US2138275A - Apparatus for effecting simultaneous functioning of a plurality of alternating current electromagnets - Google Patents

Description

Nov. 29, 1938. K. HEINRICH- 2,138,275 APPARATUS FOR EFFECTING SIMULTANEOUS FUNCTIONING OF A PLURALITY OF ALTERNATING CURRENT ELECTROMAGNETS Filed June 7, 1957 QB @fQfi QEIQI Egg El w ww hww Lgw w /5 l3 9 vi /0 /0 K027227577 EL /27mm Patented Nov. 29, 1938 UNITED STATES PATENT OFFICE APPARATUS, vFOR ,EFFECTING SIMULIA- NEOUS FUNCTIONING OF A PLURALITY F ALTERNATIN G CURRENT ELECTROMAG- NETS Konrad Heinrich,'Milwaukee, wis assignor to Allen-Bradley Company, Milwaukee, '13., a corporation of Wisconsin Application June 7, 1937, Serial No. 146,770

8 Claims.

rality of switches, or simultaneous functioning of a number of instrumentalities.

There are many instances where a number of magnetically actuated instrumentalities, especially switches, must be operated at the same time. One such instance is where'the generally available commercial electromagnetic switches I do not have a sufficiently high rating to take, care,

of a particular load. To illustrate, a one hundred ampere switch may be the largest standard switch manufactured so that where the load to be switched is one hundred and seventy-five amperes, two one hundred ampere switches might be employed with their contacts in parallel, in place of a larger and "possibly special switch if simultaneous opening and closing could be assured.

Also, two or more switches, or other magnetically actuated instrumentalities, .all controlling or working together in a single machine may be required to operate simultaneously as in a conveying mechanism driven by two or more motors.

Another instance where simultaneous opening and closing of a number of switches is desirable .is where a multiple contact switch, such as a five pole switch, is advisedly replaced by a two and a three pole -switch, five pole switches being considered special and generally not standard manufacture.v

For controlling excessively large motors, which are usually of the multiple phase type, and where the rated amperageiis in exc'ess of that capable of being handled by the regular or standard three pole switches, it would be desirable to use separate magnetic switches for' the three lines of the motor. Obviously, such switches would have to close simultaneously and open at the same time.

If one switch would drop out while the others remained closed, the motor would continue'to run on single phase, which is highlyundesirable and dangerous in view of the excessive currentv increase drawn by a loaded motor.

In all of the instances noted, it will be seen i that not only is it desirable to have simultaneous closure of all of the switches, which means simultaneous-response'of the armatures of all of their electromagnets, but that it is also essential to have all of the switches open at the same time. Heretofore, when simultaneous closure of a number of switches was desired, a parallel connection of their cells was used. This was satisfactory provided no switch coil burned out or became open circuited, as an open circuit in one switch coil prevents its switch from operating while the other switches of the group continue .to open and close with the opening and, closing of the pilot circuit. This condition is obviously objectionable.

When one switch coil becomes open circuited, all switch coils in the particular group should be rendered inoperative. Consequently, to connect the operating coils of'such switches in parallel does not suflice.

.Series connection of the operating coils of the switches theoretically provides a complete .answer to the problem for the coils would all .be energized simultaneously and deenergized at the same time, and if an open circuit occurred in any one switch coil, all switches in the group would be rendered inoperative. j However, :the many variable factors of electromagnetic switches have in the past inhibited series ponnection of the operating coils. These variable factors have a di-v rect bearing on the reluctance of the magnetic circuits of the electromagnets and thus influence the pulling power of the magnets. Perhaps the most important of these, inevitable differences resides in the friction existing between moving parts. The armature having the least friction will usually start to close first thereby immediately causing a difierencein the flux at the several electromagnets due to the difierence in the reluctance of their electromagnetic circuits.

The closure of a switch by the attraction of an armature. to an electromagnet or the performance of any other work by such motion of the armature, requires a predeterminedmagnetic flux, and where the same amount of .work is to be done by all of the electromagnets, this flux must be equal at all of them.

However, as the reluctance of a magnetic circuit is as much a factor in determining the flux as the ampere-turns of the electromagnet' producing the magnetic circuit, the inevitable difierences in reluctance of the magneticcircuits of two or more electromagnets will result in unequal flux at the several electromagnets where their coils are connected in series and the same amperone switch to close ahead of the other, and in some instances, might even result in complete failure of the second or other switches to close.

This invention therefore "contemplates as one of its objects to provide means whereby this state of unbalance resulting from differences in the variable factors of electromagnets, and especially diflerences in reluctance, is. corrected thereby allowing the operating coils of a number of electrcmagnets to be connected in series.

