US3761778A

US3761778A - Static trip control unit for electric circuit breaker

Info

Publication number: US3761778A
Application number: US00320579A
Authority: US
Inventors: H Willard
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1973-01-02
Filing date: 1973-01-02
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25
Also published as: CA981371A

Abstract

A solid state trip control unit for an electric circuit breaker is provided with field adjustable tripping characteristics by the utilization of individual selector knobs for numerous control characteristics. The unit includes a printed circuit board having separate circuit patterns on opposite sides thereof and a plurality of switching terminals fixedly connected to one of the printed circuit patterns and adapted to be selectively interconnected to conductors of the other printed circuit patterns by means of individual connector switches controlled by the positioning selector knobs. The solid state circuitry includes a fail-safe interconnection between the circuit patterns on opposite sides of the board in the event of improper or ineffective connection by the movable conductor switch and permits full visability of the setting on the trip unit while providing tamper proof isolation thereof.

Description

United States Patent [191 Willard [451 Sept. 25, 1973 [75] Inventor:

[54 STATIC TRIP CONTROL UNIT FOR ELECTRIC CIRCUIT BREAKER Henry G. Willard, Wethersfield,

Conn.

[73] Assignee: General Electric Company, New

York, N.Y.

[22] Filed: Jan. 2, 197-3 [2]] Appl. No.: 320,579

[52] U.S.C1. ..3l7/33R,3l7/l01C,317/l12 Primary Examinerlames D. Trammell I Attorney-John M. Prutzman et a1.

[57] ABSTRACT A solid state trip control unit for an electric circuit breaker is provided with field adjustable tripping characteristics by the utilization of individual selector knobs for numerous control characteristics. The unit includes a printed circuit board having separate circuit patterns on opposite sides thereof and a plurality of switching terminals fixedly connected to one of the printed circuit patterns and adapted to be selectively interconnected to conductors of the other printed circuit patterns by means of individual connector switches controlled by the positioning selector knobs. The solid state circuitry includes a fail-safe interconnection between the circuit patterns on opposite sides of the board in the event of improper or ineffective connec' 'tion by the movable conductor switch and permits full visability of the setting on the trip unit while providing tamper proof isolation thereof.

10 Claims, 5 Drawing Figures SJSlJTB PATENTED SEP25 I973 SWEET 2 EF 2 FIG. 4

v A%@% M;

STATIC TRIP CONTROL UNIT FOR ELECTRIC CIRCUIT BREAKER BACKGROUND AND SUMMARY OF THE INVENTION The present invention relates generally to a static trip control unit for electric circuit breakers. More particularly it is concerned with a new and improved solid state control panel construction for such units particularly well suited for incremental field adjustment to preselected trip signal control levels.

An object of the present invention is to provide a new and improved static trip control unit of the type described that utilizes printed circuitry and facilitates incremental adjustment in the trip control level of a circuit breaker by means of a relatively simple movable switch selectively bridging conductors on opposite sides of a printed circuit board to selectively shunt-out a portion of the interconnected circuit.

Another object of the present invention is to provide a static trip control unit for an electric circuit breaker of the type described which not only provides adjustable preselected trip control values, but further incorporates a fail-safe interconnection between the circuit patterns to assure operation of the static trip control unit in the event the selected shunting switch fails to shunt the circuit in the desired fashion.

A further object of the present invention is to provide a new and improved electric circuit breaker having a static trip control unit of the type described wherein the switch is slidably adjustable to different switching stations located at remote, distinct,'linearly spaced positions yet is captively retained by the panel to prevent inadvertent removal therefrom.

Still another object of the present invention is to provide a new and improved electric circuit breaker having a'static trip control unit of the type described which can be selectively adjusted to preselected trip control levels in such a manner so as to provide full visability of the control setting and is adapted to be encased within a sealed tamper proof covered housing.

Other objects will be in-part obvious and in part pointed out more in detail hereinafter.

