US2752556A

US2752556A - Electrical time delay apparatus

Info

Publication number: US2752556A
Application number: US507214A
Authority: US
Inventors: Jr Bryan Webb; Gilbert D Throop
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1955-05-10
Filing date: 1955-05-10
Publication date: 1956-06-26
Anticipated expiration: 1973-06-26
Also published as: CA585040A; JPS349231B1; DE1136767B; FR1153474A; GB808924A

Description

June 26, 1956 a WEBB, JR ET AL 2,752,556

ELECTRICAL TIME DELAY APPARATUS Filed May 10, 1955 2 Sheets-Sheet 1 F lg. 2.

E I 1) D L 3 I l 5 l .9 I a o I 1 G) 3' I 5 I i J G is Q Y 0 Total Magnetization Force of Windinqs AC and MC WITNESSES INVENTORS Bryon Webb,Jr. 8 W41. Gilbert 0. Throop.

I l i ATTORNEY June 26, 1956 B. WEBB, JR, ET

ELECTRICAL TIME DELAY APPARATUS 2 Sheets-Sheet 2 Filed May 10, 1955 g r .mm 6

m Mnd h 0 n M CAW H p m M T United States Patent ELECTRICAL TIME DELAY APPARATUS Bryan Webb, Jr., Sharon, and Gilbert D. Throop, fihcnango Township, Mercer County, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Application May 10, 1955, Serial No. 507,214

14 Claims. (Cl. 323-43.5)

This invention relates to time delay devices and more particularly to time delay devices utilized in conjunction with transformer tap-changing apparatus.

In applications of time delay devices relating to transformer tap-changing apparatus, the time delay device is generally used to actuate a relay for energizing a motor to change the taps on the transformer for the purpose of maintaining constant line voltage under varying load conditions. The function of the time delay device is to override minor variations in the voltage to be regulated and thus avoid needless tap-changer operations.

Typical time delay devices used heretofore in tap-changing applications utilize a thermo-sensitive mechanical element such as a bimetallic strip to open and close a pair of contacts after the thermo-sensitive element has been heated to a predetermined temperature by the passage of current derived from an actuating circuit. In order to avoid the objectionable features of such mechanical devices, such as arcing at contacts, mechanical fatigue and mechanical failure, it is desirable to utilize components having a maximum number of static electrical elements and a minimum number of elements having moving parts. Cerrain prior art devices having such qualities make use of multi-electrode, multi-grid, high vacuum, thermionic tubes which are quite fragile and not adapted to rough handling and vibration such as are commonly encountered in industrial applications.

Accordingly, one object of this invention is to provide a time delay device making use of static electrical components which are not susceptible to damage as a result of vibration and rough handling.

Another object is to provide a time delay device having long life and a minimum number of maintenance problems under operating conditions.

Still another object is to provide a time delay network particularly adapted for use with tap-changing apparatus, having improved operating characteristics.

Yet another object is to provide time delay apparatus not susceptible to mechanical fatigue and failure.

Other objects and features of our invention will become apparent upon consideration of the following description thereof, taken in connection with the accompanying drawings; wherein:

Figure l is a schematic diagram of one embodiment of our invention;

Fig. 2 is a co-ordinate plot of average output current as a function of total magnetization force of a self-saturating magnetic amplifier, which amplifier is one of the components of the embodiment of our invention shown in Fig. 1;

Fig. 3 is a co-ordinate plot of capacitor voltage as a function of time for the capacitor which is one of the elements in the embodiment of Fig. l; and

Fig. 4 is a schematic diagram, partially in block form, of tap-changer apparatus making use of another embodiment of our invention.

