US2913557A - Circuit interrupter - Google Patents

Description

Nov, 1?, i959 B. IMMEL ETAL K9115 5517 CIRCUIT INTERRUPTER Filed Oct. 22, 1956 5 $heets-Sheet w. G 3 9 B 0 4 N I 2, Ma 2 2 3 3 w b u w m m H all M5 3 w l 3 Z a ijjjj P.W a

INVENTORS Ralph B. Imm Marshal ATTORNEY wn'uesssk Dav WM Ea EMM EZL ET AL Nov. 17, 1959 v CIRCUIT INTERRUPTER 5 Sheets-Sheet 2 Filed Oct, 22, 1956 NW. 17, i59

R. B. IMMEL ETAL CIRCUIT INTERRUPTER Filed 00%. 1956 I Sec.

m Arcing Time (60 Cycles Fig. 5.

3 Sheets-$heet 3 United States Patent CIRCUIT INTERRUPTER Ralph B. Immel, Williamsville, and Marshall P. White,

Cheektowaga, N.Y., assig'nors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 22', 1956, Serial No. 611,448 Claims. or. 200-147 Our invention relates, generally, to electric circuit interrupters and, more particularly, to interrupters of the type commonly known as contactors.

Practically all commercially available D.C. contactors utilize wire or strap wound blowout coil assemblies for providing a magnetic field for lengthening the are drawn when a circuit is interrupted. A blowout structure of the prior type usually requires a large number of auxiliary parts such as iron cores, insulating tubes and washers, iron plates, etc. These parts require considerable space and increase the cost of the device. Blowout coils are often the source of the greatest amount of heat in a contactor and they may cause overheating. They also require insulation and clearance to parts of different polarity.

Prior contactors have usually been of the single-break type and required a flexible connection between the moving contact member and the fixed contact member. Woven shunts have been generally utilized for the flexible connections. These shunts have often become a major source of trouble. The shunts have also been difficult to insulate from the contactor frame.

An object of our invention, generally stated, is to provide an improved interrupting device which is small in size, efiicient in operation, and which may be economically manufactured and installed.

A more specific object of our invention is to provide an interrupting device which may be utilized in either A.C. or D.C. circuits.

Another object of our invention is to provide a contactor of the double-break type which is not aifected by the polarity or direction of current flow through the contact members.

A further object of our invention is to provide an interrupting device having a single-piece insulating member for enclosing the circuit interrupting members of the device.

Still another object of our invention is to provide a contactor having improved interrupting characteristics, particularly for low currents associated with highly inductive loads.

A still further object of our invention is to provide a contactor which does not require the utilization of blowout coils and their associated parts.

Other objects of our invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of our invention, a vertically movable double-break contact assembly is disposed in a single-piece insulating base having arc chambers therein which are identical in shape and dimensions. A permanent magnet, preferably of a ceramic type, is disposed in a pocket in the base between the stationary contact members. The magnet creates a constant magnetic field which causes the arcs drawn between the two sets of contact members to move in opposite directions. When the polarity of the current or the magnet is reversed, the directions of the arcs are reversed.

Patented Nov. 17, 1959 Since the arc chambers are identical, the interruption is the same for either polarity. Therefore, the contactor can be utilized in either A.C. or DC. circuits.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view, partly in front elevation and partly in section, of a contactor embodying the principal features of the invention;

Fig. 2 is a view, in section, of the contactor shown in Fig. 1;

Fig. 3 is a view, in perspective, of the interrupting device for the contactor, portions being broken away for clearness;

Fig. 4 is a diagrammatic view illustrating the principles of operation of the interrupting device, and

Fig. 5 is a set of curves illustrating the interrupting characteristics of the present device as compared with prior devices.

The structure shown in the present drawings is an improvement over the interrupting device described in a copending application of R. B. Immel et al., Serial No. 463,912, filed October 22, 1954, now Patent No. 2,875,303, issued February 24, 1959. The interrupting device disclosed in the aforesaid application had horizontally mounted arc horns and required both an arc box and a base to enclose the interrupting members. The present structure requires only one ceramic or cold molded insulating member for supporting and enclosing the stationary contact members and are horns. Furthermore, the circuit interrupting characteristics are considerably improved by mounting the arc horns vertically and providing identical arcing chambers as will be described more fully hereinafter.

As shown in Fig. 3, a one-piece base or are box 10 is provided with two identical arc chambers 11 and 12 each of which contains a vertically disposed conductor or are horn therein. A conductor or arc horn 13 is mounted in the arc chamber 11 and an identical conductor or are horn 14 is mounted in the arc chamber 12. As previously stated, the arc box 11 may be molded from a ceramic or other suitable insulating material.

