Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1998-11-30
2000-10-17
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Rotary
310 49R, H02K 3702
Patent
active
061336645
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a self-starting brushless electric motor of the type which comprises reluctance poles (ferromagnetic salient poles) on at least one of the two relatively moving motor parts and one or more permanent magnets in the pole system.
REVIEW OF THE RELATED TECHNOLOGY
More particularly, the invention relates to a self-starting brushless electric motor comprising
a first motor part having a plurality of pole units arranged in spaced-apart relation in a first pole row,
a second motor part having a plurality of poles arranged in spaced-apart relation in a second pole row,
bearing means supporting the first motor part and the second motor part for relative movement with the first pole row confronting the second pole row across an air gap,
the first and second pole rows constituting a pole system comprising first and second pole types, the poles of the first pole type being reluctance poles and the poles of the second pole type being permanent-magnet poles which are polarized transversely to the air gap, and
a winding system on the first motor part comprising a winding coil arranged in association with each pole unit to produce a magnetic field linking poles of the first and the second pole rows through the pole unit upon energization of the coil,
at least one of the first and second pole rows exhibiting a magnetic asymmetry providing a preferential relative direction of movement of the motor parts upon energization of the winding system.
Electric motors of this kind are described in WO90/02437 and WO92/12567. They are characterized by, among other things, a unidirectional relative movement of the motor parts (stator and rotor) resulting from a magnetic asymmetry of the poles, and a torque which is high in relation to the motor size.
In an exemplary embodiment shown in WO92/12567, the first motor part is a stator provided with a single-phase winding while the second motor part is a cylindrical rotor. The stator has a single pole row comprising four identical salient ferromagnetic poles, reluctance poles, which are uniformly spaced-apart circumferentially, and two diametrically opposed permanent-magnet poles.
The winding comprises two winding coils, each coil being disposed about a pole unit consisting of one permanent-magnet pole and two ferromagnetic poles, one on either side of the permanent-magnetic pole. Thus, the stator has two pole units which are diametrically opposed to one another and associated with respective coils.
On the rotor there is a single pole row comprising four identical salient ferromagnetic poles which are uniformly spaced-apart circumferentially. Each such pole has a main pole body and an auxiliary pole part which projects circumferentially from the main pole body and extends only over a portion of the axial width of the main pole body. Accordingly, on the rotor there are four pole units, each consisting of a single pole which is magnetically asymmetric in the circumferential direction. In conjunction with the permanent-magnet poles the unidirectional magnetic asymmetry provides for self-starting of the motor in a single, given direction of rotation, so that it is not possible to reverse the starting direction of rotation by reversing the current supplied to the winding.
In operation of the motor the winding is alternately energized and deenergized. In the energized periods of the winding, the stator poles, by virtue of the magnetic attraction they exert on the rotor poles, turn the rotor a fraction of a full revolution to a position, hereinafter referred to as the indrawn or attracted position, in which the rotor poles are magnetically aligned with the main pole body of respective magnetized ferromagnetic poles of the stator.
When the winding is deenergized, the attraction exerted on the rotor poles by the ferromagnetic stator poles disappears, allowing the permanent magnets, by virtue of the attraction they exert on the adjacent auxiliary pole parts, to turn the rotor another fraction of a full revolution to a position in which the ferromagne
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Schaer Roland
Torok Vilmos
Wissmach Walter
Nguyen Tran
Ramirez Nestor
Torok Vilmos
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