US2200968A - Electric circuit control means - Google Patents

Description

May 14, 1940. L. R. RUNALDUE ELECTRIC CIRCUIT CONTROL MEANS Filed April 15, 1938 Ihventor Lewis Rfiunaidue, b ian cffiwfim y Hi Attorney.

Patented May 14, 1940 UNITED STATES PATEnr orrics Lewis R. Runaldue, Pittsfleld, Mass, assignor to General Electric Company, a corporation or New York Application April 13, 1938, Serial No. 201,799

10 Claims.

My invention relates to electric circuit control means and more particularly to electric circuit control means energized from alternating or periodically varying current supply means.

In the control and regulation of electric circults, apparatus and devices, it is common practice to employ an electroresponsive device such as a. relay with a movable armature or plunger operative to different positions, depending upon the variation of the controlled condition above or below a predetermined value. Relays of this type, unless specially constructed, exhibit a different impedence for different operating conditions such as for difierent positions 01' the arms.

ture or plunger when operated from an alterhating current circuit. It is desirable in certain applications to maintain the impedance of the electro-responsive device substantially constant for any operating position or condition. I have found that a condition of substantially constant impedance and power factor is particularly desirable in connection with so-called nonlinear resonant circuit control and regulating devices. One of the well known forms of the nonlinear resonant circuit relays comprises a so-called series type nonlinear resonant circuit wherein a closed core inductance element, a capacitance element and a resistance element are connected in series relation with a relay connected to be energized across one of the elements, such as the capacitance, of the nonlinear resonant circuit. In this type of circuit the voltage at which the current of the nonlinear circuit changes abruptly to a higher value and hence causes the relay to pick up is known as the resonant or pick-up voltage and the voltage at which the current of the nonlinear circuit abruptly decreases to a lower value and hence causes the relay to drop out is known as the dissonant or drop-out voltage. The difierence between the pick-up and drop-out voltages is known as the holding effect. It has been found in practice that in certain applications of the nonlinear resonant circuit relays, certain circuit conditions cause a variation in the holding effect which is undesirable particularly in many regulating applications.

It is an object of my invention to provide an improved electric circuit control means.

It is another object of my invention to provide an improved electric circuit control means of the nonlinear resonant type.

It is a further object of my invention to provide a nonlinear resonant relay which shall have a substantially constant holding effect.

It is a still further object of my invention to (Cl. PIS-32M provide an improved arrangement of a plurality of nonlinear resonant relays wherein the diier ence between the voltages at which the respec tive relays operate may be maintained substan tially constant.

In accordance with the illustrated embed ments of my invention, I provide means whereby the impedance and the power factor of the relay circuit energized from the nonlinear resonant circuit are maintained substantially constant.

One of the illustrated embodiments shows a corrective inductance associated with the relay coil, while another form shows how my invention may be carried into efiect with a capacitance.

My invention will be better understood by ref erence to the following description taken in con nection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. l is a diagrammatic illustration of an embodiment of my invention wherein a corrective inductance is used; Fig. 2 shows a modification of the arrangement illustrated in Fig. 1 wherein a. corrective capacitance is used, and Fig. 3 is a diagrammatic illustration of an embodiment of my invention as applied to a plurality of relays in a regulating circuit.

Referring to Fig. 1 of the drawing, I have shown a nonlinear resonant circuit of the series type comprising a closed core saturable inductance iii, a fixed resistance I l, a variable resistance l2, and a capacitance I3 all connected in series to be energized from a suitable source of alternating current represented very diagrammatically as an alternating current generator II. An electroresponsive device, illustrated as an electromagnetic relay I5, is connected to be energized from the nonlinear resonant circuit and preferably in accordance with the voltage across the capacitance element 13. The relay [5 is shown, by way of example, as comprising an operating coil it provided with a movable core l1, although it will be obvious to those skilled in the art that my invention is not limited to a particular type of relay and is equally applicable whether core movement is involved or some form of fixed core provided with a movable armature. In its broader aspects my invention is applicable for use in connection with any type of nonlinear resonant circuit of the series, parallel, or series-parallel type, etc., and with various types of electro-responsive devices which exhibit a difierent impedance in the operated and nonoperated positions. The relay |5 is provided with circuit controlling means which are illustrated as a pair of contacts I8 and I9 arranged to control the energization of a control circuit 20 which may be energized from any suitable source, which, as illustrated, may be the source I4.

