Патент USA US2010697код для вставки
Aug. 6, 1935. ' 2,010,697 H. w. LORD PEAK VOLTAGE MEASURING DEVICE Filed May 51, 1953 F‘igl. 52 I l 5/ MW "\ " 34 53 . I5 53 '7 4 L1 55 r l ‘ c 50 - - v 45 I mmB 56 /4—'-’— 2a 49 1 ' . ‘ . a . /5 Zaiihkm“ 37’ 44 37 54 Fig. 6. . Fig. Z 72 ’ 70 7/ ,69 Inventor: Harold W. Lord, torneg Patented Aug. 6, 1935 2,010,697 UNITED STATES PATENT OFFICE Harold W. Lord, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application May 31, 1933, Serial No. 673,611 11 Claims. _ (Cl. 175-183) My invention relatesto electric measuring and testing devices and concerns particularly meth outp circuit of the tube. There are other appli cations in which it may be desirable to measure average or peak voltages during a certain portion of the duty cycle of an electrical apparatus without reference to voltages which may exist during other 5 ‘ apparatus which shall be responsive to the voltage portions of the duty cycle, and my invention may also obviously be used in connection with such acting in an electrical apparatus or a certain por applications. , tion of the apparatus while the apparatus is carry In accordance with my invention in- its pre 10 ing a load, but which shall be unresponsive to the voltage in the apparatus while no load is being ferred form I employ a peak voltmeter which has 10 carried although the voltages existing during no its terminals connected to the two points between load may be considerably greater than the volt which a voltage measurement is desired. The peak voltmeter preferably takes the form of a ages desired to be measured. ' 7 vacuum tube voltmeter, although my invention It is another object of my invention to measure obviously is not limited to any particular type of 15 the maximum value of the potential drop in the peak voltage responsive unit. A resistor having a rectifying element of apparatus for converting al relatively high resistance is connected ‘in series ternating current to direct current or vice versa with one of the leads of the peak voltmeter, and during the current-conducting period, but which 20 shall be unresponsive to the inverse voltage or means are provided for short-circuiting the peak voltmeter during the portions of the operating 20 the forward voltage while no direct currentls cycle or duty cycle of the apparatus when volt ?owing. ages exist in the apparatus which it is not desired It is still another object of my invention to pro to measure. This is preferably accomplished by vide an apparatus for measuring the maximum means of a grid-controlled discharge tube having voltage across the arc of a gaseous or vapor dis its electrodes connected in parallel with the termi 25 charge tube type of recti?er or inverter. nals of the peak voltmeter and having its control It is also an object of my invention to provide ‘grid so connected to the secondary winding of a a method for testing are discharge tubes. current transformer having its primary in series Other and further objects and advantages will with the load that the ‘grid becomes negative and 30 become apparent as the description proceeds. the tube becomes non-conducting while current is 30 In connection with the operation of vapor dis ?owing through the load, but the tube remains charge tubes used for rectifying or in inverters, I conducting while no current is flowing through ‘ have found it desirable to determine the peak value the load. In this manner the voltage in the ap of the drop in voltage across the electrodes during 35 the existence of the arc. The value of this voltage paratus is applied to the peak voltmeter only dur ing the desired portions of the operating cycle of 35 furnishes a good indication of the state of the the apparatus. tube‘ and the character of its operation.‘ In The features of my invention which I believe to creasing values of the arc drop serve to indicate be novel and patentable are pointed out in the ods and arrangements for measuring peak volt ages during certain portions of the operating cycle 5 of‘ electrical apparatus. It is an object of my invention to provide an decreasing e?iciency or improper operating con claims appended hereto. ‘ However, the potential dif A better understanding of my invention itself, 40 ference between the/power electrodes of a dis charge tube during the inverse or negative portion however, may be obtained by referring to the of the voltage wave, as well as during that portion following description in connection with the ac of the forward or positive portion of the voltage companying drawing, in which 'Fig. l is a sche wave before the tube breaks down, is obviously matic circuit diagram illustrating the use of my considerably higher than the peak voltage across invention with a rectifying vapor discharge tube 45 ‘the arc. Consequently, a simple peak voltmeter of the grid-controlled type; Figs. 2, 3, and 4 are 40 ditions of