According to one aspect of our invention a control winding of a self-saturating type of magnetic amplifier having a direct current output is coupled directly to a source of control voltage, and a second control winding is coupled to the source of control voltage through a gaseous discharge device or similar device that conducts current only at voltages above a predetermined magnitude and a voltage integrating network. A third control winding is connected to the direct current output circuit of the magnetic amplifier so as to provide a positive feedback circuit which will tend to keep the magnetic amplifier at saturation upon appearance of an output voltage therefrom. None of the control windings is capable of maintaining an output voltage from the magnetic amplifier when energized alone; only when the windings are energized in pairs are they adapted to produce an output voltage from the magnetic amplifier. A signal voltage applied to the first winding thus will not produce an output voltage from the magnetic amplifier until after the voltage output from the integrating circuit has risen to a magnitude whereat the gaseous discharge tube will fire. Upon firing of the tube, the first and second windings are energized, and the magnetic amplifier cores are immediately driven into saturation, producing an output voltage thus energizing the feedback winding which will drive the cores further into saturation. Thereafter, the second control winding may be deenergized without effecting the output of the magnetic amplifier as long as the signal voltage of greater than a given amplitude is applied to the first control winding. However, as soon as the signal voltage is removed from the first control winding, the positive feedback provided by the third control winding will be ineffective to maintain magnetic amplifier output, and thus the output circuit will be deenergized.

More specifically, and with reference to Fig. 1, there is shown a self-saturating type of magnetic amplifier making use of magnetic cores MBl and MB2 on which are wound load or output windings LW, bias windings BW, positive feedback windings PF, main control windings MC and auxiliary control windings AC. The bias windings are wound so as to drive the magnetic cores away from saturation in a given sense, while the load windings LW are wound so as to drive the magnetic source toward saturation in the given sense with the rectifiers R1 and R2 poled as shown. The rectifiers R1, R2 serve as self-saturating rectifiers and also as two elements of a bridge type rectifier circuit along with rectifiers R3 and R4 so as to provide a direct voltage between terminals T3 and T4 with terminal T4 positive with respect to terminal T3. The cathodes of rectifiers R2 and R4 are connected to terminal T4 and the anodes of rectifiers R1 and R3 are connected to terminal T3. A source of alternating current S1 is connected to the juncture of the load windings LW, and also to the cathode of rectifier R3 and the anode of rectifier R4. The positive feedback windings PF are connected to terminals T3 and T4 through resistor 22 and are wound on their respective cores so as to drive the cores toward saturation in the aforementioned given sense.

A source of signal voltage S2 has a voltage integrating circuit comprising resistor Z1 and capacitor C1 connected across the terminals T1 and T2 thereof. The resistor is preferably variable, as shown. A gaseous discharge tube NE, preferably a glow discharge tube utilizing one of the noble gases such as neon, is used to connect control winding MC across capacitor C1, the neon tube and the main control winding being serially connected. Auxiliary control winding AC is connected directly across the terminals T1, T 2. The main control winding MC and the auxiliary winding AC are wound on their respective cores so that the cores will tend to be driven to saturation in said given sense with current flowing therethrough as a result of a positive voltage at terminal T1 with respect to terminal T2.

The magnetizing force provided by windings AC and MC is such that, with maximum voltage from source S2, neither winding AC or MC alone is adapted to produce an output voltage from the magnetic amplifier. However, both windings together produce magnetizing force which is sufiicient to overcome the effect of bias winding BW and produce an output voltage across terminals T3, T4. Similarly, positive feedback winding PF will not sustain an output voltage across terminals T3, T4 unless a given magnetization force is provided by either of windings AC or MC.

The operation of the circuitry described above will be more easily understood by referring to Figs. 2 and 3. The bias winding BW will bias the magnetic amplifier beyond cutoii with zero output voltage from signal voltage source S2 as depicted at point A in Fig. 2. Assume now that the output of source S2 is increased to its maximum capabi ity. The total magnetization force in the core will thus be as shown at B, and since it is due to control windings AC alone, it is insufiieient to produce an output voltage from the magnetic amplifier. However, as shown Pig. '3, the voltage across capacitor C1 Will rise at a rate determined by the time constant of resistor Z1 and capacitor C1 until the firing voltage V1 of the neon tube is reached, as shown at time T1. Thereupon, current will flow through windings MC and the total magnetization force will increase beyond that required to produce an output voltage from the magnetic amplifier. Winding PF will thereupon be energized and the magnetic ampliher will be driven further into saturation. This condition is shown at E in Fig. 2.

