US2360954A

US2360954A - Antichattering electromagnetic control

Info

Publication number: US2360954A
Application number: US434684A
Authority: US
Inventors: Frank G Logan
Original assignee: Ward Leonard Electric Co
Current assignee: Ward Leonard Electric Co
Priority date: 1942-03-14
Filing date: 1942-03-14
Publication date: 1944-10-24
Anticipated expiration: 1961-10-24

Description

9 F. G. LOGAN 2,360,954

' ANTI-CHATTERING ELECTROMAGNETIC CONTROL v Filed March 14, 1942 iMTm/azr M ATTORNEY Patented Oct. 24, 1944 ANTICHATTERING ELECTROMAGNETIC CONTROL Frank G. Logan, Mount Vernon, N. Y., assignor to Ward Leonard Electric Company, a corporation of New York Application March 14, 1942, Serial No. 434,684

6 Claims.

This improvement is applicable to electromagnets which have a movable armature or solenoid core. It may be utilized in the operation of switches, contactors, the control of any switch contacts to their open or closed positions, or to the actuation of any device in response to the energization or deenergization of the electromagnet. relays for various purposes or in any electromagnetically operated devices.

The improvement is adapted for use where the supply of energy to the electromagnet is from an alternating current source.

The main object of the invention is to overcome the inherent disadvantages of an electromagnet energized from a direct current source and of an electromagnet energized from an alterhating current source. The former type has the general disadvantage of exerting comparatively small attractive force upon the armature or solenoid core when such parts are in their unattracted position, unless some auxiliary means is provided, such as the use of a resistor device provided with a short-circuiting contact. But it has the advantage that when the parts are in their attracted position, a comparatively strong holding force is exerted continuously. On the other hand, the electromagnet-energized from an alternating current source has the advantage of exerting a comparatively strong attractive force when the parts are in their unattracted position; but this type of electromagnet has the disadvantage of exerting a comparatively small attractive force when the parts are in their attracted position due to the reduction of the exciting current owing to the increased impedance of the circuit and also to the fact of the current value passing through the zero point upon change of direction of the alternating current. Also the average effective attractive force of the parts in their attracted position with an alternating current type of electromagnet is less than that of a direct current type of electromagnet having the same number of ampere turns. It results that the alternating current type of electromagnet gives a chattering noise or pronounced hum when the parts are in their attracted position and the parts may be thrown to the unattracted position under shocks or jars, particularly if a moderate decrease in the exciting current occurs from any :cause. In order to overcome to some extent the disadvantages of the alternatingtype when the parts are in their attracted position, resort has been taken to the provision of lag loops in the {races 01 the poles of the magnet but eventhen The improvement may be embodied in the advantages of the direct current type when the parts are in the attracted position are not attained. The present invention overcomes the disadvantages of each type and attains the ad vantages of each type to a very pronounced extent.

Another object is to avoid the use of auxiliary make and break contacts and of any auxiliary movable parts which are likely to require attention for adjustment or repairs. Another object is to provide a form of structure which will be dependable and durable in long continued use. Another object is to provide a comparatively simple form of structure which may be economically manufactured and assembled. Another object is to provide a ijorm of electromagnet structure and relationship of the exciting windings thereon that will avoid the imposition of high reversed peak voltages on the electric valves or half-wave rectifiers utilized in connection therewith. Other objects and advantages of the invention will be understood from the following description and accompanying drawing which illustrates preferred embodiments of the invention.

Fig. i is a diagram illustrating one embodl= merit of the invention with the parts in their unattracted position; Fig. 2 is a similar diagram with the parts in their attracted position; Fig. 3 is a similar diagram wherein auxiliary windings are provided for the adjustment or control of the magnetic flux where such control is desirable for particular applications; Fig. 4 is a diagram showing the invention applied to another form of core structure; Fig. 5 is a diagram showing other means of auxiliary control of the flux and with the parts in their unattracted position; and Fig. 6 is a similar diagram showing the parts in their attracted position.

