Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1998-09-28
2001-02-20
Tolin, Gerald (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S608000, C335S202000
Reexamination Certificate
active
06191947
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a circuit breaker and, more particularly, to an electronic trip unit structure and mounting method.
BACKGROUND OF THE INVENTION
It is common for a circuit breakers to employ elements which hip the circuit breakers under various over-current conditions. Such elements, commonly referred to as “hip units,” typically respond to relatively long duration overload conditions to trip the breaker when a specified current level is exceeded for a period of time.
When thermal and magnetic elements are employed to trip the circuit breaker, a bi-metallic element responds to relatively long duration overload conditions. In a typical thermal trip unit, at least a portion of the current flowing through the breaker is channelled through the bi-metallic element. The ohmic resistance of the bi-metallic element causes it to generate heat. As the bi-metallic element becomes warmer, it bends and, when it reaches a predetermined temperature, it engages a trip mechanism that releases a latch which holds the breaker contact closed. When this latch is released, the breaker contacts open.
A typical magnetic tripping element includes an armature which is attracted by a magnetic field generated by a relatively high magnitude over-current flowing through the breaker. This magnetic field is concentrated by a magnetically permeable yoke which surrounds the conductor through which the current flows. When the armature is attracted to the yoke, it also engages the trip mechanism causing the circuit breaker to open.
It is desirable to be able to configure and adjust the current levels and current durations, which cause a breaker to trip, beyond the capability of conventional thermal and magnetic trip units. It is also desirable to customize the circuit breaker to a particular application. The use of electronic trip units provides a more accurate adjustment of the current levels. In such electronic trip units, a circuit assembly with switches is used to facilitate such adjustment and configuration by the unit's user.
Although electronic trip units have proven to be beneficial, it has become recognized that the replacement or first-time installation of such electronic trip units in the field requires disassembly of the breaker. First time installation may be required when the user of the breaker desires to upgrade from one trip unit to another. Replacement may become necessary if a component of the electronic trip unit fails. It has also been recognized that different types of electronic trip units cannot be easily interchanged such as when an upgrade is desired or the application so requires.
Accordingly, it is an object of this invention to overcome the disadvantages of conventional electronic trip units.
SUMMARY OF THE INVENTION
This invention is embodied in an electronic trip unit that is adapted for connection to a circuit breaker base for circuit interruption. The electronic trip unit includes a frame module that encloses at least one transformer that is positioned between a line side bus and a load side bus. The frame module is shaped to define a recess that extends inwardly from an outer surface of the frame module.
The electronic trip unit also includes an electronic module that is releasably connected to the trip unit's frame module and to the transformer positioned within the frame module. The electronic module includes a housing that is shaped to define an interior space. A circuit board assembly is mounted within the interior space and a face of the electronic module provides access to the user for adjustment of the electronic module. The housing of the electronic module is sized and shaped to fit at least partially within the recess defined by the frame module.
An engagement surface is provided in the electronic trip unit and is positioned for providing releasable engagement between the frame module and the electronics module. The engagement surface permits removal and replacement of the electronics module from and to the frame module.
According to a preferred aspect of the electronic trip unit, the housing of the electronics module includes mating housing components and a face plate which together at least partially define the module's interior space. In one exemplary embodiment, the housing includes an interior surface that defines a guide for positioning the circuit board assembly. If the circuit board assembly includes several boards, the interior surface of the housing can include plural guides for positioning the boards and for maintaining a predetermined distance between facing surfaces of the boards.
The face plate of the electronic trip unit can define an opening. Such an opening can provide viewing access to a display such as a liquid crystal display that can be attached to the circuit board assembly. The opening can also provide access to a connector attached to the circuit board assembly. Such an opening can also provide access to a switch that is attached to the circuit board assembly.
A mounting bracket can be made a part of the electronic trip unit and it can extend between an exterior surface of the housing and an interior surface of the frame module's recess. The mounting bracket can define the engagement surface that permits releasable engagement between the housing and frame module. Also, the mounting bracket can be attached to the electronic trip unit's housing.
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Bilac Mario
Titus Solomon R.
Siemens Energy & Automation Inc.
Tolin Gerald
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