US2206920A - Apparatus for electrical control - Google Patents

Description

July 9, 1940. A. s. RIGGS 2 5 APPARATUS FOR ELECTRICAL CONTROL Original Filed Sept. 9, 1936 g v EEEEEEEEPFEI m INVEN TOR.

fly 94v Q51 514660 ATTORNEY Patented July 9, 1940 PATENT OFFICE APPARATUS FOR ELECTRICAL CONTROL Alger S. B ns, Miami Beach, Fla, assignor of one-third to John B. Brady, Washington,

Original application September 9, 1936, Serial 100,017. Divided and this application August 12, 1937, Serial No. 158,807

, 1 C a m My invention relates broadly to means for producing alternating current voltages of predetermined wave form, primarily for control purposes, as functions of rotational speeds, and more particularly to apparatus for obtaining high degrees of stability and accuracy in control systems for follow-up purposes.

This application is a division of my application Serial Number 100,017, filed September 9, 1936, for Method of and apparatus for electrical control.

One of the objects of my invention is to provide a. construction of apparatus from which an alternating current voltage functional upon ro- 1 tative speed may be derived from a rotating system for control purposes without taking torque from the rotating system.

Another object or my invention is to provide an apparatus for producing an alternating cu.-

rent voltage, as a function of rotational speed, having ireedom from commutator ripple which is present in generating equipment of conventional character.

Another object of my invention is to provide means ior producing an alternating current sigfrom a Selsyn data'transznitting system, for control purposes, which is a function of the angular velocity of rotation of the Selsyn transmitter without in any way loading the Seisyn system by producing said voltage.

@ther and further objects of my invention reside in the operation and construction of apparatus for an electrical control system as set forth more fully in the specification hereinafter fol lowing by reference to the accompanying drav ing in which: A

Figure 1 is a fundamental diagram by which the principle of operation of my device may be tory of the circuit of Fig. 1; Fig. 3 is a vertical sectional view through one form of phase changing controller constructed in accordance with my 7 invention; Fig. 4 is a transverse sectional'view 45 taken on line-H of Fig. 3; Fig. 5 is a vertical sectional view of another form of phase changing controller embodying my invention; Fig. 6 is a transverse sectional view taken on line 6-6 of Fig. 5; Fig. lf-is a longitudinal sectional view takon through a combined phase changing controller and a Selsyn motor employed in the system of my invention; Fig. 8 is a perspective View of the rotorin the apparatus of my invention; and Fig.9 is a detailed diagrammatic view 55 showing the arrangement of the windings in my understood; Fig. 2 is a vector diagram explanaphase changing controller where it is desired to add a damping component. v

My invention relates broadly to means for producing alternating current voltages, primarily for control purposes, as functions of rotational speeds and more particularly to apparatus for the electrical control circuits utilizing amplifier systems for the remote control of heavy objects, such as searchlights and guns, Where there is frequently a need for a device producing alternating current voltages as functions of rotational speeds. A conventional commutator type generator is unsuitable for this purpose because the ripple produced by the commutator may detrimentally afiect the control circuits.

By the use of a device of the character described herein, a smooth alternating current voltage depending upon rotational speed may be. produced. Moreover my device requires negligihis driving torque, inasmuch as it is not a true generator, but a speed actuated phase changing controller.

Due to the negligible toroue required to drive my device, it is practicable to utilize it for the production of alternating current voltages as a 5 function of rotational speed where the taking of high driving torque may give rise to inaccuracies in the control system.-

For instance, in data transmitting systems op erating from a so-called Selsyn system, the use of my invention permits of designing an electrical control for positioning heavy objects which may be operated in exact agreement at all speeds.

an invention utilizes the so-called generator action of an induction type alternating current motor, and is best understood by reference to the operation of such a. motor from zero speed up to its synchronous speed.

Referring to Fig. l, which is a diagrammatic drawing of a two phase squirrel cage type induction motor, the windings L1 and L2 are arranged so that their flux axesare at 90 relation to each otherconsec1uently when the rotor is at rest and an alternating current voltage is applied to the winding L1, which I term the primary, there is no voltage present at the terminals of lo, which I term, the secondary winding. Ii now the rotor is revolved, its motion in the primary flux produces a voltage due to rotation which is inductively conveyed from the rotor to .the secondary coil Lgthis voltage is proportional to rotationel speed up to the speed corresponding to synchronous speed and is 90? out of phase with 3 the voltage applied to the primary winding L i The vector Fig. 2 shows the phase function of speed, up-to synchronous speed and reverses sign upon reversing direction of rotation.

Though generator action is present in producing the secondary or speed votage. an it is also a fact that a corresponding motor action is present-any power taken from the winding In is supplied in reality from the power source connected to the primary L1, and not from the source of ori rotation of the rotor.