the tube. curves illustrating the operating‘ characteristic would be of no value since it would measure either of grid-controlled vapor recti?ers; Fig. 5 is a the maximum inverse or the maximum forward voltage curve taken from an oscillogram illus voltage and not the maximum value of the trating the operation of a grid-controlled vapor 5O voltage desired. It is, therefore, an object of my invention to provide apparatus ‘ which recti?er under certain conditions; Fig. 6 is a shall be unresponsive to .the voltages _occur-. copy of 'an oscillogram indicating the voltages ring during any portion of the , cycle when acting in a peak voltmeter used with a grid-con 55 useful direct current is not ?owing through the trolled vapor arc rectifier in accordance with my invention; Fig. 7 is a curve representing a 66‘ 2,010,697 i9 is of a type which tends to pass appreciable characteristic of a two-element vapor arc recti current only with a positive grid bias. ?er; and Fig. 8 is a circle diagram explaining a The discharge tube 33 is also provided with a method of controlling the phasev of the grid of a control grid 39 which is connected to the second grid-controlled recti?er. ary winding of a current transformer ill! having Referring now in more detail to the drawing, I its primary windingconnected in series with the have illustrated the use of my invention in anode iii of tube ii. In half-wave recti?ers measuring the arc drop in a vapor arc recti?er l i, energized by single-phase alternating current the but it will be understood that my invention is primary winding of current transformer 430 is, of not limited to use with are discharge'tubes uti course, also in series with load i2, but it will be 10 understood that if more than one are discharge 10 lized in recti?ers and inverters. The are discharge tube ii is shown as supply tube is employed or a tube with more than one ing a direct current to a load Q2 of any suitable‘ anode, the primary winding of current trans type, which may consist, for example, of a direct~ former M! is to be connected in the individual current railway system, an electrolytic plant or anode circuit in which the arc drop is to be 15 15 any other application where direct current may measured. The terminals iii and Q2 of the sec suitably be supplied by means of a vapor arc ondary winding of the current transformer M recti?er. The tube ii is energized by means of are shunted by a suitable device such as the op a suitable source of alternating current 53 positely connected glow tubes £83 and M» to pre through a transformer ML. The tube H is pro vent the secondary voltage of the current trans 20 vided with a control grid l5, an anode i5 and a former iii] exceeding a predetermined value‘ re cathode II. The electrodes i6 and II are con gardless of the magnitude of the current flowing nected in series with the load 12 and a secondary through the load l2. Preferably, a resistor [55 winding E8 of the transformer l4. To avoid com having a relatively high resistance is inserted be plicating the drawing, I have illustrated the in tween the terminal M of the secondary winding connection with apparatus employing of the current transformer 150 and the control .25 vention-in only a single tube and single-phase power supply grid 39 of the discharge tube 33. The discharge but it will be understood that the tubes in full tube 33 is preferably of the low impedance type, wave recti?ers and inverters or associated with that is, one which remains conducting unless the polyphase circuits may also be tested by means grid bias is negative, for reasons which will be 3O explained hereafter. It will be understood, how 30 of my invention. The peak voltmeteracomprises a discharge tube ever, that my invention may be carried out with l9, preferably a vacuum discharge tube, having out using a low impedance tube, in which case, a an anode 20, a cathode 2!, which may if desired higher value of resistance in the resistor 34 would be indirectly heated, and a control grid 22. Elec be desirable than when a low impedance tube is 35 trodes 2B and 2i are connected in series with a used. source of direct current 23, a resistor 2% having a Although I have shown the glow tubes 133 and relatively high resistance, and a current-respon M separately, it will be understood that a single sive instrument 25 which may take the form of device having a double set of electrodes to permit an indicating instrument, of a recording instru breakdown in either direction may also be em 40 ment or of a contact-making instrument, as de ployed, or under certain circumstances I may em sired. A condenser 26 is connected between the ploy a single glow tube with a different breakdown cathode 2| and the common terminal 21' of the voltage in one direction than in another. voltage source 23 and the current-responsive de The glow tubes M and iii are of the type