US1320598A - Electromagnet - Google Patents

Description

0. R. BLUMBERG AND B. D. HORTON.

ELECTROMAGNEL I APPLICATION FILED JUNE 2.1 9I4. 1 ,320,598, latontml Nov. 4, 1919.

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WITNESSES: INVENTORS.

% 5524 I @WMMFW UNITED STATES PATENT OFFICE.

OSCAR R. BLUMBERG AND BRYSON D. HORTON. OF DETROIT, MICHIGAN, ASSIGNORS TO DETROIT FUSE & MFG. COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

ELECTROMAGNET.

To all whom it may concern:

Be it knownflthat-we, OSCAR R. BLUMBERG and BRYSON D. HORTON, citizens of the United States,.both residing at Detroit, in the county of \Vayne and State of Michigan, have invented certain new and useful Improvements in Electromagnets, of which the following, taken in connection with the accompanying drawings, is a full, clear, and

concise description thereof.

Our present invention relates more particularly to alternating current electro-magnets of the closed magnetic circuit type and among the objects of ourinvention are to produce such a magnet that will quickly act to release its armature, will have no air gap, reduce magnetic leakage to a minimum, produce a maximum pull, and at the same time minimize the humming and chattering which is inherent in alternating current magnets.

Electro-magnets of our improved construction are especially adapted for service volving by its own momentum after the current has been cut off sets up an instantaneous current flow which passes through the main potential coils of the magnet setting up a magnetism opposed to the established residual magnetism neutralizing it and releasing the armature thus producing in both in; stances a quick acting release magnet. In both instances the armature of the magnet may be connected with the switch so that upon a drop in the line. voltage the armature will he released and through suitable intermediate mechanism releases the springs which operate the switch.

It will he noted that if the line switch were opened when the magnetic flux existed in the iron circuit of the magnet, that, due to the fact, primarily, that the core forms a Specification of Letters Patent.

Patented Nov. 4, 1919.

Application filed June 2, 1914. Serial No. 842,470.

closed magnetic circuit, a certain amount of residual magnetism would remain. Also any fault or lack of annealing, of the laminated structure forming the magnetic circuit would also tend to cause the retention of magnetism, or, in other words, result in residual magnetism. This is true, although the magnet windings may carry alternating current, for at the instant that the circuit be opened the magnetic flux existing in the iron circuit would tend to remain, from either of the above noted causes.

It will be understood that while we have chosen to point out these particular usesto which our invention may be put we do so in an illustrative sense only, as it is manifest that the same may be put to other uses with equal advantage.

We will now proceed to describe the structural details of our improved electro-magnet and its operation in connection with the instrumentalit-ies above mentioned and which cooperate to produce the useful results sought.

In the accompanying drawings:

Figure 1 is a view in side elevation of an electro-magnet constructed in accordance with our invention in electrical associationwith an alternating current motor and a three phase motor starting switch both of which are shown diagrammatically.

Fig. 2 is a top plan view of the electro- -magnet with its armature removed associated with a condenser, a bankof lamps anda controlling switch likewise shown diagrammatically.

' Fig. 3 illustrates conventionally one form of mechanism which may be employed for coi'rperatively associating the electro-magnet with the circuit controlling switch so that the pole face, and the latter may be provided with transverse slots, as shown in Fig. l of the drawings. As is well known, the passage of current through the main potential coils, will cause a surge of magnetism or lines of force through the pole pieces in a direction depending upon the direction of the current flow. These lines of force set up in the shading coil a flow of current, and that flow of current produces lines of force opposed in direction to the lines of force produced by current in the potential coils. The lines of force produced by the shading coil tend to neutralize, either wholly or in part, the counter lines of force produced in that part of the pole face by the main potential coils. Owing to this interaction of these lines of force, when the potential coils are energized with an alternating current, the pull exerted upon the armature 5 by the pole piece oscillates between the shaded and unshaded areas of the pole face, but never reaches a zero value. The

armature may be of the floating laminated iron type, and is adapted to seat closely against the pole faces without any intervening air gap. It will be observed that this construction eliminates the air gap. which is necessary in one common type of doublepole alternating current magnet, having a single potential coil. There is thus produced a practically noiseless magnet, the usual chattering and hammering being reduced to a minimum.