Referring to Fig. 1 the fixed core I which would be made up of laminations, is shown as having two outer legs and a middle leg. The movable core 2 is of similar character and is shown displaced from the fixed core in the unattracted position. The movable core has secured thereto a part 3 indicated as extending upwardly,

for the actuation of the switch contact to the closed or open position as may be desired, or may be usedfor actuation of a device of any character according to the particular purpose for which the magnet is to be used. In some cases the electromagnet may be used to close a circuit breaker automatically, and it may be used as a relay for any control purposes but as the particular use to which this invention may be. applied forms no part of the present invention, 1

the upper end of the element 3 is shown broken away. Instead of using an upwardly extending element 3, the connection of the control element to the movable core may be made in any desired manner.

On one of the outside legs of the fixed core is a coil or winding 4 and on the other outside leg is a winding 40. In practice these windings would be extended so as to embrace the two outer legs of the movable core when the parts are in closed position. An alternating current source 5 supplies energy to the electromagnet through a switch 6. One side of the alternating current line is connected to the two coils 4 and 4a from which the circuit continues through the half -wave rectifiers I and la to the other side of the alternating current supply line. The rectifiers are reversed with reference to each other in the circuit of the two exciting windings 4, 4a..

The above described relationship of the parts and their connections results in a direct current of pulsatin form passing through the electromagnet windings, giving a direct current excitation of the magnet even though an alternating supply source is utilized. This is because the alternating current half-waves in one direction pass through the winding 4 and the rectifier 1, giving a pulsating direct current in the winding 4, whereas the alternate half-wave currents in the opposite direction pass through the rectifier Ia and the winding 4a givin a pulsating direct current in the winding 4a. Thus the windings of the electromagnet apply direct current excitation to the core by reason of the reversed relationship of the half-wave rectifiers. The connections of the supply line to windings 4 and 4a on the fixed core is such as to create a flux in the same direction alternately in the outside legs as indicated by the downward direction of the arrows in the outside legs. The fiux path is shown downwardly through each of the outside legs of the fixed core to the outside legs of the movable core and then upwardly through the middle legs of the cores. The successive excitation by the windings results in a continuous energization of the common portion of the cores because the fiuxes created by the respective windings over-lap each other givin a resultant strong continuous magnetization with a moderate pulsation of the flux, and passing through a condition of zero magnetization is entirely avoided.

When the electromagnet is in the unattracted position, as shown in Fig. 1, a comparatively strong magnetic pull is exerted upon the movable element because in that position the reluctance of the magnetic paths is comparatively high with resulting comparatively low reactance of the exciting windings. This permits a comparatively high current to pass in the exciting windings, giving a comparatively strong magnetic pull of the movable element when in the unattracted position. Consequently the advantage of the usual alternating current electromagnet of exerting a strong magnetic pull when the parts are in their unattracted position is attained by this improvement. When the parts have been moved to the attracted position, as shown in Fig. 2 by the closing of a circuit. the reactance of the exciting windings is increased and the value of the current is decreased but by reason of the iact'that the reluctance of the magnetic path is greatly decreased and by reason of the magnetization of the magnet being maintained at a comparatively high value without passing through points of zero magnetization as already explained, the magnetic force exerted upon the movable element for holding it in its attracted position is continuously maintained at a comparatively high value. This secures the advantage of an electromagnet when energized from a direct current source in the attracted position. This improvement thereby avoids the comparatively poor hold-in force of the electromagnet energized by use of alternating currents and overcomes the hum and noise inherent in the alternating'type when in the attracted position. By proper proportioning of the windings and of the magnetic structure the improvement is adapted for any particular requirements.

This improvement avoids the imposition of objectlonable peak voltages on the rectifiers when alternately inactive and thereby permits the use of inexpensive low voltage rectifiers and insures their long life. Referring to Fig. 1, when the winding 4 is active, the winding 4a. will be inactive and vice versa. Let it be assumed that winding 4 is momentarily active and winding 4a inactive. The indicated direction in Fig. l of the flux due to winding 4 is then downwardly in the left-hand legs and upwardly through the middle legs of the electromagnet. But winding 4a being then inactive, a certain amount of flux due to winding 4 will pass upwardly in the right-hand legs through the winding 4a. At that time the source impresses a potential on the winding 4a corresponding to that impressed on winding 4 during the half-wave when winding 4 is active. It follows that the flux in the right-hand legs induces a potential in winding 4a which opposes the line voltage then impressed thereon. This not only avoids the imposition of a high reversed peak voltage on the rectifier 1a but reduces it below the line voltage to such a value as to avoid damage to, or break-down of the low voltage rectifier. Upon reversal of the alternating current when winding 4a then becomes active, the rectifier I is similarly protected from the imposition of high reversed peak voltages.

