US2157893A - Regulating system - Google Patents

Description

2 Sheets-Sheet 1 REGULATING SYSTEM F. H. GULLIKSEN ET AL Original Filed Nov. 3, 1934 OZOSOT? INVENTORS F7771? H Gulll'ksen and y 1939- F. H. GULLIKSEN ET AL 2,1 7,893

REGULATING SYSTEM Original Filed Nov. 3, 1934 2 Sheets-Sheet 2 Patented May 9, 1939 UNITED STATES PATENT OFFICE REGULATING SYSTEM Original application November 3, 1934, Serial No. 751,361. Divided and this application May 22, 1937, Serial No. 144,172

nected in a well-known manner to effect full wave rectification, is controlled by a grid-voltage supply circuit which includes one or more detector tubes 36 energized, through transformers 42 and 45, in accordance with the voltage of the regulated circuit [4.

Considering first the excitation-supply rectifier tube circuits, during one-half of each cycle of the alternating-current voltage which the machine It impresses upon the transformer l8, the anode elements 24 of the tums 20 are subjected, through their connection with the secondary winding 25 of the transformer I8, to a positive voltage, and during the remaining half-cycles, the anode elements 26 of the tubes 22 are similarly positively energized. From the cathodes 28 of both sets of tubes 26 and 22, the rectified currrent passes through a circuit extending through the conductor 2|, the machine field winding l6, conductor 23, and a switch 67, to the mid-point 27 of transformer winding 25. So far as the normal operation of the system is concerned, only one tube in each of the sets 20 and 22 is essential, the second illustrated tube being for the purpose of minimizing interruptions of regulator service due to tube failure.

In order to stabilize the regulating actions and to permit uncontrollable rectifier units, which are less expensive and of longer life, to be used to rectify one-half of the alternating-current wave, we connect the grid elements 32 of the tubes in set 22 only with the machine-voltage error-detecting circuit from which is supplied a potential E3 for adjusting the magnitude of exciting current supplied to the machine field winding l6 by controlling the point in each positive half cycle of anode voltage at which conduction starts. The grid elements of the remaining set of tubes 20 are connected, when tubes are used, as in Fig. 1, instead of copper-oxide or other non-controllable rectifiers, shown at 20 in Fig. 6, by means of suitable resistors 3!, directly to the tube cathodes 28, in a manner to render these tubes conductive during substantially the full duration of each positive half cycle of their anode voltage. As will be more completely explained, the inductance characteristics of the machine field winding l6 tend to automatically maintain a substantially equal division of load between the two sets of rectifier units so that, in the illustrated application, our control of the one set only affords practically the same range of adjustment as does the previously employed control of both sets.

Considering now the voltage-error detecting circuit of our improved regulating system, in

3 Claims.

Our invention relates to electrical regulators and it has particular relation to electronic tube regulators for maintaining the voltage or other characteristic of an electrical machine or circuit constant.

This application is a division of our copending application, Serial No. 751,361, for Regulating systems, filed November 3, 1934, now Patent No. 2,083,297, issued June 8, 1937, and assigned to the same assignee as this application.

One object of our invention is to simplify the equipment and control circuits of alternatingcurrent generator voltage regulators of the electronic tube type.

Another object of our invention is to increase the reliability of operation and improve the quality of performance of such regulators.

An additional object of our invention is to increase the speed of response to such regulating equipments.

A further object of our invention is to decrease the time required to correct disturbances in the regulated quantity.

Our invention, together with additional objects and advantages, will best be understoood from the following description of specific embodiments thereof when taken in conjunction with the accompanying drawings, in which:

Figure 1 is a diagrammatic representation of one preferred form of the regulating system of our invention shown as being applied to control the voltage of an alternating-current generator;

Figs. 2 and 3 are diagrams of curves illustrating certain characteristics of the thermionic detector tubes employed in the system of Fig. 1;

Figs. 4 and 5 are diagrams of curves showing the manner in which the excitation-supply recti fier tubes of the system of Fig. 1 are controlled; and

Fig. 6 is a diagrammatic representation of one manner in which non-controllable rectifiers may be used in the excitation-supply circuits of the system of Fig. 1.

Referring to the drawings and particularly to Fig. 1 thereof, the electronic-tube regulating system there illustrated is shown as applied to an alternating-current generator l0 having armature windings I2 that are connected with a threephase circuit represented by conductors l4, and a field winding l6 of which is energized by current from one phase of the circuit it through a connection which includes a transformer 18, and two sets of rectifier tubes 20 and 22. The effective current passed by these tubes, which preferably are of the grid-controlled gas-filled type and conorder to eliminate the necessity for a standard potential battery or other equivalent source of reference voltage in these circuits, we prefer to utilize one or more detecting devices 36 in the form of filament-controlled tubes, two of which are shown, in the diagram of Fig. 1. The purpose of the illustrated duplication is merely to minimize interruptions of service due to tube failure. Each of these tubes comprises an anode element 44 and a cathode or filament 40 which is supplied, through the transformer t2, with an energizing voltage which varies directly with that of the circuit M to be regulated.

