US1675680A - Magnetic thermal relay - Google Patents

Description

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VY. A Y WM Mm H H. E. WHITE MAGNETIC THERMAL RELAY Filed-Jan. 27, 1925 f i l 1 .36 34 32 29 Z8 a/ as wlNx-:ssss:

Patented July 3, 1928.

UNITED STATES PATENT OFFICE.`

HAROLD E. WHITE, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

MAGNETIC THERMAL RELAY.

Application led January 27, 1925.

My invention relates to electrical protective devices and particularly to thermal relays.

One object of my invention is to provide a thermal relay that shall have relatively few parts and that shall be easily and quickly assembled.

Another object of my invention is to provide a thermal relay that shall embody mag- Iletic means for permitting of easily and quickly varying the time of the operation thereof. i

In practicing my invention, I provide an electromagnetic switch having a core member that normally operatively engages a normally magnetic current-conducting member that is of variable area in lateral cross-section. By moving the current-conducting member laterally of the core, the amount of material thereof that is subjected to the action of the magnetic eld of the core member is varied. i

In a modified form of device, the current conducting member is of helical spring form and the distance between the adjacent turns thereof may be varied to vary the amount of material of the current-conducting member subjected to the action of the magnetic Afield of the core and the current conducting member.

In the single sheet of drawings,

Figure 1 is a view, partially in front elevation and partially in section, of a device embodying my invention with its associated electrical supply and control circuits` Fig. 2 is a view partially in front eleva# tion and partially in section, of a device embodying my invention, a modified form of current conducting member being employed with associated supply and control circuits, and v Fig. 3 is a sectional view of a portion of the device shown in Fig. 2.

Referring more particularly to Fig. 1 of the drawing, 'a thermal relay 11 comprises a supporting plate 12 of electric-insulating material upon which is mounted a winding 13 that may be covered by electric-insulating material 14 to protect the winding. A magnetizable core member 15 is mounted within the winding 13 and has vertical movement relatively thereto.

A rod 16 is secured to the upper end of the core member 15 and the upper endthere- Serial No. 5,064.

of moves in a bearing member 17 that is mounted on the front surface of the plate 12. A plurality .of collar members 18 and 1 9 are mounted on the rod 16 in spaced relation relatively to each other and a collar member 21 is loosely mounted on the rod 16 intermediate the members 18 and 19.

Springs 22 and 23 are mounted on the rod 1 and extend between the collars 18 and 21 and 21 and 19, respectively, in order to provide a resilient mounting for the collar 21, and a contact bridging member 24 that is secured to the collar 21. The contact bridging member 24 is adapted to engage fixed terminal posts 25 and 26 that are mounted on the front surface of the plate 12.

A current conducting member 27 is adjustably mounted on the front surface of the plate 12 above the lower edge thereof and in position to be normally operatively engaged by the magnetizable core member 15. The member 27 may be constituted by a bar of square or ot' rectangular shape in lateral section depending uponthe amount of cur? rent which it is to carry.

The bar 27 is'provided with an angular recess 28 at one of its sides, which recess is so located as to be on the side away from the core member 15. The eleet of the recess is to vary the areatraversed by the current for a portion of the length of the member 27. Two bearing members 29 and 31 are provided to hold the member 27 in its proper operative position laterally thereof and the form and construction of these bearing members may be of any suitable ordesired type effective for the purpose desired.

The member 27 is provided with a pair of longitudinally-extending slots 32 and 33 therein through which extend fixed studs 34e and 35. The studs 31 and 35 are fixed in the plate 12 and nuts 36 and 37 are located thereon against the outer surface of the member 27 whereby'the member 27 may be securely clamped against the plate 12 to prevent movement thereof longitudinally and whereby, further, the position of the member 27 laterally of the core member 15 may be varied as will be hereinafter -set forth in detail.

, The member 27 is made of a suitable normally magnetic material, such as invar steel, which is an allo of iron and nickel and has the property o losing its magnetism at a predetermined elevated temperature. Such material is usually said to be magnetically reversible.

An energy translating device 38, here represented as a motor, or which may be constituted by a generator, a transformer or an electric heating element is adapted to be energized from a pair of supply circuit conductors 39 and 41 through a circuit breaker 42 which is here illustrated as of the electromagnetic type in order to permit of it being suitably controlled by the thermal relay 11.

