Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Automatic circuit-interrupting devices
Reexamination Certificate
2000-09-01
2001-09-04
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Automatic circuit-interrupting devices
C335S035000, C335S036000
Reexamination Certificate
active
06285270
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electromagnetic actuator devices suitable for use in operating electrical switchgear, such as vacuum circuit breakers. The invention has particular, though not exclusive, relevance to direct current circuit breakers and vacuum circuit breakers in general.
2. Related Art
High power circuit breakers require large opening and closing forces to overcome various contact forces encountered. This requires the use of large and heavy actuators which are consequently much slower to operate than their smaller equivalents. This is disadvantageous, particularly in DC circuits where a fast circuit breaking action is required.
In addition, because the contacts of such circuit breakers tend to wear with use, it is desirable to include, in the circuit breaker mechanism, means to accommodate an increasing relative distance between the contact surfaces when open, ie. means to provide an increasing actuation distance during the lifespan of the contacts. This is typically achieved by providing an electromagnetic actuator which drives a moving contact through a closing spring coupling, which absorbs any difference between actuator stroke length and actual contact travel distance. This feature, however, results in the creation of a snatch gap which means that the actuator does not even start to open the contacts until part way through its opening stroke, thereby slowing still further the circuit breaking operation.
It is an object of the present invention to provide an improved circuit breaker providing high speed current interruption.
SUMMARY OF THE INVENTION
According to one aspect, the present invention provides a circuit breaker which comprises a heavy duly first, or primary, actuator coupled to provide the necessary power to provide closing and holding forces to relatively moveable contacts of the circuit breaker, and a secondary, faster acting, actuator coupled to provide only sufficient power to open, or initiate opening, of the contacts.
Preferably, the primary actuator is adapted to reset the secondary actuator during completion of the opening stroke, and may be further adapted to provide the closing stroke without assistance from the secondary actuator.
According to another aspect, the present invention provides an actuator for a circuit breaker that includes a drive shaft for coupling to a moveable contact of a circuit breaker, a primary actuator mechanism operable to propel the drive shaft between a first position and a second position and a secondary actuator mechanism which, upon receiving a trigger signal, shortens the effective length of the drive shaft.
Preferably, the drive shaft includes an actuator rod coupled to an armature of the primary actuator mechanism which actuator mechanism is configured to drive the actuator rod in a direction substantially parallel to its longitudinal axis, and a link or mechanism means, coupled at a first end to the actuator rod and configured for coupling at a second end to the moveable contact of the circuit breaker, the link or mechanism means having first and second link members substantially axially aligned with the actuator rod in a first condition and non-aligned in a second condition.
According to another aspect, the present invention provides an actuator for a circuit breaker having a drive link for coupling to a moveable contact of a circuit breaker, a primary actuator mechanism adapted to drive the drive link from a first position to a second position during a closing stroke, a secondary actuator mechanism, operable in concert with said primary actuator to drive the drive link from the second position to the first position during an opening stroke wherein the secondary actuator mechanism includes a latch which is tripped during the first part of the opening stroke, and which is reset by the primary actuator mechanism during a subsequent part of the opening stroke.
Preferably, the actuator drive link comprises a rotating arm which pivots about an axis, the position of the pivot axis being determined by the operation of the secondary actuator mechanism.
Preferably, the secondary actuator is coupled to the rotating arm by a spring link adapted to provide a snatch gap Alternatively, the spring link, to apply pressure to the moveable contact, could be coupled to the primary actuator.
Embodiments of the present invention will now be described in detail by way of example and with reference to the accompanying drawings in which:
REFERENCES:
patent: 1956847 (1934-05-01), Ainsworth
patent: 5172088 (1992-12-01), Morgan
Lane Stephen Ernest
Snell Martin
Barrera Ramon M.
FKI PLC
Nikolai Mersereau & Dietz, P.A.
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