well vice 25. For reasons which will be explained known in the art and serve to limit the secondary hereinafter the potential difference between the voltage of the current transformer 139 by breaking 45 plates of condenser 26 varies substantially linear down when the voltage approaches a predeter ly with the voltage which my apparatus is de mined value and drawing a variable current so as signed to determine. The high resistance resistor to maintain constant secondary voltage, as the 24 and the current-responsive device 25 permit, primary vcurrent and the burden of the trans determining the voltage of condenser 26 without former vary with the variations in the current 50 substantially varying its charge,_but it will be load I2. understood that any other means responsive to in Athe condenser 136 is preferably connected between the voltage of condenser 26 may also be employed. grid 22 of the voltmeter tube I9 and the ter The terminal 21 of the current-responsive de the minal 2'1! of the current-responsive device 25, to vice 25 is connected to the cathode ll of the arc prevent any slight surge from the breakdown of 55 discharge tube 1 I by means of conductors 28 and glow tubes 43 and M from affecting the response 29, and the control grid 22 of the voltmeter tube. I9 is connected to the anode l6 of the arc dis- of the voltmeter tube 19. The constants are so 40 charge tube H through conductor 30, resistor 3! having a relatively high resistance, and conduc 60 tor 32, thereby making the potential of the grid 22 of the voltmeter tube l9 responsive to the potential diiference between the electrodes l6 and i‘! of the arc discharge tube H. chosen that the condenser £6 with resistor 3! will have such a short time constant as to have a 00 negligible effect on the voltage applied to the voltmeter tube. A discharge resistor 41 of a rela tively high resistance serves to prevent the ac cumulation of a charge on the condenser 116, when 65 To prevent impressing on the grid 22 ‘voltages the voltmeter is not in use and the terminals 32" 65 and 29’ are not connected to the power circuit. which would exceed the peak value of the arc The are discharge tube ll, shown in Fig. 1 by drop in the tube H, a discharge tube 33 is pro way of illustration, may for example be of the type having its cathode l1 indirectly heated by means of a ?lament 48 energized by a secondary 70 winding 49 of the transformer M. As is well minal 21 of current-responsive device 25, through known, when employing arc discharge tubes of the vided having an anode 34 connected to the con trol grid of the voltmeter tube i9 through con 70 ductor 30, and a cathode 35 connected to the ter conductor 36, a grid biasing battery 31, conduc grid-controlled type, the magnitude of the direct tor 38 and conductor 28. Although I prefer to current may be controlled by controlling the employ the grid-biasing battery 37 it will be phase of the voltage impressed upon the grid l5 76 76 understood that its use is notessential if the tube 2,010,697 3 with respect to the phase of the voltage impressed 10 15 . 20 25 30 upon the anode I6. For-the sake'of illustration between zero and 90° depending upon the ratio I have shown one arrangement for accomplishing of ‘ resistance to inductance in circuit 5|--52. this result which comprises an inductor 5| con The voltage drop in inductor 5| leads that in re nected between the load terminal B of the sec sistor 52 by substantially 90° so that the voltage ondary winding | 8 of the transformer l4 and drop in inductor 5| leads the voltage supplied by the control grid l5, and a variable resistor 52 the secondary winding l8 by an amount between connected between the control grid l5 and one 90° and zero degrees'depending on the resistance . end A of a secondary winding 50 of the trans inductance ratio. The phase relationship between the voltages is former l4, having its other end connected to the cathode I‘! of the arc discharge tube II and to the illustrated graphically in the circle diagram, Fig. cathode terminal C of the secondary winding | 8. 8, where ER_52 represents the difference in poten A movable contact 53 serves to permit variation tial between the connection G to grid l5 and the of the resistance of the resistor 52. The opera terminal A of winding 50, E1._51 represents the tion of the phase-controlling device for grid l5 difference in potential between the load terminal B of the winding l8 and grid connection G to grid will be explained hereafter. Discharge tubes 33 and I9 are preferably of the I5, E18 represents ‘the voltage of winding l8, and hot-cathode type and may have their cathodes E50 the voltage of winding 50. The vector sum of ER-sz and EL—51 is necessarily equal to AB, the heated by energy supplied by a source of alternat ing current 54 through a transformer 55 having ‘voltage produced by windings 50 and I8 in series. a