Stated another way, an object of this invention resides in the provision of means in association with a plurality of electromagnets having their operating coils connected in series for effecting an equalization of magnetic flux at the several magnets to insure simultaneous response of their armatures.

It is also an object of this invention to provide means for the purpose described which does not entail altering the present accepted design of alternating current magnetic switches and does not appreciably increase the cost thereof.

A further object of this invention resides inthe provision of means for assuring the simultaneous closure of two or more electromagnetic switches whose operating coils are connected in series, even where the switches are of diflerent sizes and have differently rated capacities.

with the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as,

hereinafter described, and more particularly defined by the appended. claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of 'the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a diagrammatic view illustrating three electromagnetic switches having their operating coils connected in series, and illustrating the application of this invention thereto;

Figure 2 is a diagrammatic view similar to Figure 1, illustrating'another application of this invention; and

Figure 3 is a diagrammatic representation of two electromagnets to illustrate-the theory of this invention.

Referring now particularly to the accompanying drawing in which like numerals indicate like parts, the numerals 8, 8 and 'l designate three electromagnetieally actuated switches of the solenoid type, all of which have the same rating.

In each instance, three setsgof stationary contacts 8, and three sets of cooperating movable contacts 9 are provided; Inasmuch as one contact of each set is disposedbehin'd the other, only the forward one of each set has been illustrated. The movable' contacts of each switch.

same rating, viz., one hundred amperes.

the three magnets are series connected with a suitable source of alternating current by a conductor l5.

As pointed out hereinbefore, the mere connection of the operating coils of two or more electromagnets in series theoretically should result in simultaneous response of their armatures, but in practice there are so many variable factors affecting the operation of the electromagnet that this desirable condition heretofore could never be attained. The most common of these many variable factors affecting the operation of the electromagnets is found in the differences in reluctance of the magnetic circuits caused especially by differences in the air gaps.

Where the air gap is large, the reluctance of the magnetic circuit naturally is considerably higher than where it is small, and as the ampere-turns are alike in all of the electromagnets, (their coils being similar and connected in series), the one with the smallest air gap will have the highest initial flux. Hence, its armature will be moved rapidly while those of the other electromagnets will movemore slowly, and inasmuch as the increasing inductance of the first designated electromagnet cuts down the amperage of the current flowing in the magnet coils, the ampere-turns are correspondingly lowered. The resultant loss in magnetic eifort at the electromagnets whose armatures have not "gone home thus slows up and may entirely prevent their closures.

This objectionable condition is entirely overcome with the present invention.

To this end, a secondary winding 16 is arranged inductively to each of the operating coils l4, and all of the secondary windings ii are electrically connected by conductors I1. Where the switches are of the same rated capacity, as in Figure 1, all of the secondary windings are alike,

that is, they are wound with the same size wire and have the same number of turns for magnets of the same size.

' With these secondary windings in place, a potential is induced in each upon energization of the operating coils l4, and current flows from the secondary winding of the electromagnet having the lesser reluctance into the secondary winding or windings of the electromagnets having the greater reluctance. This adds ampere-turns to the electromagnet or electromagnets which are deficient in flux and subtracts ampere-turns from the other electromagnet or eiectromagnets. The magnetic flux in all of the electromagnets is thus equalized and their armatures respond simultaneously.

So that this condition will be more clearly understood, an actual test, and the data derived therefrom, is here given. In describing this test, reference is made to Figure 3 of the drawing.

In making the test an extreme condition was presupposed by blocking one of the switches in fully open position before energizing the switch coils. In the diagram at Figure 3, the left-hand unit designated by the'numeral 30 represents the open switch and the-'right-hand unit designated 40 represents the closed switch. The switches used were of the solenoid type shown in Patent No. 2,071,149 issued February 16, 1937, to Gustav O. Wilms and Hans Petersen, and both had the Their operating coils each had three hundred and seventy-five turns of No. 20 copper wire, and

their secondary coils had eighty turns of No. 22 copper wire.

- The primary coils were connected in series,

1. In combination: a plurality of alternating and the secondary coils were connected as shown. The line voltage, measured across the llne'by a volt-meter placed as shown, was two'hundred and twent (220) volts. The amperage through the primary coils, equal in both units because of their series connection, measured by the ammeter A was elevenand seven-tenths (11.7) amperes. Across the primary (a'-b) oi the open unit 30, the voltage measured seventy-two ('72) volts. Across the secondary (o-d) of unit 30, the voltage measured twenty-three and four-tenths (23.4) volts.

In the closed unit 40, the voltage across the primary (e-f), measured one hundred and forty-four (144) volts, and across the secondary (g-h), the'voltage was twenty-three and iour tenths (23.4) volts.

