US1570789A - Alternating-current rectifier - Google Patents

Description

Jan. 26 9 19260 H. A. SEHFKE ALTERNATING CURRENT RECTIFIER Filed Jan. 5, 1923 3 Sheets-Sheet 1 EV My.

flit B11701 HrERNAN A SEIFKE.

Jan. 26 1926. 1,570,789

H. A. SEIFKE ALTERNATING CURRENT RECTIFIER Filed Jan. 5, 1923 3 Sheets-Sheet 2 u E I. I I

H. A. SEIF'KE ALTERNATING CURRENT RECTIFIER Jan. 26 1-926; 1,570,789

Filed Jan. 3, 1923 5 Sheets-Sheet 5 fill E127 P HERMAN A SElF/ff.

' Patented Jan. 26, 1926.

HERMAN A. SEIFKE, OF SAN FRANCISCO,

CALIFORNIA, ASSIGNOR OI TWENTY-TWO AND ONE-HALF ONE-HUNDBED'IHS TO MORRIS EDELHAN,-'1WENTY-FIVE ONE- EUNDREDTHS T STEVE A. IBEAGLE,

AND TWENTY-TWO AND ONE-HALF ONE HUNDREDTHE TO MAX LEWIS, ALL 01 SAN FRANCISCO, CALIFORNIA.

ALTERNATING-CURBEN'I' nno'rrrmn.

Application filed January 3, 1923. Serial No. 610,500.

To allwhom it may concern.

Be'it known that I, HERMAN A. SnIrKE, a citizen of the United States, residing in the city and county of San Francisco and State of California, have invented a new and useful Improvement in an Alternating-Current Rectifier, of which the following is a specification.

My invention relates to lmprovemcntsun alternatin current rectifiers and the like wherein afiernating current is fed to a commutator rotated in synchronism therewith and delivered from said commutator as direct current.

The primary object of my invention is to provide an improved machine for rectifying alternating current. 0

Another object is to provide a device having improved means for regulating the voltage of the direct current output. a

A further object is to prov1de an improved device wherein the alternating current supply may be conven ently controlled to direct only a desired portion of each wave length to the direct current leads. 0

Another object is to provide an improved device wherein the current output may be regulated independently of the direct current. brushes. a

A still further. object is to provide an 1mproved construction affording increased efficiency and durability.

I accomplish these and other objects by means of the device disclosed in the drawings forming a part of the present speclfication wherein like characters of reference are used to designate similar parts throughout said specification and drawings, and in which:

. Fig. 1 is a front elevation of my improved alternating current rectifier. Fig. 2 is an end elevation of the device shown in Fig. 1, portions of the housing members being broken away.

45 i Fig. 3 is an enlarged broken sectional view of the alternating current commutator and housing showing the relation of the alternating current brush thereto.

Fig, 4 is a conventional wiring diagram of my improved rectifier.

Figs. 5, 6 and 7 are diagrammatic illustrations showing the manner in which the current supply is regulated.

. Referring to the drawing the numeral 1 is used to designate in general a synchronous motor arranged to be connected to a source of alternating current supply not shown. The motor is provided with a starting windmg. 2 and a running winding 3 and is connected through a synchronizing and ole controlling switch 4 and speed control switch 6 adapted to automatically bring the motor to synchronous speed to deliver current of a desired polarity, and to automatically maintam such synchronous speed, but as these elements of the device are fully described in a copendlng application filed the 19th day of December, 1922, Serial Number 607,906, a further description is herein unnecessary.

The motor 1 is provided with a shaft 7 upon w'hlch a pair of commutatorsv 8 and 9 are secured for rotation with the armature of the motor. The commutator 8, which for clearness will hereinafter be termed the direct current commutator, is provided with a plurality of segments 11 corresponding to the poles of the motor, said segments being insulated from the shaft and from each other. Brushes 12 and 13 are mounted in association with the commutator segments to collect direct current therefrom in a manner hereinafter more fully described.

The commutator 9 hereinafter termed the alternating current commutator, is mounted in spaced relation to the commutator 8 and is provided with a like plurality of segments 14 arranged to correspond to the segments of said commutator 8 and the poles of the motor, said segments being similarly insulated from the shaft and from each other.

