Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
1999-10-20
2001-03-20
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C361S024000
Reexamination Certificate
active
06204628
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention relates to electric motors and more particularly to signal-phase motors.
BACKGROUND OF THE INVENTION
Single-phase electric motors are typically equipped with a starting winding to improve starting torque and reduce a starting time. Once the motor reaches a running speed, the starting winding must be disconnected.
In the past mechanical devices have been used to disconnect the starting winding.
Typically a weight moved by centrifugal force is suspended from a lever which is, in turn, attached to a rotor of the motor. As the motor gains speed, the weight pressed against the lever forcing it outwards against a spring. As the motor reached full speed the force causes the lever to contact and activate a switch which disconnects the starting winding.
While the prior art mechanical devices have worked relatively well, they are prone to mechanical failure. They also require significant space due to the necessary mechanical movement. Because of the importance of single-phase motors, a need exists for a means for disconnecting starting windings that does not suffer from the deficiencies of the prior art.
SUMMARY
A method and apparatus are provided for disconnecting a starting winding of a single-phase motor during startup. The method includes the steps of disposing a heater element of a thermal switch in series with a main winding of the single-phase motor and disposing a set of contacts of the thermal switch in series with the starting winding of the single-phase motor.
REFERENCES:
patent: 4384312 (1983-05-01), Fry
patent: 4473789 (1984-09-01), Hildebrandt et al.
patent: 4716326 (1987-12-01), Fisher
patent: 5564831 (1996-10-01), Bashark
Butcher James A.
Depner Eric A.
Christensen Jon P.
Cohen Eric D.
Duda Rina I.
General Electric Company
Nappi Robert E.
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