Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-28
2001-03-06
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C219S201000, C219S494000, C361S025000
Reexamination Certificate
active
06198186
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the art of electric motors, which should be understood as described herein to include generators and other electromechanical machines that effect a conversion between mechanical and electrical power. More particularly, the invention relates to electric motors having protective heaters.
As should be understood by those skilled in this art, electric codes rate motors for use in various environments. For example, the most stringent criteria are reserved for “explosion-proof” motors. Below this level are motors rated for use in “division 2” areas. These motors need not meet the explosion-proof standards, and are therefore less expensive, but are restricted not to exceed a prescribed surface temperature.
Division 2 motors are sometimes exposed to air having a high relative humidity. To prevent condensation on the windings, space heaters have been applied on or within the motor frame, for example as a wrap on the windings or as a cartridge mounted in the frame. The heater may be controlled by the user or may be automatically activated upon deactivation of the motor. In either case, the heater is activated at a period when the motor is at or near its normal operating temperature. It may be possible, therefore, that the additional heat raises the motor's temperature above a maximum desired temperature, for example the temperature rated for a division 2 area.
SUMMARY OF THE INVENTION
The present invention recognizes and addresses disadvantages of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide an improved electric motor.
This and other objects are achieved by an electric motor including a stator having a plurality of conductive windings radially spaced about a central axis. A rotor is located radially inward of the stator and is rotationally fixed with respect to a shaft along the central axis. The rotor and stator are disposed in a frame. A heater is in operative communication with the windings. A thermostat is in operative communication with the heater and is configured to activate and deactivate the heater responsively to a motor temperature.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the description, serve to explain the principles of the invention.
REFERENCES:
patent: 3878362 (1975-04-01), Stinger
patent: 5326026 (1994-07-01), Jefferson et al.
patent: 5787568 (1998-08-01), Crowell
Swan Edward J.
Wallace Stanley E.
Farr Lloyd G
Gerasimow A. M.
Horn John J.
Jones Judson H.
Ramirez Nestor
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