US2189507A

US2189507A - Electric controlling apparatus

Info

Publication number: US2189507A
Application number: US96967A
Authority: US
Inventors: Frank G Logan
Original assignee: Ward Leonard Electric Co
Current assignee: Ward Leonard Electric Co
Priority date: 1936-08-20
Filing date: 1936-08-20
Publication date: 1940-02-06
Anticipated expiration: 1957-02-06

Description

Feb. 6, 1940. F. G. LOGAN ELECTRIC CONTROLLING APPARATUS Filed Aug. 20, 1936 2 Sheets-Sheet 1 INVENTOR l ke/1w 6'. lace/v J ATTORNEY 2 Sheets-Sheet 2 F. G. LOGAN ELECTRIC CONTROLLING APPARATUS Filed Aug. 20, 1936 INVENTOR fkA/wf 6. 1066 v M ATTORNEY nth-I:

Feb, 6, 1940.

Patented Feb. 6, 1940 ELECTRIC CONTROLLING APPARATUS Frank G. Logan, Mount Vernon, N. Y., assignor to Ward Leonard Electric Company, a corporation of New York Application August 20, 1936, Serial No. 96,967

@i. Iltl- 119) 18 Claims.

This invention relates to an improved con trolling apparatus and method of control and is particularly applicable to changing the voltage I applied to a consumption circuit over a wide range, suchas in dimmer control oi lighting circuits in. theatres and the like. The invention is particularly applicable to an auto-transformer connected to a supply circuit and wherein the voltage applied to the consumption circuit is Q changed by adjustment of the movable contact over the turns oiZ-the auto-transformer, although the invention is applicable also to various inductive windings.

means for procuring any desired output voltage but their usehas been limited in practice to comv paratively small. capacity units on'account of excesslve heating of the adjustable contact and of 20 the windings-oi the transformer when it is attempted-to increase the capacity beyond comparatively small llmits.- When the usual movable contacting brush is used, it must necessarily engage adjacent turns oi? the transformer winding and forms a short-circuit between them. The electromotive force of the short-circulted turn or'turns tends to create a large current in the short-circuited turn or turns and causes excessive heating in the windings. In order to reduce 80 the value of the local current in this local shortcirculted path, the contacting brush has been made of material having a relatively high specific resistance for the purpose of interposlng in this .local circuit a suiliciently high resistance be- 86' tween adjacent turns of the winding to reduce the value of the local current and thereby reduce its heating effect. But the making of the brush of high specific resistance material is incompatible with the requirement that the brush 40' be as of low a resistance as possible in order to reduce the heating of the brush by the passage through it of the load current. This has necessitated resorting to a brush which endeavors to effect a compromise between these two antagonisticrequirements; and although such a compromise may be serviceable for auto-transformers of comparatively small capacity, the excesslve heating in such brushes and in the windings of the transformer prevent their use for the control of voltage of the consumption circuits having comparatively large or heavy loads.

By the present invention the necessity for using a movable contact of high specific resistance is avoided and the short-circuitlng of adjacent turns of the transformer winding is also 'The use of auto-transformers with an adjustable contact affords a convenient and economicalavoided which eliminates the excessive heating and heat losses above referred to. This invention thus permits the making of auto-transformers having movable contacts, of as high a capacity as may be desired without any undue heating in the windings of the transformer or in the movable contacts. This is accomplished by an improved relationship of the movable contact or contacts to the transformer winding in such a. manner that at no time does one contactbridge, or short-circuit, adjacent turns of the winding. Other features of the invention in- I clude the provision of reactors and also a discharge path in such relationship to the movable contacts and to the load circuit that no material arcing occurs in moving the contacts along the transformer winding and no objectionable heat losses or drop in volts occurs in the load circuit.

One object of.the invention is to provide an 20 improved form of adjustable auto-transformer adapted to be made for any desired capacity. Another object is to provide such a transformer which will permit the use of contact brushes of high conductivity and avoid the heating due to short-circuiting of the windings and avoid undue heating in the movable contacts. Another object is to provide an improved form of device for controlling the voltage of the load circuit over a wide range economically and without high heat losses. Another object is to increase the number of steps of voltage control beyond the number of conductive portions of the winding engaged by the movable contact or contacts. Other objects and advantages of the invention will be understood from the following description and accompanying drawings.

