US3281733A - Synchronous circuit breaker having a movable winding - Google Patents

Description

OC- 25 1966 o. JENSEN 3,281,733

SYNCHRONOUS CIRCUIT BREAKER HAVING A MOVABLE WINDING Oct. 25, 1966 o. JENSEN 3,281,733

SYNCHRONOUS CIRCUIT BREAKER HAVING A MOVABLE WINDING Filed oct. 13, 1964 5 sheets-sheet 2 Oct. 25, 1966 o. JENSEN 3,281,733

SYNCHRONOUS CIRCUIT BREAKER HAVING A MOVABLE WINDING Filed oct. 1s, 1964 5 sheets-sheet s Oct. 25, 1966 o. JENSEN 3,281,733

SYNCHRONOUS CIRCUIT BREAKER HAVING A MOVABLE WNDING Filed Oct. 13, 1964 5 Sheets-Sheet 4 lll Oct. 25, 1966 o. JENSEN 3,281,733

SYNCHRONOUS CIRCUIT BREAKER HAVING A MOVABLE WINDING Filed OOL. 13, 1964 5 Sheets-Sheet 5 MII, l @um United States Patent O 3,281,733 SYN CHRON UUS CIRCUIT BREAKER HAVING A MVABLE WIN DING Otto `Iensen, Malvern, Pa., assigner to ll-T-E Circuit Breaker Company, Philadelphia, Fa., a corporation of Pennsylvania Filed Oct. 13, 1964, Ser. No. 403,541 Claims. (El. 335-99) This invention relates to circuit breakers, and more specifically relates to a novel synchronous A.C. circuit breaker which interrupts a circuit immediately prior to or at a current zero and automatically recloses upon an unsuccessful interruption to again `attempt a subsequent current zero interruption operation.

It is well known that circuit breaker contacts should be separated while the current through the contacts is decaying toward zero and as close to zero current as possible. Under these conditions, only a small arc which is extinguished at current zero, or no larc at all, is formed and no contact erosion takes place.

The present invention is for a novel operating mechanism which generates a contact opening force just prior to current zero and generates a contact closing force in the event of an unsuccessful contact opening operation as evidenced by continued current flow after current zero.

More specifically, and in accordance with the invention, the operating mechanism includes a magnetic ilux generating circuit which generates a magnetic flux in phase with the current in the circuit to be interrupted. A movable coil is positioned in this magnetic circuit and a current is supplied to the coil which has a phase shift slightly greater than 90? with respect to the magnetic flux and the current to be interrupted. The interaction of this coil current and magnetic ux then generates a force upon the coil which slightly leads the current to be interrupted. Thus, a positive force appears on the Coil slightly prior to the time the current to be interrupted reaches zero. This coil is then connected to the contacts to interrupt the last mentioned current whereby the contacts will be moved toward an open circuit position just prior to current zero.

The force applied to the moving coil will reverse after about 90 of current conduction thereby to apply force to the coil in a negative and contact opening direction. Therefore, if the initial current interruption was unsuccessful, the contacts will be closed to await the next current zero time, and a new interruption will take place.

Accordingly, a primary object of this invention is to provide an operating mechanism for circuit breakers which operates at just prior to current zero.

Another object of this invention is to provide a novel synchronous A.C. circuit breaker mechanism which is operable to open a circuit just prior to current zero and quickly recloses the circuit in the event of an unsuccessful prior interruption.

A further object of this invention is to provide .a novel circuit breaker operating mechanism which decreases contact erosion.

Yet another object of this invention is to provide a novel high speed circuit breaker mechanism which operates with high speed and eliminates the need for special arc interruption equipment.

3,281,733- Patented Oct. 25, 1966 A further object of this invention is t0 provide a novel circuit breaker which is less expensive than presently available circuit breakers for a given operating duty.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURE l schematically illustrates the operating mechanism of the present invention.

FIGURE 2 shows the operating characteristics of the device of FIGURE 1 as a function of time.

FIGURE 3 shows a vector diagram of FIGURE 2.

FIGURE 4 is an exploded perspective diagram of the novel operating mechanism constructed in accordance with the present invention.

FIGURE 5 is a cross-sectional drawing of the mechanism of FIGURE 4 and is taken across lines 5 5 of FIGURE 6.

FIGURE 6 is a cross-sectional drawing of FIGURE 6 taken across the lines 6 6 in FIGURE 5.

FIGURE 7 is a detailed cross-sectional view of the movable coil of FIGURES 4, 5 and 6.