In some cases it may be desirable to reduce the magnetic pull exerted when the movable element is in the attracted position and in other cases it may be desirable to increase the magnetic pull in the attracted position. This can be accomplished by automatically inserting an impedance device or by removing an impedance device in the circuit of the exciting windings when theparts are moved to their attracted position; but this has the objection of providing auxiliary controlling contacts. Fig. 3 shows means for accomplishing this result without the use of circuit making or breaking contacts or the use of any auxiliary movable parts. The structure is the same as th'at already described with similar reference characters designating the corresponding parts. Additional windings 8 and 8a are provided on the outer legs respectively of the fixed magnetic core and may be positioned on the outside of the windings 4 and 4a or located at the ends thereof and ordinarily would be of a comparatively few number of turns. One terminal of the winding 8 is connected to a. full wave rectifier 9, indicated as of the bridge-connected type, and its other terminal is connected to the terminal of the winding 8a, the remaining terminal of the latter winding being connected to the rectifier. Instead of connecting these windings in series with each other, they may sometimes be connected in parallel. An additional winding I0 is provided on the middle leg of the fixed core and is connected to the positive and negative terminals of the rectifier. An adjustableresistance, ll may be connected in the circuit of the winding ID, if desired, for securing a proper value of the direct current in the winding II). The connections of the windings 8 and 8a with reference to each other are such that the induced current supplied to the rectifier by the winding 8 is in the opposite direction from that supplied to the rectifier by the winding 8a.

When the parts of Fig. 3 are in their unattracted position, the additional windings have no appreciable controlling effect but when the parts are in their attracted position as shown in Fig. 3, the intermittent or pulsating fiux to'which the winding 8 is subjected by the action of the winding 4 will induce a current in the winding I in one direction and similarly the intermittent or pulsating. fiux due to the winding 4a will in duce a current in the winding 8a in the opposite direction from that induced in the winding 8; and in view of these induced currents being successively imposed upon the circuit of these windings, the rectifier 9 will be subjected to an input current of an alternating character. This results in the rectifier delivering a direct current to the winding Hi. It is evident that the winding 10 may be connected to the rectifier to cause its flux to act cumulatively with the flux due to the windings 4 and 4a or may by reversing the connections to the rectifier its flux may be caused to act in opposition thereto. In the former case when the parts are in their attracted position, the attractive force exerted, or the socalled hold-in pull, may be very considerably increased compared with the attractive force exerted when such auxiliary windings are not used; and in thelatte'r case the hold-in pull may be decreased. 'By proper proportioning .of the auxiliary windings any desired degree of holdin force may be made to fulfill any particular requirements.

Although in each of the figures already described the three-legged form of core is used, any other suitable form of coremay be utilized and Fig. 4 shows another desirable form of core structure of the four-legged type. The parts in Fig.4 corresponding to those of Fig. 3 are indicated by corresponding'reference characters. The fixed portion of the core or magnet frame I! is shown as having four legs and the movable portion of the core I3 is shown as having four legs and the parts are shown in their attracted position. The windings 4 and 4a instead of being dispbsed on the outer legs are positioned respectively on the two inner legs and the direction of the magnetic flux is indicated by the arrows. The auxiliary windings 8 and 8a are likewise disposed on the two inner legs respectively and the direct current controlling winding l envelops both of the inner legs and also the other windings. The mode of operation and functioning of thevarious parts are the same as that already described with reference to Fig. 3.

