US2383492A - Voltage regulator - Google Patents

Description

Aug. 28, 1945.

-H. KLEMPERER VOLTAGE REGULATOR Filed oct. 1o, 1942 l/T/L/ZA T/ON DEV/Cf l/IIIIIIII ws /fL E By A ATTY Patented Aug. 28, 1945 VOLTAGE REGULATOR Hans Klemperer, Belmont, Mass., assigner to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application October is, 1942, Serial No. 461,571

(ci. 32o- 1) 13 Claims.

This invention relates'to voltage regulators.

Certain loads are critical as to the voltage applied to them. For example, condensers supplying welding energy for resistance welding are critical as to the voltage applied to such condensers. If excess voltage is applied :to such condensers, holes may be burnt out in the work during welding, or the structure around the weld may be materially weakened. In numerous other instances outside the ileld of welding the applir cation of a constant voltage to a load is desirable. To prevent the application of such excess voltages it has heretofore been customary to utilize voltage regulators. One of the difllculties heretofore encountered in connection with such regulators has been their slowness of response. Frequently when steeply rising voltages were being transmitted to the load these regulators would operate only after a voltage substantially in excess of the desired voltage had been applied to said load. In systems where the load voltage is not critical this excess voltage is usually not material; but in systems where the load voltage is critical such regulators prove unsatisfactory.

An object of this invention is the provision of a voltage regulator which has a substantially instantaneous response so as to be capable of blocking out almost all variations ordinarily encountered in systems of this kind.

Certain types of voltage regulators operate by applying a control voltage derived from the load voltage lto a control element, such as, for example, the control grid of a tube governing the supply of load voltage. In these regulators as the load voltage rises the control voltage rises too, and when the load voltage reaches a predetermined value the control becomes sufiiciently great to operate the control element. When the control element is the control grid of a tube the control voltage is utilized to apply a bias to the control grid and when the control voltage is sulciently great further conduction in the tubeis prevented by the bias which reaches a cut-olf value when the load voltage reaches its predetermined value.

One of the difliculties heretofore encountered in regulators of the general type utilizing a control voltage derived from the load voltage is that the control voltage rises much more gradually than does the load voltage. Coupled with this is :the fact that the usual control element does not operate at a precise voltage, but varies in its point of operation. For example, the bias required to cut oil conduction in one type of tube may vary several volts. Therefore, when the control voltage rises very gradually in relation to the load voltage as in prior types of regulators and where the control element does not operate at a precise voltage. it becomes possible for the load voltage to rise substantially above its selected maximum voltage before the control element operates. Thus with such prior types of regulators it has been impossible to prevent the application of substantial excess voltages to the load. Therefore, another object of this invention is the provision of a voltage regulator which is extremely yaccurate in its operation and will prevent the application of substantially any excess voltage to the load. One of lthe features of regulators embodying this invention is that the control voltage rises relatively steeply as the load voltage rises. Another feature of this invention is that any desired steepness in the rise of the control voltage may be obtained so as to satisfy the requirements of the particular system in which the voltage regulator is used.

A further object of the present invention is the lprovision of a simple and relatively inexpensive voltage regulator of the type described.

Other and further objects and advantages of the present invention will become apparent, and the foregoing will be understood in relation to the following exempliiications thereof, reference being had to the drawing in which:

Fig. l is a, schematic diagram of an electrical system including one form of a voltage regulator embodying my invention;

Fig. 2 is a schematic diagram of a similar electrical system including a modified form of a voltage regulator embodying my invention; and

Fig. 3 is a graph indicating qualitatively rather than quantitatively certain aspects of my invention.

