The present invention relates to a reluctance motor having a stator and a rotor,
Conventional three-phase synchronous servomotors operate on the principle that the winding is introduced into the stator and the excitation magnets or field windings are introduced into the rotor. The magnetic fields produced by the stator and the rotor interact with one another, and thus produce a torque.
A further possible way to design a three-phase motor is to use a conventional three-phase winding in the stator, to introduce permanent magnets additionally into the air gap between the stator and the rotor, and to design the rotor as a reluctance profile. A motor such as this is described, for example, in DE 197 43 380 C1.
The motor which is known from the prior art offers a high torque as well as a good kT value even at low rotation speeds, in comparison to a conventional motor.
The introduction of the permanent magnets into the air gap has constructional disadvantages, however. On the one hand, the effective magnetic air gap—in contrast to the mechanical air gap—is relatively large because of the permanent magnets that are introduced. This results in a weaker stator field acting on the rotor, and thus in weaker coupling between the driving component (the stator) and the driven component (the rotor). This therefore results in less torque being produced, in comparison to a machine, which otherwise remains unchanged, with a smaller magnetic air gap.
A further disadvantage is the large amount of permanent-magnet material required, since permanent-magnet material is relatively costly.
The magnets must also be relatively thick, in order to generate a powerful permanent-magnet field for providing or transmitting force. However, the requirement for great thickness is contrary to the desire to choose the effective magnetic air gap between the stator and rotor to be as small as possible.
The object of the present invention is to modify the known reluctance motor such that it is possible to achieve a small effective magnetic air gap while nevertheless retaining the permanent magnets.
In the case of a reluctance motor of the type mentioned initially, the object is achieved
The stator teeth have a tooth clearance from the rotor in the radial direction, and the permanent magnets have a magnet clearance.
Since the magnet clearance is at least as great as the tooth clearance, the effective magnetic air gap can be minimized.
Further advantages and details will become evident from the following description of one exemplary embodiment, in conjunction with the drawings, in which, illustrated in an outline form:
As shown in
As shown in
The stator teeth 6 have a tooth clearance a from the rotor 4 in the radial direction. This tooth clearance a corresponds to the mechanical air gap 9 of the reluctance motor which, at the same time, and in contrast to the known reluctance motor, is also the effective magnetic air gap 9.
As shown in
The permanent magnets 10 are magnetized in the same sense in the radial direction. This is indicated by arrows 11 in
In order nevertheless to produce permanent-magnet fields which are dependent on the location, seen in the tangential direction, the permanent magnets 10 have associated flux guide elements 12. The flux guide elements 12 deflect the permanent-magnet fields into the stator teeth 6. In this case, the permanent-magnet fields are deflected such that they are in the opposite sense to the permanent fields in the area of the stator slots 7 in the area of the stator teeth 6. This is illustrated in
The flux guide elements 12 are composed of a material which is ferromagnetic but not permanent magnetic. The material may be the same as that from which the stator 2 is also made.
The permanent magnets 10 have a magnet clearance c from the rotor 4 in the radial direction. The magnet clearance c is preferably at least as great as the tooth clearance a.
The reluctance motor according to the invention therefore makes it possible to make the effective magnetic air gap just as small as the actual mechanical air gap 9. This reduction in the gap compensates for, or more than compensates for, the reduction in the magnetic flux which is caused by the permanent magnets 10 being separated from one another, seen in the tangential direction. Furthermore, this requires only half the amount of magnetic material as that required for the reluctance motor according to the prior art. In addition, it is easier to fit the permanent magnets 10 to the stator 2, and the entire manufacturing process for the stator 2 is simpler, as well. In particular, the air gap 9 can be manufactured more exactly because the magnet clearance c is at least as great as the tooth clearance a.
Number | Date | Country | Kind |
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10 2005 016 257.6 | Apr 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2006/061248 | 3/31/2006 | WO | 00 | 10/9/2007 |