Fig. l is a diagram and plan view of a portion of the apparatus illustrating one embodiment of the invention; Fig. 2 is a side view of one form of structure embodying the invention; 40 Fig. 3 is an end view thereof; Fig. 4 15a plan view; and Fig. 5 is a bottom view of the contact carrier.

Referring to Fig. 1, an alternating current source I supplies energy through the auto-trans- 45 former to the load circuit 2, indicated as a lamp circuit, although the load may be of any character. The transformer is indicated for simplicity as having a straight iron core 3 upon which is wound the winding 4. The turns of this winding are indicated as physical turns of wire of a comparatively large size and would ordinarily be provided withan insulating covering except at certain exposed portions. The connections to this winding and to the source and to the load and throughthe reactors are indicated as single lines in conventional diagrammatic form. At opposite sides of the winding and covering alternate turns thereof are indicated a series of insulating strips 6. The turns of the windings between these strips are flush with the surface of the outside of these strips and have their conductive portions exposed in line with the outside portions of the strips. That is, considering the conductor of the winding at the right-hand end of the transformer, this conductor passes from a connection to the source I under the core and up the front side of the-core under an insulatin strip 5 and then oven and down the rear side 01' the core where its outer conducting surface is exposed and then passes under the core and up at the front side of the core where its outer conducting surface is exposed. It then passes over the core and down the rear side under an insulating strip 5 and then under the core and up the front side under an insulating strip 5. This sequence of turns and relationship of the adjoining turns on the two sides of the core 3 continues throughout the length of the winding to its opposite end where it is connected to the other terminal of the source I. It is evident that if a movable contact be moved over the rear side of the winding from right to left, or viceversa, it will first engage and make contact with an exposed portion of a turn pi' the winding and then with an insulating strip, then make con.- nection with another turn and then. contact with an insulating strip andso on. If a; movable contact be passed along th'e-fmnt'side of the winding, it will similarly make contact first with an insulating strip, then with'one turn of the winding. then with an insulating strip and then make conductive connection with the next turn of the winding and so on, it .being understood that the insulation along the paths of the movahle contacts has been removed from the outer surface of the winding to permit the movable contacts to electrically engage the turns between the insulating strips. It follows that in this construction a movable contact on one side will successively engage every other turn of the winding and completely break connection with the winding while passing over the insulating strips, provided the width of the movable contact or brush is less than the width of the insulating strips 5. Asimilar brush on the other side of the winding will successively engage every other turn of the winding and break connection when passing over the strips 5.

In Fig. 1 two movable contacts or brushes 8. 6a are shown on opposite sides of the winding and these are mechanically related in fixed position to each other so that when one brush, for example brush 8, is making complete electrical connection with one turn of the winding, the other brush 6a is making complete engagement with one of the insulating strips and is therefore not connected to the winding at all. If now the two brushes be simultaneously moved slightly to the right so as to be over the joints between the insulating strips and the turns, of the winding, then brush 6 will partially engage one turn of the winding and brush Ba will partially engage the same turn of the winding at the other side thereof. Further movement of the brushes to the right will cause brush 8 to be wholly on an insulating strip and cause brush to to be wholly on a turn of the winding in the positions indicated by dotted lines. Upon further movement to the right both brushes will partially engage insulating strips and partially engage a. turn of the windings; and further movement will cause the brush 8 to wholly engage a turn of he winding while brush 6a wholly engages an insulating strip, taking positions corresponding to those shown in full lines in Fig. 1. It will thus be seen that as these brushes are simultaneously moved along their paths, first brush 6 engages a turn of the winding while the brush 6a is disconnected therefrom, then both brushes partially engage a turn and insulating strips, giving a condition under which both brushes engage the winding with half a turn difference between them, and then brush 6a wholly engages a turn of the winding while brush 8 is disconnected therefrom and so on. I

Brush 6 is connected through a reactor winding 1 to the conductor 8 which leads to the consumption circuit, while brush 6a is connected through .a reactor winding la to the conductor 8. An impedance device 9 which may be a noninductive resistance, is connected from a point between the brush 6: and the reactor winding 1 to a point between the brush 6aand the reactor winding 1a.

