US2015018A - Electric valve control system - Google Patents

Description

zmmms Sept, 17,, 1935. E. KERN ELECTRIC VALVE CONTROL SYSTEM Filed March 16, 1934 4 Sheets-Sheet l zmwm Sept-u 1'7, 135. E. KERN ELECTRIC VALVE CONTROL SYSTEM Filed March 16, 1934 4 Sheets-Sheet 2 Sapt 117, 19359 E. KERN ELECTRIC VALVE CGNTROL SYSTEM Filed March 16, 1934 4 Sheets-Sheet 3 Sept 117 19355.. E. KERN ELECTRIC VALVE CONTROL SYSTEM Filed March 16, 1934 4 Sheets-Sheet 4 Patented Sept. 17, 1935 UNITED STATES PATENT OFFICE ELECTRIC VALVE CONTROL SYSTEM Switzerland Application March 16, 1934, Serial No. 715,806 In Germany March 31, 1933 14 Claims.

This invention relates in general to improvements in. electric valve control systems and more particularly to means for impressing positive voltage impulses of short duration on the control electrodes of a valve.

lectric valves are frequently associated with inductive windings and suitable circuits therebetween to constitute different current converting systems such as alternating current rectifying direct current inverting, frequency converting and other systems. In such instances, it is frequently desirable that the control electrodes receive voltages which are negative relative to the cathode, during comparatively long intervals, and recurringly receive positive voltage impulses of comparatively short duration compared to the duration of the cycle of the corresponding anode voltage. More particularly, in direct current inverting systems each anode is positive with respect to the associated cathode during substantially the entire idling period of the anode, so that the periods of positive energization of the control electrodes must be comparatively short to avoid undesired release of the flow of current during the idling period of the anode. Such result is not easily obtainable when sinusoidal voltages are impressed on the control electrodes and it is, therefore, preferable to impress on the control electrode a non-sinusoidal voltage wave having for example a vertical front and having a tail presenting a non-sinusoidal shape. Such a voltage impulse may be obtained by means of circuits comprising reactors and auxiliary valves supplied with alternating current in relation with the voltage cycle of the anodes.

It is, therefore, one of the objects of the present invention to provide a control system for an electric valve in which the control electrodes of the valve are positively energized during intervals of short duration relative to the cycle of the anode voltage.

Another object of the present invention is to provide a control system for an electric valve in which the control electrodes of the valve receive voltages having vertical wave fronts.

Another object of the present invention is to provide a control system for an electric valve in which the control electrodes of the valve receive voltages having a non-sinusoidal wave tail.

Another object of the present invention is to provide a control system for an electric valve in which the control electrodes of the valve are energized from inductive means associated with auxiliary valve means.

Other objects and advantages will be apparent from the following description when read in connection with the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates one embodiment of the present invention applied to the con- 5 trol of an alternating current rectifying or direct current inverting system;

Fig. 2 is a diagram of some of the voltages and currents present in the circuits of the embodiment illustrated in Fig. 1; 10

Fig. 3 diagrammatically illustrates a portion of a modified embodiment of the present invention differing from the embodiment illustrated in Fig.

1 in the connections between the elements of the auxiliary circuits and in the method of regulation of the total current; and

Fig. 4 is a diagram of some of the voltages and currents present in the circuits of the embodiment illustrated in Fig. 3.

Referring more particularly to the drawings by characters of reference, reference numeral 6 designates an alternating current line herein represented as a three phase line which will be considered as a supply line, the operation of the system being described assuming that alternating 5 current received thereby from line 6 is to be rectified and supplied to a direct current line ll, :2. Line 6 is accordingly connected with the primary winding 1 of a transformer 8 having a secondary winding 9 comprising a plurality of phase displaced portions arranged in any suitable manner, such portions being connected, for example, in star toform a neutral point connected with conductor II. The different portions of winding 9 are severally connected with the anodes 13 of an electric valve 14 of any suitable type, such as a valve of the vapor type, having a cathode l6 connected with conductor !2. Valve i4 is provided with the usual ignition and excitation means which are well known and, therefore, not shown.

