US1445988A - Method and apparatus for rectifying high-tension alternating current - Google Patents

Description

Feb,20,1923. 1,445,988. =G,A .wnTE.

METHOD AND APPARATUS FOR RETIFYING H iGH TENS|0N\ALT ERNATING CURRENT.

, FILED APRQa. 1919.

50 ,3 -34 4 3 a P 2 15 35 I 3 W INVENTOR I Cum P 4W ATTORNEY Patented Feb. 20, 1923.

UNITED STATES I PATENT OFFICE.

GUSTAV A. WITTE, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO INTERNA- TIONAL PRECIPITATION COMPANY, OF LOS ANGELES, CALIFORNIA, A CORPORA- TION OF CALIFORNIA.

METHOD AND APPARATUS FOR RECTIFYING HIGH-TENSION ALTERNA'IING CURRENT.

Application filed April 8, 1919. Serial No. 288,652.

To all whom it nlay concern: 7

' Be it known that I, GUSTAV A. urn, a citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a new'and useful Method and Apparatus for Rectifying High-Tension Alternating Cur-- rent, of which the following is a specification.

This invention relates to the rectification of high tension alternating current by means of a mechanical rectifier that is to say, a mechanical device operated in synchronism with the alternating current and-acting to make and break connection between the supply circuit and a load or translating device, in such manner that only unidirectional impulses will be transmitted to the latter. In apparatus of this character, the connection established thereby generally includes air gaps between the shoes or stationary conductors and moving conductors thereof, and

there is, in general, a tendency to sparking between such stationary and moving conductors, especially at the moment of break or interruption of circuit, this resulting not only in objectionable wear on the shoes or conductors, but also in objectionable current phenomena in the load circuit. This is particularly the case where the load supplied through the rectifier is one presenting high capacity and considerable conductance, such as a treater for precipitating suspended material from gases by electrical action. In such case, the sudden fluctuations or surges produced in the load circuit upon occurrence of sparking at the rectifier shoes or contacts. interfere seriously with the efliciency of the precipitating opeaation. The main object of the present invention is to wholly or largely eliminate such sparking at the rectifier shoes or contacts. This object attain by applying to the shoes or contacts at or adjacent to the point of interruption of t-he current finely divided solid material in the form, for example, of dust.

The accompanying drawings illustrate embodiments of my invention, and referring thereto:

Fig. 1 is a vertical section of one form of apparatus suitable for carrying out my invention;

Fig. 2 is'a section on line 2-2 in Fig. 1;

Fig. 3 is a vertical section of another form of the invention. 1

Referring to Fig. 1. the rectifier therein shown comprises a shaft 1 mounted on suitable bearings to rotate within a. box orcasing 2; an insulating disc 3 carried by said shaft, metallic segments 4 and): on said disc'and stationary shoes 5?, 5 5 and 5 mounted in fixed position adjacent to the periphery of said disc. The respective shoes aforesaid are shown as arranged 90 apart and the metallic segments 4 and 4* on the rectifier disc 3 are about 90 long so that. said segments will establish connection successively between adjacent pairs of shoes in well known manner. Opposite shoes 5 and 5 are mounted on insulators 6 and are 0011- nected by wires 7 and 8 to opposite ends of" the high tension coil 9 of a step-up transformer whose low tension coil 10 is connected to alternating current supply circuit wires 11 and. 12. Said wires 7 and 8 areinsulated in any suitable manner, to provide for high potential difference, say 50,000 volts or more, between the same. A conductor. 14 is connected to shoe 5 mounted on an insulator 6 and is connected to a wire 16 leading to the load to be supplied from the rectifier. Shoe 5 is grounded by a connection 19. Suitable insulators 13 are provided for Wires 7 8 and 14 where they pass through the walls of easing 2. Shaft 1 is rotated in synchronism with the alternating current to be rectified, for exampla'by means of a synchronous motor '15 connected by wires 17 and 18 to the alternating current supply circuit 11 and 12, or, as is well known in this art, said shaft may be direct driven from a motor generator set, which serves to produce the high tension alternating current on the wires 7 and 8 in well known manner, and as set forth iii-patent to F.- G. ottrell. No. 895,729, dated August 11.. 1908. Insulators 6 for shoes 5", et cetera, are shown as bars carried by a frame 24 mounted in bearings 25 and 25 and adapted for angular adjustment by suitable means indicated at 26, to synchronize the operationv of the apparatus with the alternating current supply circuit. Stuffing boxes 27 may be provided where the bearings 25 and 25 pass through the wall f? (will of casing 2 and a stufiing'box 27 where shaft 1 passes through bearing 25 My invention comprises means .for supplying dust or other vapor producing means to the breaks orgaps between the shoes and rotating conductors of the rectifier. For this mr ose I ma as shown in Fi 1 rovide means for supplying dust to the interior of easing 2, such means consisting, for example, of an air blast pipe connected to a suitable source of compressed air and provided with means, indicated at 21, for feeding dust thereinto, and with a valve 20 for regula-' ting the supply of air, or a manhole or door 22 may be. provided for introducing the dust. In order to protect the bearings of shaft 1 from grit present in the dust, said bearings are preferably outside of the casing 1, as