;-- It is evident th-at in the above-analysis, of

the circuit changes accomplished by the movement of the brushes '6 and to, that in the position shown with brush 6 engaging a turn of the winding and the brush 6a insulated from the winding, the full load current will pass from the source I through the left-hand portion of the transformer'- winding to the brush 6 then through reactor! and conductor 8 to the load and then from the load back to the source i. When the brushes are bridging portions of insulating strips and portions of a turn of the winding, current will pass from the source I through the left-hand portion of the transformer winding to both brushes, approximately half of the current passing through brush 6 and reactor to the conductor 8 and the other approximate half of the current passing through brush 6a and reactor 1a to conductor 8 in parallel and then through the load back to the source I. Further movement to increase the voltage sup-- plied to the load results in brush 5 wholly engaging an insulating strip while brush to wholly engages a turn of the winding. Current then hand portion of the transformer winding to brush 6a and then through reactor la and conductor 8 to the load and then back to the source. This sequence of changes of current paths takes place as the brushes are moved throughout the length of the transformer winding 'in either direction when changing the voltage supplied to the consumption circuit.

It will be appreciated that when the movable contacts 6 and 6a are in bridging positions and engaging the same turn of the winding at points one-half turn apart, there is an electromotive force due to such half turn imposed upon the local circuit from one brush through the two reactor windings in series back to the other brush. This causes a local exciting current to pass through the reactor windings which however serve as chokes to limit the value of this exciting current. The number of turns of the reactor windings and the cross-section area of the cores of these windings are designed such as to limit .this exciting current to a desired minimum the iron of the cores at or near the knee of the magnetization curve. Under such conditions although approximately one-half of the load current is also passing through each oi the reactor windings, the increase in magnetization of the iron due to the load current is comparatively small and consequently the drop in volts due to the efi'ect of the reactors upon the load circuit is not increased to any objectionable amount. Similarly when only one brush is in engagement with the transformer winding and one reactor only is conducting the full load current, the magnetization of the core of this reactor is not appreciably increased beyond the knee of the magnetization curve and consequently the drop in volts due to the comparatively small reactance of this reactor with reference to the full load current is limited to an unobjectionable amount.

It is thus apparent that the reactors in the local circuit between the brushes serve to limit the local exciting current to an amount which may be made comparatively small so that there is no undue heating of the windings of the transformer and that these reactors may be designed so that the drop in volts as regards the load circuit is not objectionable and that the reactors may be located apart from the transformer winds ing so that any heating of the reactors does not affect the heating of the transformer winding or of the contacting brushes. It will likewise be evident that since the movable contacts do not bridge adjacent turns of the transformer winding, there is no necessity for making them of high specific resistance material. They may therefore be made of metal of the highest conductivity such as copper which permits excellent conductive engagement with the turns oi the transformer winding and heating of the movable contacts or brushes is avoided. Thus the'objections which limit the use of adjustable autotransformers to units of comparatively small capacity when brushes of high specific resistance material are used, causing excessive heating of the contacting parts and of the transformer windings, are entirely overcome.

In passing from a condition where one contact makes sole connection with the winding to the condition where the other contact makes sole connection with the winding,- the intermediate condition of joint connection to the winding by both contacts gives an additional step of voltage control over that obtained with the usual type of auto-transformer and thereby doubles the number of voltage control steps over that obtained in the usual. type, because the joint condition of contact provides additional steps by reason of the provision of the reactors. If, however, the voltage drop due to the load current in the reactors is permitted to be undesirably high, the control voltage in passing through successive steps" would be irregular. In order to obtain a progressive increase or a progressive decrease in the control voltage in each step, the number of turns of the reactor windings and the cross-sectional area of the cores of these windings are designed not only to limit the exciting current to a desired minimum amount, but the parts are preferably proportioned to cause the exciting current to bring the magnetization of the cores at or near the knee of the magnetization curve.

as already explained. This will ordinarily reduce the drop in the reactor windings to such value that an increase or a decrease of the controlled voltage is obtained in passing through each successive stage in the movement of the contacts. In order to obtain this result the drop in volts in each reactor when carrying the full load current should be less than the voltage across adjacent conducting portions of the transformer winding in the path of one of the contacts; and more uniformity oi control is obtained in passing through successive steps the smaller the drop in volts due to the load current in the reactors. However, as above explained suiiicient reactance must be provided to insure proper limitation of the current in the local circuit through the reactors when the contacts are in joint connection with two portions of the winding.