FIGURE 8 is a cross-sectional view of a detail of FIG- URES 4 and 5 showing the uSe of guide laminations in the magnet structure.

FIGURE 9 is a side plan view of another form which the movable coil could take.

FIGURE 10 is a cross-sectional drawing of FIGURE 9 taken across the lines 10-10 in FIGURE 9.

FIGURE l1 is an enlarged sectional view of FIGURES 9 and 10 to illustrate the bond between various components.

FIGURE 12 shows the combination of a spark gap and non-linear resistor with the main contacts of FIGURE l.

Referring first to FIGURE 1, I have schematically illustrated therein the principle of the present invention. Thus, a circuit conductor 20 which carries a current Ip is connected in series with a suitable contact means 21, a suitable fault sensing means 22 and is coupled to a magnet structure 23, as schematically illustrated, by winding 24. The magnet structure 23 has an air gap 25 therein, which carries a flux 4S caused by current Ip and in phase with current Ip. A suitable secondary winding means, shown las series windings 26 and 27, are then wound on magnet structure 23. A current Is is induced in said windings by flux qb. Windings 26 and 27 are then connected in series with a movable coil 28 located in air gap 25 and which passes the ilux qa. The movable coil 28 is then connected to contact means 2l, as indicated by the dotted line, and is oper-able to move the contact means 21 between a contact engaged and contact disengaged position depending on the direction of motion of coil 28. The fault sensor 22, which may be of any desired type, and which may be manually operable, is then connected to a suitable latch means for contact means 21 to be 4operated by coil 28 when the fault sensing means measures a predetermined condition in line 20.

The operation of the mechanism of FIGURE l -is best understood by reference Ito FIGURES 2 and 3. 'I'he cur- :rent Ip and iiux qa are shown in phase in curve 30 of FIGURE 2 and in the diagram of FIGURE 3. The flux g5 [induces a total voltage Es in windings 26 and `27 which theoretically flags flux p by 90. However, there is a voltage drop 1/zISR caused mainly by the resistance of windings 26 and 27 so that the act-ual driving voltage of the circuit in series with coi-l 12.8 is the voltage Es. rIhe reactance of coil 28 then causes the current Is (shown in dot-ted line 31 in FIGURE 2) to lag the voltage ES, as shown in FIGURE 3. Therefore, the current Is lags the current ID and ux by more than the theoretical 90. It is this additional phase 4shift between Ip and Is that gives rise to the results of the present invention.

As lis well known, the interaction of current Is in coil 28 land the llux through coil 28 gives rise to a force perpendicular to the interacting current and llux. It will be `seen later that coil 28 lis not circular so that a net force moving the coil yup or down is generated. This force is shown in FIGURE 2 as line 32 which encloses 1a shaded area and is posi-tive (in a ldirection to open contact means 121) when gb and Is are yboth either positive or negative, and is negative (in a directi-on to close contact means 21) when Is and qt are of opposite polarity. Thus, the force varies w-it-h twice lthe frequency of the current IS or ux qb. Moreover, and due to a phase shift of greater .than 90 4between current Is and linx g5, the negative closing torce magnitudes are higher than the positive opening force magnitudes.

In operation and assuming :that contact means 21 is closed and a fault causing lincreasing current Ip is measured by fau-lt sensor 22, the latch means of contact means 2.1 is released. The' current Is at this time will be negative so that the force `acting on coil 28 is negative thus holding .the cont-act means 2|1 engaged with high pressure. Some time after the fau-lt current has reached its peak Value and has .started to ldecay, the force `on coil 28 reverses and coil 28 will move to open the contacts just prior to zero cur-rent for current Ip. Thus, in FIGURE l it is seen that contact separation occurs 10" prior to c-urrent Zero for current Ip. Note that there has been a time delay in FIGURE y2 from the Zero force time to actual contact separation time. This time .delay is due to the inertia of the lmoving contact members and mechanical linkages and the lost motion which .is inevitable in such mechanical structures. By proper :selection of lost motion, mass, and force, the contact separation can be made to take place at high velocity at some predetermined time.

When contact separation occurs, an `arc will be estab- Ilished which will burn until :actual current zero is reached and the arc will extinguish. lf the movable contacts have sufficiently separated at this time, there will be no restrike and :the -current II, is successfully interrupted.

However, if a restrike should occur as due to late fault occurrence and Ithus an insuicien-t force pulse -d-urin-g the opening stroke, the force pulse will reverse and a negative torce pulse is applied to the contact means 21. The contact means 21, which is conducting through an arc, will therefore reclose with great force and will remain closed until the current Ip again `decays toward zero.