One circuit condition which causes a variation in the holding eflect of a relay energized from a nonlinear resonant circuit is a variation in the wave shape of the applied voltage. In accordance with my invention, I maintain the impedance and power factor of the relay circuit substantially constant so that the pick-up and drop-out voltages of the relay will be aflected equally byvarlations in wave shape and hence the holding eifect will be maintained substantially constant. In the form of relay shown in Fig. 1 when the core I! is pulled into its winding IS, the impedance of the relay is higher than when the core is in its drop-out position. In order to keep the impedance and the power factor, both in magnitude and sign, oi the relay circuit substantially constant, I provide a compensating circuit comprising a resistance 2i and an inductance element 22 to be connected in parallel relation with the relay it when the relay moves to its pick-up position, so that the impedance and power factor of the relay circuit are substantially the same in the pick-up position of the relay as in the drop-out position. Obviously, no particular value of the compensating impedance can be specified for all cases since the various types of relays will vary widely as to im pedance values in the pick-up and drop-out positions, respectively. However, with a nonlinear resonant relay now used commercially, I have found that a compensating circuit comprising henrys in series with 1000 ohms of resistance compensates satisfactorily for the changes in impedance and power factor of a commercial relay used in connection with distribution regulators wherein the relay impedance increase in the pickup position is of the order of five times the impedance in the drop-out position. In the embodiment illustrated in Fig. 1, the compensating circuit 2i--22 is connected automatically in parallel with the relay coil l6 through the control circuit contact l3 of the relay l5. However, it will. occur to those skilled in the art that the connection of the compensating circuit may be effected in a number of ways, such as by separate sets of contacts as shown in other embodiments of my invention, without departing from my invention in its broader aspects.

In Fig. 2 I have shown another embodiment of my invention which utilizes a capacitance compensating means and in which the impedance of the relay circuit in the drop-out position of the relay is maintained at the same value as the impedance of the relay in its pick-up or closed position. In this illustrated embodiment of my invention, elements corresponding to those oi Fig. 1 have been assigned the same reference numerals. The compensating circuit in this arrangement comprises a capacitance 23 which is connected through separate contacts 24 of relay l5 in parallel relation with the relay coil IS in the drop-out position of the relay and automatically disconnected when the relay is in its pick-up position. In commercial applications it may be desirable to include a resistor 23' in series relation with the capacitor 23 for purposes of adjustment. The main contacts l3 and IQ of relay I5 control the energization of the control circuit 20, but in this case the control circuit is arranged to be energized from a, separate source 25. However, it is immaterial, so far as my invention is cona,aoo,ess

c'erned, what source is utilised to energise the control circuit 23.

In Fig. 3 I have shown an embodiment of my invention in connection with each resonant relay ot a plurality oi relays so that a substantially constant regulating band width may be maintained in spite of changes in wave shape of the voltage applied to the respective resonant relay circuits. In this arrangement the circuit 23 represents diagrammatically an electric circuit, such as a feeder circuit, connected to beenerglzed from a. source 21. Load devices are schematically indicated by a resistance 23, inductance 23, and capacitance 30 connected to be energized from circuit 23. A regulator 3|, which is to be taken as illustrative of any of the known types of regulators, whether oi. the rheostatic, inductive or step type, is diagrammatically represented as a single phase induction regulator connected to the circuit 28 in the well known manner and arranged for operation by any convenient electric means shown as a reversible motor 32.. The motor 32 is illustrated, by way of example, as of the capacitor type having two controlling circuits 33 and 34 for selectively determining the direction of rotation of the motor and acommon return conductor 35. The motor 32 is arranged to operate the regulator 3| through suitable gearing 36 and is connected to be energized from any convenient source, such as from the circuit 23 through transformer 37. The return conductor 35 is connected permanently to one side of the secondary winding of transformer 31, while the conductors 33 and 34 are arranged to be selectively connected to the other side of the secondary winding of transformer 31 in accordance with the operation of circuit control means 33.