The shunting impedance 8 in this form of construction provides a discharge path between its points of connection and serves not only to avoid any tendency to arcing at the movable contacts when interrupting connection with a turn of the transformer winding but also serves to permit a discharge current to pass from the reactor which is being disconnected from the load circuit to permit the core of this reactor to approach the condition of non-magnetization in case the interruption of the circuit is made at a pear or near a peak of the alternating magnetization. Thus when the adjustable contacts are moved to cause the re-establishment of the current through this reactor, the iron has in the meantime been conditioned to a point considerably below the peak of magnetization, resulting in a reduction of excessive or undesirable transient current conditions.

In prior practice, two adjustable contacts have been connected through an inductive reactor having a common core and using a mid-tap for the circuit connection. Ii such a device were substituted for the reactors i and 1a of the present improvement and ii the impedance or resistor 5 were eliminated, the result would be that when contact 6 was in connection with the winding and contact to on'an insulating strip, a voltage would be built up from the center tap to the contact 8a which would be a function of the passing load current. Also the polarity of this voltage would be reversed with respect to the polarity of the turn with which it will next come in contact. This would result in excessive arcing and sparking, as has been found to be the case in practice. The use of individual or independent inductive reactors together with the shunt resistor 9 gives a very great advantage over the prior tapped inductive reactor. For example, when the contacts 6 and Ba are moved from a position where they both engage the winding 4 to a position where contact 8a is on an insulating strip, the iron of the reactor 1a may have been left at any point on its magnetization curve. However, although full load current is now passing through reactor '5, its magnetization can have no effect upon reactor Ia, which is quite different from the condition when a tapped reactor having a common core is used. The impedance or resistor 9 of the present improvement now permits the flux in the core of reactor la to collapse and permits the iron to return to a condition at or near zero magnetization. Thus when contact la nemt engages an adjacent turn The transformer is shown as having two hori-- zontally extending legs l joined by crosspieces H at then ends. The transformer winding is made up of one portion l2 on the upper leg, the turns of which are adapted to be adjustably engaged by the movable contacts; and a few turns l2 cf the winding are shown enveloping one end of the lower leg of the core, as it is often unnecessary to cut out all of the transformer winding Irom the circuit. The winding I2 instead of being engaged on opposite sides as indicated in Fig. 1, is arranged to have both contract devices engage the winding on. its top surface. The two paths of contact engagement are each formed of a contacting portion of the winding and then a non-electrical contacting portion over the adjacent turn of the winding and then an exposed contacting portion over the next turn of the winding and so on. That is, referring to the lead l3 at the left-hand corner of Fig. 2, this is shown passing under and aroundthe rear side of the core and then, as shown in Fig. 4, it passes under an insulating strip I4 on the top of the core for about half its length and then rises to form anexposed contacting portion i5, and then" passes down andflaround the core and up on the rear side of the core and then forms an exposed'contacting portion l5a. on the top of the core for aboutnh'alf the width of the core and then under an insulating strip Ha for about half the width of the top of the core. .lhe winding then continues around the core and up on the rear side where it first passes under an insulating strip i i and then forms an exposed portion i5 and so on throughout the length of the winding i2. It is thus evident that when a contact passes along one or these paths, it will alternately contact electrically with a portion of the winding, then pass over a non-conducting space represented by an insulating strip covering the next turn of the winding and then engage a contacting portion of the winding and so on.

