US1340502A - Apparatus and method for rectifying high-tension alternating current - Google Patents

Description

, W. A. SCHMIDT AND L. BRADLEY. APPARATUS AND METHOD FOR RECTIFYING HIGH TENSION ALTERNATING CURRENT.

APPLICATION FILED SEPT. 15, 1915.

Patented May 18, 1920.

3 SHEETSSHEET 1 f/ vemora: Wa/fer Aug/Jar (Sch/211M? Lin/7 Brad/ey.

W A. SCHMIDT AND L. BRADLEY. APPARATUS AND METHOD FOR RECTIFYING HIGH TENSION ALTERNATING CURRENT.

' APPLIICATION FILED SEPT. 15; 1915;

1 40,502. tented May 18,1920.

3 SHEETS-SHEET 2.

W. A. SCHMIDT AND L. BRADLEY.

APPARATUS AND METHOD FOR RECTIFYING HIGH TENSION ALTERNATING CURRENT.

' APPL'ICATION FILED SEPT. I5, 1915.

1,340,502., Patented y 18,1920.

3 SHEETSSHEET 3.

UNITED STATES PATENT OFFICE.

WALTER AUGUST SCHMIDT, 0F Los ANGELES, CALIFORNIA, A D LINN BRADLEY, OF EAST ORANGE, NEW JERSEY, ASSIGNORS To REsEARcH coEPoRATIoN, OF NEW YORK, N. Y., A CORPORATION or NEW YORK. I

APPARATUS AND METHOD FOR RECTIFYING HIGH-TENSION ALTERNATING CURRENT.

To all whom it may concern I Be it known that we, WALTER AUGUST SCHMIDT and LINN BRADLEY, citizens of the United States, residing, respectively, at Los Angeles, in the county of Los Angeles, State of California, and East Orange, in the county of Essex, State of New Jersey, have invented a new and useful Apparatus and Method for Rectifying High-Tension Alternating Current, of which the following is a specification.

This invention relates to the rectification of alternating currents, particularly for application in connection with the precip tation.of suspended matter from gases. Such precipitating operations, when carried out on a commercial scale, require the use of such high potentials and such large surface of electrodes, that the electrostatic capacity of the operating circuit becomes an import-- ant factor in the operation of the system. When a high tension electromotive force is suddenly applied to a circuit of high. capacity and appreciable conductance, the charging of the capacity requires an appreciable time and there is a'tendency .of the charges to surge back into the line immediately after such charging is completed. An important object of our invention is .to provide for minimizing such back surgingv of the'charge, and to insure that substantially the whole energy of the charge willbe retained in the apparatus except in so far as it is utilized in discharge through the apparatus. For this purpose we provide for breaking the connection to the apparatus, preferably at the rectifier, as soon as the charging of the apparatus is completed, and the charging current is therefore substantially reduced to zero. This not only safeguards the line transformer and rectifier from high potential surges, but breaks the rectifying connection at the most favorable time for elimination or mitigation of sparking or a'rcing atthe rectifier contacts, namely the time-of minimum current flow.

Another object of the invention is to provide rectifying means of simple construc- Specification of Letters Patent.

Patented May 18, 1920.

Application filed September 15, 1915. Serial No. 50,793.

tion and presenting minimum loss by windage or ,OthBI'WlSG.

vide improved means for shifting the phase of the rectifier relatively to the phase of the alternating current supplied thereto.

In the accompanying drawings:

1' gure 1 is a side elevation of a rectifier embodying our invention.

Fig. 2 is asection on line w 'a2 in Fig. 1.

Fig. 3 is a section on line m w in Fig. 2.

Fig. .4 is an elevation of one of the variable-length contact shoes. i

Fig; 5 is a longitudinal section of the the invention as shown in Fig. 10. Fig. 12 is a rear elevation of the stationarymember sdi own inFig. 11.

The rectifier comprises a stationary member 1, mounted on a frame 2, and a rotary member 3 carried by a shaft 4, which is journaled in bearings 5- on said frame. Frame 2 may consist of a base and standards 2 on said base, said standardsbeing provided with the bearings 5 for shaft 4 and with bearings 7 on which the stationar member is mounted so as to be angularly a justable around the axis of the rotative member.

Stationary of end spiders or members 8 rotatively mounted on the respective bearings 7 and longitudinal rods 9 and 9' connecting said spiders 8. Said rods are preferably arranged in'pairs, rigidly connected to arms 8 of spider ,8. One of these pairs of rods the device member 1 preferably consists- Another object of the invention-is to pro (9') may be ofmetal, the other rods 9 being of insulating material. Contact" holders are mounted on the respective pairs of rods, each holder comprising a clamp10 rigidly secured to a pair of rods 9 or 9', bolt 11,

bar 12, which is slotted as at 12' to receive the bolt and which carries a contact shoe 14. To provide for adjustment of the length of the contact shoe in the direction of motion of the rotor, said shoe may be provided with an extension 14', formed as a segment slotted to' slide on bolts 15 on member 14, and means are preferably provided for adjustment of these parts while the machine is in motion, such means consisting for example, of a pinion 16 engaging a rack 13 on each member 14, said pinion being operated, through an insulating shaft, 40, by manual operating means 41. The sta tionary frame 1 is also preferablyprovided with means for angular adjustment thereof while the machine is in motion, said means comprising, for example, a rod 42 pivoted thereto, and adjustably clamped in a guide 43, by clamp screw 44.