secondary winding 56 connected to the cathode The locus of the point G, representing the poten 20 35 of discharge tube 33, shown as a ?lamentary tial of the grid, is a circle, and the phase rela cathode, and a secondary winding 51 connected tionship between Em, the voltage supplied to the to the ?lament 60 serving to heat indirectly the anode, and EG, the potential difference between cathode 2| of the voltmeter tube I9. The sec the grid connection G and cathode connection ondary windings 56 and 51 are preferably pro C, obviously depends upon the ratio of resistance 25 vided with taps 58 and 59 respectively at their to inductance in circuit 5|—-52. By changing the setting of the tap 53 of the rheostat 52, the midpoints to serve as cathode connections. Al though I prefer to employ an indirectly heated ratio of resistance to inductance in the circuit 5|—52 may be varied, and consequently the phase cathode in tube l9 if alternating current is used relationship of the anode and grid voltages may 30 as the heating source, it will be understood that be varied at will. the tubes | 9 and 33 may be of either the ?lamen For example, if the ratio of resistance to inductance is decreased, the grid tary cathode or of the indirectly heated cathode potential may be retarded to the point G’ to give types. a grid voltage of Ed’. 35 Arc discharge tubes of the grid-controlled type Fig. 5 is an oscillogram representing the volt operate on the principle that the tube is conduct age between the anode and cathode of a grid ing only when the anode is positive and the con controlled arc discharge tube, with the grid phase trol grid is positive, or is only very slightly nega relationship adjusted to cause an arc to be struck tive, depending upon the design of the tube. In just before the middle of the positive half cycle 40 Fig. 2, the curve 6|‘represents the potential of the of the anode voltage, that is, with a slightly anode l6 of the arc discharge tube 1 |, and the ‘longer conducting period than the condition 40 curve 62 represents the potential of the grid ‘illustrated in the curve of Fig. 3. The portion l5, the ‘positive portion 62' of the grid potential 65 of the curve in Fig. 5 represents the inverse curve 62 being shown dashed. In the particular design of tube illustrated by way of example, the tube becomes conducting whenever the anode potential is positive and the grid potential is more positive than certain values indicated by the dashed curve 63. If the grid potential 62 re 50 mains more negative than the curve 63 through out the positive half cycles of the anode potential curve 6|, the tube remains non-conducting. In voltage, between the electrodes of the are dis charge tube. The portion 56 of the curverepre sents the forward voltage or the voltage during the positive portion of the half cycle before the tube has become conducting. The portion 61 of the curve represents the voltage between the electrodes after the tube has become conducting] 50 or the are drop in the tube, which is the voltage which it is desired to measure in certain tests on the condition shown in Fig. 2, however, the grid are discharge tubes. potential curve 62 crosses the curve 63 at a point It will be seen that the voltage indicated in the 55 a in each cycle, and the tube I I becomes con portion 61 of the curve is of a much lower order ducting at the point a in each cycle and remains of magnitude than the voltages in the portions 55 conducting for the remainder of the‘ half cycle. 65 and 66. Consequently, a voltage-responsive In the condition shown in Fig. 3, the phase rela device having a range well adapted to measure tionship of the grid potential curve 62 has been accurately, the voltage in the portion 61 would 60 advanced so that the curve 62 crosses the curve 63 at the point b, and the tube H is conducting during the shaded portions 64 of'the positive half cycles. In the condition shown in Fig. 4, the phase of the grid has been further advanced so 65 that the tube || conducts duringalmost the en tire positive half cycles. - , ( Any suitable means may be employed for vary be overloaded and badly damaged if subjected 60 to the voltages existing in the portions 65 and 65 of the curve. Furthermore, an indication of \the average value or of the R. M. S. value of . voltage during the entire cycle would be wholly valueless as an indication of the value of the arc voltage 61, since the inverse voltage 65 and the forward voltage 66 are so much greater in magni ing the phase relationship of the grid |5. .In the tude and bear no ?xed. relation to the desired arrangement illustrated in Fig. 1, the grid I5 is value. , connected at the ‘common terminal of induc tance 5| and rheostat 52. Owing to the induc -The curve shown in Fig. 6 is an oscillogram 70 representing the voltage between the grid 22 tance of the element 5| the current in the circuit