This relationship of electrical contacting portions and non-contacting portions may conveniently be constructed by forming a moulded strip of insulating material, such as Bakelite. Such a strip would have a top surface wherein along one path are located alternate depressed and raised portions extending crosswise and a similar path on the remaining half of the top surface with the depressed and raised portions staggered with reference to the similar portions of the other half. That is, where the winding passes under the strip l4 there is a slot in the insulating strip [6 as shown at 16a in Fig. 3. and opposite this slot is located the raised portion 5b of the insulating strip over which the portion l5 of the winding passes as shown in Fig. 3. The next turn of the winding passes over .a raised portion corresponding to l6b which is located at the right-hand side of Fig. 3 and then down into a slot corresponding to |6a which is located at the left-hand side of Fig. 3. After the winding is thus formed on the insulating strip and on the core of the transformer the insulating strips corresponding to M, Ma,

and lb are inserted over the depressed portions of the winding, as shown in Fig. 3. After the structure is thus formed, insulating varnish may be applied to cover the parts and then be heat treated to cure the varnishand Bakelite to form a solid, strong, firm structure. The topsurface of the unit is then smoothed oil in a surface grinder to obtain smootkpaths for the movable contacts to travel over. This grinding and smoothing operation will remove the insulation from the top surface of the winding so that e1ectrical connection may be made therewith by the movable contacts. A winding having a condor tor of square orv rectangular cross-section Will be found most convenientfor forming the structure and in giving a suitable exposed contact surface where the insulation is removed. It is evident that instead of having one turn only between successive electrical contacting portions of the winding, a number of turns may be provided where desired and built up in each depressed portion and over each raised portion of the insulating strip i6, in which case the turns will preferably be banked to'bring the exposed contacting portion at the top. This relationship of electrical contacting portions and non-electrical contacting portions in two paths may, of course, be formed in other ways.

Although movable contacts in the form of brushes of high conductive material might be used in some cases, a,structure using rollers as the movable contacts is shown in Figs. 3 to 5, as they are, when properly constructed and mounted, more certain to give and maintain uniformity of contact with the winding and avoid the possibility of minute arcs which might occur with the use of brushes owing to possible irregularity of contact. The avoidance of arcing, of course, is desirable as itpermits the contacting portions to maintain smooth contacting surfaces and insures continuance of good contact at all times and in all portions of the parts. Although one contact roller might be used for engaging each path of the winding in theory, the irregularities of manufacture make it desirable to use two rollers for engaging each path with one slightly displaced with reference to the other.

The rollers theoretically make a line contact with the contacting portions of the windings and the distance between the line contactsof the two rollers in a direction at right angles to the line contact should be less than the width of the insulating strips M, a, etc. In practice it is desirable to make this relative displacement of the brushes equal toabout one-half of the width of these insulating strips.

The contact rollers are mounted upon a carrier formed of an insulating plate I! which serves as a support for the rollers. Each of .the rollers i8a, I81), I80 and Net is rotatably mounted between two ears I9 depending from metal strips Illa. These strips extend in a lengthwise direction with reference to the core and are each loosely supported at their inner ends by a downwardly extending post 20 which is fixed at its upper end to the insulating plate I! and is provided with a pin 20a at its lower end which passes loosely through an opening in the end of the strip I911. The other end of each strip is guided by a post 2|, as shown in Fig. 2, which is fixed at its upper end to the insulating plate H, the lower end passing loosely through an opening in one end of the strip l9a. A spring 22 encircles each post 2| and seats at its upper end against the underside of the plate I1, the lower end seating against the upper surface of the strip i9a. Each strip is shown of U-form at its left-hand end in order to conveniently accommodate the reception of the past 2| and spring 22 as shown. It is evident that the spring 22 Y exerts a downward pressure on one end of the strip Na and thereby forces the contact roller with a uniform pressure into engagement with the top portion of the transformer winding, the post and pin 20a serving to guide and support the other end of the strip lfla.

The contact rollers or wheels are made of copper to give good electrical contact and to avoid heating and are tightly fixed upon hubs 23 made of copper graphite composition to provide an anti-friction bearing on the supporting steel axle carried by the ears l9. These hubs form'a good electrical connection with their supporting axles, the axles being fixed to the depending ears l9. trical contact with the rollers and from each end of these strips flexible copper leads 24 and 24a are connected to blocks or contact shoes 25 and 25a. These shoes are mounted on top of the insulating plate I! and are located at each of its corners. The pair of shoes 25 and 25a on one side of the plate I! are in electrical connection by the flexible leads 24 and 24a with the two rollers 18c and I8d which engage One path of alternate contacting and non-contacting portions of the winding. The two shoes 25 and 25a on the other side of the plate I! are in electrical connection with the two rollers |8a and [8b which engage the other path of alternate contacting and non-contacting portions of the winding. Furthermore, as shown in Fig. 5, one roller of each pair is advanced slightly with reference to the other roller of its pair for securing the displacement of line contact of the two rollers so that the distance between their lines of contact in a direction at right angles thereto will be less than the width of the insulating strips H, a, etc. This displacement is accomplished by slightly offsetting the mounting of the strips lid on the insulating plate IT, as shown in Fig. 5.