We have thus found it possible by the use of a symmetrical construction, provided with two main potential coils and two symmetrically-arranged shading coils, to eliminate the disadvantageous features attendant upon the use of an air gap between the armature and one of the pole faces.

It will be noted that the shading coils 4 are completely embedded in the cores 2 adjacent the pole faces whereby it is possible to have a perfectly smooth plane face presented to the armature, whereby the arma ture may be in intimate contact with the pole faces.

' It will also be noted that the members or conductors. forming these shading coils are symmetrically arranged with respect to thecenterline of the pole face. By this means it will be seen that the alternating magnetic fluxes passing from the pole face always hear a symmetrical relation to the center line of the pole facethat is to sav, in the particular embodiment shown upon the magnetism increasing in the core 2 and passing outwardly from the pole face it will first pass to the outside of the shading coil members and will thereafter pass through the inside or between the members of the shading coil. It will be seen from this that with regard to the center line, the alternating fluxes always bear a symmetrical relation and do not tend to produce a sidewise or endwise drag upon the armature as would be the case if the shading coils were not symmetrically arranged with relation to the central line of the pole face.

Therefore, an electro-magnet of the closed magnetic circuit type as constructed in accordance with our invention, has both pole faces provided with shading coils which produce an identical phase displacement, both legs being of identical construction the electrical resistance and magnetic reluctance will be the same in each leg, the floating armature being adapted to seat itself flush on the pole faces there will be no air gap thus obtaining a maximum phase displacement, and reducingchattering to a minimum. It will furthermore be observed that a magnet of this construction reduces the magnetic leakage to a minimum and increases the magnetic pull to a maximum by reason of the absence of the air gap Which is present in other magnets of the closed magnetic circuit type of which we are aware.

Of course, it will be understood that the shading coils are properly proportioned with respect to the magneto motive force to produce the maximum pull for a given E.-

M. F. Our invention in addition to the structural constitution of the electro-magnet itself comprehends the said magnet in combination with the other illustrated instrumentalities. -'Tlie combinations now to be described show useful employment for the electro-magnet and constitute peculiar cooperative combinations which produce results new in the art and upon which we found certain of the following claims.

While we describe and claim the electromagnet in combination as applied to specific uses, we do not restrict ourselves thereto but on the contrary desire it to be distinctly understood that we may employ the electromagnet in any way that may be desirable or found useful without departing from the spirit and scope of our invention as defined by the appended claims.

lVe have illustrated our electro-magnet as a low or no voltage release magnet, that is to say. the armature is released upon a lowering of the current voltage in the line circuit. The armature is cooperatively associated with the circuit controlling switch so hat upon its release the switch is opened. In Fig. 3 we have shown conventionally intermediate operating bell crank levers 6 and 7. Bell crank lever 6 engages the floating armature 5 of themagnet, the latter being pivoted at 8, while the bell crank lever 7 engages the arm 9 of the switch 10. The magnet armature 5 upon being released upon the deenergization of the main potential coils breaks contact under the tension of spring 11. this causes the bell crank lever 6 to rotate around its pivot by reason of its engagement with the bell c ank 7 the latter causing the switch arm 9 toraise. The breaking movement of the switch is accelerated by the spring 12, the latter, however, being of insufficient strength to normally break the switch contact, being overcome by the frictional adherence between the contacts when in on position. A. spring 13 normally exerts its power to hold the bell crank lever 7 in the position shown so that the bell crank lever 6 is in contact with the floating armature '5 of the magnet. It will be understood from'this description that whenever the armature 5 is released the switch 10 will be thrown to its off position.

When the electro-magnet is employed as a quick acting release magnet for a-contIOlllIlgSWllZCll 1n connection with an alternating current motor, that disturbing infiuence known as residual magnetism which is always present in a magnet of the closed magnetic circuit type with the iron to iron contact of armature and core is neutralized by the back surge of an E. M. F; from the motor itself after the switch has been thrown off while the motor is acting momentarily as a generator.

