Electrical generator or motor structure – Dynamoelectric – Rotary
Utility Patent
1999-09-28
2001-01-02
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S091000
Utility Patent
active
06169353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electromagnetic machines and, more particularly, relates to a method for constructing, and apparatus comprising, an electromagnetic machine having superconducting rotor windings.
2. Discussion of the Related Art
Electromagnetic machines are known to include generators and motors, and include armature windings that create a magnetic field to rotate a rotor. Synchronous motors are well known in the art as comprising a rotor that rotates as a result of magnetic flux created between a rotor winding and a stator winding. Synchronous motors having superconducting rotor coils are known to have a notably higher efficiency than conventional motors. Superconducting coils are unique in that they operate without any resistance to electrical current. As a result, higher current densities may be achieved that are not possible in conventional conductors which, in turn, allows for stronger magnetic fields in electromagnetic machines.
Presently, superconducting coils for rotating machines are manufactured as a separate entity and are mounted onto the rotor. In previous applications, the superconducting coil is maintained at a desired temperature by submerging the coils into a liquid helium bath.
Conventionally, the superconducting coils are attached to the rotor via a bolting assembly in which inserts and spacers are implemented in conjunction with the coils and bolted on to the rotor. This method, however, has proved costly and inefficient because it requires high precision machining of all parts involved, and the system of auxiliary inserts and spacers adds further cost and complexity to the installation. Additionally, it is desirable to have minimal structure between the rotor and the stator to avoid widening the air gap between the rotor and stator coils, thereby decreasing the efficiency of the motor. The use of bolts, inserts and spacers to mount superconducting coils onto the rotor according to conventional techniques consumes valuable space between the rotor and stator coils. The larger air gap results in higher magnetic losses, and therefore a lower magnetic coupling, between the rotor and the stator.
The need has therefore arisen to implement a method for assembling, and apparatus comprising, a rotor having superconducting windings in an efficient and cost effective manner.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to attach a superconducting coil onto a rotor of a synchronous motor in a cost effective and efficient manner.
It is a second object of the invention to minimize the air gap between the armature windings and the stator windings.
It is a third object of the invention to manufacture a rotor assembly having an apparatus that protects the coils from possible structural damage due to thermal, electrical and centrifugal loads.
In accordance with a first aspect of the invention, a rotor comprises a rotor shaft that is attached to a rotor body. Oval-shaped grooves are then machined into an outer surface of the rotor body and the superconducting coil and adhesive are placed into the grooves. Superconducting coils are inserted such that the outermost portions of the coils are disposed slightly below the outer surface of the rotor body. Once the adhesive dries, aluminum inserts are then bonded to the coils such that the outer portions of the aluminum inserts extend beyond the outer surface of the rotor body. The outer surfaces of the aluminum inserts are then machined down until they are generally flush with the outer surface of the rotor body.
In accordance with a second aspect of the invention, the superconducting coils are disposed within grooves that extend inwardly into the rotor body using an adhesive. Because bolts and spacers are not used to mount the coils, the coils may be disposed in closer proximity to the stator, and the air gap between the rotor windings and stator windings is minimized. The result is an increased magnetic flux linkage between the rotor and the stator, thereby increasing the coupling between the rotor and the stator.
In accordance with a third aspect of the invention, an aluminum shell is provided and adhesively bonded onto the outer surface of the rotor body. The aluminum shell serves as an electromagnetic shield for the superconducting coils and as coil external structural support. For assembly purposes the shell is split in the middle and electrical contact between the two parts is established after the bonding via soldering for example.
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Aized, D. et al., “Status of the 1,000 hp HTS Motor Development,” posted Jun. 1999.
Driscoll David I.
Shoykhet Boris A.
Forman Adam J.
Horn John J.
Ramirez Nestor
Reliance Electric Technologies LLC
Waks Joseph
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