Referring now to Fig. l, a load which may be critical as to the voltage applied thereto, for example, condenser I, is adapted to have a voltage applied thereto from a Voltage source 2 through a power transformer 3 having its prlg mary 4 connected to the source 2 and one end of its secondary 5 connected directly to one side of condenser I, the other end of said secondary 5 being connected to the other side of condenser I through a. controlled electrical space discharge device or tube 6. Tube 6 may be of the gaseous type having a continuously energized cathode 'I connected to the positive side of condenser I and having its anode 8 connected to one side of the secondary 5 of power transformer 3. Tube 6 is also provided with a control element or control grid 9. Condenser I may be connected through a switch I0 to any suitable utilization device I8 and its discharge may be utilized to supply energy to said utilmation device I8, which may be, for example, a welding transformer. It is to be understood that condenser I in this system may be critical as to the voltage applied thereto and that excess voltages are to be avoided. To prevent the application of such excess voltages I have provided the following means.

A potentiometer II has its resistance I2 arranged across condenser I, and its moveable arm I3 connected in series with a constant voltage device, such as, for example, a glow tube I4 and a resistance I5 to the positive side of condenser I. Point I6, intermediate glow tube I4 and resistance I5, is connected in series with a grid resistance I'I to the grid 8 of tube 6. The method of operation of this device is as follows. As the voltage derived from source 2 is applied to condenser I through tube 6 the potential drop across condenser I and across resistance I2 of potentiometer II rises. This rising voltage reaches a value at which the potential drop across the series circuit consisting of glow tube I4 and resistance I5 is equal to the starting voltage of glow tube I4, whereupon tube I4 ilres and a potential drop appears across resistance I5. This potential drop is impressed between the grid 9 and cathode 1 oi tube 6. At the breakdown voltage of glow tube I4 the potential appearing across resistance I5 preferably is insuiilcient to cut oil conduction in tube 8. When, however, the voltage on condenser I continues to rise, the voltage across resistance I5 rises in accordance therewith until it reaches a value suiiicient to cut oi further conduction in tube 6. By varying the position of arm I3, or if desired, by varying the value of resistance I5, the precise voltage on condenser I at which further conduction by tube 6 is prevented may be selected. How this operation produces a steep control voltage will be described hereinafter in connection with Fig. 3.

Referring now to Fig. 2, a modified form of the system disclosed in Fig. 1 is depicted. Instead of a single glow tube I4 a plurality of such tubes in series, to wit, three, are employed. By the use of three such tubes it is apparent that the voltage required to cause conduction in said tubes must be three times as large as the voltage required to cause conduction in the single tube I4 of Fig. l. As will be more fully understood from the description in connection with Fig. 3 the use of three such tubes results in the production of an even steeper characteristic for the control voltages.

In one system em-bodying the system illustrated in Fig. 1 the following were the constants used: the maximum voltage to be applied to the condenser I was 8000 volts, the glow tubes I4 had a. starting voltage of 110 volts, and a constant operating voltage oi' 105 volts, and in tube 5 a negative bias of volts applied to its grid would prevent further conduction therein. From the foregoing it will be apparent that when a voltage of 110 volts was applied to the series circuit in Fig. 1 consisting of glow tube I4 and impedance I5 tube I4 would ilre and thereupon the voltage drop across tube I4 would become constant at 105 volts, while the drop across resistance I5 would be 5 volts. As the voltage drop across condenser I increased the voltage drop across resistance I5 also increased until said voltage drop was equal to 25 volts, whereupon the bias applied to the grid 9 was sufllcient to prevent further conduction of tube S. At this time the voltage across condenser I would be 3000 volts. The voltage across con- III denser I at the time tube I4 fires is approximately 2538 volts.

The foregoing operation is represented by curve R ln Fig. 3 in the graph in which the voltage on condenser I is plotted along the horizontal line, while the voltage across resistance I5 is plotted on, the vertical line. From said graph it will be seen that no drop appears across resistance I5 until the potential on condenser I is about 2538 volts, whereupon tube I4 ilres and a. potential of 5 volts appears across resistance I5. As the voltage on condenser I rises from 2538 to 3000 volts the potential across resistance I5 rises from 5 volts to 25 volts.

