw pole version can also be realized on an internal rotor motor. In this case, the working air gap is arranged on the inner circumference of the two annular coils, so that the claw poles protrude there along the working air gap over the two toroidal coils. The magnetic circuit is closed by a to be attached to the outer circumference of the toroidal coils return ring made of soft magnetic material, which connects the pole plates on the outer circumference. Due to the phase shift of the adjacent claw poles by 120 ° electrically, the

Synchronous motor can be controlled with conventional three-phase voltages. In this case, it is fundamentally irrelevant whether a block commutation, a sine-wave control or another three-phase current application method is used. With the exception of the ohmic resistances, the synchronous motor according to the invention forms a symmetrical three-phase machine with regard to the upstream converter. This results in three equal induced voltages between the converter bridges, which are electrically out of phase with each other by 120 °. Likewise, the inductances between the inverter bridges are identical. The prerequisite for this, however, is that the magnetic circuit is not significantly saturated. However, should arise due to the resistive asymmetry in the control of the synchronous motor irregularities, they can be optionally eliminated by appropriate controls of the semiconductor switches. For example, in block commutation, the firing angle and block length can be made asymmetrical. As a semiconductor switch can In principle, the synchronous motor according to the invention with electronic commutation can be used for all possible drives. However, a preferred field of application results in smaller actuators, especially in motor vehicles with a DC power supply. For larger power drives, claw pole systems with multi-layered electrical sheets can be used. This allows the active surface of the claw poles in the working air gap and the claw pole thickness to be adapted to the magnetic requirements. In all variants, however, is equally essential to the invention that the electronically commutated synchronous motor is equipped only with a two-strand stator winding, which acts together with a common Klauenpolsystem and works as the three-phase synchronous motor.

Claims

claims

1. Electrical machine, in particular electronically commutated synchronous motor (15) with a permanent excitation in the rotor (20) and with a polyphase winding (18) in the stator (16), which is enclosed by a claw pole system (19) and three terminals (R, S , T) for a three-phase inverter (12), wherein runner and stator via a working air gap (24) cooperate, characterized in that the multi-phase winding (18) consists of two juxtaposed and mutually connected in series ring coils (29, 30) whose connection (34) and its beginnings each form one of the three connections (R, S, T) and in that annular pole plates (25 to 28) are arranged on the outer and inner sides of the two annular coils (29, 30), of which from each in an alternating sequence a claw pole (31, 32, 33) along the working air gap (24) over at least one of the two toroidal coils (29, 30) hinwegragt.

2. Electrical machine according to claim 1, characterized in that between the two toroidal coils (29, 30) two adjacent pole plates (27, 28) are arranged, each for forming a claw pole (33) mutually oppositely angled claws (33a, 33b ) to have.

3. Electrical machine according to claim 2, characterized in that in a synchronous motor (15) with axial working air gap (24), the two annular coils (29, 30) are arranged axially adjacent to each other and that the pole plates (25 to 28) on the end faces of the toroidal coils (29, 30) are fastened, so that the claw poles (31, 32, 33) protrude axially beyond both annular coils (29, 30).

4. Electrical machine according to one of the preceding claims, characterized in that the claw poles (31, 32, 33) over the entire length of the working air gap (24) are guided.

5. Electrical machine according to one of the preceding claims, characterized in that the pole plates (25 to 28) with their claw poles (31, 32, 33) are punched from sheets and formed by deep drawing.

6. Electrical machine according to one of the preceding claims, characterized in that the thickness and width of the claw poles (31, 32, 33) remain the same over their entire length.

7. Electrical machine according to one of the preceding claims, characterized in that in a multi-pole, preferably eight-pole rotor (20), the pole plates (25 to 28) are each provided with at least one, preferably with four claw poles (31, 32, 33).

8. Electrical machine according to one of the preceding claims, characterized in that in an EC synchronous motor (15) with external rotor (20) the claw poles (31, 32, 33) of the stator (16) on its outer circumference via the toroidal coils (29, 30) protrude axially.

9. Electrical machine according to claim 8, characterized in that the pole plates (25 to 28) are fastened on an axis forming the magnetic yoke (17) whose free end (17a) has a bearing point (22) for a pot-shaped external rotor (20 ) having.