Clearly, with this type arrangement the arc energy will be reduced to just a few percent of the energy in a conventional breaker with random contact separation.

FIGURES 4-8 show a novel manner in which an operating mechanism can be built to car-ry out the operation schematically described Vin FIGURE 1. More specifically and as best shown in FIGURES 4 and 5, the magnet structure 23 of FIGURE 1 is formed of opposing .stacks 40 and 41 of -semicircular magnetic la-minations which are held together by suitable bolts or clamps such as bolts 42 and 43 for stack 40 and bolts 44 and 45 (FIGURE 5) for stack 41. The opposing lamination stacks may have interposed therein extending guide laminations such as laminations 46 through 50 in stack 40 (FIGURES 4 and 8), and opposing laminations such -as laminations 51 and `52 in stack 41 (FIGURE 8) which serve to guide a movable coil, as will be described later. g

The opposing lamination stacks 40 `and 41 dene upper an-d lower ,air Igaps 53 and `54 which each serve the purpose of gap 25 of FIGURE 1.

Each of .stacks 40 and 41 then receive semicircular bus conductors 56 and 57 respectively which constitute two halves of a slotted circular conductive bar and are in parallel with one another. Conductors 56 and 57 correspond to the winding -in line 20 of FIGURE 1 and serve tas a single turn primary winding for magnetic structures 40 and 411. Thus, in FIGURE 4 conductors 56 and 57 are electrical-ly connected from a first termina-l 58, through the fault sens-ing mechanism 22, to `a line terminal 59. At the other end conclue-tors 56 .and 57 are electrically connected to a suitable stationary contact 60. Stationary contact 60 cooperates with a movable contact 61 suitably carried on 'a pivotally mounted contact arm 62. The contact arm 62 is then connected to a second line terminal 63.

Each of the magnet structures 40 and 41 then receive secondary windings, equivalent to windings 26 and 27 of FIGURE `1 in their pole faces. Thus as .shown in FIG- URES 4 and 5, the upper portion .of stack 40 has two elongated slots 64 and 65 therein which receives the upper and lower sections 66 `and 67 of winding 68 (FIGURE 4). The opposite pole face in stack 41 has a similar winding having upper and lower sections 69 and 70 in sui-table slots, as shown in FIGURE 5. The two windings 68 and the winding having `sections 69 and 70 may then be connected in series relation. Note that any number of tiuns could be used.

The lower air 'gap 54 has a similar secondary winding arrangement in its pole faces, as shown by winding halves 71-72 in stack 40 and winding halves 73-74 in stack 41. Clearly, all of the secondary winding-s are connected in series with one another.

A movable winding `80, corresponding to Winding 28 of FIGURE 1, is then disposed in the air gaps 53 and 54. More specifically and as shown in FIGURES 4, 5 and 6, three pivot pins 81, 82 and y83 are lixed in opposing conductor halves 56 and 57. lPivot pins `811, 82 and 83 then carry double crank arms `84, 85 and 86. The upper ends of crank arms 814, 85 and I86 then externally pivotally receive operating rods 87 and 88 by a suit-able pin engagement arrangement.

Operating rods `87 and 88, as schematically shown by dotted lines in FIGURE 4, are then connected to movable contact 61. Alternatively and as shown in FIGURE 6, crank 84 can have an extending arm y89 which can be connected to the contact drive structure.

The movable coil is then disposed between the double crank arms 84, l and 86 and is secured thereto by suitable pivot pins, such as pins 90, -9-1 and 92 respectively, in the rightwardly extending portions of the cranks 84, 85 and 86. As shown in FIGURE 7, a suitable insulation washer, such as washer 93, can be embedded in the portion of winding 80 which receives pins 90, 91 and 92.

Movable coil .80* is shown to be a two turn structure in the drawings and is comprised of a multilayer construction including outer aluminum conductors and 101 which are bonded together in high strength insulated relation by a central epoxy layer 102 (FIGURE 7). Conductors 100 and 101 may be lof the order of 0.01 inch thick. The strength of the winding is further increased by a central leg section 103 (FIGURES 4 and 6) which has air gaps 104 and 105 in layers 100 and 1011 respectively to prevent a short circuiting turn. Similarly, the right-hand leg of winding 80 has air gaps 106 and 107 in conductors 100 and 101 respectively to prevent short circuiting.