These and related objects are accomplished in accordance with the present invention by providing a new and improved static trip control unit for an electric circuit-breaker including a printed circuit board having first and second printed circuit patterns on opposite planar surfaces thereof and a plurality of apertures extending fully through the board at predetermined locations. The first printed pattern includes electrically conductive contact pads substantially concentric with the apertures and abutting the edges thereof while the second printed pattern includes contact pads individually enveloping a plurality of selected apertures and spaced from the enveloped apertures to provide insulating areas concentric with and abutting the apertures. A plurality of switch terminals are mounted on the board at the apertures in electrical contact with the contact pads of the first pattern. The terminals extend through the apertures and outwardly from the surface of the board carrying the second printed circuit pattern in such a manner as to maintain the terminals separated from the enveloping contact pads of the second printed pattern by at least a portion of the concentric insulating area. A removable switch contact connector having a smooth contact wiping surface is selectively mounted on one of said individual terminals for each condition controlled by the trip control unit for causing positive bridging between conductors of the first and second circuit patternsv A better understanding of the invention will be obtained from the following detailed description and the accompanying drawings which set forth an illustrative embodiment indicative of the way in which the principles of the invention are employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. l is a top plan view of a circuit breaker embodying the features of the present invention, the cover thereof being partially broken away.

FIG. 2 is a side elevational view of the circuit breaker of FIG. l with the side of the housing removed to expose the internal components of the circuit breaker.

FIG. 3 is a top view of one embodiment of a printed circuit board used in the static trip control unit of the circuit breaker of FIG. ll.

FIG. 4 is a bottom view of the printed circuit board of FIG. 3; and

FIG. 5 is an enlarged sectional view taken along the line 5-5 of FIG. I and illustrating the manner in which the adjustable switch connector is mounted on the printed circuit board.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings in greater detail wherein like reference numerals indicate like parts throughout the several figures, a multiphase electric circuit breaker is illustrated as comprised of a generally rectangular insulating case 10 enclosably housing a separable contact assembly 12 for each phase controlled by the breaker and a single operating mechanism 14 for simultaneously moving the contact assemblies in unison either manually between their open and closed circuit positions or automatically from the close circuit position illustrated in FIGS. 1 and 2 to an open circuit position. Additionally,each phase of the circuit breaker is provided with a low profile current transformer 16 associated with each phase conductive strap 18. The transformers 16 are provided with suitable leads 20 connected through a plug 22 to a static trip control unit, generally designated by the numeral 24.

The static trip control unit or programmer 24 of the electric circuit breaker is a self-contained easily removable modular unit adapted to provide control over various characteristics or conditions that occur within any one of the three phases controlled by the circuit breaker. The trip control unit is adapted to receive signals from the current transformers 16 and in turn is electrically and operatively connected to a magnetic trip actuating device 26 for activating the actuating device to effect tripping of all three phases of the breaker upon receipt of a preselected signal from the current transformers.

The modular static trip control unit M is contained within a suitable housing 28 removably secured to the insulating casing 10 of the circuit breaker by means of a pair of bolted brackets 32 secured to interior walls 34 of the casing. The trip control unit housing 28 includes a multi-slotted control panel or face plate 36. As illustrated in FIG. 1, the multiple slots 38 in the control panel are in spaced parallel arrangement and are of generally rectangular configuration with the longitudinal dimension extending along the length of the breaker. Each slot 38 is preferably labelled as shown to indicate the particular characteristics being controlled and the multiple settings possible.

In accordance with the present invention, a plurality of adjustable control knobs 40 extend through the control panel 36 and are arranged so that each elongated slot 38 of the control panel provides a raceway for a single control knob 40. The control knobs are mounted on one of a plurality of threaded switch terminals 42 positioned inside the trip control unit immediately beneath the front control panel 36 and in registry with the elongated slots 38.

'As shown in FIG. 1 and as mentioned hereinbefore, the operating conditions controlled by the static trip control unit are printed on the front panel together with an indication of the appropriate values for each setting of the control unit. This setting is accomplished by moving the thumb-controlled knobs 40 to the appropriate location overlying a single terminal 42 and tightening the knob onto the particular terminal selected.

The terminals 42 are fixedly mounted on a printed circuit board 44 located within the interior of the static trip control unit 24 immediately beneath the front panel 36 and project upwardly toward the panel but do not extend therethrough. The control knobs 40 are held captive by their respective slots 38 in the front panel so as to permit sliding movement of the knob along the elongated generally rectangular slot to its selected position.