of the voltmeter tube l9 and the terminal 21 of 5|-52, and consequently the voltage drop in the‘ the current-responsive device 25 when my device resistor 52, tends to lag behind the voltage sup is used to measure the peak value of ‘the are 75 plied by the secondary winding I 6 some amount drop in an arc discharge tube, adjusted to give the 75 2,010,697 4 condition shown in Fig. 5. It will be seen that in the portion 69 of the curve of Fig. 6 correspond ing to the inverse voltage 65 of Fig. 5 and in the portion ‘it! in the curve of Fig. 6 corresponding to the forward voltage 66 of Fig. 5, the grid poten tial is negative and the voltmeter tube l3 remains non-conducting. During the portion ‘l l , however, of the curve shown in Fig. 6 which corresponds to the arc drop‘ of Fig. 5, the grid 22 of the volt 10 meter tube I9 is positive and the voltmeter tube becomes operative to provide an indication of the arc voltage. If the voltmeter tube I9 is arranged to measure instantaneously in a manner which is well under stood in the art, the portion ‘H of the curve of Fig. 6 may be ‘reproduced, or with a suitable cur rent-responsive instrument in the plate circuit of the voltmeter‘tube H the average value of the the tube i9 does not draw any current, the re sistor 3| does not interfere with the equality of potential between anode l6 and control grid 22. The potential of the control grid 22 of the volt meter tube l9 during the maintenance of the arc in tube'll is shown at ‘H in Fig. 6. If the con denser 26 were omitted, the plate current in the voltmeter tube i9 would obviously vary with the grid voltage of the voltmeter tube l9, and the current-responsive device 25 connected in the 10 plate circuit could be calibrated to indicate the arc drop. However, in connection with are discharge tubes I have found that the quantity which is of greatest value to the operator or tester is the peak value of the arc voltage. This value tends to increase as a tube becomes less eiTicient with age or if for any reason the tube becomes defec tive. The peak value of the arc drop provides a better indication of the condition of the tube than invention illustrated in Fig. 1, however, the volt the average arc drop during the conducting meter tube l9 has been arranged to measure the period, since a defect causing a peak of short peak value of the arc drop. This operation re duration will a?ect only slightly the average dur sults from the fact that the condsenser 26 is con ing the conducting period. As already explained,~ arc drop may be measured. In the form of my nected in shunt to the resistor 26 and the current-._ the average potential difference between anode responsive instrument 25. The reason the cur rent-responsive instrument 25 indicates the peak and cathode during the entire cycle would be value of the arc drop will become apparent from wholly valueless. Where several arc discharge a consideration of the operation of the apparatus. tubes are used in parallel or in combination, my It will be assumed that the grid voltage of the method of testing is also of great value. By de~ 30 arc discharge tube il has been so adjusted in tecting defective operation of one of the tubes, phase as to give a condition similar to that, for overloading of the other tubes, which might not example, shown in Fig. 5. While the anode volt otherwise be apparent, may be prevented. The current-responsive device 25 may be made age of the arc discharge tube H is negative the grid potential of the control grid 22 of the volt responsive to the peak value of the arc drop by meter tube !9, which is connected to the anode connecting the condenser 26, as shown. It is l6, will obviously also be negative as shown in obvious that while the arc is maintained and the the portion 69 of curve 6. When the anode grid 22 of the voltmeter tube 19 is positive, as potential of the arc discharge "tube ll becomes shown at ‘I! in Fig. 6, the voltmeter tube i9 will positive, as shown at 66 in curve 5, the potential conduct current. Consequentlyha path will be 40 of the control grid 22 of voltmeter tube I9 would provided from the positive terminal 23’ of the voltage source 23 to the cathode side of the con I ordinarily tend to become positive likewise. However, as yet no current is flowing through the denser 26, which has its opposite plate already anode circuit of tube H, and the current trans connected to the negative terminal 23" of the former 40, likewise the control grid 39 of the voltage source 23. Consequently, the charge low-impedance discharge tube 33, is una?ected. stored in the condenser 26 will tend to rise as Consequently, the discharge tube 33, being de long as the tube I9 is conducting. Owing to the signed as a low-impedance tube, is conducting increasingcharge on the condenser 26, the po- . and serves to connect the negative terminal 31' of tential of the cathode -2[ of the tube I9 will rise the grid bias battery 37 to the control grid 22 of until it has reached such a potential that the the voltmeter tube is. As shown by the portion tube it’) shuts off. The tube I9 becomes non-con 50 50 16 in curve 6, the control grid 22 is maintained ducting when its cathode 2| becomes equal in po . negative and the operation of the voltmeter tube tential to its grid 22, or slightly more positive I9 is prevented. Owing to the magnitude of the by a ?xed amount than grid 22, depending upon resistance of the resistor 3!, this operation may the characteristics of the tube l9 selected. The take place in spite of the fact that the anode l6 voltage attained by condenser 26, therefore, bears 55 a linear relationship to the maximum potential of the arc discharge tube H is positive. When the arc discharge tube ll breaks down, however, as indicated by the discontinuity be tween portions 66 and 61 of the curve of Fig. 5, current flows in its anode circuit and in the pri 60 mary of the current"transformer'll0 as‘ a result of the are taking place between the cathode l1 and the anode 16 of the tube H. The flow of current in the ‘primary winding of the current of the control grid 22, which corresponds to the peak value of the arc drop of discharge tube ll. Consequently, the magnitude of the charge stored in condenser 26 provides an indication of the 60 peak value of the arc drop. The resistor 24 has a very high resistance, so that the discharge of condenser 26 which tends to take place through resistor 22 and current-responsive device 25 is transformer 40 results in a voltage between the very gradual and is substantially without e?ect terminals 4| and 42 of the current transformer ‘ upon the magnitude of the charge stored in con 40, which is so connected that the grid 39 of the denser 26. The current-responsive device 25 is low-impedance discharge tube 33 becomes nega chosen to be su?iciently sensitive to indicate the tive with respect to the cathode 35 of the dis magnitude of the discharge current, which obvi charge tube 33. Consequently, the discharge tube ously is proportional to the charge stored in con 70 33 becomes non-conducting and the potential of denser 26 and the potential di?erence between terminals produced by the charge. The cur the control grid 22 of the voltmeter tube It! is its rent-responsive device 25 ‘therefore responds to permitted to follow the potential of the anode N5 of the arc dischargetube ll. 75 the peak value'of the arc drop in tube H. The Owing to the fact that the control grid 22 of condenser 26 obviouslycontinues to discharge 2,010,697 5 during the portions of the cycle when the control grid of voltmeter'tube I9 is negative, as shown conductivity of said tube and the operation of said current-responsive device to depend upon at 69 and 10 of Fig. 6, but as already stated the magnitude of the resistance of resistor 24 is so the electrical condition of said electric circuit, chosen that the rate of discharge is slow enough means limiting'the' flow of current to said control grid, a second grid-controlled discharge tube hav to maintain a charge in condenser 26 which is ing a control grid, an anode connected to they proportional to the peak value of the arc drop. I have explained the operation of my invention control grid of said ?rst-mentioned discharge in connection with an arc discharge tube of the tube and a cathode connected to the cathode of 10 grid-controlled type, but it will be understood the ?rst-mentioned discharge tube, thereby nor that my invention is not limited thereto. For mally providing a low impedance path between 10 example, in connection with vapor orgaseous the grid and cathode of said ?rst-mentioned dis 15 20 25 30 ‘ discharge tubes of the two-electrode type, or the charge ‘tube and suspending its operation, means type not employing a control grid, it is also for maintaining the control grid of said second desirable to be able to measure the peak value tube negative with respect to its cathode while of the arc drop or the peak value of the voltage power is ?owing in the circuit in which a meas 15 between the electrodes duringthe period when urement is to be made, thereby. making the im current is ?owing. For example, in Fig. 7, the pedance of said second tube relatively high and sine curve ‘i2 represents the voltage which is ap permitting the operation of said ?rst tube, so plied to a recti?er of the arc discharge type by that the operation of said current-responsive de a source of alternating current. The curve 13 vice is controlled only by the electrical condi 20 tion of said measured circuit while the circuit represents the voltage between the electrodes of is under load. ~ ‘\ the rectifylngtube. It is a characteristic of such 4. Apparatus for measuring the forward arc tubes that the arc does not commence imme drop in a vapor discharge