Capacitor C1 will now discharge through the neon tube and winding MC until the extinguishing voltage V2 of the neon tube NE is reached as shown on Fig. 3 at time 12. Thereupon winding MC will be deenergized but the full output voltage of the magnetic amplifier will continue to appear across terminals T3, T4 inasmuch as both windings AC and PF are still energized. Capacitor C1 may therefore continuously charge and discharge, thereby energizing and deenergizing the main control winding MC without effecting the output voltage from the magnetic amplifier. Upon removal of the signal voltage from source 52 or reduction of the signal voltage below a predetermined value, the output voltage of the magnetic amplifier will fall to zero as shown at G in Fig. 2.

With reference now to Fig. 4, there is shown a complete voltage regulating system making use of a transformer having a plurality of taps on either the primary or secondary winding thereof and associated tap-changing mechanism such as are well-known in the art. The tapchanging mechanism and transformer are shown in block form and designated by reference numeral 2. The unregulated AC line feeding the transformer is designated by the reference numerals 4, 6. The primaries of transformers 5 and 7 are connected across voltage regulated lines 1, 3, which are in turn connected to the secondary winding of transformer 2. The secondary winding of transformer '7 is connected across serially-connected rectifier 21 and capacitor 23, and also across serially-connected rectifier and capacitor 27. Rectifiers 21 and 25 are oppositely poled so that voltages of opposite polarities appear across

capacitors

23 and 27.

The secondary of transformer 5 energizes the control. windings of relays 9, 11 and '13. Relay 11 picks up with a relatively low voltage appearing across the secondary of transformer 5 so as to close contacts 19. Relay 13 picks up with a relatively high voltage corresponding to the maximum voltage to be permitted between regulated lines, 1 and 3, thus closing contact 17. At a voltage slightly lower than the voltage at which relay 13 picks up, low voltage relay 9 will pick up to open contact 15.

V The voltage at which relay 9 picks up corresponds to the 4 minimum voltage to which regulated lines 1, 3 will be permitted to fall.

Relay contacts 15 and 17, respectively, connect

capacitors

23 and 27 across

terminals

31, 29. Thus, at a predetermined low voltage capacitor 23 will supply a voltage of one polarity across

terminals

31, 29 so that terminal 31 is positive with respect to terminal 29, and at a predetermined higher voltage relay 17 will connect capacitor 27 across

terminals

31, 29 so that terminal 31. is negative with respect to terminal 29.

Magnetic amplifiers MAI and MA2 correspond in every detail to the magnetic amplifier of Fig. l. Magnetic amplifier MAI has load winding LW1 connected to a bridge rectifier including rectifiers 71, 73, 75 and 79 and to AC supply busses 65, 67 so as to provide a selfsaturating magnetic amplifier having a D. C. output such that output terminal 72 is positive with respect to terminal 7'). Similarly, load winding LWZ of magnetic amplifier M112 is connected to

rectifiers

81, 83, and 87 and to supply

busses

65, 67 so as to provide a self-saturating magnetic amplifier having a D. C. output voltage such that terminal 86 is positive with respect to terminal 82. Positive feedback winding PFI is connected to the output terminals 72, 77 through resistor 69, and positive feedback winding PFZ is connected to

terminals

82, 86 through resistor 89. The bias windings BWI and BW2 are serially connected to a single direct current source. Auxiliary control windings AC1 and AC2 are serially connected to

terminals

31 and 29 through contact 19 of relay 11, normally closed contact 55 of cam actuated switch 59, and resistor 35. Windings AC1 are wound on their

respective cores

70, 74 so as to set up flux in the cores opposite to that produced by bias windings BWI with current flowing as shown by arrow 96; i. e. with terminal 29 positive with respect to terminal 31. Windings AC2 are wound on

magnetic cores

80, 84 so as to oppose the flux set up by bias winding BW2 with current flowing therethrough in the direction opposite to arrow 96.