As shown in Figs. 1 and 2, the arc box may be mounted on a supporting panel 15 by means of two bolts 16 which extend from the front of the arc box through the box into the panel 15. The conductors 13 and 14 may be retained in the arc box by means of bolts 17.

As shown in Fig. 4, each conductor 13 and 14 has a stationary contact member or portion 18 secured to the lower end of the conductor. The conductor 13 has an integrally formed terminal portion 21 which is offset from the vertical portion of the conductor and extends above the top of the base 10 for making an electrical connection thereto. Likewise, the identical conductor 14 has a similar terminal portion 22 for making an electrical connection. As shown, the arc chambers 11 and 12 are opened at the top, thereby permitting gases to escape from the top of the chambers.

As shown most clearly in Figs. 2 and 4, a generally U-shaped bridging member 23 has two contact members or portions 19 secured thereto for engaging the spaced stationary contact members 1 8. The bridging member 23 is slidably disposed in a generally U-shaped yoke 24. As shown, the sides of the bridging member 23 are notched at 25 for receiving the legs of the yoke 24. The upper ends of the legs of the yoke 24 have inwardly extending portions 26 for retaining the bridging member 23 in the yoke. A spring 27 is disposed between the base of the bridging member 23 and the base of the yoke 24 to maintain a predetermined contact pressure between the contact members 18 and 19 when they are closed.

As shown in Figs. 1 and2, the yoke 24 is attached to an insulating carrier or cross bar 23 by means of a screw 29. The carrier 28 is moved vertically to engage the contact members 19 with the stationary contact members 18 by means of an electromagnetic device 31.

As shown in Fig. 2, the insulating carrier 28 is attached to a bolt 32 by means of a bracket 33. The bolt 32 extends through a fixed portion 34 of a solenoid core and is attached to a movable portion 35 of the solenoid core. A cup-shaped insulating member 30 is disposed between the screw 29 and the head of the bolt 32.

A coil 36, which surrounds the core of the solenoid, may be energized to cause the electromagnetic device to raise the carrier 28 and the bridging member 23. When the coil 36 is deenergized, a kickout spring 37 assists gravity in lowering the cross bar 28 and separating the contact members 18 and 19. As shown, the spring 37 is disposed between a guide washer 38 for the core 35 in the base of the electromagnetic device 31 and a washer 39 attached to the core 35 by the bolt 32. Thus, the spring 37 is compressed when the coil 36 is energized to move the core 35 upwardly.

As shown more clearly in Figs. 2 and 3, a permanent magnet 41 is disposed in a separate compartment 42 in the base or are box 10. The magnet 41 is located between the conductors 13 and 14 and extends below the stationary contact members 18. Thus, the bridging member 23 straddles the magnet 41 when the contact members are closed. The magnet 41 is preferably of a ceramic type, for example one composed of a magnetic mixed oxide compound having the formula BaO.6Fe O The magnet 41 may be composed of any suitable magnetic material, but, the ceramic material is preferable because of its lower cost, resistance to demagnetization and high electrical resistivity.

The basic principles of the arc interrupting device are illustrated in Fig. 4. Assuming that the magnet 41 is disposed in the arc chamber with its polarity as indicated by the letter N, the magnetic field set up by the magnet is illustrated by the broken lines and arrows. Also, as suming that the instantaneous alternating current or direct current flow through the conductors 21 and 22 and the bridging member 23 is as shown by the arrows, an are drawn between the front contact members 18 and 19 is moved to the left and upwardly along the arc horn 13 because of the magnetic field and the thermal rise of the hot gases. An are drawn between the rear contact members 18 and 19 will move to the right and upwardly along the arc horn 14 because of the same forces.

The arcs move in arcing chambers which are identical in both size and shape. As shown in Fig. l, the conductor 13 is disposed midway between the sidewalls of the arc chamber 11. Furthermore, the sides of the arc chamber are symmetrical in size and shape. Likewise, the conductor 14 is disposed midway between sidewalls of the arc chamber 12. As previously stated, the chambers 11 and 12 are identical in shape and dimensions.

When either the magnetic =field or the terminal polarity is reversed, the arc drawn between the front contact members 18 and 19 will move to the right and the rear arc will move to the left. If both the magnetic field and the terminal polarity are reversed, there will be no change in the arc movement. Therefore, the present device will operate satisfactorily no matter how the magnet 41 is placed in the structure with respect to its polarity or to which polarity the terminals 21 and 22 are connected. Accordingly, the present device can be used on either alternating current or direct current circuits. Since identical arcing chambers are provided on both sides of the stationary conductors and contact members, there are no differences in. he interrupting characteristies for either AC. or D.C.