Shaft 4 is preferably grounded, for example, by a brush 50, mounted in a holder 51 on bearing 5, and pressed against the shaft by a spring 52. In order to provide the requisite'insulation for the rotor, shaft 4 may be covered with an insulating sleeve 4 of any suitable insulating material. Rotative member 3 preferably consists of a disk of insulating material, such as hard fiber, treated by impregnation with suitable insulating material, so as to give it the necessary high insulating property. The apparatus shown is adapted to rectify a single phase alternating current, using four stationary contact shoes 14 on the stationary member, and two conductors on the rotative member, said conductors being formed, for

example, as metallic segments 18 secured to the disk 3, and provided with radial projections 17 forming a pair of contact members for each conductor. Disk 3 may be mounted onshaft 4 by 'means of a hub 20 on said disk, having split tubular end portions 20 formed with taper screws engaged by nuts 22 to clamp the hub to the shaft.

The rotative member is rotated in synchronism with the alternating current which is to be rectified. This is effected by connection of shaft 4 to a'motive device operating in synchronism with such current. For this purpose we may connect the shaft 4 to the shaft 25 of a motor generator set, indicated at 26 in Fig. 2, the generator member 28 of which is connected to the primary circuit 30 of a step-up transformer 31. The secondary winding .of said transformer is connected at opposite sides thereof, by-wires, 32 and 33 respectively, to two of the contact shoes 14 onopposite sides of the stationary member. Oneof the other two opposite contact shoes may be grounded as at 34, and the other is connected by'wire 37 to the high tension electrodes 38 of a precipitating apparatus, the opposite electrodes 38'" thereof being said bolt also clamping to said holder a Qgrounded as indicated at 39. Asynchronous ductors of the rotative member are here called contact members or shoes, but it will be understood that with the high tensions used in connection with this apparatus, it is not necessary for the rotative conductors to actually contact with these stationary members, and in general they will be so arranged as to pass the stationary shoes without touching, but sufficiently close to enable the current to pass through the intervening medium. l/Vhile it may in some cases be desirable to form the conductors on the rotative member with contact members 17 projecting therefrom so as to break connectio'n with the stationary members at two points simultaneously, for each rotative conductor, we may, in other cases use a continuous segment making connection throughout the whole or any part of its length, with the stationary members. Furthermore, our invention is not limited to two pairs of rotative conductors, or of stationary conductors, but may comprise any desired number of such conductors, connected to accomplish-the same result as the construction above described, it being understood that in any case the rectifier will be driven at such speed that its period of rectification synchronizes with the period of alternation of the' supply current.

The operation of the apparatus above described is as follows: The rotative member is rotated by the shaft 4 in such mannerthatat a certain point in each half wave of the alternating current, the conductors of the rotative member occupy the positions shown in Fig. 2, so that each of said conductors bridges or makes a connection across the space between one of the stator shoes connected to the sup ly circuit, and the stationary shoe at tlie rear thereof, thereby putting the supply circuit momentarily in connection with the load and causing current to fiow in a certain direction through the load, and during a corresponding point in the next succeeding half wave, the conductors of the rotative member occupy positions 90 degrees in advance of the positions just described, so as to bridge or connect across from each stationary shoe connected to the supplycircuit, to the load-connected stationary shoe in advance thereof; the connections of the supply-connectedstationary shoes to the load connected stationary shoes being thereby reversed, and as the polarity of the stationary shoes has been reversed at the same time, the electric current impulse delivered to the load is in the same direction as before.

In carrying out our method of supplying current through a load acting as a leaky condenser, we vary the angular position of the stationary member, so as to change the time of make and break relatively to the phase of. the "supply current, and vary the length of the contact shoes, (by the adjusting means 16 above described) so that at each half wave of the alternating current the effective connection between the supply circuit and the load, through the rectifier,

' is maintained for a suflicient time to charge the load,acting as a capacity, to'substantially the momentary potential difference of the supply circuit, the charging current being then a minimum (being only that due to the leakage from the load, acting as a corona load or resistance) and at thls moment the connection is interrupted by the rectifier so that surging is reduced to a minimum by reason of the smallness of the current atthe moment of break and also by reason of the fact that the load,-acting as an electrostatic capacity, and being momentarily at the same potential difference as the transformer, does not tend to either draw current from the 'transformer, or to discharge back to the transformer. This time of interruption is also'the most favorable for successful operation of the rectifier as it minimizes the sparking or arcing at the moment of break, and the operator may determine the proper adjustment of the stationary members, as to length and angular position, by noting the sparking or arclng action, and adjusting for minimum thereof.

The above described construction of the rotative member, of the rectifier, in which an insulating disk is used as the means for carrying the rotative member contacts, is of great advantage in that it provides high insulation together with ample mechanical strength, and also in that it reduces windage loss to a minimum.

