US2032932A - Electeostatic device - Google Patents

Description

March 3, 1936. F- HAUFFE ET AL 2,032,932

ELECTROSTATIC DEVICE Filed March 20, 1935 Inventor: Fritz Hauffe,

Claus Fr'cihmer,

eh Attorney.

' duce an electrostatic voltmeter of high sensitivity,

Patented Mar. 3, 1936 PATENT OFFICE EIIJEIC'IIIIRK)STATIC DEVICE Fritz Haul'fe, Berlin-Friedman, and Claus Friihmer, signors to General Ele ration of New York Application March 20,

Berlin- Charlottenburg,

Germany, asctric Company, a corpo- 1935, Serial No. 12,064

In Germany April 13, 1934 8 Claims. (01.171-95) 1 Our invention relates to electrostatic devices and concerns-particularly-such devices arranged as voltmeters.

The principal object of our invention is to proespecially one which is suitable for high-voltage circuits. Other and further objects and advantages will become apparent as the description proceeds. I

The features of our invention which are believed to be novel and patentable are pointed out in the claims appended hereto. A better understanding of the invention may be obtained by referring to the following description taken in connection with the accompanying drawing in which Fig. 1 represents schematically, partially in perspective, one embodiment of our invention; Fig. i 2 represents in elevation several elements of the apparatus of Fig. 1, separated to avoid confusion but showing the relative position of the parts of the several elements; and Fig. 3 represents another embodiment of our invention.

The apparatus illustrated in the drawing includes a grounded low-potential terminal I and a high-potential terminal |2 mounted on an insulating part l3. A plate ll, whichmay be circular in shape, is attached to the high-potential terminal |2 to serve as a high-potential electrode. There is provided opposite the electrode l4 and substantially parallel thereto a rotatable disc l5 carrying a plurality ofsectors IE to 2| of conducting material symmetrically arranged about the center of rotation of the disc l5. Suitable means, such as the motor 22, are provided for rotating the disc l5 and the conducting sectors at a uniform speed. In the case of alternatinga synchronous motor fed by a current of the same frequency as that of the voltage to be measured.

A grounded shield. 23 composed of conducting material or faced with conducting material is interposed between the high-potential electrode l4 and the rotatable disc I5 with its conducting sectors |62|. The shield 23 is provided with sector- shaped openings 24, 25 and26, symmetrically placed about a central point and registering with alternate conducting sectors of the disc l5 when it is in the .proper angular position. There are, however, only half as many openings in the shield 23 as conducting sectors on the disc I5.

In order to produce an indicating current of constant polarity, a commutator 21 is provided which is mechanically connected to the disc l5 or arranged to rotate synchronously with it. The commutator 21 has as many segments as there are conducting sectors on the disc l5, and corresponding segments and sectors are electrically connected. Alternate sectors on the disc |5 are also electrically connected. If desired, alternate sectors |6, l8, and 20 may be connected by a conductor 29,. alternate sectors ll, I9, and 2| by a conductor 28, and the corresponding alternate segments of the commutator 21 may likewise be connected to form two groups. Then only two connectors and 3| need be provided to effect the connection between corresponding disc sectors and commutator segments.

Brushes 32, cooperating with the commutator 21, are-provided for drawing off the electrostatic charges collected by the conducting sectors on the disc. I5 and a current-responsive device 33 is previded for measuring the amount of the charge collected. For the sake of safety, it is preferable to ground the circuit of the instrument 33 in some suitable manner as by connecting one of the brushes 32 to the grounded terminal M. It is obviously a decided advantage of our invention that the arrangement permits grounding or keeping at low potential all the apparatus with which an operator is most likely by inadvertence to come in contact.