The printed circuit board 44 illustrated in FIGS. 3 and 4 depicts one embodiment of the circuits that may be employed in accordance with the present invention. As shown, the insulating plastic board 46 is provided with separate and isolated printed curcuit patterns on opposite planar surfaces of the board. In the particular embodiment illustrated, the board is provided with a plurality of terminal mounting apertures 48 arranged in rows corresponding to the slots in the control panel 36. The top surface of the printed circuit board is provided with a first printed circuit pattern that includes a plurality of generally rectangular, spaced, parallel contact pads 50 of elongated configuration arranged on the board so as to register with the elongated slots 38 on the front control panel 36. Each contact pad 50 fully envelopes a plurality of isolated circular insulating areas 52 individually surrounding the terminal mounting apertures 48. Each pad 50 extends well beyond the edges of the slots and is provided with a printed connector 54 extending toward one edge 56 of the board and terminating in one or more printed edge terminals 58. Each pad of the first circuit pattern is electrically isolated from each of the other pads in the pattern and from the upstanding switch terminals 42 enveloped thereby. Additionally, the board is provided with a plurality of component mounting holes 60 located generally outside of the elongated contact pads 50 and suitably arranged to provide appropriate interconnection of mounted solid state components with the second printed circuit pattern located on the back side of the printed circuit board.

As shown in FIG. 4, the underside or bottom planar surface of the printed circuit board is provided with a second printed circuit pattern having appropriate printed conductors, such as the conductors 62 interconnecting the component mounting holes 60 and the terminal mounting apertures 48. The second printed circuit pattern includes electrically conductive contact pads 64 substantially concentric with the terminal mounting apertures 48 and abutting the edges of these apertures to provide for electrical contact between the terminals and the printed circuit pattern on the underside of the printed circuit board. As shown, suitable printed connectors such as connector 66 of the second circuit pattern also extend from a component mounting hole 60 to one or more printed edge terminals 68 located along the same edge 56 of the board as the terminals 58 of the first printed circuit pattern.

Referring now to FIGS. 1 and 5 an adjustable switch is provided for each condition controlled by the circuit breaker. The switch consists of the threaded terminal 42 having a circular flange-like base portion 70 of substantially smaller radius than the insulated area 52 of the first printed circuit pattern and a depending mounting post 72 of suitable dimensions so as to extend fully through the aligned apertures 48 in the circuit board by a rivet or other similar technique so as to provide electrical contact with the concentric contact pad 64 of the second printed circuit pattern while at the same time fixedly securing the terminal to the printed circuit board. The terminal 42 also includes an integral threaded stud portion 74 upstanding from the base flange 70 and provided with a thread of the fine thread series. Forexample, good results have been obtained by using a No. 8 fine thread containing 36 threads to the inch and having a lead angle of approximately 3.5".

The thumb-controlled knob 40 adapted to be threadably mounted on the terminal stud portion 74 consists of a generally cylindrical switch connector 76 having a centrally threaded cavity 78 for threadable mounting on the stud. Additionally, the connector is provided with a radially extending pedestal-like portion 80 having a smooth flat circular base surface 82 substantially free of burrs or other imperfections. This base wiping surface 82 of the connector is located at a suitable radial distance from the stud 74 so as to engage the enveloping contact pad 50 of the first printed circuit pattern when the connector 76 is threadably mounted on the terminal stud 74. The flat circular surface 82 of the pedestal-like portion will provide wiping contact with the enveloping contact pad 50 as the low pitch screw thread connector 76 slowly is brought into positive electrical contact with the pad. The connector 76 is affixed to the exposed thumb controlled knob 40 positioned on the outer side of the front control panel 36 and is mountably connected to the electrical connector 76 in such a manner as to be captive with the slot 38 of the control panel, the pedestal portion 80 and the thumb controlled knob 40 being of sufficient size to v prevent their passage through the elongated slots 38 in the front panel. In this manner, the thumb controlled knob 40 is limited to movement along the single slot through which it is originally mounted.

' In the embodiment illustrated, the printed circuit patterns of the printed circuit board are arranged so as to also provide a fail-safe interconnection between the circuit patterns on opposite sides of the printed circuit board. For example, referring to FIGS. 1, 3 and 4 and the Trip Point adjustment of the Ground Fault" condition, it will be noted that the printed conductive connection 54 to the enveloping contact pad 50 of the first printed circuit pattern is electrically connected through a suitable electronic component 84 to printed connectors 62 of the second printed circuit pattern. In

like manner the other solid state components 86 are connected in series to complete the circuit between the printed terminal 68 and the printed terminal 58.