In Fig. 1 an alternating current motor is diagrammatically illustrated at 14. The release magnet is shown as connected in parallel in phase a of the motor so that should the voltage suddenly drop, the rotor of the motor revolving by its own momentum will set up an instantaneous current flow in this phase. which,- passing through the main potential coils of the magnet will set up a magnetism opposed to the established residual magnetism thus neutralizing it and releasing thearmature 5. The same operation occurs should the switch 10 be opened. This will be readily understood if we consider that the switch is suddenly opened, while the current passing through the main coils is at a maximum value. lVhen this condition occurs the pole pieces will be magnetized in accordance with the current which was flowing through thecoils 3 at the instant 'the current was interrupted. This magnetization. in the absence of some counteracting force, wouldretard the release of the armature; however, the counter E. M. F. produced in the phase a by the continued revolution of'the rotor of the motor through its momentum. will establish a reverse current in that phase which will negative-the residual magnetism set up in the pole pieces, and will instantly release the armature. A similar phenomenon occurs when the main line voltage suddenly drops.

hen our electro-magnet is used to release a switch operating a circuit containing a straight inductive or noninductive load such as a transformer ora bank of lamps. this neutralizing influence for the residual magnetism is not present and it is therefore necessary to meet this condition by using a condenser.

In Fig. 2 we have illustrated diagrammatically a bank of lamps, 15 as the load. anda condenser 16 which is inserted in the circuit parallel with either potential coil.

This condenser which takes up a charge of electricity discharges that charge (when the voltage at the main line is lowered or taken off or when the circuit through magnet isibroken) through the potential coils of the magnet, thus setting up a magnetism in the core opposed to the established residual magnetism neutralizing the same and releasing the armature in the manner heretofore, described. It will be further seen that when the circuit is opened or otherwise disturbed the auxiliary circuit including one coil of the magnet and the condenser remains intact. This circuit constitutes to some extent. an electrically resonant circuit in which a periodic oscillating decaying current flows. upon anv disturbance of the electrical conditionof this auxiliary circuit, such as opening the line switch. and so forth. In one or the other of the directions in which this surge current flows. the magneto motive force produced thereby would be opposed to any residual magnetism which might exist in the closed iron circuit and would thereby neutralize the same and produce a quick release of the magnet armature.

It. will also be noted that the alternating current passing through'the left hand coil, Fig. '2. is the vectorial sum of the currents passing through the condenser and the right hand coil. Consequently. the current in the left hand, coil will differ in phase from that in the right hand coil. This will produce magnetic fluxes which correspondingly differ in phase and thereby produce a more nearly continuous pull from the magnet.

It will further be noted that the current flowing ,through the two main coils are slightly difl'crent in phase relation, and the" fluxes each differing in phase from the other two and thereby produce a very uniform magnetic pull. 'We thus take care of and neutralize the residual magnetism which is a disturbing factor in magnets of this type thereby producing a quick acting magnet new to the art.

Having thus described our invention what we claim as new herein and desire toy secure by Letters Patent ist I 1. The combination with an alternating current electro-magnet comprising a main core portion, a movable armature having intimate contact in attracted position, whereby a closed magnetic circuit is formed when the armature is in attracted position, and an energizing winding on said main core, of a condenser connected in circuit'with a por tion of said Winding. whereby a substantially uniform pull'is secured when the magnet is energized and a quick release secured when the magnet becomes inactive.

2. In a single phase alternating current.

electro-magnet, the combination of a core and armature, a multiple main winding and an auxiliary conductor surrounding said core, with associated means, whereby when the magnet is energized, three magnetic fluxes are produced, each diflering in phase from the other two, thereby producing a substantially uniform pull upon the armature.

8. In a single phase alternating current electro-magnet having a core and armature, the combination of two main windings and shading coils with a condenser bridging one of said main coils whereby when the magnet is energized, three magnetic fluxes are produced, each bearing a different phase relation to the other two.

In witness whereof we have hereunto set our hands in the presence of two subscribing witnesses.

OSCAR R. BLUMBERG. BRYSON D. HORTON. lVitnesses:

JOHN B. PLATE, ALBERT E. STUTZNER.

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