It is apparent that the high-potential electrode l4 will produce an electrostatic field proportional in strength to the voltage to be measured. The charges collected by the sectors l6 and 2| as they are exposed by the openings in the shield 23 will, therefore, be dependent upon the voltage to be measured. As the two groups of sectors l6, l8, and 20, and I1, I9, and 2| are charged alternately and the connections to the current-responsive device 33 are alternated as often as a sector becomes fully exposed to the electrostatic field, the sectors will be discharged through the currentresponsive device 33 and a current will flow in device33 dependent upon the rate at which electric charge is collected by the sectors. The voltage measured by the device as shown is, of course, the voltage of the high potential electrode H with respect to ground potential and the ground terminal serves as the low potential terminal of the apparatus.

Inasmuch as the charge'acquired by a fiat plate forming one of the plates of a condenser is proportional to the product of the voltage and the area of the plate, the increment of charge 001- lected by one of the sectors IE to 2| as they become exposedto the electrostatic field will be dq=kE.ds Where I: is a constant, E is the voltage and ds is the increment oi. exposed area'of one of the sectors on the disc l5. It is apparent, therefore,

that the sensitivity of the apparatus will increase with the number of sectors. For example,

by employing six sectors as shown, a current i is obtained which is three times that which would beobtained if there were only two semicircular sectors on the disc 15 and one semicircular opening in the shield 23, other conditions being unchanged.

Although we have illustrated an arrangement in which the shield 23 is stationary and the conducting sectors I6 to 2| are movable, it will be understood that our invention is not limited to this precise arrangement but obviously includes arrangements in whichthe shield 23, instead of the sectors, rotates or in which both shield and sectors rotate.

For example, in the arrangement of Fig. 3, the insulating disc IS with the sectors Hi to 2| is stationary, having an axial opening therein to permit a shaft 34 driven: by the motor 22 to project through the disc l5 and rotate the shield 23. Although the parts are shown separated for the sake of clearness in the drawing, it will be understood that the shield 23 and the disc l5 are pref- I erably as close together as mechanical consideraa desired, by a brush 35.

tions permit.v The shield 23 may be grounded, ii.

In the arrangement of Fig. 3, no commutator is needed and the conducting sectors IE to 2|- may be connected directly to the indicating instrument 33.- If the instrument 33 is of a type responsive only to direct currents, a rectifier 36, for example, a bridge connected full-wave rectifier of the copper-oxide type; may be interposed in the circuit of the instrument 33.

While we prefer to utilize the shield 23 with its openings 24, 25, and 26 in order that the conducting sectors I 6 to 2| will definitely be subjected to and withdrawn from the influence of the electrostatic field from the electrode l4, our invention is not limited to the precise arrangement shown but obviously includes any arrangement for subjecting a plurality of conducting surfaces to the influence of an electrostatic field proportional to a voltage to be measured and withdrawing the surfaces from the influence of the field, such as, for example, forming the electrode as a plurality of coplanar sectors corresponding to the openings in the shield 23 and then omitting the shield 23. j While we have described the shield 23 and the disc l5 as being planar and the openings and conducting. surfaces 24 to 25 and It to 2| as being sector-shaped since the electrode I4 is shown as planar, it will be understood that cooperating surfaces of some other shape may be employed.

Inusing the apparatus to measure alternating voltages, it will be understood that the motor 22 is to be driven-at such a speed that'each conducting sector is always fully exposed to the influence o; the electrostatic field when the voltage has a given polarity, more particularly at a given point in the voltage wave, preferably the peak.

In the arrangement shown, with six conducting segments, the motor-22 would accordingly be arranged to-run at a speed in revolutions equal to one-sixth the frequency in cycles of the alternating voltage to be measured. For example, a

twelve-pole synchronous motor might be. em-- ployed, energized from the same power systemas the voltage be measured. 7

I In accordance with the provisions of the patent statutes, we have described the principle of operation of our invention together with the apparatus which we now consider to represent the best embodiment thereof but we desire to have it understood that the apparatus shown is only 11- lustrative and that the invention may be carried out by other means.