Windings MCI and MC2 of magnetic amplifiers MA1 and MAZ are also serially connected, and are connected to terminals 29 and 31by means of contact 19 and serially connected resistor 33 and gaseous discharge tube 93 which may be a neon glow-discharge tube as previously mentioned in conjunction with Fig. 1. Capacitor 91, which corresponds to capacitor C1 of Fig. l, is connected across serially connected neon tube 93 and main control windings MCI and MC2. The winding MCI is wound on its cores so that, with current as shown by arrow 9 (i. e. with terminal 29 positive with respect to terminal 31) the flux set up thereby will oppose the flux of bias winding BWI. Similarly, windings MCZ are wound on their respective cores so that the flux set up thereby opposes the flux set .up bias winding BW2 with current flowing through windings MC2 in the direction opposite to arrow 94.

Thus, it may be readily apprehended that with the magnetic amplifiers functioning as described with reference to Fig. 1, windings AC1 and MCI will produce an .output voltage across terminals 72, 77 with current flowing therethrough in the direction of arrows 94, 96 and that an output voltage will appear across terminals 52, 86 with current flowing through windings AC2 and MCZ in a direction opposite to that of arrows 96, 94.

The motor driven tap-changing mechanism 2 is driven by D. C. motor ,45'having two field windings 49 and 5?. which are respectively serially connected with the armature of motor 45 across terminals 36, 46 by means of

contacts

37 and 39, respectively. It is to be understood that an A. C. motor may be used in this application if desired. Contact 371s a part of relay 41, the coil of which is energized from the output terminals 72, 77 of magnetic amplifier .MAI. Contact 39 is a part of relay 43, the coil of which is energized by the output of magnetic amplifier MAZfmm the

terminals

82, 86.

For the purpose of discharging capacitor 91 at the end of a tap-changing cycle, cam actuated relay 59, the cam 61 of which is driven by motor 45 through mechanical connections 63, is provided with contact 57 which closes a circuit through discharge resistor 53 so as to discharge capacitor 91.

In operation, energization of transformer 2 will produce an output voltage across lines 1, 3 and pick up relay 11 to close contact 19. Low voltage relay 9 will remain closed until the voltage rises to the predetermined value at which it will pick up. Should the initial voltage across terminals 1, 3 be insufiicient to actuate relay 9 after a predetermined time interval which is determined by the time constant of resistor 33 and capacitor 91, neon tube 93 will fire thus producing an output from magnetic amplifier MA 1 energizing relay 41, closing contact 37, to actuate motor 45 and change the tap of transformer 2 to increase the voltage thereof. At the end of the tap-changing cycle, cam 61 will trip switch 59 closing contact 57 to discharge capacitor 91, and opening contact 55 to deenergize winding AC1 of magnetic amplifier MAI, which will in turn deenergize relay 41 opening contact 37. Thereafter, if the voltage is still too low, the apparatus will go through another cycle until relay 9 is actuated. Should the voltage thereafter drop below that required to pick up relay 9 a discharging cycle as described will be brought about.

Should the voltage across lines 1, 3 rise to a value so as to pick up relay 13, neon tube 93 will fire after a predetermined time interval, thus producing an output voltage from magnetic amplifier MAZ, picking up relay 43, thus closing contact 39 and energizing motor 45. This will actuate the tap-changing mechanism so as to decrease the output voltage from the transformer. At the end of the tap-changing cycle cam 61 will again close contact 57, discharging capacitor 91, and open contact 55 deenergizing winding AC2 of magnetic amplifier MAZ which in turn deenergizes relay.43, opening contact 39.