The circuit breaker 42 comprises, besides the usual lixed and movable contact members, a holding coil 48, a core member 44 energized thereby and connected to the movable contact members, together with a spring member 45, that is adapted to open the cirf,

cuit when the winding 43 has been de-energized. The winding 43 is connected in lseries circuit relation to the contact members 25 and 26 and the contact bridging member 24 and across the supply circuit conductors 39 and 41.

The Winding 13 is here illustrated as comprising a relatively large number o'f turns of high resistance wire in order to permit of its being connected across the supply circuit conductors 39 and 41, as by conductors 46 and 47.

Referring more particularly to Fig. 2 of the drawings, a modified form of current conducting member is there illustrated in combination with other partsof a thermal relay, such as has been described in connection with Fig. 1 of the drawings.

A thermal relay 48, differing only from the relay 11 in the construction and mounting of a current conducting member 49, here shown as a helically wound strip, rod, bar or Wire of invar'steel. One end of the member 49 is connected to a short stud 51 that projects through an opening in a supporting member 52, of substantially L-shape, that is secured against the front surfaceof the plate 12 by means of a stud 53 and a nut 54. A nut 55 is provided on the member 51 ateach side of the support 52, to hold it in proper operative position relatively to the support. The other end of the member 49 is connected to an exteriorly threaded stud 5'6 that extends through an opening 57 in a bearing and supporting member 58, of substantially L-shape. The member 58 is secured against the surface of the plate 12 by a bolt or stud 59 and a nut 61. An adjusting nut 62 is located on the outer end of the member '56 and suitable provision is made to prevent a turning movement of the rod member 5 6 relatively to its support 58 as by a-slot or groove 63 extending longitudinally of the member 56, that has an integral vportion of the member 58, extending thereinto.

Referring more particularly to the construction illustrated in Fig. 1 of the drawing, the current traversing the Venergy translating device 38 traverses also the current conducting member 27 and the lateral dimensions of the current conducting member are selected in accordance with the value of this current. lt is evident that if a relatively heavy current be caused to traverse the member 27 for a sutlicient length of time, the member 27 will be heated and the temperature of that portion thereof that is of reduced section by reason of the-recess 28, will be heated to a higher'temperature than the other portionsthereof and the magnetic properties thereof Will be lost at a predetermined temperature depending upon the com-` positionof the material, in a manner well known in the art. It is further evident that that portion of the current-conducting member that has the least area in cross-section, will reach this critical temperature before the other parts, thereof. y l

During the normal operation of the device, When the parts are in the positions illustrated in F ig. l of the drawings, the Winding 13 is energized and tends to move the core member 15 upwardly and away from the normally magnetic current-conducting member 27, but such movement is prevented by reason of the fact 'that the member 27 acts as an armature or keeper for the core member and restrains it from any upward movement, or in other Words, the member 15 and the member 27 are differentially associated.

The member 27 is heated not only by the current traversing the same, but also by the eddy currents generated therein, caused by the alternating current flux traversing the same and the core member 15 in case alternating current is employed. However, the current-conducting member is heated only by the current traversing the same, Where direct current .is employed.

If it be assumed that the current conducting member 27 has been moved to the left, so that the minimum area of cross-section of the member is below the core member 15`and in contact therewith, and if this portion is heated to such temperature as to lose its magnetic properties, it is evident that the core lmember 15 will be moved upwardly-through the action of field generated by the current traversing the winding 13, `whereby the contact bridging member 24 is disengaged from the contactmembers 25 and 26 and the circuit through t-he holding coil 43 of the breaker 42 is interrupted. This permits the spring 45 to function to move the contact arms to the right and to interrupt the circuit through the energy translating device 38 and through the current conducting member 27.