A rectified or pulsating unidirectional current is impressed upon the tube anode elements M, by means of a transformer 45 which is energized by the voltage of circuit l4 and in the secondary winding circuit of which a rectifier Z8 is connected. A capacitor 58 and a resistor 5! are connected in parallel across this anode-voltage supply circuit for the detector tubes to partially filter or smooth out the voltage pulsations. The current drawn by these tubes is passed through a resistor 53, the voltage drop E2 across which thus varies in accordance with the temperature of the tube filaments M3, and a second capacitor 54 connected in parallel with the tubes. This capacitor serves to produce cyclic pulsations of current through the resistor, which pulsations are superimposed upon the average value of the resistor voltage drop.

The control potential E3 impressed upon the excitation-supply tube grids is made up of voltage E2 and a second component E1, in the form of a portion of the relatively constant voltage appearing across the capacitor 50 and the resistor 5!, which opposes voltage E2. As is indicated by the simplified curves of Fig. 4, this latter voltage is somewhat the greater and hence maintains the grids at an average potential which is negative with respect to the tube cathodes. In Fig. 4 the major reference line 56 applies to the excitation-supply tube cathodes 28, the curve Ea indicates the voltage impressed upon the anodeelements 26 of the tubes 22, and the curve E'g represents the critical values of negative potential which, when impressed upon the grid elements 32 of the tubes, prevents the tubes 22 from becoming conducting. No attempt has been made to represent the individual alternating-current ripple components of the two voltages E1 and E2. The major or direct current component of voltage E2 is controlled by the detector tubes 36 and its alternating-current component is determined by the current drawn by the capacitor 54. To more readily displace the phase position of the ripple in control voltage E3 from that of the anode voltage Ea of the excitation supply tubes by the amount, which, as is shown in Fig. 4, is most advantageous for controlling the conduction starting point of these tubes, we prefer to supply it, as indicated by the diagram of Fig. 1, from a different phase of the circuit it than that which supplies the tube-anode circuits. It will be understood, however, that, if desired, other expedients may be utilized for accomplishing the same result.

The detector tubes 36 are, in the system of Fig. 1, preferably operated at an anode voltage sufil ciently high to saturate or place them in a condition in which all of the electrons emitted by the cathodes are attracted to the anodes. In the diagram of curves of Fig. 2, which show the manner in which the current Ip through the tube varies with changes in the anode voltage Ep when diiferent values of energizing voltage E: are applied to the cathode or filament element, such a saturating voltage Epl is indicated by the dotted line which identifies a region in which changes in the value of anode voltage have little effect upon this tube current. At such a voltage, however, a change in the magnitude of the filament heating voltage from Erz to En or Era effects, as indicated by the Wide separation of the curve of Fig. 2, a substantial change in that current.

The exceedingly rapid manner in which the tube current is thus caused to vary is indicated by the curve of Fig. 3. Within the voltage range which includes En, a high factor of amplification is thus obtained. Such a filament-controlled detector being essentially a temperature-actuated device, indicates the root-mea-n-squared value, instead of the average as does an anodecontrolled rectifier tube, of the alternating-current voltage and thus, in addition to being highly sensitive, provides a character of response which is especially desirable when the generator wave form is subject to deviations or changes.

The conversion, by detector tubes 36, of changes in the voltage of the regulated circuit l 4 into much larger changes in the direct-current component of voltage E2 which forms a part of the excitation tube control potential efiects a corresponding shift in the position of the axis 60 of this potential E3 with respect to the tube anode voltage axis 56 and the critical grid voltage curve Eg. By increasing this separation an increase in the regulated voltage delays the point of tube current conduction to reduce the current passed by the tubes 22, and, by decreasing this separation, a decrease in the regulated voltage similarly initiates conduction at an earlier point in each positive half cycle of tube anode voltage to thereby increase the effective current passed by these tubes.

As before pointed out, such adjustments are accompanied by comparable changes in the eifective current passed by the opposition connected rectifiers 26 even though these tubes are conductive throughout their entire corresponding half cycles of anode voltage, as indicated by the shaded area 66 of Fig. 5. This substantially equal division of current results from the predominating inductance characteristics of the machine field winding It in which changes in current during succeeding half cycles of energizing voltage are balanced by action of the energy stored in the magnetic field surrounding the winding. This field of energy causes counterelectromotive forces to be set up which oppose the passage of current through the continuously conducting tubes 20. Control of the exciting current supplied to the field winding I6 is thus effected as satisfactorily as if the rectifier units 2i! (Fig. 1) or 26 (Fig. 6) were grid-controlled by a control voltage responsive to the regulated quantity, an arrangement which would require a doubling of the minimum permissible current capacity of the detector output circuit and which further would not permit the non-controllable units (20) or (20') to be employed.