Figs. and 6 show another way of modifying the attractive force of the magnet when in the attracted position. The structure is the same as that shown and described with reference to Figs. 1 and 2 except in the provision of auxiliary means for increasing the reactance of the exciting circuit when the parts are in the attracted position and thereby reducing the hold-in pull compared with the structure of Figs. 1 and 2. In Figs. 5 and 6 an auxiliary device in the form legged core 14 and a movable" corresponding three-legged core l5. The latter core is mechanically connected with the movable core or armature 2 of the magnet as by means of a connecting element I 6. A winding 1 is provided high reluctance of the total magnetic circuit including the separated portions l4 and I5 of the reactor and the resulting low reactance of the winding l1. When the parts are in their attracted position, as shown in Fig. 6; the gap between the two portions and 15 of the reactor core is closed. This results in the reactance of the winding I! being increased and in view of this winding being in series in the circuit of the exciting windings of the magnet, the value of the current in those windings is reduced. This reduces the hold-in pull of the magnet which may be desirable under certain conditions. By proportioning the winding l1 and the reactor core portions I4 and I5, the hold-in pull of the magnet may be reduced to any desired amount.

" The size of the auxiliary reactor for this purstructures may be varied in 'form, as well as the of a reactor is provided having a fixed three- 76 relationship'of the parts for adaptation to particular purposes. In some casesthe. windings may be applied to and carried by the movable magnetic element, or partly by one element and partly by the other. Likewise the auxiliary controlling means for affecting the hold-in pull may be replaced by other means and various other modifications made without departing from the scope of the invention.

I claim:

1. An electromagnet adapted for operation from an alternating current source comprising a magnetic structure having a movable element and a ,fixed element, one of said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, and half-wave rectifiers connected in series with said windings respectively to the source, said rectifiers being reversed with reference to each other for alternately supplying pulsating direct currents to said windings, and said magnetic structure providing return for the flux created by each of said windings independently of passage through the other of said windings.

2. An electromagnet adapted for operation from an alternating current source comprising a magnetic structure having a movable element and a fixed element, one of said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, half-wave rectifiers connected in series with said windings respectively to the source, said rectifiers being reversed with reference to each other for alternately supplying pulsating direct currents to said windings, said magnetic structure providing return for the flux created by each of said windings indepen-' dently of passage through the other of said windings, and auxiliary means for affecting-the attractive force between said two elements when in the attracted position.

3. An electromagnet adapted for operation from an alternating current source comprising a magnetic structure having a movable element and a fixed element, one of said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, half-wave rectifiers connected in series with said windings respectively to the source, said rectifiers being reversed with reference to each other for alternately supplying pulsating direct currents to said windings, said magnetic structure providing return for the flux created by each of said windings independently of passage through the other of said windings, and auxiliary means afiected by the exciting current in said windings for affecting the attractive force between said two elements when in the attracted position.

4. An electromagnet adapted for operation from an alternating current source comprising a. magnetic structure having a movable element and a fixe delement, one of said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, half -wave rectifiers connected in series with said windings respectively to the source, said rectifiers being reversed with reference to each other for alternately supplying pulsating direct currents to said windings, said magnetic structure providing return for the flux created by each of said windings independently of passage through the other of said windings, auxiliary windings subjected to the flux of said first named windings, means for rectifying the current supplied from said auxiliary windings, and a. control winding on said magnetic structure supplied with direct current from said means for afiecting the attractive force between said two elements when in the attracted position.

5. An electromagnet adapted for operation from an alternating current source comprising a magnetic structure having a movable element and a fixed element. one oi said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, half-wave rectifiers connected in series with said windings respectively to the source, said rectifiers being reversed with reference to each other for alternately supplyin pulsating direct currents to said windings, said magnetic structure providing return for the flux created by each of said windings independently of passage throughthe other of said windings, a reactor having a winding connected in series in the exciting circuit of said first named windings, and means for increasing the reactance or said reactor winding when said movable element is moved from its unattracted position to its attracted position for affecting the attractive force between said two elements when in the attracted position.

6. An electromagnet adapted for operation from an alternating current source comprising a magnetic structure having a movable element and a fixed element, one of said elements having a plurality of legs, a winding on one of said legs supplied with current from said source, a second winding on another of said legs supplied with current from said source, and half-wave rectiflers connected in series with said windings respectively to said source, said rectifiers being reversed with reference to each other for alternately supplying pulsating direct currents to said windings, said magnetic structure providing return for the flux created by each of said windings independently of passage through the other of said windings, and said windings being relatively connected to cause that portion of the return flux from the then active winding which passes through the then inactive winding to be in a direction which induces a potential in the inactive winding in opposition to the voltage then applied to the inactive winding.

FRANK G. LOGAN.