When the current has been interrupted for a suiicient length of time to permit of the member 27 cooling tosuch temperature as will restore its normal magnetic property,

the core member 15 Will be again attracted towards the current conducting member and caused to operatively engage the same whereby a circuit is again established through the holding coil'43 and the energy translating deviceis again energized. i

The springs 22 and 23 serve to cushion the engagement of the contact bridging member with the contact members, thereby insuring a longer life of the device. Y

It' it is desired to employ a thermal relay of the type disclosed in Fig. 1, to control the energization of the energytranslating device having a high currentl rate, it is only neces sary to move the member 27'. in such direction that a larger amount of magnetic material is directly under the core 15, whereby, as hereinbefore stated, the temperature at which that portion of the current-conducting member 27, subjected directly to the influence of the magnetic field of the core member, is increased. 4

A greater current is necessary or the same current must traverse the current-conducting member for a longer period of time in order to result in that portion of the current-com ducting member operatively engaged by the.

core member reaching a suliiciently high temperature to become non-magnetic to permitv the core member to be released therefrom.

Referring to Fig. 2, the method of varying the amount of material directly subjected to the influence of the magnetic field traversing the core member 15 and the current conducting member 49, differs slightly from that de scribed in that it is only necessary to increase the distance between the adjacent turns of the member 49 to reduce the amount of ma- 'terial that is subjected to the action of the magnetic ield traversing the core member 15.

This action not only reduces the 'amountA of material that is subjected to magnetic action,but also increases the ventilation, and both of these aiect the value of the current at which the core member 15 will be disengaged from the current conducting member 49. A barrier 64 may be provided immediately below the current conducting member 49 and the core member 15, which may also be varied as to its position and as to its width in order to permit of calibrating the thermal relay for a range of current values or for adjusting the same for this range of current values, as may be desired in connection with the use of such thermal relays with energy translating devices of different eapacities.

The device embodying my invention thus provides a relatively simple electromagnetic switch device dependent for its action upon the loss of magnetic properties of a normally magnetic current conducting member that may be adjusted to vary the exact value of the current at which the device will operate vor the time required for the device to oper- Various modilications and changes .may-

be made without departing from the spirit and scope of the invention, and I desire therefore that only such limitations shall be placed thereon as are imposed by the prior art.

I claim as my invention:

1. A thermal relay comprising an energizing winding, a magnetizable core member therefor, contact members controlled by the movement of said core member, a normally magnetic member, and means for permittin of varying the amount of material of said normally magnetic member that is subjected to the action of the magnetic lield of said core member and Winding.

2. A thermal relay comprising an energizing winding, a magnetizable core member therefor, contact members controlled by the movement of said core member, a normally magnetic, current-conducting member operatively engaged by said core member, and means for varying the ratio of area of 'that portion of the current-path directly subjected to the influence of the magnetic' field of the core member to the radiating surface thereof.

3. In a thermal relay, the combination with an electromagnetic switch having a movable core member, of a normally magnetic-member normally operatively engaged by said core member, and means for permitting of varying the amount of material of said normally magnetic member.that is subjected to the action of the magnetic lield of said core member and winding.

4. In a thermal relay, the combinatio with an electromagnetic switch having a movable core member, of a normally magnetic current-conducting member normally operatively engaged by said core member, and adjustable laterally of said core member to effect a variation in the operation thereof.

5. In a thermal relay, the combination with an electromagnetic switch having a movable core member, of a normally magnetic currentconducting member normally operatively engaged by saidcore member, and means for permitting of moving said current-conducting member laterally of Said coremember to vary the amount of material thereof that is subjected to the action of the magnetic field of said core member and winding. l

6. An electrical protective device comprisible member, a movable magnetizable memher differentially associated therewith, and means for altering the effect of the current on said movable magnetizable member, said magnetically reversible member being rendered nonemagnetic at a predetermined current value.

7. In combination, a coil, a movable core therefor, and a current-traversed magnetically reversible member for normally engaging said core, said magnetically reversible member having a portion the currentconducting area of which varies from one point to another.

8. In combination, a coil, a movable core therefor, and a current-traversed magnetically reversible member for normally engaging said core, said magnetically reversible member having portions of minimum and maximum current-conducting areas and an intervening portlon the current-conducting area of which increases gradually from the portions of minimum area to maximum4 area of which varies from one'point to an other, and means for adjusting the position of the point of contact between said portion and said core.

In testimony whereof, I have hereunto subscribed my name this 21st day of January, 1925. Y

HAROLD E. WHITE.

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