In order to form a two turn device, a conductive rivet 108 (FIGURES 4, 6 and 7) connects aluminum conductors above gap 106 `and below gap 107. Thus, current ilow from winding sections 64-65, 69-70, 71-72 and 73- 74 is connected by suitable llexible conductors (not shown) to terminal 110 (FIGURE 4) of conductor 100. The current then flows around conductor 100 to rivet 108 and through to conductor 101. Thereafter current ows around conductor 101 to terminal 111 (FIGURE 4) and back to the other terminal of the driving windings.

The operation of the structure of FIGURES 4-8 is similar to that described for FIGURE 1 in FIGURES 2 and 3. Thus, when there is a fault, or some other signal requiring the contacts 60 and 61 to be opened at current zero, a latching mechanism is -opened to permit contact 61 to be moved solely by operating rods 87 and `88. The current iliow through conductors S6 and 57 causes a flux b in phase therewith to be set up in air gaps 53 and 54. This induces a voltage Es (FIGURE 3) in winding sections 64, 65 and 6944 which causes a current Is to fiow in the two turn winding 80.

When the breaker is closed, winding 80 will be in its lowest position, shown in the right-hand side of FIG- URE 6. The interaction of the curernt IS in winding 80 and the flux p in the air gaps 53 and 54 will then cause a force |on winding 80 which drives it upward to the position at the left-hand side of FIGURE 6 and in FIGURE 5. Note that this force is such that contact separation will occur just prior to current zero through contacts 60 and 61. The upward motion of winding 80 will cause cranks 84, `85 and 86 t-o rotate counterclockwise about pivot pins 8'1, 82 and 83 respectively, thus thrusting rods 87 and 88 to the right to cause the opening of contacts 60 and 61.

The reclosing operation due to failure to extinguish the arc is the same as described for FIGURE 1.

The construction of movable winding 80 is made as strong and as light Ias possible. This is required to obtain sufficient contact motion in the last 10 electrical degrees prior to cu-rrent zero and to withstand lthe recovery voltage across the contacts immediately after successful current interruption. Moreover, to keep the magnetizing current required to drive flux across gaps 53 and 54 as small as possible, these gaps must be narrow. Thus, the movable winding 80 must be very thin but with enough strength to withstand the bending forces created by the electromagnetic forces involved.

It will also be noted that at the end of the operating stroke the electromagnetic drive is no longer needed. Therefore, coil 80 can be moved yout of the air lgap with a substantial savings in material.

An alternate form for the movable winding 80 is shown in FIGURES 9, 10 and 11 wherein two magnesium plates 120 and 1211 serve as a support frame for a Itwo turn winding formed of aluminum conductors 122 and 123. More particularly, magnesium plates 120 and 121 may have a thickness of the order of 0.005 inch and are stamped t-o have aligned openings, such as openings 124, 125, 126 and 127 therein. The two plates are then secured to one another as by spot welding around their peripheries and at locations, such as locations 128-137 (FIGURE 9). Suitable bushings 138440 are then formed in the plates to receive pins y90, 91 and 92 (FIGURE 6). The main aluminum conductors `122 and 123, which may have a height of 0.250 inch and a thickness of 0.01 inch, are then placed in stamped peripheral depressions in plates 120 and 121 respectively and are secured therein as by an insulating epoxy adhesive. The conductors 122 and 123 are then suitably connected in series and used as described in FIGURES 4 through 8.

As a further feature ofthe invention, it has been found useful to combine a jump gap and non-linear circuit in parallel with the interrupter contacts of a synchronous circuit breaker. Thus, as shown in FIGURE 12, which shows a modifica-tion of the circuit of FIGURE 1, adds a spark gap 140 and a series resistor 141 in parallel with contact means 21. The resistor 141 is one of such nature that its resist-ance increases with temperature. Thus, the resistor is non-linear.

When the contact means 21 opens by the synchronous mechanism of FIGURE l, just before zero current in line 20, an arc of low intensity is established which extinguishes of itis own accord at the first current zero. It is however possible that the recovery voltage across opened contact means 21 will tend to reignite an arc after it extinguishes. In accordance with the `additional feature of FIGURE 12, the gap 140 is designed to have a lower rliashover voltage than the gap of contact means 21, so that flashover action will prefer the gap 140.

Resistor 141 in series with gap 140 will then conduct fault current. The resistor, whose resistance increases with temperature will then limit fault current and at the Ifirst voltage zero, the resistor current will reach zer-o. The recovery voltage now sinusoidal so that the arc gap 140 is extinguished without high recovery voltage.