4. Furthermore, the interrupting characteristics are greatly improved over those of prior devices. The blowout field of prior contactors having series wire or strap wound blowout coils varies directly with the current. With low currents and highly inductive loads, the current interruption is poor. With the constant magnetic blowout field provided by the permanent magnet in the present device low currents associated with highly inductive loads have been satisfactorily interrupted. The present device does not require conducting plates or pole pieces in addition to the magnet 41 as the leakage of the magnet is effective in extinguishing the arcs.

The difference between the operating characteristics of the old devices and the present device is illustrated by the curves shown in Fig. 5 in which arcing time is plotted against current. Curve 1 illustrates the characteristics of the present device and curves 2 and 3 illustrate the characteristics of two prior devices having different current ratings and a different number of turns in their blowout coils. From curve 1 it will be seen that the interrupting time of the present device decreases with the current. From curves 2 and 3 it will be seen' that the interrupting time of the prior devices increases as the current decreases so that the arc hangs on and is not extinguished at low values of current.

As shown in Fig. 1, auxiliary contact members 45 and 46 may be mounted on the cross bar 28 to engaged fixed contact members 47 and 49, respectively, when the cross bar is actuated to actuate the main contact members of the contactor. The auxiliary contact members 45 may be of the normally open type and the contact members 46 may be of the normally closed type. Thus, the auxiliary contact members are operated in conjunction with the main contact members, and they may be utilized in control or indicating circuits in a manner well known in the art.

From the foregoing description, it is apparent that we have provided an interrupting device which has excellent arc interrupting characteristics. The present device is relatively small in size and of a simple and rugged construction. Therefore, it is suitable for utilization in electromagnetic contactors which are requlred to function under severe operating conditions. Furthermore, the present device may be manufactured at a relatively low cost.

Since numerous changes may described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit interrupter comprising a single-piece insulating member having two are chambers therein, each chamber being open at the top and having totally enclosing side walls, a single stationary contact member in each arc chamber, a combined terminal and are horn for the contact member in each arc chamber, a permanent magnet disposed between said contact members, a bridging conducting member having a contact member thereon for engaging each stationary contact member, electromagnetic means for raising said bridging member to engage the contact members thereon with said stationary contact members, and spring means for lowering the bridging member to disengage said contact members and draw arcs between the contact members, said magnet causing an arc to travel up one side of each arc horn during one polarity of the arc current and up the opposite side of the arc horn during another polarity of the arc current.

2. In an interrupting device, in combination, an insulating arc boX having two are chambers therein, said arc chambers being open at the top and identical in shape and dimensions, only one elongated vertically dis be made in the above posed conductor in each arc chamber and extending through the open top of the chamber, said conductors being identical in shape and dimensions, each conductor being equidistant from opposite sides of its chamber, a stationary contact member on the lower end of each conductor, a pennament magnet disposed in a separate compartment in said insulating member between said conductors, and a vertically movable bridging conducting member having a contact member thereon for engaging each stationary contact member.

3. In an interrupting device, in combination, an insulating arc box having two are chambers therein, said arc chambers being substantially identical in shape and dimensions and open at the top, only one elongated conductor vertically disposed in each chamber equidistant from opposite sides of the chamber, each conductor having an integrally formed terminal portion offset laterally from the upper end of the conductor and extending above the top of the insulating member, a stationary contact member secured on the lower end of each conductor, a permanent magnet disposed in a separate compartment in said insulating member between said conductors, and a vertically movable conducting member having spaced contact members thereon for engaging said stationary contact members.

4. In an arc interrupting device, in combination, an arc box having at least two are chambers therein, said are chambers being substantially identical in shape and dimensions, only one elongated generally flat conductor vertically disposed in each chamber equidistant from opposite sides of the chamber, a stationary contact portion at the lower end of each conductor, a movable contact member separable from each stationary contact portion to draw an arc therebetween, and permanent magnet means for producing a magnetic field which moves the arc to a position where one end of the arc travels upwardly along one side of said conductor during one polarity of the arc current and along the opposite side of the conductor during another polarity of the are current.

5. In an interrupting device, in combination, a singlepiece molded insulating member having two are chambers therein, said are chambers being substantially identical in shape and dimensions, each chamber being open at the top and having totally enclosing side walls, only one elongated conductor having opposite sides vertically disposed in each chamber equidistant from opposite sides of the chamber, a stationary contact member secured on the lower end of each conductor, a permanent magnet disposed in a separate compartment in said insulating member between said conductors, and a vertically reciprocable conducting member having spaced contact members thereon for engaging and disengaging said stationary contact members, said magnet causing arcs drawn in said are chambers to change sides on said conductors with a reversal of the polarity of the arc current.

References Cited in the file of this patent UNITED STATES PATENTS (2nd addition to 981,687)

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