Electricity: motive power systems – Motor-reversing – Armature or primary circuit control
Patent
1975-05-07
1977-05-24
Rubinson, Gene Z.
Electricity: motive power systems
Motor-reversing
Armature or primary circuit control
318223, 318225R, H02P 144
Patent
active
040258335
ABSTRACT:
The application discloses a thermally actuated switch for electric motors which have some inherent starting torque, such as shaded pole and permanent split capacitor motors. The switch operates only upon abnormal torque demand, to cut out one of the windings of a motor having two windings, or to cut out part of a tapped single winding. The switch normally occupies a first position in which both windings, or the entire winding, are energized. It includes a bimetallic element and a heater coil in series with the windings. Under normal starting and running torque conditions the switch is in the first position, and insufficient heat is generated in the heater coil to trip the switch to its second position. In the event of an abnormal starting or running torque demand, the locked rotor current will persist and will exceed the running current, and heat will be generated in the heater coil. Thus, after delay, the switch will trip to the second position, in which one of the windings, or a part of a single winding, is cut out, whereby the torque is increased. Immediately upon switching to the increased torque position, losses in the heater cease. Shortly thereafter the device resets to the first position. Under normal conditions the device remains in this first position.
REFERENCES:
patent: 2203927 (1940-06-01), Rutherford
patent: 2266088 (1941-12-01), Shea
patent: 2417912 (1947-04-01), Clark
Robbins & Myers, Inc.
Rubinson Gene Z.
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