The flow of current through each anode i3 is controlled by means of a control electrode ll associated therewith, such control electrode be-- ing energized at voltages of variable signs and magnitudes referred to the potential of cathode It as datum. The control potentials for control electrodes ll are obtained from circuits receiving alternating currents from line 5 through a trans" former l 8 having a primary winding is connected with line 5 and a secondary winding 2|. Winding 2! preferably comprises a plurality of phase displaced portions arranged in a manner similar to the arrangement of the phase portions of winding 9 and each supplying current to one of a plurality of circuits each comprising an auxiliary valve 22, inductive means such as a reactor 23, and resistance means such as a rheostat 24. In the embodiment illustrated in Fig. l, the anodes of the valves 22 are directly connected with winding 2i and the movable contacts of rheostats 24 are jointly connected with the neutral point of winding 2|.

Each valve 22 is bridged by an associated circuit comprising an adjustable resistor 26 and a reactor 21. The voltage appearing across the terminals of each reactor 21 or a component thereof is impressed on the corresponding control electrode by suitable means such as a secondary winding 28 arranged on the core of reactor 21. The connection between each control electrode I! and cathode l5 then comprises the usual current limiting resistor 29, a winding 28, the connection of the several control electrode circuits with cathode I6 being completed through a common negative bias battery 3| if so desired. The several rheostats 24 are arranged to form part of a regulator 32 having an actuating systom 33 energized from a shunt 34 inserted in conductor l2 and arranged to move the taps of the rheostats against the action of suitable restraining means such as a spring 36.

In operation, the system being connected as shown and line 6 being energized, winding 9 impresses, on. the several anodes l3, alternating voltages of equal magnitudes but relatively displaced in phase, but the operation of only one particular anode I3 will be considered in detail. The voltage of such anode with respect to the neutral point of winding 9 may be represented by curve 31 in Fig. 2, the circuit containing the corresponding valve 22, reactor 23 and rheostat 24 then receiving, from winding 2|, a voltage in suitable phase relation with the anode voltage and represented by curve 38. Such voltage becomes positive at a time represented by point A to cause the flow through valve 22, reactor 23 and rheostat 24 of a current which, if allowed to reach the steady state flow thereof, would follow a sine wave curve 39 lagging behind curve 38.

As will appear hereinafter, the flow of current through the circuit does not begin in the positive direction corresponding to the positive half wave at time A but begins at a somewhat later instant B. The current wave is then represented by curve 3!] when read with respect to an exponential curve 4| intersecting curve 39 at a point corresponding to time B, and having ordinates decreasing at a rate depending upon the rela tive values of the inductance of reactor 23 and the resistance of the portion of rheostat 24 in circuit. Such flow of current continues until an instant C corresponding to the second intersection of curves 39 and 4|. The flow of current then reverses but as a result of the valve action of valve 22, the current must then also flow through resistor 26, reactors 21 and 23 and rheostat M. The steady state current curve is then, accordingly, not the negative portion of curve 39 but another curve 42 instead as the current is reduced in magnitude and is generally given a phase displacement as a result of the flow thereof through resistor 26 and reactor 21, The flow of current, which is then negative, follows curve 42 read with respect to an exponential curve 43 intersecting curve 42 a second time at a point corresponding to time D in the following cycle and following time B at an interval of one cycle. The flow of current occurs in the same way during the successive cycles of the voltage of line 6.

tion with the inductances of such 1 etc The voltage drop across the terminals 0.. reactor .27 is accordingly represented by a curve 56 follow ing the axis during interval BC and proportional to curve 44 during intei CD. Such cu possesses a dissyrnmetiic alternating current component and direct current 0 nt, e alternating current component being npzesced in reverse direction on control elect ode l! by winding 28, the voltage thus tren ed being represented by curve i'i s ar to curve i taken in opposite sign and read with respect to an a 58 to eliminate the direct current component thereof. The voltage represented by curve l! suddenly passes from a negative value to a positive value at time C and control electrode il accordingly releases ti flow of current through anode l3 at such time. Such. operation sequen tially repeated for all the anodes of valve i during each cycle of the voltage of line and valve M therefore delivers current to line l :2 at a voltage represented by curve If a battery is utilized, curve is to be 35 read with respect to an axis M7 distant from axis 48 by an amount representing the voltage of battery 3!. Curve 4'! becomes positive time corresponding to a negative portion of curve and a positive portion of curve Ell, the c tions of winding 21 with the associated circuits being so adjusted that the volt es represented that it is desired to maintain the flow of eurr through line Ii, 5 at a substantially constant value. If the intensity of the current is be ow the desired value, spring overcomes actor-1 of element 33 and causes the regulator to increase the portions of rheostats 1M inserted in 50 the circuits thereof. The ratio of induct ce to resistance of the valve ci cuit decreased and the lag of the currents reactor and reactor l? is decrcl is advanced in the cycle of the voltage a flow of current through valve it o rs increased voltage. Such actio cm the output voltage of valve M- is r extent suflicient to bring the flow the desired value. If the flo of current is greater than desired, such flow is returned to the normal value thereof in a manner opposite to that above described.

