Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Automatic circuit-interrupting devices
Patent
1991-10-21
1994-07-19
Donovan, Lincoln
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Automatic circuit-interrupting devices
335 14, H01H 8300
Patent
active
053313011
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to circuit breakers and in particular to circuit breakers of the type having both over-current and earth leakage protection, commonly referred to as residual current circuit breakers (RCCB's).
PRIOR ART
Over-current protective devices have limitations such as delay in operation in situations where there is a relative high earth loop impedance. Further, over-current protective devices do not detect earth fault currents below their operating current, which currents in certain circumstances may constitute a fire hazard. Accordingly, there is an increasing demand for protective devices providing both over-current and earth leakage protection.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a residual current circuit breaker which is reliable in operation and relatively simple to manufacture.
According to one aspect, the invention provides a circuit breaker for use in a system having live, neutral and ground leads, comprising:
a housing;
a breaker assembly in the housing for making and breaking an electrical connection between a movable contact and a stationary contact;
an operating handle for the breaker assembly;
an over-current sensing means for tripping of said breaker assembly; the over-current sensing means including a coil and an armature core in the coil; the armature core having an axial bore extending therethrough;
and an additional tripping mechanism;
the additional tripping mechanism comprising:
a plunger means mounted within the axial bore of the armature core;
an actuating device for controlling the movement of the plunger means from a non-tripping position to a tripping position;
the plunger means being independently movable through the axial bore in the armature core when moving between the non-tripping and tripping positions, and
reset means being provided for re-setting of the plunger means to the non-tripping position.
In a particularly preferred aspect the circuit breaker is a residual current circuit breaker and includes a residual current detection circuit for detection of a residual current in the system, and the actuating device comprises a residual current actuating device for controlling the movement of the plunger means between a non-tripping position and a tripping position when a residual current fault is detected by the detection circuit.
In one embodiment of the invention the actuating device comprises a drive rod which is movable on detection of a residual current fault between a non-tripping position and a tripping position in which the drive rod engages the plunger means to drive the plunger means into the tripping position, biassing means for urging the drive rod into a tripping position, and retaining means for retaining the drive rod in a non-tripping position.
Preferably the retaining means comprises a permanent magnet to hold the drive rod in the non-tripping position and electromagnet to neutralise the effect of the permanent magnet on the drive rod on detection of a residual current fault.
In one arrangement the biassing means comprises a spring means for driving the drive rod into a tripping position engaging the plunger.
Preferably the reset means comprises a reset lever interposed between the drive rod and the plunger and a reset actuator for moving the lever to return the drive rod into the non-tripping position against the action of the biassing means.
In a preferred arrangement the reset actuator comprises the circuit breaker operating handle which engages the reset lever when the handle is moved from the on or non-tripped position with the contacts closed to the off or tripped position with the contacts opened.
Preferably the reset lever is pivotally mounted to the housing intermediate the ends thereof and comprises a first lever arm for engagement by the operating handle and a second lever arm interposed between the drive rod and the plunger means. Typically the reset lever is of substantially L shape in plan view.
In a preferred embodiment of the invention the plunger means comprises a single plun
REFERENCES:
patent: 5089796 (1992-02-01), Glennon et al.
Bosch Hendrik A.
Burke Raymond
Darmohoetomo Soedjiemat F.
Early James
Glennon Oliver
Donovan Lincoln
Golden Larry I.
Irfan Kareem M.
Square D Company
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