AU611239B2 - Polyphase circuit fuse condition indicating device - Google Patents

Description

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OPI DATE 23/05/89 WOR AOJP DATE 29/06/89 APPLN. ID 27238 88

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PCT NUMBER PCT/US88/03517 INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TIEATY (PCT) (51) International Patent Classification 4 (11) International Publication Number: WO 89/ 04030 G08B 21/00 Al Inter naublj ion V e: r 5 ay 1989 (05.05.89) (21) International Application Number: PCT/US88/03517 (81) Designated States: AE (uro patent), FR (European patent), GB (European patent), IT (European (22) International Filing Date: II October 1988 (11.10.88) patent), JP.

(31) Priority Application Number: 110,117 Published With international search report.

(32) Priority Date: 19 October 1987 (19.10.87) (33) Priority Country: US (71) Applicant: SQUARE D COMPANY [US/US]; Executive Plaza, Palatine, IL 60067 (US).

(72) Inventor: BROOKS, Stanley, J. 417 Fairfield, Lexington, KY 40503 (US).

(74) Agent: GUTTMAN, Richard, Square D Company, Executive Plaza, Palatine, IL 60067 (US).

(54)Title: POLYPHASE CIRCUIT FUSE CONDITION INDICATING DEVICE OA FA 22 08

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B 0C F C LINE LOAD LINE LOAD LINE LOAD r r- r~ r n r- RI R3 I R RR3 I I RS RI I I I L- J L SS L_ J L RSS L RSSS 12A 20 12 8 1 2C S- i- I swi SWI o) -SWI R4 R5 R6 (57) Abstract A polyphase circuit fuse condition indicating device (10) includes three substantially identical circuits (12A, 12B, 12C) forming a Y-connection across each fuse (FA, FB, FC) through first and second leads. Each circuit has an indicator light (14) and a switch (SWI) with resistors in the leads. The respective circuits are interconnected through a lead having a resistance for each circuit so that an indication will be rendered without a load across the fuse.

i WO 89/04030 PCT/US8/03517 POLYPHASE CIRCUIT FUSE CONDITION INDICATING DEVICE

DESCRIPTION

Technical Field The present invention relates to fuse indicator devices and more particularly to devices for indicating the condition of fuses in a polyphase electric circuit.

m Y WO 89/04030 PCT/US88/03517 2 Background Art There is a need for indicating the condition--blown or still good--of fuses protecting a polyphase electrical circuit, such as is used to power industrial equipment.

The fuse condition indicators have been developed to be mounted on the front of the fuse-containing cabinet so that an activated lamp indicates the blown fuse. This aids service personnel in locating the problem area quickly to return the equipment to service.

Typically, these devices have pairs of leads extending from a housing to be connected to the opposite sides of a cartridge fuse holder.

When the fuse blows, an associated neon lamp in the housing becomes lit.

These devices also provide a single push-button switch arrangement for testing the circuit of the fuse condition indicator device, while the line is present, from the line side of the fuse to the indicator lamp.

Service personnel can test the operation of the indicator lamps by depressing the pushbutton switch while the line is present; a properly operating circuit will light the three lamps. This also avoids opening the cabinet and inserting a test probe to determine whether the line power is present at the fuse.

The leads extending from the housing also have included axial resistors connected h WO 89/04030 PCT/US88/03517 3 in series, without any supports, for reducing the voltages appearing in the housing and to limit currents that can flow through the components in the housing. Mounting the resistors without supports results in undesired tensile strain in the leads of the axial resistor.

More particularly, the prior devices include circuits in the housing that present a loop extending between the pairs of leads for each phase. Each loop connects to the loops for the other phases at two points spaced from one another. From the line side, the loop includes in series, a first rectifier diode S with the cathode cronnected to the lead, a series connected thyristor, a neon lamp, a first resistance and a second rectifier diode whose cathode is connected to the extending lead. A second resistance connects across the loop at the anodes of the two rectifier diodes and the gate control lead of the thyristor connects to between the first series resistance and the anode of the second rectifier diode. The connection between the circuit loops of each phase occur at the cathode of the first rectifier diode and between the neon lamp and series resistance.

This results in applying a direct current to the neon lamps by way of the rectifier diodes rectifying the AC power received from the line. Applying DC to the IIi -4neon lamp causes sputtering within the neon bulb and shortened life. Further, this circuit arrangement uses many parts and expensive thyristors.

It would be beneficial to obtain a fuse conditiion indicator having a small parts count and that applies AC to the neon bulb. Such a device would be less expensive than the known device while obtaining lower manufacturing costs and like operation.