Small variations in voltage produced by momentary surges will thus be overridden by virtue of the time delay provided by our invention. The static components of the magnetic amplifier eliminate the deleterious eltect or mechanical devices utilized heretofore. The components are generally rugged and insensitive to shock and vibration, and are long lived relative to time delay devices making use of vacuum tubes. The reset action provided by our invention is practically instantaneous in comparison with the relatively long reset required by thermally actuated devices found in the prior art. It has been found that time delays of from 5 seconds to 180 seconds may be readily achieved with practically instantaneous reset.

The invention is not to be restricted to the specific structural details, arrangement of parts or circuit conditions herein set forth as various modifications thereof may be effected without departing from the spirit and scope of this invention.

We claim as our invention:

1. A time delay network for coupling a source of control voltage to a load, comprising: first electrical energy translating means having a direct-current output circuit, the output voltage of said translating means being responsive to signals imposed on first, second and third control circuits therein; means coupling said first control circuit to said source of control voltage including resistor means and capacitor means serially connected across said source of control voltage, and a gaseous discharge tube serially connected with said first control circuit across said capacitor; said second and third control circuits being respectively directly connected across said source of control voltage and said output circuit; said first, second, and third control circuits being individually unable to produce an output voltage from said translating means, said first and second control circuits when energized by a voltage of predetermined magnitude derived from said control voltage source being adapted to produce an output voltage from said translating means; said second and third control circuits together being effective to maintain a given output voltage from said translating means when said signal voltage is greater than a given magnitude.

2. A time delay network for coupling a source of control voltage to a load, comprising: first electrical energy translating means having a direct-current output circuit, the output voltage of said translating means being responsive to signals imposed on first, second and third control circuits therein; means coupling said first control circuit to said source of control voltage including voltage integrating having an increasing output voltage the amplitude of which is a time function of said source of signal voltage serially connected across said source of control voltage, and a gaseous discharge tube serially connected with said first control circuit across the output of said voltage integrating means; said second and third control circuits being respectively directly connected across said source of control voltage and said output circuit; said first, second, and third control circuits being individually unable to produce an output voltage from said translating means, said first and second control circuits when energized by a voltage of predetermined magnitude derived from said control voltage source being adapted to produce an output voltage from said translating means; said second and third control circuits together being effective to maintain a given output voltage from said translating means when said control voltage is greater than a given magnitude.

3. A time delay circuit for coupling a source of control voltage to a load, comprising: self-saturating magnetic amplifier means having a direct-current output circuit, the average output voltage of said magnetic amplifier being variable in accordance with the magnetic force provided by first, second and third control winding means inductively associated therewith; means coupling said first control winding means to said source of control voltage including resistance means and capacitance means serially coupled across said source of control voltage, and a gaseous discharge tube serially connected with said first control winding means across said capacitance means, the firing voltage of said gaseous discharge tube being of magnitude less than the magnitude of said control voltage; said second control winding means being coupled across said control voltage source, the magnetomotive force produced by said second control winding means being effective to produce substantially zero output voltage from said magnetic amplifier, said third control winding means being coupled to the output of said magnetic amplifier so as to be energized thereby, the magnetomotive force produced by said third control winding means alone being insufiicient to maintain output voltage from said magnetic amplifier; the ampere turns produced by said first and second control winding means in combination being of a value to produce output voltage from said magnetic amplifier, and the combined magnetomotive force from said second and third control winding means being sufiicient to maintain output voltage from said magnetic amplifier when said control voltage is greater than a given magnitude.