The operation of the above described system when such system is utilized for inverting direct r current from line H, I2 into alternating current supplied to line 6 will readily be deduced from the above description by any one skilled in the art and, therefore, does not need to be specifically described.

In a system such as described above, therefore, winding 9 and valve I4 constitute electric translation means connected with line (i, and the circuit comprising valve 22, inductance means and resistance means 24 is connected to receive during the iv terval 5 an electromotive force similar to an electromotive force of winding 9 from winding 21 operating as a source of alternating current. The resulting current is controlled by means of valve 22. Resistance means 26 and inductance means 2? with the connections therefore constitute another circuit connected across valve 22. The connections between cathode i6 and the control electrode it constitute a load circuit on which winding 28 impresses a voltage component similar to the alternating component of the portion of the second circuit which consists of reactor 2?. Battery 3i, impresses on the load circuit a voltage effective to prevent the flow of current through valve ii and which is overcome by the voltage of winding .28. Regulator 32 varies the value of rheostat 24 and therefore regulates the effect thereof for modifying the relation between the electromotive force of winding 2! and the current in the circuit supplied therefrom in response to an operating condition of the system, i. e. the magnitude of the current in line i i, l2.

In the embodiment illustrated in Fig. 3 the anode of each valve 22 is directly connected with the neutral point of winding 2| and is connected with cathode it through battery 3|. The cathode oi each valve is connected with one of the phase portions of Winding 2i through the corresponding reactor 2-3 and rheostat 24. Each control electrode ii is connected with cathode it through a resistor 29, a reactor 27 and battery 3!. Each reactor 23 is provided with a direct current saturating winding 5!, the several windings being preferably serially connected across a source of direct current through the rheostat 52 of a regulator Regulator 53 is similar to regulator 32 but is provided with only one rheostat and. is energized in response to the magnitude of the voltage in line ll, 52 as a result of the connection of the actuating windings thereof across such line. The action of regulator 53 is to maintain the voltage of line H, l2 at a substantially constant value and such line may therefore be utilized as a source of direct current for windings ill.

The operation of the control circuits of the present embodiment is readily understood by comparison of the circuits in Figs. 1 and 3. The modified voltage and current relations in the control circuits of Fig, 3 are shown in Fig. 4 in which the modified curves have been designated with the same reference numerals as the origi nal curves of Fig. 2. As a result of the reversal of the connections of the valves 22, the interval CD, during which reactor 2'? carries current, now occurs mostly during the positive portion of curve St. The phase relation between curves Lil 38 has been modified accordingly by suitable modification of the connections of winding 2 l Reactor 2'5 being inserted in series in the circuit of control electrode ll, both the alternating current and he direct current component of the voltage thereof are impressed on the control electrode. The voltage of the control electrcde is then represented by curve 65, read with respec to axis ie if a battery 3! is utilized.

If the voltage of line H, 12 is lower than the value desired therefor, regulator 53 decreases the amount of rheostat 52 inserted in the circuit thereof, thereby causing windings 5! to receive an increased current to increase the degree of saturation of the cores of reactors 23. The inductance of each reactor is thereby decreased and time C is caused to occur earlier in the voltage wave of line 6 to cause the output voltage of valve M to increase. Such action continues until the voltage ol": the line has reached the de sired value, whereupon regulator 53 remains in the position reached thereby. If the voltage of line M, ii is greater than the desired value such voltage is decreased in a manner opposite to that above described.

The system of the present embodiment is also suitable for inverting direct current from line I I, t2, the duration of positive impulses impressed on each control electrode I? being reduced to any desired extent by suitable choice of the voltage of battery 35. In the present embodiment, regulator 53 operates in response to the magnitude of the voltage in line H, it for varying the value of reactor to thereby regulate the effect of such reactors.

