Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Tripping means
Reexamination Certificate
2000-02-18
2001-03-13
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Tripping means
C335S014000, C335S132000
Reexamination Certificate
active
06201460
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of circuit breakers and more particularly to a molded case circuit breaker with an undervoltage release device.
BACKGROUND OF THE INVENTION
In general the function of a circuit breaker is to electrically engage and disengage a selected circuit from an electrical power supply. This function occurs by engaging and disengaging a pair of operating contacts for each phase of the circuit breaker. The circuit breaker provides protection against persistent overcurrent conditions and against the very high currents produced by short circuits. Typically, one of each pair of the operating contacts are supported by a pivoting contact arm while the other operating contact is substantially stationary. The contact arm is pivoted by an operating mechanism such that the movable contact supported by the contact arm can be engaged and disengaged from the stationary contact.
There are two modes by which the operating mechanism for the circuit breaker can disengage the operating contacts: the circuit breaker operating handle can be used to activate the operating mechanism; or a tripping mechanism, responsive to unacceptable levels of current carried by the circuit breaker, can be used to activate the operating mechanism. For many circuit breakers, the operating handle is coupled to the operating mechanism such that when the tripping mechanism activates the operating mechanism to separate the contacts, the operating handle moves to a fault or tripped position.
To engage the operating contacts of the circuit breaker, the circuit breaker operating handle is used to activate the operating mechanism such that the movable contact(s) engage the stationary contact(s). A motor coupled to the circuit breaker operating handle can also be used to engage or disengage the operating contacts. The motor can be remotely operated.
A typical industrial circuit breaker will have a continuous current rating ranging from as low as 15 amps to as high as 400 amps. The tripping mechanism for the breaker usually consists of a thermal overload release and a magnetic short circuit release. The thermal overload release operates by means of a bimetallic element, in which current flowing through the conducting path of a circuit breaker generates heat in the bi-metal element, which causes the bi-metal to deflect and trip the breaker. The heat generated in the bi-metal is a function of the amount of current flowing through the bi-metal as well as for the period of time that current is flowing. For a given range of current ratings, the bi-metal cross-section and related elements are specifically selected for such current range resulting in a number of different circuit breakers for each current range.
In the event of current levels above the normal operating level of the thermal overload release, it is desirable to trip the breaker without any intentional delay, as in the case of a short circuit in the protected circuit, therefore, an electromagnetic trip element is generally used. In a short circuit condition, the higher amount of current flowing through the circuit breaker activates a magnetic release which trips the breaker in a much faster time than occurs with the bi-metal heating. It is desirable to tune the magnetic trip elements so that the magnetic trip unit trips at lower short circuit currents at a lower continuous current rating and trips at a higher short circuit current at a higher continuous current rating. This matches the current tripping performance of the breaker with the typical equipment present downstream of the breaker on the load side of the circuit breaker.
In certain situations, it may be advantageous to disconnect an electrical system by opening a circuit breaker in the circuit. Such circumstances can include applications for maintenance and control. It may also be used in applications to prevent use of electrical equipment under a specified or selected voltage. One device used for tripping a circuit breaker because low voltage is detected is an undervoltage release accessory. The undervoltage release accessories currently used have several disadvantages. Some such undervoltage release accessories must be installed in the circuit breaker housing behind the main cover and in close proximity to electrically live parts and connections. Further examples of present undervoltage release accessories are designed to be used with a single circuit breaker frame, i.e., for each current rating of the circuit breaker a specially designed undervoltage release accessory is required.
Thus, there is a need for an undervoltage release accessory to open a circuit breaker that can be installed in the main cover of the circuit breaker without exposing the electrically live parts of the circuit breaker. There is a further need for an undervoltage release device that can be used with several circuit breaker frame sizes, that is a single undervoltage release device that will operate over a wide range of current ratings for the circuit breaker. There is an additional need for an undervoltage release device with which a customer can connect its control wiring directly to the undervoltage release device without any additional rewiring. And further, there is a need for an undervoltage release device for a circuit breaker that can be installed in a circuit breaker utilizing a common latching protrusion that provides a noticeable snap fit installation.
SUMMARY OF THE INVENTION
The present invention provides an undervoltage release device for a molded case circuit breaker having an operating mechanism, a trip bar, a line terminal, a load terminal, and a cover. The undervoltage release device comprises a housing, a solenoid assembly having a coil, a plunger, and a frame. It further includes upper and lower actuators pivotally mounted on a solenoid frame, aligned with a plunger, and in selective contact with a trip bar; a plunger reset lever pivotally mounted on the solenoid frame and having a plunger reset tab engaged with the plunger and having a reset member; and an actuator reset lever pivotally mounted on a solenoid frame and having a plurality of tabs, with at least one tab in contact with the upper actuator, at least one tab in contact with the lower actuator, at least one tab in contact with the operating mechanism, and at least one tab in contact with a plunger reset lever. The present invention also includes a pair of terminals mounted on the accessory housing and in electrical contact with a solenoid coil and a line terminal side of the circuit breaker, wherein the magnetic force of the solenoid coil is proportional to line voltage on the circuit breaker.
Another embodiment of the present invention provides a molded case circuit breaker including a molded housing provided with a breaker cover, a first terminal and a second terminal mounted in the case, a contact electrically coupled to the first terminal, and a movable contact electrically coupled to the second terminal. It also includes an operating mechanism having a pivoting member movable between an ON position, an OFF position, and a TRIPPED position, wherein the pivoting member is coupled to the movable contact; an intermediate latching mechanism mounted in the housing and coupled to the operating mechanism; and a trip unit having a trip bar and coupled to the movable contact in the second terminal with the trip unit in selective operative contact with the intermediate latching mechanism. This embodiment also includes an accessory pocket formed in the breaker cover on either side of an opening for the pivoting member, with the accessory pocket in communication with the housing and configured to accept a plurality of different types of accessories; a latching protrusion in the pocket for engaging an accessory; a removable accessory cover sized to cover the accessory mounted in the accessory pocket; and an undervoltage release device installed in the pocket. The undervoltage release device includes an accessory housing, a solenoid assembly having a coil, a plunger, and a solenoid frame mounted in
Blessitt Elizabeth J.
Green Russell Bryant
Rodriguez Mauricio
Winslett Michael Troy
Donovan Lincoln
Nguyen Tuyen T.
Siemens Energy & Automation Inc.
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