4. A time delay circuit for energizing a load a pre determined time'interval after coupling a source of signal voltage to said circuit, said circuit including: first and second self-saturating magnetic amplifier means each including two polarized series circuits each including a reactor winding and a rectifier, the two series circuits being connected in parallel circuit relationship in an opposite sense; first, second and third control winding means in inductive relationship with each of said reactor means; bridge rectifier means having input terminals connected to said reactor providing means for deriving a direct-current output voltage therefrom; said first control winding means being connected to the output terminals of said bridge rectifier; said second control winding means being directly connected to said source of signal voltage; and said third control winding means being coupled'to said source of signal voltage through series connected resistance means and glow-tube means, said resistance means forming one element of a series resistance-capacitance circuit connected across said source of signal voltage; the ampere turns produced by said second control winding means alone being insufiicient to produce an output voltage in said output circuit with maximum control voltage applied thereto; the ampere turns produced from said first and second control winding means together being sufiicient to produce an output voltage of predetermined magnitude from said output terminals; the ampere turns of said first and second winding meansrwith a predetermined output voltage from said magnetic amplifier being sufficient to maintain the output voltage of said magnetic amplifier at least at said predetermined value; the ampere turns of said first control winding means alone being insutficient to maintain an output voltage from said magnetic amplifier.

5. In combination with a magnetic amplifier having a direct-current output circuit the magnitude of the output voltage from which is variable in accordance with the magnitude of control voltages imposed on first, second and third control circuits thereof; a source of control voltage directly connected to said second control circuit, said third control circuit being energized by said directcurrent output circuit in a positive feedback circuit: resistor means and capacitor means serially connected across said source of control voltage; a gaseous discharge tube having an ignition voltage which is lower than the magnitude of said control voltage coupling said first control circuit across said capacitor means; said first, second and third control circuits being unable to produce an output voltage from said magnetic amplifier when energized individually; said first and second control circuits being adapted to produce an output voltage from said magnetic amplifier upon simultaneous energization of said second control circuit by control voltage of predetermined magnitude and of said first control circuit by a voltage of magnitude between that of said control voltage and the ignition voltage of said gaseous discharge tube; said second and third control circuits being adapted to maintain an output voltage from said magnetic amplifier until said control voltage drops to a second predetermined magnitude less than said first predetermined magnitude.

6. in combination with a magnetic amplifier having a direct-current output circuit the magnitude of the output voltage from which is variable in accordance with the magnitude of control voltages imposed on first, second and third control circuits thereof: a source or control voltage directly connected to said second control circuit, said third control circuit being energized by said direct-current output circuit in a positive fee back circuit: voltage integrating means having an input circuit and an output circuit, said input circuit being connected to said source of control voltage; a gaseous discharge tube having an ignition voltage which is lowerthan the magnitude or" said control voltage coupling said first control circuit acrossisaid output circuit; said first, secnd and third control circuits being unable to produce an output voltage from said magnetic amplifier when energized individually; said first and second control circuits being adapted to produce an output voltage from said magnetic amplifier upon simultaneous e ergization of said second control circuit by control voltage of predetermined magnitude and of said first control circuit by voltage of magnitude between that of said control voltage and the ignition voltage of said gaseous discharge tube; said second and third control circuits being adapted to maintain an output voltage from said magnetic amplifier until said control voltage drops to a second predetermined magnitude less than said .first predetermined magnitude.

7. An electrical time delay network for producing an output voltage a predetermined time interval after impressing a signal voltage across a pair of voltage terminals thereof, said network comprising: resistor means and capacitor means serially connected across said signal voltage terminals, magnetic amplifier means having direct-current output circuitry and at least first, second and third control winding means for controlling output current from said amplifier means in accordance with magnetomotive force produced by said winding means; said first winding means being coupled across said capacitor by bi-directional gaseous discharge tube means having a breakdown voltage of magnitude less than the maximum amplitude of said signal voltage; said second winding means being coupled across said serially-connected capacitor and resistor means; said third winding means being connected to said direct-current output circuit as a positive feedback loop; said first, second and third winding means being individually inoperative to etfect fiow of output current from said output circuit, said first, second and hird winding means being adapted to produce output current from said magnetic amplifier means when energized at least in pairs with signal voltages of a predetermined magnitude impressed on said signal voltage terminals.

