Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1985-12-23
1987-01-20
Salce, Patrick R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 42, 310262, H02K 1502, H02K 2114
Patent
active
046382003
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improvement in rotating machines having magnets on the rotor and in particular to high-performance machines such as generators having a very high speed of rotation.
The development of the technology of high-performance current generators led to the construction of generators having magnets on the rotor in which the rotors are made to rotate at very high speeds, as they are, for example, directly driven by a turbine.
Owing to overall size and performance, arrangements for ensuring a mechanical fastening of the magnets are obsolete and there is therefore a tendency to employ generators having magnets which are adhered or, better still, brazed to the rotor, as described, for example, in Pat. No. 83 11,325 filed on July 7, 1983 in the name of the applicant. However, when speeds of rotation resulting in tangential velocities of more than 100 meters per second, for example 200 meters per second, are exceeded, the safety of the fastening of the magnets is no longer ensured so that such speeds cannot be reached in practice.
This is also the case of machines having magnets fixed in the conventional manner to the rotor and maintained in position by a sleeve performing the function of a hoop, the presence of which one attempts to avoid, owing to the resulting large increase in the air gap and the behavior which at high speeds of rotation does not contribute to the strength and behavior of the rotor.
The German publication DOS No. 32 24904 states that it is known to surround magnet rotors with a non-magnetic hoop composed of a material such as titanium, which, however, does not permit attaining extremely high speeds of rotation and moreover leads to the use of thick and heavy hoops which are of little benefit from the point of view of the magnetic behavior of the assembly. This is why this publication prescribes the construction of high-strength steel hoops constituted by a cylindrical sleeve which is pre-stressed by driving in wedges.
However, this solution presents drawbacks since the wedges are part of the mass and the thickness of the hoop is locally increased. The mass of the hoop is not constant over its length and the stressing requires enormous radial forces which often result in seizure. Further, this solution requires the insertion of supplementary magnetic materials for partly saturating the interpolar zones of the hoop so as to avoid a magnetic short-circuit on the rotor, and this constitutes a great complication.
Another solution resides in forming a hoop constituted by a sleeve of synthetic resin reinforced with carbon fibers and in pre-stressing the sleeve also by the insertion of wedges. However, this solution excludes any use of the device in wide temperature ranges, not only owing to the bad behavior of the hoop when there are large temperature variations but also owing to differential expansion coefficients which result in a large variation of the hoop pre-stressing, depending on the temperatures.
Various other documents describe a peripheral hooping of rotors provided with permanent magnets but do not permit the attainment of high speeds of rotation.
Thus, U.S. Pat. No. 3,531,670 desribes a hoop of non-magnetic metal such as Inconel hot shrunk onto the rotor. The allowed speeds of rotation are low relative to those required of modern permanent magnet electric machines.
The mounting of such a hoop formed by a sleeve in moreover a very delicate operation.
The Japanese patent application No. 57-78,540 describes a hoop formed by a winding of a very thick ferro-magnetic metal wire and only permits a low speed of rotation if it is compared with that of the aforementioned German patent aplication.
U.S. Pat. No. 4,117,360 describes a very thick and complex hoop for a low-speed rotor.
U.S. Pat. No. 3,077,026 describes a rotor having a low speed of rotation surrounded by a complex hoop constituted, at the two ends, by annular parts interconnected by spacer members carrying discontinuous strips. Such an arrangement allows only very low speeds of rotation and presents great
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patent: 3956650 (1976-05-01), Field, II
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patent: 4339874 (1982-07-01), Mc'Carty et al.
patent: 4469970 (1984-09-01), Neumann
patent: 4531071 (1985-07-01), Kintz, Jr. et al.
"Sandwiched Magnetic Wafers", Machine Design, 31/17/150, 20 Aug. '59, p. 150.
Le Corre Loic
Rolland Albert L.
Precision Mecanique Labinal
Rebsch D. L.
Salce Patrick R.
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