It is to be noted that resistor 140 is fabricated of any material, such as pure iron wire, which has a positive temperature characteristic. lBy way of example, in a pure iron Wire, the resistivity will be of the order of 0.0048 at C. and increases approximately linearly to 0.18 at 850 C. From y850" C. to its melting point of 1500 C. it decreases from 0.18 to .0068.

As a typical example, a resistor can be made of 32 meters of 0.7 millimeter diameter pure iron wire. This resistor will have a cold value -of 10 ohms which within 1A cycle on a fault condition in a circuit of the type shown in FIGURE 12 will be heated to approximately 550 C. and increase in resistance to approximately 35 ohms whereupon the resistor current will be successfully limited and interrupted without excessive recovery voltage.

Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.

The embodiments of the invention in which an exclusive privilege Ior property is claimed are defined as follows:

1. A synchronous circuit breaker comprising a magnetic structure, an elongated air gap in said magnetic structure, a pair of cooperable contacts, a first winding wound on said magnetic structure and connected in series with said pair of cooperable contacts, operating means connected to one of said pair of cooperable contacts and movable for moving said pair of cooperable contacts into and out of engagement with one another, a second winding wound on said magnetic structure, and a third winding connected in series with said second winding; said second winding coupled to said third winding by the flux in said magnetic core, thereby to energize said third winding responsive to the current in said first winding; said third winding being positioned in said air gap and being in a plane substantially perpendicular to the magnetic flux across said -air gap; said third winding being movable in a direction perpendicular to the direction of the magnetic iiux `across said air gap at a predetermined time with respect to the phase of the current in said iirst winding; said third winding mechanically connected to said operating means; said first winding comprising rst and second parallel spaced elongated conductors; said magnetic structure comprising a first and second stack of magnetic disk sections and a slotted elongated conductor; said first and second stack of magnetic disk sections partially enclosing a respective half of said slotted elongated conductor; the opposing surfaces of said first and second stack of magnetic disk sections defining said air gap Aand being aligned with the space between said first and second elongated conductors.

2. The device substantially as set forth in claim 1 wherein said third winding is a thin rigid rectangular conductor elongated in the elongated direction of said elongated conductors.

3. The device substantially as set forth in claim 1 wherein said second winding is carried around the air gap defining the surface of said first stack of magnetic disk sections extending above said first elongated conductor.

4. The device `substantially as set forth in claim 2 which further includes guide surface means connected in the opposing air lgap defining surfaces of said first and second stacks of magnetic disk sections for guiding the motion of said ythird winding.

5. The device substantially as set forth in claim 1 wherein `said third Winding comprises `a first and second parallel frame of thin rectangular conductors, an insulation layer; said insula-tion layer being connected to opposing sides of said `thin rectangular conduct-ors; and connection means extending between said thin rectangular conductors for dening at least two electrical turns.

8 References Cited by the Examiner UNITED STATES PATENTS 2,546,818 3/1951 Curtis 317-11 3,215,796 11/1965 Leisi 200-91 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, IR., Assistant Examiner.

Claims (1)

1. A SYNCHRONOUS CIRCUIT BREAKER COMPRISING A MAGNETIC STRUCTURE, AN ELONGATED AIR GAS IN SAID MAGNETIC STRUCTURE, A PAIR OF COOPERABLE CONTACTS, A FIRST WINDING WOUND ON SAID MAGNETIC STRUCTURE AND CONNECTED IN SERIES WITH SAID PAIR OF COOPERABLE CONTACTS, OPERATING MEANS CONNECTED TO ONE OF SAID PAIR OF COOPERABLE CONTACTS AND MOVABLE FOR MOVING SAID PAIR OF COOPERABLE CONTACTS INTO AND OUT OF ENGAGEMENT WITH ONE ANOTHER, A SECOND WINDING WOUND ON SAID MAGNETIC STRUCTURE, AND A THIRD WINDING CONNECTED IN SEREIS WITH SAID SECOND WINDING; SAID SECOND WINDING COUPLED TO SAID THIRD WINDING BY THE FLUX IN SAID MAGNETIC CORE, THEREBY TO ENERGIZE SAID THIRD WINDING RESPONSIVE TO THE CURRENT IN SAID FIRST WINDING; AND THIRD WINDING BEING POSITIONED IN SAID AIR GAP AND BEING IN A PLANE SUBSTANTIALLY PERPENDICULAR TO THE MAGNETIC FLUX ACROSS SAID AIR GAP; SAID THIRD WINDING BEING MOVABLE IN A DIRECTION PERPENDICULAR TO THE DIRECTION OF THE MAGNETIC

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