device comprising diately after the voltage becomes positive; in voltmeter of the discharge tube type having tera stead, the voltage between the electrodes rises minals connected to said vapor discharge device, 25 during an initial portion of the 'half cycle.to a peak value shown at ‘M, and the discharge a relatively high resistance connected in the leads between said voltmeter and said discharge de does not take place until an instant later, shown vice, and means for substantially short circuit at 75. In order to measure the maximum value of the arc drop it is therefore necessary to em ing said voltmeter except whilesaid discharge 30 ploy a device which will be unresponsive to the peak ‘M and will not become responsive until the point 75 at which the arc, commences. The 35 device which I have invented is therefore of con siderable value also in connection with two-elec device is conducting current, thereby making said voltmeter unresponsive to back voltages and to open circuit forward voltages. 5. An arrangement responsive .only to volt ages existing in electrical apparatus while said 35 apparatus is under load, comprising a voltage trode arc discharge tubes. . In accordance with the provisions of the pat responsive device having terminals connected ent statutes I have described the principle of op to said electrical apparatus and means for mak ing said voltage-responsive device unrespon 40 eration of my invention together with the ap paratus which I now consider the best embodi sive while said electrical apparatus is not under 40 load, said latter means comprising means tend ment thereof, but I desire to have it understood ing to limit the ?ow of current to said voltage that the apparatus shown and described is only illustrative and that the invention may be car responsive device, a discharge tube having an anode and a cathode connected across the ter-' ried out by other arrangements. minals of said voltage-responsive device and hav What I claim as new and desire to secure by ing a control grid, a. current transformer hav 4:5 Letters Patent of the United States is: ing a primary winding connected in series with 1. A device responsive only to the peak value said electrical apparatus and a secondary winding of the drop in voltage across the arc of an elec 50 tric discharge element having electrodes between having terminals connected to the cathode and the control grid respectively of said discharge ’ which current is carried by an arc, comprising a tube, said tube normally having a relatively low peak voltage-responsive unit having terminals impedance, tending to short circuit said voltage connected to the electrodes of said discharge ‘element, and means for making said peak voltage responsive device and make it non-responsive, responsive unit unresponsive to the voltage be said current transformer being so connected that the potential of the grid of said discharge tube tween said electrodes during the period that the becomes negative with respect to the cathode of 55 arc in said discharge element is extinguished. said discharge tube when current flows in said 2. Apparatus responsive only to the peak value electrical apparatus, whereby said voltage-re of voltage drop in an electrical appliance during sponsive device is permitted to become responsive 60 the period of time that power is being trans only to voltages acting during the period said 60 mitted, comprising a peak voltage-responsive de electrical apparatus is loaded. _ vice connected to said appliance, and means for 6. Apparatus responsive to the maximum arc making said peak voltagerresponsive device un responsive to the voltage in said appliance dur drop in an arc discharge, device comprising a peak ing the period of time that no power is being voltage-responsive device connected to the elec trodes of said arc discharge device, means tend transmitted. 3. An electrical measuring and testing device ing to limit the ?ow of current to said voltage comprising a grid-controlled electric discharge responsive device, a three-element discharge tube tube having an anode, a cathode and a control having an anode and a cathode connected to said grid, a source of. current and a current-respon voltage-responsive device and having a control sive device connected in series between said anode ‘grid, a current transformer having a primary 70 winding connected in series with the output circuit and said cathode, ‘said cathode and said con of said are discharge device and a secondary trol grid being connected to an electrical cir cuit in which a measurement is to be made, winding having one terminal connected to the thereby tending to cause the grid potential, the cathode of said discharge tube and a second ter minal connected to the control grid 'of Saiddis~ 76 6 2,010,139? of the cathode of said ?rst-mentioned dis charge tube, thereby normally providing