Another embodiment of our invention is illustrated in Figs. 8 and 9, wherein the statlonary member is shown as comprising four arms 41 carried by a hub 43, whose shaft 44 is mounted to turn in a bearing 45,and four supplementary arms 41' carried by a hub 43 whose shaft 44' extends through the shaft 44, the respective arms 41 and 41 carrying the contact shoes or members" 46 and 46. Arms 41 and 41 are preferably formed as rods of insulating material and the shoes 46 and 46 may be formed as plates carried by rods 47 and 47" mounted on arms 41 and 41 by clamping means 48 and 48'. Springs or flexible connections 50 connect each of the arms 41 with one of the arms 41 so that the contacts 46 and 46' carried by the two arms connected by such spring form in effect a single contact member, whose effective length may be varied by rotating the set of arms relatively-to the set 41 so as to vary the distance of each contact 41 from the corresponding contact 41. Means such as arms 52 and-52 may be provided on the respective shafts 44 and 44 to adjust the angular position of the respective sets of arms 41 and 41. Said arms may be operated byrods 53, 53 from any suitable controlling means.

The rotative,member in this form of our invention may consist of an insulating disk 55 provided with contact segments 58 and carried by a hub 56 on the shaft 57 of a motor, such as a synchronous motor 59 or other motive means adapted to rotate in synchronism with the alternating current which is to be rectified. The segments 58 in this case are shown as of uniform height throughout their length. And this construction of the segments is of a special advantage for the reason that the outer edge of each segment remains close to the shoes or conductors 41 and 46 throughout the time of closure of contact, and at uniform distance therefrom, thereby maintaining a constant zone of conducting gas at the gap between the stationary shoes, or conductors, and saidsegments, and reducing to a minimum the oscillation or surging of current due to sudden changes of resistance at the break or gap. The circuit connections to the respective contact members 46 are the same as above described, and the operation is the same, except that by the adjusting or shifting means 52' all of the contact mem-- bers 46 may be-shifted simultaneously with relation to the contact members 46, so as to vary the duration of contact.

Instead of making all of the stationary member contacts on two relatively adjust able members, as in Fig. 8, we may make only one of the opposite pairs of contacts on relatively adjustable members, as shown in Fig. 10, the contacts 61 of the stationary member being carried by opposite arms 62.

connected together. and rotatably mounted on bearing 65, and the other contact member of the stationary member comprisin two sets of contact shoes 66 and 66' carried respectively by opposite arms 67 and 0p site arms 67 which are independently rio; 'tatable on the bearing 65, each shoe- 66 be.- ing connected by a spring or flexible member 68'to the adjacent shoe 66. The rota tive member 70 may be similar to that above described.

Any suitable means may be provided for adjusting the arms of the device ShOWIl' liiO Fig. 10, for example, the means shown in Figs. 11 and 12, in which two of the arms 67, 67 are-shown as extending downwardly from the shaft mounting therefor, and vprovided with swivel nuts 75 engaged by reverselythreaded portions 76, 76 on a shaft 77' rotatably mounted in an arm 78 extending from the cross arm 62. The shaft77 is provided with an operating handle 7 9, whereby the shaft may be moved bodily to turn all of the arms of the stationary member, in unison about the axis of the rotor 70, so as to change the time of make or break, or, by rotating the shaft 77, to move the arms 67 67 of each pair, closer together or farther apart so as to vary the duration of contact. "The parts may then be set into position by tightening nut 80 on shaft 65, which constitutes the bearing for said parts.

What we claim is:

1. A rectifier for high tension alternating current comprising supporting means provided with bearings, a shaft mounted to rotate in said bearings, an insulating rotary disk carried by said shaft and provided with peripheral conducting segments, a stationary member mounted for angular adjustment around the axis of said shaft and provided with means for holding it-in angu-' larly adjusted position and with insulating rods, and conductors mounted on the respec tive insulating rods and provided'with shoes extending ad acent to the path of the conconnections and load connections.

2. A rectifier according to claim 1 wherein the said shoes are movably mounted on the supporting conductors therefor, for adjustment' toward or from the periphery-of the disk and are provided with means for clamping the same in adjusted position.

,3. A rectifier for high tension alternating currents, comprising supporting means provided with two bearings, a shaft mounted to rotate in said bearings, an insulating rotary disk carried by said shaft and having peripheral conducting se ments, two spiders rotatably mounted on t e respective bearings, insulatin rods and a conducting rod connecting sai spiders to form a frame angularly adjustable around the axis of rotation of said disk, and shoes mounted, respectively, on said insulating rods and on the conducting rod and extending adjacent to the path of rotation of said conducting segments so as to be connected in pairs by said segments, said shoes having, respectively, suppl circuit and load circuit connections.

4. X rectifier according to claim 3 wherein said rods are provided in pairs, and a shoe supporting means is clamped on each pair of rods 'to rigidly hold the shoes.

WALTER AUGUST SCHMIDT. LINN BRADLEY.

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