8. In a voltage regulating system including an electrical transformer having primary and secondary windings, and motor driven apparatus for changing taps on said windings and for varying the secondary voltage of said transformer, the combination comprising: first and second direct voltage producing means of opposite polarities having a common first terminal, first relay means responsive to secondary voltages less than a first given magnitude operative to connect the free end of said first direct voltage producing means to a second terminal; second relay means responsive to secondary voltages greater than a second given magnitude operative to connect the free end of said second direct voltage producing means to said second terminal; a motor for driving said motor driven apparatus; third and fourth relay means having contacts which when closed energize said motor for rotation in one direction or the opposite; time delay apparatus for selectively energizing said third and fourth reiay means in accordance with the polarity of the signal voltage across said first and second terminals; resistor means and capacitor means serially connected across said signal voltage terminals; magnetic amplifier means having direct-current output circuitry and at least first, second and third control winding means for controlling output current from said amplifier means in accordance with magnetomotive force produced by said winding means; said first winding means being coupled across said capacitor by bi-directional gaseous discharge tube means having a breakdown voltage of magnitude less than the maximum amplitude of said signal voltage; said second winding means being coupled across said serially-connected capacitor and resistor means; said third winding means being connected to said direct-current output circuit as a positive-feedback loop; said first, second and third winding means being individually inoperative to efiect flow of output current from said mag netic amplifier means when energized at least in pairs with signal voltage of a predetermined magnitude impressed on said signal voltage terminals; said third and fourth relay means being connected to said output of said magnetic amplifier means so as to be energized thereby by output voltages of opposite polarity; and switch means actuated by a cam driven by said motor operative to short circuit said capacitor at the end of a tap changing cycle.

9. A time delay network for coupling a source of signal voltage to a load, comprising: first electrical energy translating means having a direct-current output circuit, the output voltage of said translating means being responsive to signals imposed on first, second and third control circuits therein; means coupling said first control circuit to said source of control voltage including resistor means and capacitor means serially connected across said source of signal voltage, coupling means coupling said control circuit across said capacitor only when the voltage across said capacitor exceeds a predetermined magnitude; said second and third control circuits being respectively directly connected across said source of control voltage and said output circuit; said first, second, and third control circuits being individually unable to produce an output voltage from said translating means, said first and second control circuits when energized by a voltage of predetermined magnitude derived from said control voltage source being adapted to produce an output voltage from said translating means; said second and third control circuits together being effective to maintain a given output voltage from said translating means when said signal voltage is greater than a given magnitude.

10. A time delay network for coupling a source of signal voltage to a load, comprising: first electrical energy translating means having a direct-current output circuit, the output voltage of said translating means being responsive to signals imposed on first, second and third control circuit therein; means coupling said first control circuit to said source of control voltage including voltage integrating having an increasing output voltage the amplitude of which is a time function of said source of signal voltage serially connected across said source of signal voltage, coupling means coupling said control circuit across said capacitor only when the voltage across said capacitor exceeds a predetermined magnitude; said second and third control circuits being respectively directly connected across said source of control voltage and said output circuit; said first, second, and third control circuits being individually unable to produce an output voltage from said translating means, said first and second control circuits when energized by a voltage of predetermined magnitude derived from said control voltage source being adapted to produce an output voltage from said translating means; said second and third control circuits together being effective to maintain a given output voltage from said translating means when said signal voltage is greater than a given magnitude.

11. A time delay circuit for coupling a source of control voltage to a load, comprising: self-saturating magnetic amplifier means having a direct-current output circuit, the average output voltage of said magnetic amplifier being variable in accordance with the magnetic force provided by first, second and third control winding means inductively associated therewith; means coupling said first control winding to said source of control voltage including resistance means and capacitance means serially coupled across said source of control voltage, and coupling means coupling said control circuit across said capacitor only when the voltage across said capacitor exceeds a predetermined magnitude less than the magnitude of said control voltage; said second control winding means being coupled across said control voltage source, the magneto-motive force produced by said second control voltage means being effective to produce substantially zero output voltage from said magnetic amplifier, said third control winding being coupled to the output of said magnetic amplifier so as to be energized thereby, the magnetomotive force produced by said third control Winding alone being insuflicient to maintain output voltage from said magnetic amplifier; the ampere turns produced by said first and second control winding means in combination being of a value to produce output voltage from said magnetic amplifier, and the combined magnetomotive force from said second and third control winding means being sufiicient to maintain output voltage from said magnetic amplifier when said control voltage is greater than a given magnitude.