As will be appreciated, the printed ciruit patterns on both sides of the board, together with the'components 84, 86, provide a closed circuit between the first and second circuit patterns regardless of a connection through the knob controlled switch connector 76. However, in this instance, the fail-safe circuit includes all the components 84 and 86 electrically connected between the

terminals

58 and 68. When the switch knob 40 is placed in the positionshown in FlG. 1, Le, at the trip point labelled 0.4x it in effect short circuits or shunts the connection to eliminate current flow through the component 84 and thereby adjusts the ground fault condition which controls tripping of the circuit breaker. Similarly, movement of the thumb controlled knob 40 to a different location on the ground fault control panelwill provide a comparable adjustment of the condition being controlled.

As is apparent from FIG. 1, a transparent cover plate 90 encloses the static trip control unit 24 within the circuit breaker casing while at the same time permitting full visibility of the control settings on the unit. In accordance with the preferred embodiment, the transparent cover portion is also provided with a tamper proof leaded seal 92 permitting only authorized removal of' the transparent cover 90 when it is required to effect field adjustment of the setting on the control panel.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the teachings of the present invention.

I claim:

l. A static trip control unit for an electric circuit breaker adapted for incremental trip signal adjustment including a printed circuit board of insulating material having first and .second printed circuit patterns on opposite planar surface thereof and a plurality of apertures extending fully through the board in predetermined locations; said first printed circuit pattern including electrically conductive contact pads substantially concentric with said apertures and abutting the edges thereof; said second printed circuit pattern including contact pads individually enveloping a plurality of selected apertures and spaced from the enveloped apertures to provide insulating areas concentric with and abutting said apertures; a plurality of contact studs mounted on said board at said apertures and secured to said board in electrical contact with the conductive contact pads of said first circuit, said studs extending through said apertures and outwardly from the surface of said board carrying said second printed circuit pattern, said studs being separated from the enveloping contact pads of said second printed circuit pattern by at least a portion of said concentric insulating area; and a removable contact connector having a smooth contact wiping surface, said connector being selectively mounted on one of said individual studs for causing positive engagement between said contact wiping surface and the contact pad of said second circuit pattern enveloping the mounted stud and effecting an electrical connection between said first and second circuit patterns through said stud.

2. The trip control unit of claim 1 including a plurality of solid state components mounted on said printed circuit board in electrical contact with one of said first and second printed circuit patterns, one of said components additionally providing electrical continuity between said first and second patterns to complete the circuit and assure fail-safe operation of said unit irrespective of said engagement between the wiping surface of the removable connector) and the contact pad of the second circuit pattern.

3. The trip control unit of claim ll including an enclosure for the printed circuit board provided with a control panel having an elongated slot for each individual tripping characteristic controlled by the unit, said removable contact connector being captively and slidably movable along said slot to selected control levels and having an exposed positioning selector knob thereon facilitating field adjustment and selection of the trip control level for the individual tripping characteristic. I

4. The trip control unit of claim 3 wherein the control panel is provided with a plurality of said elongated slots, said contact studs being positioned within rows in registry with said slots for permitting slidable movement of a contact connector along each row and mountably receiving the connector on one of said studs.

5. The trip control unit of claim 1 wherein the printed circuit board carries first and second printed circuit patterns for a plurality of different tripping characteristics controlled by the circuit breaker, the circuits for each individual characteristic including a plurality of solid state components mounted on the board in electrical contact with a least one of said circuit patterns, at least one of said components being connected to both of said circuit patterns to complete the circuit and provide electrical continuity through all of the solid state components in said circuit.

6. The trip control unit of claim 5 wherein the solid state components are electrically connected between contact pads of said first circuit pattern and the circuit connection provided by said removable contact connector and an intermediate contact stud of the first circuit pattern provides a shunt that bridges conductors of the first and second circuit patterns to electrically bypass selected solid state components in said circuit.

7. In an electric circuit breaker comprising an insulating casing, separable contacts movable between the open and closed circuit positions and a tripping mechanism for automatically moving the contacts to their open circuit position, the combination comprising a modular static trip control unit for controlling the operation of said tripping mechanism, said unit including a front control panel, a positioning selector knob for each tripping characteristic controlled by the unit mounted of the exposed surfaces of said control panel and a transparent cover secured to the casing for enclosing the static trip control unit while permitting full visibility of the positioning selector knobs carried by the control panel.