A ring 16 mounted upon the shaft 7 ad jacent the commutator 8 is engaged by a brush 17, said ring being electrically connected to alternate segments 11. The brush 17 is connected to a terminal 18 arranged to receive one side of an alternating current supply line by means of a suitable connection 19.

The segments '11 of the commutator 8 which are not connected to the ring 16 are electrically connected to all the segments 14 of the commutator 9. The electrical connection between the commutators 8 and 9 may be efl'ected in any suitable manner, the drawings illustrating a construction wherein rings ,21 and 22 are mounted adjacent the cominutators 8 and 9 respectively and connected to segments by means of suitable conductors, connection between the rings being effected by means of a pair of brushes 23 and 24 connected by a suitable conductor. This construction permits the commutator 9 to be mounted entirely apart from the commutator-8, but this construction may, of course, be modified in a great number of ways without departing from the spirit of the present invention. The segments 14 of the alternating current commutator are connected through a brush 25 and conductor 26 to a terminal 27 receiving the other side of the alternating current line.

From the above description it will be noted that alternate segments 11 of the direct current commutator are connected to opposite sides of the alternating current line so that at any instant adjacent segments will be of opposite polarity. Thesegments are made of a length equivalent to 180 electrical degrees so that when the commutator is rotated at synchronous speed the time required for any segment to pass a given point will be equal to the period of a half cycle. When now the motor and commutator are rotated in synchronism with the alternating current supply the polarity of the segments will be reversed after each 180 electrical degrees of rotation and b positioning the brushes 12 and 13 180 electrical degrees apart at points corresponding to the neutral points it will be seen that the polarity of the segments engaged by each brush will at all times be the same and the polarity at one brush will be opposite to the polarity of the other brush thereby causing the flow of current between said brushes to be at all times in the same direction and a direct current obtained.

If the connection through the alternating current commutator 9 be assumed to be constant the diiference in potential between the brushes l2 and 13 will be equal to the difference in potential between the alternating current terminals and the current will be delivered at a voltage equal to the mean effective voltage of the alternating current supply. However, as it is highly desirable to control the direct current output to obtain current at a desired voltage other than the voltage of the alternating current supply, I have arranged to control the direct current output b means of varying the alternating current eed. I accomplish this in the following manner.

The brush 25 is mounted for angular adjustment relative to the commutator 9 whereby the point of engagement between the segments 14 and the brush may be varied. This is accomplished by securing the brush upon a ring 28 pivotally movable upon a supporting member 29 and arranged to enclose the commutator 9. A spring contact the alternating current to obtain a maximum degree of voltage regulation. The segments 14 are made relatively narrow and are separated by correspondingly wide insulated portions. The brush 25 is made of a width substantially greater than the width of the segments 14, but less than the width of the intervening portions of insulation, so that the connection between the'commutator and the alternating current supply willbe momentarily broken between the time one segment 14 moves out of engagement with the brush and the succeeding segment moves into engagement with the brush, and only a portion of each alternating current cycle directed through the alternating current commutator 9 to the direct current commutator segments 11 connected thereto. By adjusting the brush to engage the commutay tor 9 at a desired point with respect to the neutral points of the commutator as deter- I through the commutator 8 and brushes 12 a and 13 as direct current, and the voltage of the direct current output thereby regulated between the limits hereinafter explained. The principle of this regulation is illustrated diagrammatically in Figs. 5, 6 and 7, of the drawings. In Fig. 5 it is assumed that the brush 25 is positioned in such manner that at the instant the alternating current reverses a segment-14 will be just approaching the brush, and the segment will move into engagement with the brush at the same instant that the segments 11 of the direct current commutator engage the brushes 12 and 13. In this position the circuit to the commutator 8 will be complete so long as the segment 14 remains in engagement with the brush 25, and the segments engaged by the brushes 12 and 13 being thus connected to opposite terminals of the alternating current line a difference in potential will exist between adjacent segments and as a result current will flow through the direct current connections to said brushes 12 and 13. At the instant the segment 14 disengages the brush 25 the connection between one of the segments 11 and the alternating current line will be broken and as a result the difference in potential will cease to exist between the brushes 12 and 13 and there rent commutator and picked up by the direct current brushes, and the flow of current interrupted during the remainder of the half cycle, the portion delivered to the direct cur.- rent connections being shown in heavy line while the ineffective portion is shown in light lines. In this manner it is seen that the voltage of the current delivered Wlll vary in accordance with the sine wave from zero at the start of each impulse, to the voltage at the moment the connection is broken, and the effective voltage delivered will be the average of the voltage of that portion of the wave which is intercepted distributed over theperiod of a half cycle.