12. A time delay circuit for energizing a load a predetermined time interval after coupling a source of signal voltage to said circuit, said circuit including: first and second self-saturating magnetic amplifier means each including two polarized series circuits each including a reactor winding and a rectifier, the two series circuits being connected in parallel circuit relationship in an opposite sense; first, second and third control winding means in inductive relationship with each of said reactor means; bridge rectifier means having input terminals connected to said reactor providing means for deriving a directcurrent output voltage therefrom; said first control winding means being connected to the output terminals of said bridge rectifier; said second signal voltage means being directly connected to said source of signal voltage; and said third control winding being coupled to said source of signal voltage through resistance means serially connected with first means adapted to establish electrical conduction only upon application of a voltage of predetermined magnitude thereto, said resistance means forming one element of a series resistance-capacitance circuit connected across said source of signal voltage, said capacitance further being connected across said third control winding and said first means in series; said resistance means forming one element of a series resistance-capacitance circuit connected across said source of signal voltage; the ampere turns produced by said second control winding alone being insufficient to produce an output voltage in said output circuit with maximum control voltage applied thereto; the ampere turns produced from said first and second control windings together being sutficient to produce an output voltage of predetermined magnitude from said output terminals; the ampere turns of said first and second windings with a predetermined output voltage from said magnetic amplifier being sufficient to maintain the output voltage of said magnetic amplifier at least at said predetermined value; the ampere turns of said first control Winding means alone being insuificient to maintain an output voltage from said magnetic amplifier.

13. In combination with a magnetic amplifier having a direct-current output circuit the magnitude of the output voltage from which is variable in accordance with the magnitude of control voltages imposed on first, second and third control circuits thereof; a source of control voltage directly connected to said second control circuit,

- said third control circuit being energized by said directcurrent output circuit in a positive feedback circuit: resistor means and capacitor means serially connected across said source of control voltage; coupling means coupling said first control circuit across said capacitor means only when the voltage across said capacitor is greater than a given magnitude; said first, second and third control circuits being unable to produce an output voltage from said magnetic ampl fier when energized individually; said first and second control circuits being adapted to produce an output voltage from said magnetic amplifier upon simultaneous energization of said second control circuit by control voltage of predetermined magnitude and of said first control circuit by a voltage of magnitude between that of said control voltage and said predetermined given magnitude; said second and third control circuits being adapted to maintain an output voltage from said magnetic amplifier until said control voltage drops to a second predetermined magnitude less than said first predetermined magnitude.

14. In combination with a magnetic amplifier having a direct-current output circuit the magnitude of the output voltage from which is variable in accordance with the magnitude of control voltages imposed on first, second and third control circuits thereof; a source of control voltage directly connected to said second control circuit, said third control circuit being energized by said directcurrent output circuit in a positive feedback circuit: voltage integrating means having an input circuit and an output circuit, said input circuit being connected to said source of control voltage; coupling means coupling said first control circuit across said capacitor means only when the voltage across said capacitor is greater than a given magnitude said first, second and third control circuits being unable to produce an output voltage from said magnetic amplifier when energized individually; said first and second control circuits being adapted to produce an output voltage from said magnetic amplifier upon simultaneous energization of said second control circuit by control voltage of predetermined magnitude and of said first control circuit by a voltage of magnitude between that of said control voltage and said predetermined given magnitude; said second and third control circuits being adapted to maintain an output voltage from said magnetic amplifier until said control voltage drops to a second predetermined magnitude less than said first predetermined magnitude.

No references cited.