In the embodiment of Fig. 2 the same constants are employed, except that there are three glow tubes I4 each having a starting voltage of 110 volts and a constant operating voltage drop of volts. Curve S of Fig. 3 represents the operation of this system. Before the glow tube I4 fires, a voltage of 330 volts must be impressed across the series circuit consisting of the three glow tubes I4 and resistance I5. These tubes then ilre and the voltage drop across these tubes falls to 315 volts, while a drop of 15 volts appears across resistance I5. At this point, that is when the three glow tubes I4 fire the voltage across condenser I is about 2912 volts. As the potential on condenser I rises from about 2912 volts to 3000 volts, the voltage across resistance I5 rises from 15 volts to 25 volts.

It will be seen that the rise of curve S is steeper than the rise of curve R. These curves may be contrasted with the curve that would be produced if the control voltage was obtained simply by the use of a voltage divider and the potential derived from said voltage divider were applied to grid 9. Resistance I2 may be used as the voltage divider and the potential derived therefrom between the arm I3 and the point I6, without the intervening tube I4, might be impressed on grid 9. Referring now to curve T which represents this derived voltage, this voltage would be zero when the voltage across condenser I is zero and wouldfrise linearly to 25 volts when the voltage across condenser I would be 3000 volts.

It will be seen that the control voltage derived from a voltage divider has a relatively gradual rise in relation to the rise of potential across condenser I, whereas the rise of the control voltage in a system such as in Fig. 1 would be much steeper, and in Fig. 2 even more steep. As is apparent the steeper the slope of the control voltage applied to the grid 9 of tube 6, the more positive the operation of the voltage regulator. It will therefore be seen that the systems illustrated in Figs. l and 2 are more positive in their operation and consequently more accurate. It will also be apparent that in order to obtain a steeper control voltage characteristic than that shown in curve S it is only necessary to add more constant voltage tubes in series with the three there illustrated or to use tubes having a larger constant voltage drop.

It will be noted that the glow tubes I4 in effect subtract a constant value of voltage from the potential appearing on the potentiometer arm I3. This means that if the voltage at the arm I3 in Fig. l, for example, were to change by a value of one volt, the voltage at the point I6 would vary by exactly the same amount. Therefore insofar as any time variation is concerned the voltage changes at the point I6 are exactly parallel with the voltage changes at the arm I3, differing there from by a constant value determined by the drop through the tubes I4. As more and more glow will produce a variation of one volt in the voltager impressed on the control grid 9.

Of course it is to be understood that in place of glow tubes having the constant voltage drop mentioned, other constant voltage devices or other glow tubes having different constant voltage drop values might be employed. Furthermore, whilev I have illustrated a half-wave rectiiier system, it is to be understood that a full-wave rectiilersystem might be employed in a, manner readily understood by those versed in this art from the foregoing description. Likewise a multiphase voltage source might be employed instead of the single phase system here described. A plurality of tubes, such as the gaseous type tube 6, or other rectifying tubes or devices subject to control might be substituted in place of tube 6. In addition, while I have described the load in this instance as being a condenser, other types of loads might be used. Because of the swift and positive operation of voltage regulators of my invention, it becomes feasible to employ them for controlling the voltages across loads where the voltage varies more rapidly than can be taken care of by prior voltage regulators.

Other and further variations within the scope of this invention will occur to those versed in the art. It is accordingly desired that the appended claims be given a broad interpretation commensu-f rate with the scope of the invention Within the art What is claimed is:

1. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a, constant voltage device and an impedance arranged in series and means to impress at least a portion of the voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said load 'appears across said impedance, and means responsive to said control voltage for disconnecting said load from said source when said control voltage reaches a pre determined value.

2. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a glow tube and an impedance arranged in series and means to impress at least a portion of the voltage across the load on said glow tube and said impedance whereby a control voltage responsive to the voltage across said load appears across said impedance, and means responsive to said control voltage for disconnecting said load from said source when said control voltage reaches a predetermined value.

3. An electrical system comprising a. load, a voltage source, means for connecting said load to said source, a constant voltage device and an impedance arranged in series and means to impress a voltage responsive to the voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said load appears across said impedance, and means responsive to said control voltage for disconnecting said load from said. source when said control voltage reaches a. predetermined value.

4. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a circuit for connecting said source to said load including a controlled electrical space discharge device having a control element, a constant voltage device and an impedance arranged in series and means to impress a voltage responsive tothe voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said load appears across said impedance, said control voltage being impressed upon said .control element and being adapted to cut off conduction in said controlled electrical space discharge device when said control voltage reaches a predetermined valueto thereby disconnect said source from said load.

5. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a circuit for connecting said source to said load including a controlled electrical space discharge device having a control grid, a constant voltage device and an impedance arranged in series and means to impress at least a portion of the voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said load appears across said impedance, said control voltage being impressed upon said control grid and being adapted to cut off conduction in said controlled electrical space discharge device when said control voltage reaches a predetermined value to thereby disconnect said source from said load.

6. An electrical system comprising a condenser, a voltage source, means for charging said condenser from said source, a constant voltage device and an impedance arranged in series and means to impress at least a portion of the voltage across the condenser on said constant voltage device and said impedance, whereby a portion of the voltage on the condenser appears across said impedance, said portion being a control voltage, and means responsive to said control voltage for disconnecting the condenser from said source when said control voltage reaches a predetermined value.

7. An electrical system comprising a condenser, a voltage source, means for charging said condenser from said source, a constant voltage device comprising a glow tube and an impedance arranged in series and means to impress at least a portion of the voltage across the condenser on said constant voltage device and said impedance, whereby a portion of the voltage on the condenser appears across said impedance, said portion being a control voltage, means responsive to said control voltage for disconnecting the condenser from said source when said control voltage reaches a predetermined value, a utilization device and means for discharging said condenser through said device.

8. An electrical system comprising a load, a voltage source, means for connecting said load to said source, means for deriving a voltage from at least a portion of the voltage across said load, means effective when the derived voltage reaches a predetermined value for subtracting a constant voltage from said derived voltage to obtain a control voltage proportionate to and having a value less than said derived voltage by a constant predetermined amount, and means responsive to said control voltage for controlling the flow of current in a portion of said system when said control voltage 4reaches a predetermined value above its initial value.

9. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a controlled electrical spaced discharge device having a control element for controlling the flow of current in a portion of said system, a constant voltage device and an impedance arranged in series and means to impress a voltage responsive to the voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said loa'd appears across said impedanoe, said control voltage being impressed upon said control element and being adapted to control conduction in said controlledelectrical space discharge device when said control voltage reaches a predetermined value.

10. An electrical system comprising a load, a voltage source, means for connecting said load to said source, a controlled electrical space discharge device having a control grid for controlling the flow of current in a portion of said system, a constant voltage device and an impedance arranged in series and means to impress at least a portion of the voltage across the load on said constant voltage device and said impedance, whereby a control voltage responsive to the voltage across said load appears across said impedance, said control voltage being impressed upon said control grid and being adapted to control conduction in said controlled electrical space discharge device when said control voltage reaches a predetermined value.

11. An electrical system comprising a load, a voltage source, means for connecting said load to said source, means for deriving -a voltage from at least a portion of the voltage across said load, means effective when the derived voltage reaches a predetermined value for obtaining a control voltage proportionate to and having a value less than said derived voltage by a constant predetermined amount, and means responsive to said control voltage for disconnecting said load from said source when said control voltage reaches a predetermined value above its initial value.

12. In combination, a condenser, a source of current for charging said condenser, means for deriving a voltage proportionate to the voltage across said condenser, means for obtaining a control voltage from said proportionate voltage, said control voltage diiering from said derived voltage by a predetermined constant value, and means for cutting oir the supply ot charging current to said condenser when said control voltage reaches a predetermined value above its initial value.

13. In combination, a condenser, a source oi current for charging said condenser, means for deriving a voltage continuously proportionate to and substantially less than the voltage across said condenser, means for obtaining a control voltage from said proportionate voltage, said control voltage being less than said proportionate voltage by a predetermined constant value, and means for cutting ofi the supply of charging current to said condenser when said control voltage reaches a predetermined value above its initial value.

HANS KLEMPERER.

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