The circuit control means 33 includes a pair of relays 39 and 43. Relay 33 may comprise an operating winding 4| having a movable core member 42 for closing a pair of contacts 43 in the control circuit conductor 33 when the relay winding 4| is deenergized below a predetermined value or in its drop-out position. This relay is provided with an inductance compensating circuit, as

shown in Fig. 1 of the drawing, which includes a resistance 44 and an inductance 43 arranged to be connected in parallel with the operating winding 4| through relay contacts 45 when relay 39 is in its pick-up position. Similarly, relay 43 may comprise an operating winding 41 having a movable core member 48 for closing a pair of contacts 43 when the winding 41 is deenergized below a predetermined value, or the relay is in its dropout position, and for simultaneously opening contacts 43 and closing contacts 33 in the control circuit conductor 34 when the relay 43 is in its pick-up position. The relay 43 is similarly provided with an inductance compensating circuit comprising the resistance 3|, and inductance 32 which are arranged to be connected in parallel with the relay winding 41 through relay contacts 53 when the relay moves to its pick-up position. The contacts 43 of relay 33 when closed complete the circuit including conductors 33 and 33 if contacts 49 of relay 40 are closed for operating the motor 32 in a direction to raise the voltage of circuit 26 and hence relay 33 may be referred to as the raise relay. The contacts 33 of relay 40 when closed complete the circuit including conductors 34 and 35 for operating motor 32 in a direction to lower the voltage of circuit 23 and hence relay 40 may be referred to as the "lower" relay. Since the lower" relay must be in its drop-out position in order for the raise relay all) to complete the raising circuit, an electrical interlock is thereby provided so as to prevent closing of both motor control circuits at the same time.

Relays 39 and 40 are each controlled by a different nonlinear resonant circuit indicated generally by R and L, respectively. The nonlinear resonant circuit R, for controlling relay '9, is shown as a series type circuit comprising a capacitance it, a saturable inductance I! and a resistance 56. Both the inductance and resistance may be made adjustable, as shown, in order to adjust the holding effect of the relay. The inductance may be made adjustable by various known means and, by way of example, I have shown a rotatable core member 51 operating in a gap in the core and so shaped, such as a seg ment of a cylinder as shown, that upon rotation the reluctance of the core may be changed to vary the inductance of the inductance element 55. The drop-out or dissonant voltage of the relay is adjusted primarily by adjusting the resistance 56, whereas the pick-up or resonant voltage is adjusted by adjusting the inductance element 55. log All of relay 39 is connected to be energized in accordance with the voltage of capacitance 5d. The nonlinear resonant circuit L is similarly shown as comprising a series type of circuit including a capacitance 58, an inductance 59 and a resistance to. The inductance element 5t is made adjustable in a manner similar to the in ductance element by means of the core reluc tance varying means 5t.

The nonlinear resonant circuits El and L are connected to be energized from the circuit 2% in any desired manner in order to be responsive to the condition to be controlled, and l? have shown, by way oi example-a lrnown arrangement which comprises an auto-transformer 52 having adjustable taps til and 6%, respectively, connected to the different conductors of circuit 26. One side of the nonlinear resonant circuits may be perms." neatly connected to some appropriate point in the transformer lit and the other side of each of the nonlinear circuits may be connected, rcspectively, through adjustable connecting means 65 and St to other points oi different potentials.

in voltage regulating systems it is common practice to hold on the regulated current some selected voltage such as 115 volts. Under such conditions, it is common practice to require a band of several volts between operating voltages of the raise and lower relays. This band may be, for example, 3 volts. It is also desirable to have some holding effect, for example 0.5 volt. to insure positive action of the mechanism. The adjustment of the band width may be obtained by adjusting the dissonant or drop-out voltage of the raise relay 39, for example by adjusting the resistance 55 of the raise nonlinear resonant circuit. The holding effect of relay 39 is adjusted by adjusting the resonant of pick-up voltage by means of the inductance adjusting means 51. The lower relay 40 is adjusted by means of the inductance varying means 6| so that its resonant or pick-up voltage will lower the voltage when the relay pulls in. The dissonant or drop-out voltage of relay 40 may be adjusted by means of the resistance to give the proper holding effect. Thus with the holding effect of the respective relays adjusted and the band width adjusted, my compensating circuit, as employed with each relay, will maintain the holding effect of each relay substantially constant and will at the same time maintain the band width constant in spite of Thewindvariations in wave form. Although the pick-up and drop-out voltages of the respective relays may vary, the difference between these voltages for any one relay, or the diiference between the drop-out voltage of one relay and the pick-up voltage of another, may be maintained substan tially constant.

