Generator Containment System

In generator constructions, failures due to a seized or burst rotor in which the rotor impacts the stator so as to be stopped immediately, the generator stator and case may be torn loose from its supports with catastrophic results. This is true whether the generator is on a vertical or horizontal axis. Although such failures are disastrous in any event, such failures are particularly serious in nuclear power plants where absolute protection against disaster must be provided.

According to the present invention, the possibility of a rotor failure that may cause sudden stopping of the rotor within the case is anticipated by supporting the generator stator within a surrounding case by energy absorbing structures that will permit a limited amount of turning of the stator within the case but with such damping provided as to absorb the rotational energy imparted to the stator when the rotor fails. This arrangement provides that the outer case will remain on its supports and contain the failed rotor.

The foregoing and other objects, features, and advantages of the present invention will become more apparent in the light of the following detailed description of preferred embodiments thereof as illustrated in the accompanying drawing.

FIG. 1 is a sectional view through a generator embodying the invention.

FIG. 2 is a fragmentary sectional view of a form of energy absorbing device .

In the arrangement shown, the generator includes a rotor 2 journaled in bearings 4 and 6 in end pieces 8 and 10 on the ends of the stator 12 that surrounds the rotor. The stator 12 is supported within an outer case 14 which surrounds the stator and rotor and rests on a supporting structure 16. The case 14 may have an internal flange 18 at its bottom end to support the stator endwise and the stator is supported concentrically to the outer case by energy absorbing structures 20 that normally hold the stator in fixed position within the outer case. The rotor may have a projecting shaft 22 at the bottom end through which the rotor is driven and may have a projecting end 24 at the top for controls if desired. The outer case is securely attached to the supporting structure, this attachment being shown by way of example as bolts 26 through a mounting flange 28 on the outer case.

As above stated, the stator is turnable within the outer case. For example, the stator rests on the flange 18 and is slidable thereon, and is guided at the top by another similar flange or cap 30, essentially a part of the case. Should the rotor seize or burst, thereby imparting a severe high torque to the stator, the latter is permitted to turn to a limited extent within the outer case with adequate damping provided by the devices 20 to absorb the energy of the rotor without tearing the outer case from its mountings.

This damping action, or energy absorption is accomplished by a mechanism that permits this limited turning movement of the stator with the energy absorption devices effective to reduce the forces transmitted to the outer case to such a level that they will not affect the stability of the outer case on its supporting structure. One example of an energy absorbing structure is shown in FIG. 2 in which the stator member 12 has a projecting lug 34 carrying a bolt 36 that extends substantially tangentially of both the stator member and the outer case member. The outer case member 14 carries a cooperating lug 38 having a die 40 therein to receive the bolt and so constructed that as the lugs are moved apart by a turning of the stator within the outer case the bolt is extruded through the die and energy is thus absorbed. Such a device extends the time over which the forces are transmitted from the stator to the outer case and thus reduces the forces to a level that allows an economical and stable structure. Although the drawing shows only four of these devices it will be understood that any necessary number are utilized to absorb the energy forces within the permissible turning of the stator.

Although the device is described with respect to a vertical generator it will be understood that it is equally usable on horizontal-axis generators. It is particularly useful in nuclear power plants where absolute protection against catastrophic failures is a requirement. The arrangement is such that a failed rotor, that might otherwise result in tearing loose the entire generator, will, by these energy absorbing devices, be contained and the generator assembly will remain in position in the power plant.

Although the invention has been shown and described with respect to a preferred embodiment thereof, it sould be understood by those skilled in the art that other various changes and omissions in the form and detail thereof may be made therein without departing from the spirit and the scope of the invention.