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Summary of the Invention The present invention provides a fuse condition indicating device adapted to be connected to a polyphase electric circuit in which said electric circuit includes .9 for each phase a line lead, a load lead and a fuse Oi connected between said line and said load lead, said device comprising: plural indicator means, one associated with each of said phases of said polyphase electric circuit, each of said indicator means having first and second sides, and each of said indicator means for producing user recognizable indications of the condition of said corresponding fuse; plural first resistor means, 9. .0 S one associated with each of said phases of said polyphase electric circuit, each of said first resistor means having first and second sides, each of said first resistor means So connected between said first side of said corresponding indicator means and one of either said line or load lead of said corresponding fuse, each of said first resistor means providing a substantially resistive load; plural second resistor means, one associated with each of said phases of said polyphase electric circuit, each of said second resistor means having first and second sides, each of said second resistor means connected between said second side of said corresponding indicator means and the other of either the line or load lead of said

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-4acorresponding fuse, each of said second resistor means providing a substantially resistive load being substantially less than that of the first resistor means; and, plural third resistor means, one associated with each of said phases of said polyphase electric circuit, each having a first side connected to the second side of said corresponding indicator means and a second side connected to the second sidesof the other third resistor means, each of said third resistor means providing a substantially resistive load between said second side of said corresponding indicator means and said second sides of said other indicator means.

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L1 WO 89/04030 PCT/US88/03517 According to a further aspect of the present invention, the fuse condition indicating device is embodied in a housing that can readily be installed into a control panel without any modification thereof and essentially forms a Y-connection with opposite sides of the fuse. More specifically, the housing has a collar integral with a rear wall and a translucent front wall with the indicator means mounted on a board supported in the housing. The board also supports the resistors and the interconnection between the respective circuits as well as the switch means.

The switch means in the respective circuits each include a pair of contacts located on opposite sides of a slot with a conductive spring means in the housing and normally bridging the contacts. An actuator in the form a non-conductive member has prongs received into the slots so that application of a force on the actuator will simultaneously open all of the switches to test the indicator lights.

Brief Description of Drawings PIG. 1 is a circuit diagram of the present invention; FIG. 2 is a side view of the indicating device of the invention; WO 89/04030 PCT/US88/03517 6 FIG. 3 is a cross-sectional view as viewed along line 3-3 of FIG. 2; FIG. 4 is a front view of the housing of the device, as viewed along line 4- 4 of FIG. 2; FIG. 5 is an exploded view of the housing; FIG. 6 is a plan view of the circuit board in the housing; FIG. 7 is a side view of the switch actuator; and, FIG. 8 is a fragmentary crosssection, as viewed along line 8-8 of FIG. 6.

Detailed Description While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to embodiment illustrated.

FIG. 1 of the drawings shows an electric circuit embodying the invention. The circuit of the present invention is generally designated by reference numeral 10 and includes three identical circuits 12A, 12B and 12C respectively connected to the line and WO 89/04030 PCT/US88/03517 7 load side of three fuses FA, FB and FC, respectively connected in series with the three phases A, B and C of a polyphase circuit.

Each circuit 12 consists of an indicator means 14 in the form of a neon light which is connected through a lead 16 to the line side of the fuse FA. The lead 16 includes series connected first resistor means 18 consisting of resistors R1 and R2, which will be described in more detail later. The circuit 12 also includes a second lead 20 that includes series connected resistor means 22 in the form of series resistors R3 and R7. These also will be described in more detail presently. Line 20 also has a switch SWl connected in series between resistance means 22 and neon lamp 14. The respective identical circuits 12 are interconnected by a common lead 26 through resistors R4, R5 and R6 respectively connected between the indicator means 14 and the switch SWI in the leads extending to the respective circuits 12.

In operation, and with a good fuse F, the voltage drop across resistor means 22, I resistors R3 and R7 is low enough to keep neon lamp 14 extinguished. When fuse F opens or blows, resistor means 22 is no longer in the circuit and the voltage across the lamp 14 increases cau&ing it to light. The switches Li -1 i I I WO 89/04030 PCT/US88/03517 8 SWI are in series with the resistor means 22 to cause the same effect as a blown fuse.

This obtains a fuse condition indicator with a minimal component count, with no expensive components such as thyristors and using AC to light the neon lamp 14.

According to one aspect of the invention, the fuse condition indicating device is packaged in a manner such that it can readily be installed into a conventional opening found in a control panel which houses the fuses and can be readily visible from outside the housing in viewing the control panel. Thus, as shown in FIG. 2, the packaging includes a housing 30 having a threaded collar 32 extending from a rear surface thereof intermediate upper and lower ends with the front surface 34 being formed of a non-metallic transparent, preferably colored material having the three phases A, B and C (FIG. 4) identified thereon. The indicator means 14 are respectively mounted on a printed circuit board 36 that fits in the housing so that the respective lights 14 mount behind the three raised letters indicating the phases A, B and C. Also, the resistors R4, R5 and R6 mount on the board 36 and connect between the respective circuits 12 and lights 14 through soldered connections on the printed board.