In practical use of the device for control purposes it is sometimes objectionable for the motor component to be present, since once started the device tends to run as a single phase A. 0. motor. The motor component maybe reduced to a negligible quantity try electrically log the secondary Winding, and may; he still fin'ther re duced by the dynamic brag action of the we tor in revolving in a D. C. field. I

In order to provide ping action for the ole vice when required, I provide a separate winding upon the stator having a out number of poles than the A. C. We! as illustrated for example in Fig. 9 and energized from a suitable source of D. 0. power. For instance, in one form machine must have a high degree of wave dorm purity-so that the nipple caused by the squirrel cage is seriously detrimental. In such cases I provide a rotor having laminated discs with out slots and simulate the squirrel cage eflect by a conductive sleeve pressed and/or Y I struction in Fig. 3.

In some instances even the rotation of the laminated portion of the rotor gives rise to production of detrimental wave form distortion, and to prevent this I provide a still further form of rotor consisting of a conducting sleeve rotatably mounted, with provision for the'iron core corresponding to the rotor core remaining stationary with the stator and the machine, the construction is shown in Fig. Where it is desired to provide a voltage functional upon the angular velocity (0r rotational speed) of a.Selsyn"data system I propose to directly connect and rigidly attech 9. device of the type shown in Fig.5 to a conventional Selsyn" typereceiver or synchro motor, as I have shown in Fig. 7.

Referring to the drawing in detail, Fig. 3 shows one form of my device for producing a. voltage proportional to rotative speed, composed of the laminated stator I having distributed windings II; the stator is held by means not shown, between the end frames 4 and 9. The rotor consists of the laminated core II which is pressed on the shaft H; the laminated rotor core I! is completely surrounded by the nonmagnetic but electrically conductive cylinder or sleeve II which performs the function of, the squirrel cage illustrated diagrammatically in Fig. 1. The rotor shaft is supported in the bearings II and I2, and a cap I! is provided near the end of the shaft opposite the driving end. Fig. 4, having like parts similarly designated as Fig. 3 is a transverse section at 4-4 of Fig. 3. In Fig. 4 the general means of locating the windings is I repeater motor.

' in the stator.

asoaaao illustrated, the coils 56 being held in the slots by wedgw i8 as in conventional motor practice. The rotor is free to revolve in the stator which it clears by the air gap shown at H.

Fig. 5 is an improved form of my device in which the entire magnetic core is stationary, and having as a rotor only the conducting non-magnetic shell 24. Referring to Fig. 5, the stator core is made up of the laminated .core 1, held between the end frames l9 and 2|, and the laminated core 26 attached by the bolt 25 and nuts 21 and 28 to the frame 20. The laminated core 25 is the counterpart of the rotor core 85 in.Flg. 3. The spacer 30 holds thelnner core 25 in correct relation to the main stator core 1. The rotor consists of the conductive-but non-magnetic cylinder 24 which is attached at 29 to the shaft 23 and supported on bearings 29 and 22. The construction shown in Fig. 5 provides a stationary magnetic structure composed of the main stator core I and the concentrically located inner core 25 with a double air gap ill and Na in which ves the rotor 25%. 6 ice transverse section of Fig. 5 on the line 6-8 and clearly shows the concentric relation of the rotor 24, main stator core 5 and inner core 25.

Fig. '7 is a section of another form of my device which I refer to as a data speed responsive controller, composed of a device as shown in Fig. 5 directly connected to a KSelsyn" type of repeater motor. ferrlng to Fig. 7 the stator core I is held between the end frame 32 and the bonnet 3|; the inner core 25 is held by the bolt 28, and the nuts 2'! and 28 to the and frame 32 and spaced therefrom by the spacer 30. The rotor 24 is attached to the shaft 31 at 38. The

shaft 31 is mounted in the bearings "and to rotate the rotor 24 and the rotor 34 of the Selsyn" The fSelsyn repeater motor is shown for purposes of illustration as composed of the stator 4| held between the and frame 33 and the bonnet and the rotor 34 operating connected to the terminals lll--ll2. 'Ihe primary coils III- l are two pole and the secondary coils ll5ll6 are two pole windings at right angles to the primary, the damper windings compose a four pole winding having poles V as shown and the primary-and secondary and damper windings are all inductively non-reactive upon each other. The D. C. flux produced by the damper winding drags the rotor and prevents motor torque being developed by the speed responsive controller which might produce detrimental eflects when driven by a Selsyn" type rep'eater motor.

Though I have shown specific apparatus for illustration and description of the invention, I desire to be limited only by the-scope of the appended What I claim as new and desire to secure by Letters Patent of the United States is as follows:

A device for producing a voltage proportional A surge damping device as voltage across the other of said windings in said first set, and means for energizing said second set of windings with direct current, a rotor revolvably mounted in the common fiux fields of all of said windings, and external means for 5 driving said rotor for controlling the voltage across said other of' said windings in said first set.

ALGER S. RIGGS.

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