The general system shown in Fig. 3 and the operation thereof is known in the art and only a brief description thereof, sufliclent to explain the manner in which my compensating means operates in such a system, is believed to be necessary. Let it be assumed that it is desired to hold 115 volts on circuit 26 and that the raise relay 39 is adjusted to have a drop-out voltage of 113.5 volts and a holding effect of 0.5 volt and hence a pick-up voltage of 114 volts. If the band width is to be 3 volts, then the lower relay adjustment must pick up at 116.5 volts with a holding effect of 0.5 volt and will drop out at 116 volts. If the voltage of circuit 26 drops to 113.5 volts, the relay 39 will drop out and close an energizing circuit through its contacts 43 and circuit 33 to cause motor 32 to operate in such a direction as to increase the voltage of circuit'26. When the voltage of circuit 28 reaches the assumed pick-up value of il volts, relay 39 picks up and the regulator brings the regulated voltage up to the nominal value of 115 volts. When relay 39 picks up it closes its contacts 46 to connect the compensating circuit 48-45 in parallel with the relay winding M and thereby keeps the impedance of the relay circuit at the same value as for the drop-out position of the relay and hence maihtains the holding effect constant. if new the voltage of circuit 26 increases to the pick-up value of relay cc, which is assumed to be lldd volts, relay ct picks up, closes its contacts 50 in control conductor 3 to cause motor 32 to operate in such a direction as to decrease the voltage of circuit 28. At the same time, the compensating circuit 5l-tt is connected in parallel with the relay winding ll so that the impedance of this relay circuit is kept at the same value as for the drop-out position of the relay. When the volt' age of circuit at decreases to the assumed dropout voltage of 116 volts, relay Ml drops out and the regulator brings the voltage down to the nor mal value of 115 volts. Since the holding effect of the respective relays is maintained constant. then'the band width will therefore be maintained constant even though there may be slight simultaneous and equal variations in the pick-up and drop-out voltages of the respective relays. For example, if the drop-out voltage of the raise relay changes to 114 volts, then the pick-up voltage of relay 40 will increase a like amount to 117 volts and the band width will still remain 3 volts.

While I have shown and described particular embodiments of my invention, it will occur to those skilled in the art that various changes and modifications may be made without departing from my invention and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an electric circuit, a branch circuit including an electroresponsive device connected to be energized from said circuit and normally having different impedance values for different operating conditions of said electroresponsive device, and means operative in accordance with an operating condition of said electrodill responsive device' for varying the impedance of said branch circuit for maintaining the impedance of said branch circuit substantially constant for different predetermined operating conditions of said electroresponsive device.

2. In combination, an electric circuit, a branch circuit connected to be energized from said electric circuit and including an electromagnetic relay having two operating conditions and normally having a diil'erent impedance in one operating condition than in the other, and means operative in accordance with the operation of said relay from one operating condition to the other for maintaining the impedance of said branch circuit substantially the same for either operating condition of said relay.

3. In combination, an alternating current circuit, an electromagnetic relay connected to be energized from said circuit, said relay having a magnetic element movable from one operating position to another and normally having a higher impedance for one position of said magnetic element than the other, a branch circuit comprising an inductance element having such a value when connected in parallel relation with said relay at its normally high impedance position as to render the impedance and power factor of said branch circuit substantially the same as for said other position of said magnetic element, and circuit control means operated by said relay for connecting said inductance element in parallel relation with said relay when in its higher impedance position.