What we claim as new and desire to secure by Letters Patent in the United States is:

' 1. A static voltage-responsive device comprising in combination, a high-potential electrode; a

rotatable disc of insulating'materi'al carrying a .plurality of sectors of conducting, material symmetrical with respect to the center of rotation of said disc, a grounded shield between said highpotential electrode andsaid disc having half as many sector-shaped openings therein symmetri-v cally placed around a center'point as the number of sectors'in said disc adapted to register with said conducting sectors, a commutator having segments electrically connected -to corre- ,sponding sectors on said disc, alternate segments being also connected together, brushes, one of V which is grounded, cooperating with said commutator to alternate connections as often assaid conducting sectors are-either fullyexposed or fully covered by said shield, a current-responsive device connected to said brushes, and means for rotating said commutator and said disc.

2. A static voltage-responsive device comprising in combination, a high-potential electrode, a rotatable member including a plurality of insulated sectors of conducting material, a shield between said high-potential electrode and said rotatable member having half as many sectorshaped openings therein as the number of sectors in said rotatable member adapted to regis- 'ter with said sectors, a commutator having segments corresponding to said rotatable sector's, al-. ternate rotatable sectors and alternate commutator segments being electrically connected, brushes Y cooperatingwith said commutator, a current-re-' sponsive device connected to said brushes, and means for rotating ments. l

3. An electrostatic device comprising in combination a high-potential electrode, a chargecollecting member including a plurality of in,- sulated sectors of conducting material, a shield betweensaid high-potential electrode and said charge-collecting member having half as many sector-shaped openings therein as the number 01.

said commutator and said seesectors in said charge-collecting member adapted to register with said conducting sectors, said shield and said charge-collecting member being relatively rotatable, a commutator having segments electrically connected to corresponding sectors of said charge-collecting member, and

- brushescooperating with said commutator, said brushes and said commutator being relatively rotatable.

4. A static voltage-responsive device comprising in combination, a high-potential electrode, a

stationary member including an even number of insulated sectors of conducting material, a rotating shield between said high-potential electrode and said stationary member having half as many sector-shaped openings therein as the number of sectors in said stationary member adapted to register with said sectors, alternate conducting sectors being connected, and a current-responsive device connected between adjacent conducting sectors.

5. A voltage-responsive device comprising in combination, a high-potential electrode, a chargecollecting member including a plurality of insulated areas of conducting material, a shield between said high-voltage electrode and said chargecollecting member having half as many openings therein as the number of said conducting ,areas on said charge-collecting member adapted to register with said conducting areas, said shield and said charge-collecting member being relative- 1y movable, means for producing relative motion thereof, and a current-responsive device connectable between adjacent conducting areas on said charge-collecting member.

6. A voltage-responsive device comprising in combination, a high-potential electrode, a chargecollecting member including a plurality of insulated areas of conducting material, means for subjecting said areas to the influence of the electrostatic fleld from said high-potential electrode and withdrawing said conducting areas from the influence of said electrode alternately, a low-potential terminal, a current-responsive device having a terminal connected to said low potential terminal anda second terminal, and means for connecting each of said conducting areas to the second terminal of said current-responsive device and to said low-potential terminal alternately.

'7. A voltage-responsive device comprising in combination, a high-potential electrode, a charge ber, one of said current terminals being connect- "ed to said low-potential terminal.

8. A voltage-responsive device comprising in combination, a high-potential electrode, a chargecol'lecting member including a plurality of insulated areas of conducting material, means for removing the influence of the electrostatic field surrounding said high-potential electrode from said conducting areas alternately and, while the voltage to be measured has a predetermined polarity, subjecting said conducting areas alternately to the influence of said electrostatic field, a low-potential terminal, a current-responsive device having a terminal connected to said lowpotential terminal and a second terminal, and

means for connecting each of said conducting areas to the second terminal of said currentresponsive device and to said low-potential terminal alternately.

FRITZ HAUFFE.

CLAUS FRCiHMER.

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