Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1982-02-11
1984-09-18
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310261, 335272, H02K 2112
Patent
active
044726503
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to electromechanical engineering, and more particularly to rotors of high-speed electric machines.
The present invention can be most advantageously used in electric drives for centrifuges, high-pressure pumps and fans, machine tools, and other high-speed equipment.
BACKGROUND OF THE INVENTION
One urgent problem in development of high-speed electric machines is to increase their rotation speed, resulting in a smaller size and mass both of the machines and of the driving mechanisms, while keeping the machine power unaltered.
The rotation speed of high-speed electric machines is raised by increasing the rotor speed.
Rotors of the following types are used for high-speed electric machines: windings).
A rotor with a laminated magnetic ring and a winding has the lowest strength leading to its limited use in high-speed electric machines, since high stresses developed by centrifugal forces exerted on the rotor in operation cause it to be rapidly destroyed.
The rotor with a solid magnetic ring with a salient pole system has significant losses (both electromagnetic and, particularly, aerodynamic) which are required to be minimized by evacuation of the cavity of a high-speed electric machine incorporating the rotor, thus considerably impairing the technological efficiency of the machine.
The rotor with a smooth solid magnetic ring is the most rugged of all the rotor types mentioned. This rotor, however, exhibits significant losses causing it to be severely heated, which brings about a sharp decrease in the efficiency of the high-speed electric machine in which it is employed, and hence lower machine power.
The rotor with a smooth solid magnetic ring with permanent magnets is somewhat inferior to the preceding one in its ruggedness. This rotor, however, offers great advantages over the other rotors, being essentially free from electromagnetic losses, and the magnetic flux of the permanent magnets obviates the need to consume the energy for electric machine excitation. As a result, the high-speed electric machines incorporating this rotor have a high efficiency. The high efficiency of the high-speed electric machine gives the advantage of smaller size of the rotor for machines of the same power and rotation speed, i.e. the rotor with permanent magnets will have a smaller size, and hence lower mechanical stresses.
In summary, rotors with a smooth solid magnetic ring are to be preferably used in high-speed electric machines.
Known is a rotor of a high-speed electric machine, comprising a shaft, a smooth solid magnetic ring fitted to the shaft, permanent magnets disposed around the magnetic ring, and a retaining ring fitted over the permanent magnets [V. A. Balagurov, F. F. Galteyev, A. N. Larionov, "Electricheskie mashiny s postojannymi magnitami" ("Electric machines with permanent magnets"), publication of 1964, Moscow, Energy Publishing House, p. 52].
The retaining ring, permanent magnets, and magnetic ring all arranged on the shaft in concentric relation to one another constitute a prestressed system due to pretensioning between the magnetic ring and the permanent magnets as well as between the permanent magnets and the retaining ring. As the rotor is operated, stresses caused by centrifugal forces are added to the stresses developed in its members as a result of pretensioning. These additional stresses are increased with an increase in the rotor speed, the maximum stresses occurring in the retaining ring which is farthest removed from the rotor axis. The tensile forces increase with an increase in the rotation speed of the rotor lower the pretension, and hence, the stress in the retaining ring determined thereby, cause the stresses to be redistributed [the stresses due to centrifugal forces are increased, while those due to the tension are decreased]. The residual tension defined as the difference between the pretensioning force and the tensile forces, with the rotation speed of the rotor held constant, should provide for the torque transfer from the shaft to th
REFERENCES:
patent: 2579318 (1951-12-01), Hershberger
patent: 2722617 (1955-11-01), Cluwen
patent: 3032670 (1962-05-01), Fritz
patent: 3466476 (1969-09-01), Snowdon
patent: 4012651 (1977-03-01), Burson
patent: 4095129 (1978-06-01), Tanai
B. A. Balagurov et al.; Permanent-Magnet Electric Machine; p. 52, Publishing House "Energie"; 1964; Moscow, U.S.S.R.
Advolotkin Nikolai P.
Lebedev Nikolai I.
Ovchinnikov Igor E.
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