Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1990-09-04
1992-07-07
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 43, 310 45, 310 67R, 310271, 318254, H02K 2112
Patent
active
051285754
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an electric machine comprising a first functional part having a permanently magnetic excitation system and a second functional part having a conductor system, the first functional part and the second functional part being movable relative to each other along the active area of an air gap.
This definition describes an electric machine in its broadest form, and only the indication of a permanently magnetic excitation system reveals a more specific sector in the field of electric machines. Electric machines of this type are found most often in the form of direct current motors in which permanently magnetic north poles and south poles alternate with each other at the active area and in which the functionally required magnetic return path between adjacent magnet poles is effected either by an iron back on the back or rear side of the permanent magnets facing away from the active area, or in that the permanent magnets are partial regions of a uniform magnetic body which are magnetized in different directions. The second functional part comprises the conductor system as a rule in the form of windings or coils which are associated with individual poles. For rendering the electric motor operative, the current direction in the individual windings must be reversed by a specific distance after each relative movement of the two functional parts, which can be carried out by mechanical or electronic commutation.
SUMMARY OF THE INVENTION
It is the object of the invention to make available an electric machine of the type indicated at the outset, which on the basis of its construction can be built with higher torque and power density related to weight or volume.
To meet this object the electric machine, according to the invention, is characterized in that the first functional part comprises--as seen progressively in the direction of relative movement--an alternating sequence of permanent magnets, which are magnetized in the direction of relative movement, and of magnetically conductive material portions, that the magnetically conductive material portions each have--facing the active area--a magnetic flux outlet area which is smaller than the sum of the magnetic flux cross-sectional areas of the two adjacent permanent magnets, so that the magnetic flux of the permanent magnets is concentrated for the active area, and that the width of the permanent magnets, measured in the direction of relative movement, increases as their distance from the active area increases, while the width of the magnetically conductive portions decreases as their distance from the active area increases.
In conventional electric machines the magnetic field strength of the permanent magnets of the excitation system is limited upwardly by the material used for the permanent magnets, thereby establishing an upper limit for the magnetic flux density across the active area. When, after exhaustion of these parameters, the torque of a conventional electric machine is to be increased, it is necessary to enlarge the active area. In case of a rotating electric machine, this means a larger diameter or a greater axial length.
The invention provides a fundamentally different approach, by achieving an air gap field strength across the active area from the first functional part to the second functional part which is considerably higher than the residual flux density of the permanent magnets used. The "conversion factor"of the B-field, i.e., the magnetic field having a magnetic flux density B is determined in essence by the ratio of the size of the magnetic flux cross-sectional area of a permanent magnet to half of the magnetic flux outlet area into the active area of the magnetically conductive material portion adjacent the permanent magnet on one side. The conversion factor may easily be greater than 1.2 or greater than 1.3 or greater than 1.5, or even greater than 2.0.
When the B-field in the air gap is larger, the number of windings at the poles of the conductor system is decreased when the size of the machi
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Ehrhart Peter
Grundl Andreas
Heidelberg Gotz
Heidelberg Motor Gesellschaft fur Energiekonverter mbH
Skudy R.
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