The amperage in the secondary circuit as measured by the ammeter A was ten (10) amperes. Y

The computation oi. ampere-turns tor the respective units thus was as follows:-- I

For unit 30 Total ampere-tums=5180 For unit 40 375 x 11n=4aao A-T' -so 1o =-aoo A-T V Total ampere-turns libfll u 'Thesez figures show how the provision of the connected secondary coils adds to theampereturns of the electromagnet which, because. of

a higher reluctance in its magnetic circuit, is deficient, and subtracts ampere-turns from the electromagnet whosereluctance is low. While in actual use, conditiorismaly not be as exaggerated will compensate is limited, a fifty ampere switch nection with the accompanying drawing, it will as reproduced by this test, it will be readily apparentlthat the desired balance is at all times attained. I

With the armatures closed there is-only a comparatively small current flowing in the secondary circuit. The amount which may be flowing in this circuit is only that required to equalize the flux in the several magnetic circuits.

With an appropriate selection of wire size and number of turns in the secondary windings, this invention is also applicable to switches of dif- Ierent sizes and differently rated, capacities,,as

' illustratedin Figure 2. While the difference in size and rated capacity which this invention and a one hundred ampere switch can be used together with their operating coils connected in series. Figure 2 illustrates two such switches,

and as will be noted, the operating coil 20 of the one hundred ampere switch has a greater number of turns than that of the smaller switch, but

its secondary winding 2| has a lesser number of turns than the corresponding coil 01 the fifty ampere switch. v

From the foregoing description taken in conbe readily apparent to those skilled in the art, that this invention permits the use of series connections for the operatin coils of a number of alternating'current electr magnets and insures simultaneous response of their armatures regardless of differences in the reluctance or other inevitable variable factors of the electromagnets.

What I claim as my invention is:

current electromagnets equipped with armatures and having theircoils connected in series so as to be capable of simultaneous energization and deenergization; and a closed electrical circuit having parts thereof arranged in inductive relation to the coils of the electromagnets so that the coil of any electromagnet which for various reasons has a greater flux than another electromagnet of the plurality induces a current how in said closed circuit to bring about an equalization all of the electromagnets.

3. In combination: a plurality of alternating current electromagnets having coils adapted to be energized; means for connecting the coils of all of the electromagnets in series with a-source of alternating electromotive force; the energization of said coils setting up a magnetic flux inv of the effective flux at the several electromagnets I and thus, insure response of the armatures of the electromagnets; and means deriving electrical energy from the coils of the eleotromag nets for equalizing the effective magnetic flux over all of the electromagnets.

4. In combination: a plurality of electromagnetically actuated switches having operating coils; means for connecting the coils of said switches in series with a source of alternating current; and means for insuring substantially simultaneous closure and opening of all of said switches comprising, a closed electrical circuit having a winding arranged inductively to each of said operating coils so that any electromagnet which has a greater magnetic flux than any other electromagnet of the plurality induces a current flow in said closed circuit to the windings oi the closed circuit at such other electromagnet or electromagnets as are deficient in magnetic flux.

5. In combination: a plurality of switchesjan electromagnet tor each switch; means for connecting the operating coils of all of the electromagnets in series with a source of alternating current; a secondary coil arranged inductively to each of the operating coils; and a closed circuit" "including only said secondary coils for connect-.

ing the same with each other so that current may flow from one to the other to bring about a predetermined magnetic flux distribution at the different electromagnets.

6. Means for insuring substantially simultan ous closure of two electromagnetically actuated switches which may be difierent as to the characteristics of their magnetic circuits and in which each switch is equipped with an operating coil adapted to be energized:means for simultaneously energizing said operating coils; a secondary winding arranged inductively to each operating coil; and circuit connectlons'between said secondary windings to permit current to flow from one to the other.

7. In combination with a plurality of alternating current electromagnets equipped with mov-q able armatures and having their coils connected I in series so that the same amperage flows in all: means for compensating for difl'erences in the reluctance of the magnetic circuits or the several electromagnets to insure a predetermined distribution of flux over the several electromagnets necessary to effect simultaneous response of all of the armatures upon energization of the mag net coils, said means comprising a secondary coil arranged inductively to each of the magnet coils; and means electrically connecting these secondary coils so that current may flow from one to 10 the other.-

8. In combination: a plurality of alternating current electromagnets equipped 'with armature: and having their coils connected in series so as to be capable of simultaneous energization and deenergization; and means inductively associated with the coils of the electromagnets for subtracting ampere turns from the electromagnet whose armature is nearest home as to the time required for such movement, and adding the same number of ampere turns to the other electromagnet or electromagnets.

KONRAD HEINRICH.

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