8. The circuit breaker of claim 7 wherein the transparent cover is provided with a tamper proof seal preventing unauthorized removal thereof from the casing.

9; A printed circuit board switch suited for use in a static trip control unit for an electric circuit breaker comprising a printed circuit board of insulating material having first and second printed circuit patterns on opposite planar surface thereof and an aperture extending fully through the board, said first printed circuit pattern including an electrically conductive contact pad substantially concentric with said aperture and abutting the edge thereof; said second printed circuit pattern including a contact pad enveloping said aperture but spaced therefrom to provide an insulating area concentric with and abutting said aperture; a contact stud mounted on said board at said aperture in electrical contact with the conductive contact pad of said first circuit pattern, said stud extending through said aperture and having a threaded terminal projecting outwardly from the surface of said board carrying said second printed pattern, said stud being separated from the enveloping contact pad of said second printed circuit pattern by at least a portion of said concentric insulating area; and a removable contact connector having a smooth contact wiping surface on the base thereof; said connector being threadably mounted on said terminal for causing positive engagement between said contact wiping surface and the contact pad of said second circuit pattern and effecting an electrical connection between said first and second patterns through said stud.

10. The switch of claim 9 wherein said threaded terminal is provided with a low pitch thread of the fine thread series to facilitate smooth wiping contact between said wiping surface and said contact pad.

Claims

1. A static trip control unit for an electric circuit breaker adapted for incremental trip signal adjustment including a printed circuit board of insulating material having first and second printed circuit patterns on opposite planar surface thereof and a plurality of apertures extending fully through the board in predetermined locations; said first printed circuit pattern including electrically conductive contact pads substantially concentric with said apertures and abutting the edges thereof; said second printed circuit pattern including contact pads individually enveloping a plurality of selected apertures and spaced from the enveloped apertures to provide insulating areas concentric with and abutting said apertures; a plurality of contact studs mounted on said board at said apertures and secured to said board in electrical contact with the conductive contact pads of said first circuit, said studs extending through said apertures and outwardly from the surface of said board carrying said second printed circuit pattern, said studs being separated from the enveloping contact pads of said second printed circuit pattern by at least a portion of said concentric insulating area; and a removable contact connector having a smooth contact wiping surface, said connector being selectively mounted on one of said individual studs for causing positive engagement between said contact wiping surface and the contact pad of said second circuit pattern enveloping the mounted stud and effecting an electrical connection between said first and second circuit patterns through said stud.

3. The trip control unit of claim 1 including an enclosure for the printed circuit board provided with a control panel having an elongated slot for each individual tripping characteristic controlled by the unit, said removable contact connector being captively and slidably movable along said slot to selected control levels and having an exposed positioning selector knob thereon facilitating field adjustment and selection of the trip control level for the individual tripping characteristic.

6. The trip control unit of claim 5 wherein the solid state components are electrically connected between contact pads of said first circuit pattern and the circuit connection provided by said removable contact connector and an intermediate contact stud of the first circuit pattern provides a shunt that bridges conductors of the first and second circuit patterns to electrically by-pass selected solid state components in said circuit.

9. A printed circuit board switch suited for use in a static trip control unit for an electric circuit breaker comprising a printed circuit board of insulating material having first and second printed circuit patterns on opposite planar surface thereof and an aperture extending fully through the board, said first printed circuit pattern including an electrically conductive contact pad substantially concentric with said aperture and abutting the edge thereof; said second printed circuit pattern including a contact pad enveloping said aperture but spaced therefrom to provide an insulating area concentric with and abutting said aperture; a contact stud mounted on said board at said aperture in electrical contact with the conductive contact pad of said first circuit pattern, said stud extending through said aperture and having a threaded terminal projecting outwardly from the surface of said board carrying said second printed pattern, said stud being separated from the enveloping contact pad of said second printed circuit pattern by at least a portion of said concentric insulating area; and a removable contact connector having a smooth contact wiping surface on the base thereof; said connector being threadably mounted on said terminal for causing positive engagement between said contact wiping surface and the contact pad of said second circuit pattern and effecting an electrical connection between said first and second patterns through said stud.