Although but two embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a system for generating a periodic potential, a circuit including a source of alternating current, resistance and inductance means in said circuit, electric valve means controlling the how of current through said circuit, another circuit connected across said valve means, impedance means in the second said circuit, a load circuit and means coupling the said another circuit with said load circuit for impressing thereon a voltage component similar to a component of the voltage across a portion of the second said circuit.

2. In a system for generating a variable potential, a circuit including a source of alternating current, resistance and inductance means in said circuit, electric valve means controlling the flow of current through said circuit, another circuit connected across said valve means, resistance and inductance means in the second said circuit, a load circuit, and means coupling the said another circuit with said load circuit for impressing thereon a voltage component similar to a component of the voltage across a portion of the second said circuit.

3. In a system for generating a variable po tential, a circuit including a source of alterhating current, resistance and inductance means in said circuit, electric valve means controlling the flow oicurrent through said circuit, another circuit connected across said valve means, resistance and inductance means in the second said circuit, a load circuit, and means coupling the said another circuit with said load circuit for impressing thereon a voltage component similar to a component of the voltage across the second said inductance means.

4. In a system for generating a periodic potential, a circuit including a source of alternating current, resistance and inductance means in said circuit, electric valve means controlling the flow of current through said circuit, another circuit connected across said valve means, resistance and inductance means in the second circuit, a load circuit, means coupling the said another circuit with said load circuit for impressing thereon a vol -e component similar to a component of the voltage across the second inductance means, and means for regulating the effect of the first said resistance means.

5. In a system for generating a periodic potential, a circuit including a source of alternating current, resistance and inductance means in said circuit, electric valve means controlling the flow of current through said circuit, another circuit connected across said valve means, resistance and inductance means in the second said circuit, a load circuit, means coupling the said another circuit with said load circuit for impressing thereon a voltage component similar to a component of the voltage across the second said inductance means, and means for regulating the efiect of the first said inductance means.

6. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the fiow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, and means coupling the said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across a portion of the second said circuit.

7. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the sec ond said valve, resistance and inductance means in the second said circuit, and means coupling the said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across the second said inductance means.

8. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, means for impressing between said control electrode and said cathode a voltage effective to prevent the flow of current through the first said valve, and means coupling the said another circuit with said control electl'ode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across a portion of the second said circuit to overcome the effect of the first said voltage.

9. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current Winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, and means coupling said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across the second said inductance means, and means responsive to an operating condition of the system for modifying the relation between said electromotive force and the current in the first said circuit.

10. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, and means coupling the said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across the second said inductance means, and means responsive to the magnitude of the current in one of said lines for modilying the relation between said electromotive force and the current in the first said circuit.

11. In a system for controlling the now oi electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, means coupling the said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of F the relation between said electromotive force and ,H

the current in the first said circuit.

12. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, means coupling the said another circuit with said control electrode and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across the second said inductance means, and means responsive to an operating condition of the system for varying the value of the first said resistance means.

13. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and including an alternating current winding and an electric valve having an anode with an associated control electrode and a cathode, an electric current output line connected with said translation means, a circuit connected to receive an electromotive force similar to an electromotive force of said winding, a second electric valve controlling the flow of current through said circuit, resistance and inductance means in said circuit, another circuit connected across the second said valve, resistance and inductance means in the second said circuit, means coupling the said another circuit with said control electrode 5 and with said cathode for impressing therebetween a voltage component similar to a component of the voltage across the second said inductance means, and means responsive to an operating condition of the system for varying the value of the first said inductance means.

14. In a system for controlling the flow of electric current, an electric current supply line, electric translation means connected with said line and comprising an alternating current winding 5 and an electric valve having a plurality of anodes with associated control electrodes and a cathode, an electric current output line connected with said translation means, a group of circuits each comprising an inductance, a resistance and an electric valve connected to receive an electromotive force similar to an electromotive force of said winding, another group of circuits each comprising an inductance and a resistance severally connected across the second said valves, and means severally coupling the said another group of circuits with said control electrodes and said cathode for impressing therebetween a voltage component similar to a component of the voltage across a portion of one of the second said circuits.

ERWIN KERN.

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