At each end of the core is clamped, by the end plates 26, the lower ends of an inverted U-shaped strip 21. Above the transformer core and extending longitudinally therewith is a pair of contact rails preferably made of brass and which are of angular form as shown in Fig. 3. The ends of these rails extend within the upper portion of the inverted U-strips 21 and are fixed thereto by bolts 3|, intervening insulation material 32 being interposed between these rails and the U-supports 21, the bolts likewise being insulated from the supports 21 by insulating washers 33 and the shank of these bolts being likewise insulated from the supports 21. The top surface and outer sides of the contact shoes 25 and 250 are in sliding contact with the inside surfaces of the two angle rails 30 respectively, as well shown in Fig. 3. It is therefore evident that the current from the two pairs of rollers is conducted respectively to the two conducting rails 20.

Referring to Fig. 2 it will be seenthat one of the end clamping plates 26 of the core is extended and forms an outwardly extending flange 35. On the outer face of this is mounted an insulating strip 36 on which are mounted three terminal bolts 31a, 31b and 310. These bolts are of course insulated from the supporting flange 35. connection is made to the terminal 31a from one end of the portion [2 of the transformer winding, as shown in Fig. 2. Connection to the terminal 31b is made to the other end of the transformer winding as shown by the lead I; in Fig. 2. The two terminals 31a and 31b are connected to the source of energy, such as the source I of Fig. 1. The terminal 31c is connected to one side of the consumption circuit by a conductor which corresponds to the lead 8 of Fig. 1.

Secured to the upper portions of the sides of The strips 19a are thus in good electhe left-hand U-support 21 are strips 40 which extend to the left and have outwardly projecting flanges, as shown in Figs. 2 and 4. The front pair of flanges support the iron core 4| of a reactor having a winding a. The flanges 40 at the rear side of the unit support a similar core 42 of a reactor having a winding 42a. The lead 43 from the rear terminal bolt 3i is connected to one terminal of the reactor winding 42a thereby placing this winding in electrical connection with the rear rail 30 and the rear pair of brushes. A lead 44 from the other terminal of this winding is connected to the upper terminal 310. A lead 45 from the front terminal bolt 3! is connected to one terminal of the reactor winding a, thus placing it in electrical connection with the front pair of brushes. The other terminal of this winding is connected to the terminal 31c by a lead 46, thus bringing the terminals of the reactor windings to a common connection from which the lead 8 of Fig. 1 extends to one side of the consumption circuit. A point in the lead 43 is connected to one terminal of the impedance or resistive device 8a, the other terminal of which is connected to a point in the lead 45, thus forming a discharge path connection between these points corresponding to the discharge path provided by the impedance 8 as shown in Fig. 1.

In order to move the carrier assembly over the two paths of the transformer winding, a handle or any other convenient means may be provided. In the drawings a yoke is shown pivotally mounted at a fixed point 5| below the unit and having the sides of the yoke extending upwardly and embracing the two sides of the unit. The upper ends of the yoke are slotted to engage a pair of rollers 52 which are rotatably'mounted on pins 53 formed on the ends of a square rod which is secured to the underside of the insulating plate I1 and extending crosswise thereto. The controlling yoke is provided with a handle 54 below the pivot 5| and it is evident by moving the handie, the contact carrier assembly may be moved along to any position desired for adjustment of the voltage applied to the load circuit. Instead of providing an operating handle 54, this part may be connected to other operating means for securing control as desired in relationship to other controlling devices and arranged for obtaining presets of lighting scenes and graduation of control in a manner which will be understood by those skilled in the art. It will be appreciated that the springs 2| not only serve to press the contacting rollers or wheels into proper engagement with the contact portions of the transformer winding but also serve to force the contact shoes 25 and 25a upwardly into engagement with the angle rails 30, thus securing and maintaining good electrical contact in all positions of adjustment.