' shown in F i g. 2, wherein one end of the shaft is mounted in a bearing 23 and the other end of the shaft is connected to or constitutes an extension of the shaft of the driving motor or generator 15.

In the operation of the rectifier the dust present in the chamber 2 and supplied thereto by the air blast means 20, or, ifdesired, through door 22, is stirred up or agitated by the windage of the rectifier, aided by the air blast, so that the atmposhere in which the rectifier rot-ates is charged with dust and suflicient dust is present between the stationary shoes and rotary conductor members to alreason of such lowering of resistance the current is decreased more slowly and gradually on interruption thereof than would otherwise be the case. This gives a more gradual and less violent break and a smoother and more efiiciently operating current supply on the load circuit.

If the casing 2 is sufficiently charged with dust the windage of the rectifier itself may be sufficient to maintain the circulation of the dust therein without requiring'the air blast or agitating means aforesaid.

The invention may also be carried out by direct supply of the dust to the rectifier, for example, as shown in Fig. 2, wherein a dustfeeding means is mounted in position to drip or sprinkle dust onto the rotating member ofthe rectifier. rSaid feeding means com prising, for example, a pan 30 pivoted at 31 and agitated or vibrated by rotating tappet' means'32, said pan being directly below a dust feed pipe 33 so as to receive dust from the pipe and discharge it into the rotary rectifier member 3, the windage of such rectifier member carrying the round to the several sets of contact. The re, .fer prothis invention has been just such as is obtainable from electrical precipitating apparatus used in collecting the dust and fume from cement kilns. Such dust contains a considerable proportion o't volatile alkaline material and it is assumed that the beneficial efl ect of this dust presented at the point of current disruption is due largely to the presence of vapors of such alkaline material produced from the dust by the heat the electric sparks passing therethrough or the heatof the discharge between the shoes and the moveable contacts of the rectifier, and my invention includes any equivalent means for producing vapors at or adjacent to such shoes or contacts. Heated vapors of alkalies or metals are generally more conducting than the air or other dielectric in which the current disruption takes place, and the effect of the presence of such vapors is therefore to produce a zone of comparatively conducting vapor between the shoes and movable conductors of the rectifier in such manner that the interruption of current takes place gradually, as the comparatively conducting vapor affords a path of gradually increasing resistance for. the current between the moving conductors :and the stationary shoes, which can be drawn out to a considerable extent before the resistance thereof becomes so high as to actually break the connection.

Another advantage of this invention is that the relatively high conductivity of the vapor Zone interposed between the shoes and the moveable conducting members re- .05 duces the effective resistance ofthe rectifier as a whole as compared with the ordinary air' gap rectifiers now in use wherein the drop of voltage at the rectifier, due to resistance of the air gap between the shoes and 1m rotating conducting members of the rectifier, decreases appreciably the potential difference actually applied to the load.

The characteristic feature of the invention in its broadest aspect is the applica- 6 tion of a substance which directly or indirectly increases the conductivity of the dielectric at the point of interruption. Solid material to be applicable must necessarily be in a state of fine subdivision. In the claims ruption.

'cent. to but out of contact with -ber provided with means for operation thereof in synchronism with I the alternating current and with conductors rotating adjasaid stationary conductors to interrupt the connection a from the supply current to the load circuit through air gaps betweenthe rotary and stationary conductors, and means for sup plying finely divided solid material to said air gaps. I

4. An apparatus according to claim 3 wherein the rectifier is enclosed in a casing provided with means for supplying dust L thereto and for agitating the air within the casing to keep said dust in suspension;

In testimony whereof I have hereunto subscribed my name this 31 day of March GUSTAV A. WITTE.

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