If now it is desired to increase the effective voltage, the brush 25 is moved to a position such that the segments 14 will be engaged during the periods when the voltage carried thereby is at a maximum as shown in Fig. 6. In this position, no connectlon to the direct current commutator is efiected until after the valtage of the alternating current impulse has reached a desired point,

I connection being maintained while the voltage is at its maximum and again broken as the voltage decreases toward the succeeding neutral point. In the drawing the effective portion of each half wave length is shown in heavy lines and it will be readily seen the effective voltage of the portions intercepted will be substantially greater than that shown in Fig. 5.

When it is desired to decrease the voltage, the brush is set up in a position such as that illustrated in Fig. 7 whereby only the extreme end of each impulse and the beginning of the succeeding impulse is intercepted. In this manner connection is only effected when the voltage of the alternating current is at its minimum and as a result a very low mean effective voltage will be collected by the brushes 12 and 13.

From the above explanation it will be readily seen that a slight adjustment of the alternating current brush will obtain a wide range of regulation with respect to the direct current output Without interfering in any manner with the direct current commutator and brushes. By limiting the range of adjustment the minimum voltage delivered is prevented from dropping below an opposing voltage in the direct current line such as may occur when storage batteries 'are being recharged, and possible damage due to such back electromotive force is thus avoided.

As above mentioned, the segments 14 are preferably made relatively short and the brush 25 made long. This is done because of-thejfact that the tendency for sparking when the alternating current connection is broken is materially reduced and the result of such sparking made less damaging by this arrangement. In order to further reduce the sparking I also provide a permanent horseshoe magnet 34 having'its poles arranged upon opposite sides of the brush 25 so as to create a magnetic field across the contact between the brush and the comma tator. The commutator 9 being made entirely distinct from the direct current commutator may also be caused to run in oil enclosed with the ring 28 and supporting member 29 to further reduce the sparking and damage caused thereby. In order to prevent an alternating current from being directed over the direct current connections I provide an automatic cut out switch 36 arranged to normally break the direct current line until the motor and commutators have attained synchronous speed. This switch is actuated by an auxiliary circuit connected to the polarizing and synchronizing switch 4. in a manner entirely analogous to the arrangement shown and described in the copendln-g application above referred to and a detailed description of this feature of the device is therefore omitted.

While I have illustrated and described only one arrangement of my improved rectifier, the structural features are, of course,

subject to wide variation without departing from the spirit of my invention. I, therefore, do not wish to restrict myself to the specific construction and arrangement disclosed but desire to avail myself of all modifications embodying the principles described and which may fall within the scope of the appended claims. I

Having thus described my invention What I claim as new and desire to secure by Letters Patent is:

1. In a rotary rectifier, the combination with a synchronous motor and a direct cur-- current commutator to make connection i ii iii":

thereto from the other side of the alternating current supply line during portions of each rotation to direct current during a portion of each alternating cycle to the direct current commutator, said brush being adjustable to interrupt the alternating current supply independently of the direct current commutator and its connections 2. In a rotary converter, the combination with a synchronous motor and direct current commutator associated therewith for rotation in synchronism with an alternating cur rent supply and having a direct connection to one side of an alternating current line connected to said supply, of an alternating current commutator mounted for rotation therewith, said alternating current commutator having a plurality of relatively narrow seg ments corresponding to the poles of the motor and electrically connected with alternate segments upon the direct current commutator; a relatively long brush mounted in association with the alternating current commutator to make connection thereto from the other side of the alternating current supply line during portions of each rotation to direct current during a portion of each alternating cycle to the direct current commutator and to interrupt the alternating current supply independently of the direct current commutator and its connections; and means for angular-1y adjusting said brush relative to its commutator to vary the portion of the alternating current ivave length directed to- I the direct current commutator.

In witness whereof I hereunto set my signature.

HERMAN A. SEIFKE.

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