a rela voltage charge tube rises to a potential bearing a fixed tively low impedance current path in shunt to relationship to that of the control grid and shuts said voltage-responsive device causing it to re o? said ?rst-mentioned discharge tube when said main unresponsive, the connections of said. trans condenser has attained a voltage dependent upon former being such that the control grid of said the maximum voltage of said electrical apparatus discharge tube becomes negative with respect to load. the cathode while current is flowing‘ in the output under 8. An arrangement for permitting the opera ‘ circuit of said recti?er, and said discharge tube tion of an electrical device only during the dura becomes non-conducting and permits said volt tion of load in an electrical apparatus with which 1O 10 age responsive device to become operative, where device is associated, which comprises an by said peak voltage-responsive device is made said electric discharge tube having an anode and a responsive only to voltages existing while current cathode connected in circuit with the device to is ?owing in the output circuit and an arc exists in said are discharge device. be controlled, and a control grid, a current trans former having a primary winding connected in 15 7. An arrangement responsive to a peak volt series with said electrical apparatus and a sec 15 age in an electrical apparatus existing during ondary winding having a terminal connected to periods when said apparatus is under load com the control grid of said discharge tube and an prising a discharge tube having an anode, a other terminal connected to the cathode of said cathode and a control grid, a source of direct cur discharge tube, said current transformer being 20 20 rent having its positive side connected to the so connected that the potential of said control anode of said tube, a condenser connected be grid is varied with respect to the potential of the tween the negative side of said current source cathode while said electrical apparatus is loaded and the grid of said tube and means responsive for the purpose of varying the conductivity of to the voltage of said condenser, a second dis said discharge tube, thereby permitting said elec charge tube having a control grid and having an trical device to operate only during the period anode connected to the control grid of said ?rst that said electrical apparatus is loaded. mentioned discharge tube and a cathode con 9. In combination with an arc discharge tube nected to, the negative side of said condenser, said a pair of electrodes, 2. peak voltmeter con second tube normally providing a low impedance having nected to said electrodes and means for allowing 30 30 path and suspending the operation of said ?rst said voltmeter to respond to the potential di?er mentioned tube by maintaining its grid at a low ence between said electrodes only while an arc potential, means limiting the flow of current to said ?rst-mentioned discharge tube from said electrical apparatus, a current transformer hav 35 ing‘ a primary, winding connected in series with ‘ the output circuit of said electrical apparatus and a secondary winding having a terminal connect ed to the control grid of said second-mentioned discharge tube and another terminal connected to the cathode of said second-mentioned dis V40 charge tube, the connections of said current transformer being such that the potential of the control grid of said second-mentioned discharge tube becomes negative with respect to the cathode 45 thereof while current is ?owing inthe output cir cuit of said electrical apparatus thereby making said second-mentioned discharge tube non-con ducting while said electrical ‘apparatus is under load, permitting the control" grid of said first 50 mentioned discharge tube to assume the voltage of said electrical apparatus, thus permitting said ?rst-mentioned discharge tube to become con ducting and to charge said condenser until the exists therebetween. 10. A method of testing an arc-discharge tube in which an arc can exist only when the supply voltage has a given polarity, referred to as posi tive, which method comprises connecting a uni directional voltage-measuring device between the electrodes of said tube to respond to positive voltages, preventing the interelectrode voltage 40 from affecting said voltage-measuring device during the non-conducting portion of the posi tive half-cycle of the supply voltage, and meas uring the maximum value of the voltage affect ing said voltage-measuring device. 11. A method of testing an arc discharge tube which comprises connecting the voltage-measur ing device to the electrodes of the tube, prevent ing the interelectrode voltage from affecting said device while the tube is non-conducting, and 50 measuring the maximum value of the voltage af fecting said voltage-measuring device. HAROLD W. LORD.