According to one further aspect of the invention, the respective switches SWl for WO 89/04030 PCT/US88/03517 9 the three phases of the circuits mount on the circu.it board 36 such that they can readily all be simultaneously actuated through the use of one actuator. Thus, as illustrated in FIGS. 6, 7 and 8, each switch consists of first and second copper-clad contacts 40 that are respectively located on opposite sides of a generally rectangular slot 42 formed in the board 36. A coil spring (FIG. 8) 44 mounts between the housing and circuit board 36 to bridge the respective copper-clad contacts when no external force is applied, thereby completing the circuit across the copper-clad contacts. Of course, the copper-clad contacts 40 are interconnected with the respective circuits 12 through leads 46 printed on the board 36.

The actuator for simultaneously actuating all three switches SWl is illustrated in FIG. 7 and includes a nonconducting member 50 that has a circular center button 52 extending from one surface and has three rectangular projections or prongs 54 extending from an opposite surface and adapted to be received into the respective slots 42. The circular button 52 extends through an opening 56 in the cover 34 and thus A all three switches can be simultaneously actuated by pushing a single button that is readily accessible. Depressing the button causes the three prongs to depress and move b WO 89/04030 PCT/US88/035 17 the springs 44 out of engagement with the contacts 40, opening the switches SW1.

According to one further aspect of the invention, all of the respective resistor means 18 and 22 for each of the circuits 12 are mounted on boards such that the leads of the resistors are not subjected to any tensile forces when pulling forces are applied to the leads. Thus, as illustrated in FIG. 3, each lead 16 includes a support board 60 which supports the respective resistors, such as resistors R1 and R2, and the leads of the respective resistors are connected to lead 16 through soldered connections on the board.

The board is then encapsulated with a heat shrinkable material 62 so that the resistors and connections are externally sealed by the non-conductive heat shrink material. The encapsulation also includes a rubber strip to prevent the solder connections from piercing the heat-shrunk material.

The indicating circuit is designed to be utilized with circuits of varying voltage and the following chart is exemplary of the resistances that are utilized for different voltage sources: Ref. Design. 240 Vac. 480 Vac. 600 Vac.

R1 82K 200K 240K R2 82K 200K 240K R3 15K 30K 36K R4 82K 270K 390K fuse, each of said first resistor means providing a substantially resistive load; WO 89/04030 PCT/US88/03517 11 82K 270K 390K R6 82K 270K 390K R7 15K 30K 36K With these values, the resistance of the first resistance means 18 is substantially greater than the resistance means 22 by about five times. The resistance of the third resistance means, resistors R4, R5 and R6, in series between the circuits 12 is substantially equal to the resistance of the first resistance means 18 and is substantially greater than the resistance of the second resistor means 22 by about five times.

While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying Claims. For example, the details of the resistances and other components can be varied while remaining within the scope of the Claims.

Claims (8)

1. 2. The device of claim i, in which the resistance of each of the first resistor means is greater 0 than five times the resistance of each of the 08 corresponding second resistor means.
2. 3. The device of claim i, in which the *0 :0 resistance of each of the third resistor means is substantially equal to the resistance of each of said corresponding first resistor means.
3. 4. The device of claim 1, in which the resistance of each of the third resistor means is substantially greater than the resistance of each of the 0*0000 S* corresponding second resistor means. 0000
4. 5. The device of claim i, in which the resistance of each of the third resistor means is greater S. than five times the resistance of each of the corresponding second resistance means.
5. 6. The device of claim i, including a switch having pairs of contacts, one pair associated with each of said phases of said polyphase electric circuit and connected between one of said second side of said indicator means and said corresponding second resistor means so that operating said switch opens all of said contacts to activate and test the operability of said plural indicator means.
6. 7. The fuse condition indicating device of claim 1 further comprising a housing, and said plural indicator means each includes an indicator light, said housing having a pair of leads leading from each of said indicator lights and respectively connected to the line and load leads of said corresponding fuse, plural manually actuated 44 U -14- switch means in said housing each connected in series with one of each of said leads, each of the other of said pair of leads having said corresponding first resistor means external of said housing with a corresponding first board supporting said corresponding first resistor means, said second resistor means in each of said one of said corresponding pair of leads externally of said housing with a corresponding second board supporting said second resistor means, and encapsulating means for encapsulating said corresponding first and second boards and said corresponding first and second resistor means.
7. 8. A fuse condition indicating device as defined in claim 7, further including a board in said housing supporting said indicator lights and said plural third resistor means.
8. 9. A fuse condition indicating device as defined in claim 8, in which each switch means includes first and second contacts respectively positioned on opposite sides of a slot with spring mana \normally bridging said slot, :o and a common actuator received into said slots for simultaneously compressing said spring means to open said 0* OS switch means. A fuse condition indicating device substantially as described herein with reference to the drawing. DATED this FIFTH day of MARCH 1991 Square D Company Patent Attorneys for the Applicant SPRUSON FERGUSON