The operation of the structure shown in Figs. 2 to 5 will be understood from the description already given in connection with Fig. 1. However, by reason of the two paths of travel of the contacts being on the top side of the transformer winding in Figs. 2 to 5, as distinguished from being on two opposite sides as indicated in Fig. 1, it will be appreciated that when the rollers are in bridging position between contacting portions of the transformer winding and adjoining insulating strips, one turn of the transformer winding is in series with the reactive devices in the local circuit, as distinguished from a half turn under the same conditions in Fig. 1.

Where the claims refer to the inductive reactive devices as having individual iron cores, it should be understood that this means the flux of each of the cores isnot materially aflected by.

i1,-. Electric controlling apparatus comprisin an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions or the'winding with intermediate non-contacting portions in another path along the winding, contacts movable along said paths respectively, means for continuously maintaining said contacts in the same relative position to each other at all times including the time of simultaneous movement along said paths, longitudinal conductors extending over said paths respectively, and means for maintaining electrical connection between.

said contacts and said conductors respectively when said contacts are moved along said paths.

2. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts movable along said paths respectively, means for continuously maintaining said contacts in the same relative position to each other at all times including the time of simultaneous movement along said paths, longitudinal conductors extending over said paths respectively, contacts engaging said conductors and electrically connected with said first named r ies'with each or said contacts respectively and connected between said contacts and said com- 'mon connection, said reactive devices being proportioned to cause their cores to be magnetized approximately in the region of the knee of the magnetization curve when they are jointly connected in the load. circuit and to be magnetized beyond the knee of the curve when individually connected in the load circuit.

5. Electric controlling apparatus comprising an adjustable inductive winding, contacts electrically connected to each other and having a common connection to a load circuit and adapted 'to be alternately connected to said winding and to be jointly connected tosaid winding between the alternate connections, an individual iron cored inductive reactive device connected in series with each of said contacts respectively and connected between said contacts and said common connection, said reactive devices being proper tioned to cause their cores to be magnetized approximately in the region of the knee of the magnetization curve when they are jointly connected in the load circuit and to be magnetized beyond the knee of the curve when individually connected in the load circuit, and an impedance device connected irom a point between one of said contacts and its reactive device to a point between the other oi said contacts and its reactive device.

contacts respectively, and means for yieldably forcing said first named contacts in one direction into engagement with their respective paths and for yieldably forcing said second named contacts in the opposite direction in engagement with their respective conductors.

3. Electric controlling apparatus comprising an adjustable inductive winding, contacts electrically connected to each other and variably connected to said winding and having a common connection to a load circuit. an individual iron cored inductive reactive device connected in series with each of said contacts respectively and connected between said contacts-and said common connection, said reactive devices being proportioned to cause their cores to be maintained at approximate saturation under all operating conditions, and an impedance device connected from a point between one of said contacts and its reactive device to a point between the other of said contacts and its reactive device. 1 4. Electric controlling apparatus comprising an adjustable inductive winding, contacts electrically connected to each other and having a common connection to a load circuit and adapted to be alternately connected to said winding and to be Jointly connected to said winding betweenthe alternate connections, and an individual iron cored inductive reactive device connected in seintermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for maintaining an offset electrical contact condition between one of said contacts and its path and that of the other of saitd contacts and its path when moved along said pa hs.

7. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively and having a common connection to a load circuit, an individual iron cored inductive reactive device permanently connected in series with each of said contacts respectively and permanently connected between said contacts and said common connection, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time 01 their simultaneous movement along" said exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts electrically connected to each other and movable along said paths respectively and having a common connection to a load circuit, an individual iron cored inductive reactive device permanently connected in series with each of said contacts respectively and permanently connected between said contacts and said common connection, an impedance device connected from a point between one of said contacts and its reactive device to a point between the other of said contacts and its reactive device, and means for maintaining said contacts in fixed mechanical relation to each other for alternately and jointly making engagement with said contacting portions of the respective paths when moved along said paths.

9. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively, the contacting portions of said contacts in the direction of movement having a width less than the space between the contacting portions of said winding, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for alternately making engagement with said contacting portions of the respective paths when moved along said paths.

10. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively and having a common connectionto a load circuit, the contacting portions of said contacts in the direction of movement having a width less than the space between the contacting portions of said winding, an individual iron cored inductive reactive device per manently connected in series with each of said contacts respectively and permanently connected between said contacts and said common connecion, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for alternately and jointly making engagement with said contacting portions of the respective paths when moved along said paths.

11. Electric controlling apparatus comprising an inductive winding having alternate-exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts electrically connected to each other and movable along said paths respectively and having a common connection to a load circuit, the contacting portions of said contacts in the direction or movement having a width less than the space between the contacting portions of said winding, an individual iron cored inductive reactive device permanently connected in series with each of said contacts respectively and permanently connected between said contacts and said common connection, an impedance device connected from a point between one of said contacts and its reactive device to a point between the other of said contacts and its reactive device, and means for maintaining said contacts in fixed mechanical relation to each other for alternately and jointly making engagement with said contacting portions or the respective paths when moved along said paths.

12. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts movable along said paths respectively, means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths, and conductors permanently electrically connected together extending in a direction parallel with said paths respectively and in electrical connection with said contacts respectively.

13. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts movable along said paths respectively, conductors permanentlyelectrically connected together extending in a direction parallel with said paths respectively and in: electrical connection with said contacts respectively, said conductors having a common connection to a load circuit, an individual iron cored inductive reactive device permanently connected in series with each of said conductors respectively and permanently connected between said conductors and said common connection, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for alternately and Jointly making engagement with said contacting portions of the respective paths when moved along said paths.

14. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions oi the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively, said paths being located adjacent to each other, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for maintaining an oflset electrical contact condition between one 01 said contacts and its path and that of the other 0! said contacts and its path when moved along said paths.

15. Electric controlling apparatus cmnprising 16 electrical contacting portions 01 the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate,"

exposed contacting portions of the winding with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively, one of said paths being located on one side of said winding and the other of said paths being located on another side of said winding, and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement along said paths and for maintaining an ofiset electrical contact condition between one or said contacts and its path and that of the other of said contacts and its path when moved along said paths.

16. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions of the winding with intermediate non-electrical contacting portions in a path along the winding and other alternate exposed contacting portions of the winding with intermediate non-contacting portions in another path along' the winding, contactspermanently electrically connected to each other and movable along said paths respectively, each 01' said paths comprising alternate raised and depressed portions of the winding and insulating material covering said depressed portions to provide smooth contacting surfaces for engagement by said contacts, each raised portion in one path and depressed portion in the other path forming portions of the same turn of the winding, and means for maintaining saidcontacts-in fixed mechanical relation to each other for maintaining an offset electrical contact condition between one of said I contacts and its path and that of the other of said contacts and its path when moved along said paths.

17. Electric controlling apparatus comprising an inductive winding having alternate exposed electrical contacting portions 01' the winding with ,intermediate non-electrical contacting portions f in'a path along the winding and other alternate exposed contacting portions oi. the winding ,with intermediate non-contacting portions in another path along the winding, contacts permanently electrically connected to each other and movable along said paths respectively, each of said paths comprising alternate raised and depressed portions of the winding and insulating material covering said depressed portions to provide smooth contacting surfaces for engagement bysaid contacts, each raised portion in one path and depressed portion in the other path forming portions of the same turn of the winding, and the raised and depressed portions in one path of said winding being in staggered relation to the raised and depressed portions of the winding of the other path. and means for maintaining said contacts in fixed mechanical relation to each other for maintaining an oii'set electrical contact condition between one of said contacts and its path and that of the other of said contacts and its path when moved along said paths.

18. Electric controlling apparatus comprising an adjustable inductive winding, contacts electically connected to each other and variably connected to said winding and having a common connection to a load circuit, an individual iron cored inductive reactive device permanently connected in series wtiheach or said contacts respectively and permanently connected between said contacts and said common connection, said reactive devices being proportioned to cause their cores to be maintained at approximate saturation under all operating conditions,and means for continuously maintaining said contacts in the same relative position to each other at all times including the time of their simultaneous movement for alternately and Jointly making engagement with said'winding when moved to make a variable connection to said winding.

FRANK G. LOGAN.