4. In combination, an alternating current circuit, an electromagnetic relay connected to be energized from said circuit, said relay having a magnetic element movable from one operating position to the other and normally having a relatively high impedance for one position of said magnetic element and a relatively low impedance for the other position of said magnetic element, a branch circuit comprising a capacitance element normally connected in parallel relation with said relay in its low impedance position and having such a value as to render the impedance and power factor of said branch circuit substantially the same as for the high impedance position of said magnetic element, and circuit control means operated by said relay for disconnecting said capacitance when said magnetic element moves to its high impedance position.

5. In combination, a nonlinear resonant circuit comprising a saturable inductance and a capacitance, a branch circuit connected to be energized from said nonlinear circuit and including a relay normally having relatively high and low impedance operating positions, a second branch circuit including an impedance having such a value of impedance when connected to said first branch circuit as to render the impedance and power factor of said first branch circuit substantially the same in both operating positions of said relay, and means controlled by said relay for connecting said second branch circuit to said first branch circuit in one of the operating positions of said relay.

6. In combination, a nonlinear resonant circuit comprising a saturable inductance and a capacitance, a branch circuit connected to be energized from said nonlinear circuit and including a relay having normally relatively high and low impedance operating positions, a second branch circuit comprising an inductance element having such a value when connected in parallel relation with said relay in its high impedance position as to render the impedance and power factor or said branch circuits substantially the same as for the low impedance position or said relay, and switching means operative in accordance with the position of said relay for connecting said second branch circuit in parallel relation with said first branch circuit when said relay is in its normally high impedance position.

7. In combination, a nonlinear resonant circuit comprising a saturable inductance and a capacitance, a branch circuit connected to be energized from said nonlinear circuit and including a relay having normally relatively high and low impedance operating positions, a second branch circuit comprising a capacitor connected in parallel relation with said first branch circuit when said relay is in its low impedance position and having such a value of capacitance as to render the impedance and power factor of such branch circuits substantially the same as for said high impedance position of said relay, and switching means operative in accordance with the por-' 'tion of said relay for disconnecting said second branch circuit from said first branch circuit when said relay is in its high impedance positions.

8. In combination, an alternating current circuit, an electroresponsive device, a pair of electromagnetic relays each being connected to be energized from said circuit and arranged for controlling said electroresponsive device, said relays each having two operating positions and each normally having relatively high and low impedance positions, means for adjusting the holding efiect of each relay, means for adjusting the band width of said relays, impedance means in,

operative connection with each relay, and circuit controlling means for changing the connection of said impedance means with its associated relay for maintaining the impedance and power factor of each relay circuit substantially the same in either of its operating positions so as to maintain the band width of said relays substantially constant.

9. In combination, an alternating current circuit, an electroresponsive device, a pair oi nonlinear resonant circuits connected to be energized from said circuit, a pair of electromagnetic relays each having normally relatively high and low impedance operating positions and each connected to be energized from a different nonlinear resonant circuit, said relays being arranged for controlling said electroresponsive device, means for adjusting each nonlinear resonant circuit for adjusting the holding effect of the relay associated therewith, means for adjusting each nonlinear resonant circuit for adjusting the band width of said relays, a pair of branch circuits each including an impedance element having such a value relative to the value 01' its associated relay as to render the impedance and power factor of each relay substantially the same for either of its operating positions, and switching means operated by each relay for changing the connection of its associated branch circuit when said relay changes from one operating position to the other so as to maintain the band width 01' said relays substantially constant.

10. In combination, an alternating current circuit, an electroresponsive device, a pair of nonlinear resonant circuits connected to be energized from said circuit, a pair of electromagnetic relays each having a normally relatively high impedance in its pick-up position and a relatively low impedance in its drop-out position, each of said relays being connected to be energized from a difierent nonlinear resonant circuit, said relays being arranged for controlling said electroresponsive device, means for adjusting each nonlinear resonant circuit for adjusting the holding effect of the relay associated therewith, means for adjusting each nonlinear resonant circuit for adjusting the band width of said relays, a pair of branch circuits each including an inductance element having such a value when connected in parallel m relation with its associated relay in its pick-up position as to render the impedance and power factor of said relay and its associated branch circuit substantially the same as for the drop-out position of said relay. and switching means operated by each relay for connecting its associated branch circuit in parallel relation therewith when each relay is in its pick-up position so as to maintain the band width of said relays substantially constant.

LEWIS R. RUNALDUE.

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