Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-07-11
2004-03-02
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S266000, C310S181000, C310S214000, C310S168000
Reexamination Certificate
active
06700272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a reluctance motor with a stator which has a three-phase current stator winding for generating a rotary magnetic field and a rotor which is located on a shaft and which is made primarily of a ferromagnetic material. In particular, the invention relates to such a reluctance motor in which the rotor has a set number of angular regions of the same peripheral angle which adjoin one another in the peripheral direction, preferably having at least one pair of flux guidance regions facing the stator, with flux guidance properties which differ in the main direction of the rotary field.
2. Description of Related Art
Reluctance motors are known from the prior art (compare, for example, Lueger, Lexikon der Technik, vol. 14, Lexikon der Feinwerktechnik, page 315) as independently accelerating synchronous motors. The stator of a conventional reluctance motor is no different from the stator of a conventional synchronous or induction motor which is conventionally operated with three-phase current, as is the conventional reluctance motor. The three-phase current stator winding is designed on a standard basis such that the center plane of each of the coils assigned to one of the three phases lies on the axis of the reluctance motor. In a conventional reluctance motor, as in a synchronous or induction motor, windings with a pole number p greater than two and a number of holes q greater than 1 are allowable.
Typically the three-phase current stator winding of a conventional reluctance motor is made with 4 poles with coils being assigned to each of the three phases and with the coils being distributed in the slots over the entire periphery of the stator; see, for example, S. A. Naser,
Electromechanics and Electric Machines,
John Wiley & Sons, Inc. 1979.
Accordingly, the rotor of the conventional reluctance motor, in four angular regions of the same peripheral angle which adjoin one another in the peripheral direction, has a pair of flux guidance regions facing the stator with flux guidance properties which differ in the main direction of the rotary field. In the conventional reluctance motor, the pairs of flux guidance regions facing the stator are formed with flux guidance properties which differ in the main direction of the rotary field in angular regions of 90° each by the rotor in half of the angular regions, therefore over an angle of 45°, being countersunk. Since the main direction of the rotary field in a block rotor always points in the radial direction of the rotor, the countersinking in the rotor results in flux guidance regions with different magnetic resistances, and therefore, different flux guidance properties.
Conventionally, the rotor of a conventional reluctance motor is made as a squirrel-cage rotor. Therefore, in the operation of a conventional reluctance motor, two torques take effect. In the acceleration range, the conventional reluctance motor develops an asynchronous torque, as a result of the widening of the air gap due to the countersinking in the rotor, the characteristics deteriorate compared to an undamaged rotor of an induction motor. At synchronous rpm, a synchronous so-called reluctance or reaction torque is formed because the rotor, which turns synchronously with the rotary field, tries to assume a position in which the magnetic energy in the air gap is smallest. When the motor is loaded, the rotor would like to remain in this position, it must however lag by a small spacial angle (load angle). The highest torque occurs at a load angle of 90°/p and is called the pull-out torque. Conversely the transition from the asynchronous characteristic to synchronism takes place suddenly as a synchronization process. Whether this dynamic pulling into synchronism is possible depends on the stationary load torque and the moment of inertia to be accelerated.
The existing statements indicate that a conventional reluctance motor runs with a speed of 6000/p rpm. Since, for a plurality of applications, clearly lower rpms are necessary and since the speed of a conventional reluctance motor can be reduced only to a limited degree by increasing the pole number p, to reduce the rpm and/or increase the torque, mechanical gearing and/or electric frequency converters are regularly used. These additional components, on the one hand, increase the production costs of a conventional reluctance motor with low rpm, and on the other hand, adversely affect the efficiency.
One alternative for ensuring low synchronous rpm is represented by the subsynchronous reluctance motor which is, likewise, known from the prior art (compare, for example, Lueger, Lexikon der Technik, vol. 14, Lexikon der Feinwerktechnik, page 315). This subsynchronous reluctance motor is operated single-phase and on its stator in a number of angular regions of the same peripheral angle which adjoin one another in the peripheral direction, a number which corresponds to the number of angular regions on the rotor, has one pair of flux guidance regions facing the rotor with flux guidance properties which differ in the main direction of the rotary field. For the subsynchronous reluctance motor, the flux guidance regions of different flux guidance properties are produced by the countersinking in the stator. As already mentioned, in the subsynchronous reluctance motor, the number of angular regions in the rotor corresponds to the number of angular regions in the stator. The number of angular regions P
SL
can be chosen independently of the pole number of the stator winding. The rpm of the subsynchronous at reluctance motor is 3000/P
SL
rpm.
The subsynchronous reluctance motor can be used only to a very limited degree, since it must be started to the synchronous rpm and then develops only a synchronous torque which pulsates with twice the main frequency from zero to a maximum. Accordingly, the pull-in torque of the subsynchronous reluctance motor is very small.
In addition to the conventional reluctance motor and the subsynchronous reluctance motor, the electronically switched reluctance motor is known from the prior art (compare, for example, Encyclopaedia Britannica CD 97, “Energy Conversion”, “Reluctance Motors”). This electronically switched reluctance motorworks, as the name says, with an electronically switched direct current. The electronically switched direct current magnetizes, at the same, time, two coil windings on the flux guidance areas which are opposite one another in the stator with low magnetic resistance, therefore ferromagnetic poles. The center planes of the two coil windings therefore run tangentially to the block rotor. The numbers of angular regions in the rotor and stator are different in an electronically switched reluctance motor in order to generate a torque which engages the rotor when the direct current is switched from one coil pair to another coil pair. Since the direct current of this type of reluctance motor is electronically switched, theoretically all rpm can be effected for the rotor; of course, here, an electronic control unit is necessary for this purpose. However, such is problematic in the electronically known reluctance motors that only relatively low torques can be transmitted so that additional gearing is necessary to achieve the desired drive torques. In addition, in these motors in the lower rpm range, a rpm fluctuation frequently occurs which is caused by torque fluctuations and which must be corrected by an expensive electronic control.
SUMMARY OF THE INVENTION
Proceeding from the aforementioned prior art, the object of the invention is to make available a reluctance motor which is improved especially with reference to the possibilities of step-down and dynamic pull-in.
In particular, it is an object of the present invention to obtain a reluctance motor which is able to step down the rpm of the rotor without the use of gears or electronic control of the rotating field to do so.
According to the first teaching of the invention, the indicated objects are achieved by the stator, in a stipulated number of angular re
EMF 97 Elektro-Maschinen-Vertrieb-Magnettechnik- und Forschungs
Nixon & Peabody LLP
Safran David S.
LandOfFree
Reluctance motor with gearless step-down without electronic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reluctance motor with gearless step-down without electronic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reluctance motor with gearless step-down without electronic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3248489