In placing the complete regulating system shown in Fig. 1 into operation, the regulated generator i5] is excited, during its starting period, from a separate source of direct current, indicated as a battery 65, which may be connected to the field winding by shifting the transfer switch blade 61 to its upper position. As soon as the generator voltage has reached its substantially normal value, the switch 61 is returned to the lower or illustrated position in which the field winding I6 is connected for self-excitation through the rectifier tubes comprised by our improved regulating system.

In the operation of the system, so long as the magnitude of the voltage supplied by the generator to the regulated circuit I4 is of the normal or desired value, the filaments of the detector tubes 36 are heated to an intermediate temperature and the control voltage impressed upon the grids of the excitation-supply tubes is of such character that they supply to the generator field winding that value of exciting current which maintains the generator voltage at this desired value.

Upon the occasion of a decrease in this regulated voltage, the voltage impressed upon the detector filaments correspondingly decreases and the tubes pass a smaller value of anode current. The resulting lowering of this current correspondingly so modifies the rectifier tube control potential as to raise the value of exciting current supplied to the machine field winding and restores the voltage of machine I back to its desired value.

In a similar manner, upon a rise in the voltage of the regulated circuit l4, the temperature of the detector filaments is increased, and the detector tubes draw more current. This so modifies the control voltage E3 as to lower the exciting current and restore the voltage of machine III to its desired value.

The value of voltage which the regulator will maintain may be changed by adjusting the position of a tap connection 55 along the detectorcircuit resistor 53. Such an adjustment varies the value of the control potential component E2 and thereby requires that the detector filament operate at correspondingly changed temperatures to maintain their control of the excitationsupply tubes.

By duplicating the detector tubes 36, we have found that interruptions in service due to tube failure may be greatly minimized. In the filament supply circuit of these parallel connected devices we connect a resistor 68 which functions to so increase the voltage across the filament of one tube in case of failure of the other as to cause this remaining operative tube to continue to maintain the regulated voltage at its normal value. To produce this desired effect the resistor must, of course, be rather closely adjusted in resistance value.

A similar duplication of tubes in each of the excitation-supply rectifier sets 20 and 22 also minimizes interruption of service due to the tube failure, inasmuch as an inoperative condition of one of the tubes in each or both of these sets is found not to detrimentally affect regulator operation, the change in excitation supply circuit impedance being compensated for by a readjustment which the detector circuits automatically make in the character of the control voltage E3.

We have discovered that the system just described is inherently stable in operation and exhibits no tendency to hunt or overshoot in its corrective actions. We believe that such stability is the result of the before-discussed inductive balancing action between the two sets of excitation-supply rectifier units when taken in combination with the action of the ripple-amplifying capacitor 54 in the control voltage supply circuit. This capacitor appears to introduce a slight delay in the attainment by the detector tube circuit of its final or newly adjusted condition upon a change in filament temperature. In any case, the regulator of Fig. 1 exhibits a high degree of stability. It further has a much higher speed of response and requires very much less time to settle disturbances in the regulated voltage than do previously known systems of comparable character. Upon actual test, sensitiveness of regulation approaching one-tenth of one percent were observed upon varying the load of the regulated generator from zero to 125 percent of its rated capacity.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications hereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the scope of the appended claims.

We claim as our invention:

1. In a system comprising an alternatingcurrent power circuit, a load circuit of inductive nature to be supplied with a unidirectional current therefrom, and a pair of rectifiers connected between said circuits in a manner to effect fullwave rectification, the combination of control means adapted to act upon one of said rectifiers only, changes in the current passed by the other being caused to follow those of the first by virtue of the counter-electromotive force induced in the load circuit.

2. In a system comprising an alternatingcurrent power circuit, an inductive load circuit, and means for supplying a unidirectional current from said power circuit to said load circuit comprising a pair of rectifiers connected between said circuits to effect full-wave rectification, of control means for controlling the conductivity of one of said rectifiers only, the conductivity of the other rectifier being controlled only by the inductive nature of the load circuit.

3. In a system comprising an alternatingcurrent power circuit, an inductive load circuit, and means for supplying a unidirectional current from said power circuit to said load circuit comprising separate rectifier means for rectifying the alternate half waves of the alternatingcurrent circuit, the rectifying means for rectifying one half of the wave being grid controlled tubes, the rectifying means for rectifying the other half of the wave being uncontrolled valves responsive to the inductive nature of the load current.

FINN H. GULLIKSEN. JOHN W. DAWSON.

Images