US2023626A - System of electrical distributions - Google Patents

Description

Dec, 10, 1935. A. c. TURTLE SYSTEM OF ELECTRICAL DISTRIBUTIONS 4 Sheets-Sheet 1 Filed April 9, 1934 E g m H? mm ALFREDGTURTLE AT TORNEY Dec. 10, 1935. A. c. TURTLE 2,023,626

SYSTEM OF ELECTRICAL DISTRIBUTIONS Filed April 9, 1934 4 Sheets-Sheet 2 TUMOTOR 7E ||||]|||||||||||||||||IIMIMIII I NV'ENTOR ALFRED-CJ'URTLE ATTORNEY Dec. 10, 1935.

A. C. TURTLE SYSTEM OF ELECTRICAL DISTRIBUTIONS Filed April 9, 1954.-

COLUMN-D 4 Sheets-Sheet clRcurr. A cmcums cmcunrc DEGREES VOLTS AM DEGREES YOLTS A? DYGREYSVOLTS AHR WATT-DEG WATTDE VMITDEG.

COLUMN-E SHUNT O 1 HBO E80 TOTA L 360 DEG.

TOTAL 360 DEG.

TOTAL 36ODEG.

TOTAL TOTAL TOTAL 5680 3680 3680 INVEN TOR ALFREllG-TU RTLE WWI/1% I ATTORNEY Dec. 10, 1935. A, c. TURTLE SYSTEM OF ELECTRICAL DISTRIBUTIONS Filed April 9, 1934 4 SheetsSheet 4 v cownuF COLUMN-G I a cmcumA cmcums cmcumc cm-n cmncmc DEGREES VOLTS AMP DEGREES YOLTS AMPDEGREES VOLTS AMP WATT DES WATTDEGWATT DEG.

O 56 o 56 IO 3 56 a 0 n2 n2 56 10 a 56 102 56 suumo 51801120 0 56 snum o 56 10 2 56 lo a o 1180 i 56 1O 6 56smm10 5610 2 M80 0 1520 56 10 e 5610 '2 565mm 01x20 "20 0 T OTA L TOTA L TOTAL TOTAL TOTAL TOTA L 560 560 360 4720 4720 4720 INVENTOR ALFRzncxun'ru-z ATTORNEY Patented Dec. 10, 1935 UNITED STATES PATENT OFFICE 15 Claims.

This invention relates to systems of electrical distribution and particularly to the automatic regulation of load circuits, such as the lamp circuits or" a railway car lighting system, whereby the volt-age and wattage characteristics of each circuit is maintained approximately constant irrespective of a wide range of voltage fluctuations at the terminals of the current source from which the circuits are fed.

The primary object of this invention is the provision of improved voltage regulating means whereby the voltage across each of a plurality of circuits connected to a common variable voltage source may be maintained constant at a value either substantially above or substantially below the maximum voltage available at the terminals of said source.

Another object is the provision of voltage regulating means which is effective to maintain the voltage of each of said circuits constant throughout an exceptionally wide range of voltage fluctuations, in either direction, at the terminals of said source.

A further object is the provision of a selfregulating system of electrical distribution in which a plurality of circuits are supplied with alternating current from a direct current source through the agency of circuit regulating means that is also effective to maintain a constant potential difierence across each circuit during a wide range of potential variations at the terminals of said direct current source.

A still further object is the provision of a selfregulating system of electrical distribution in which a plurality of circuits are supplied with alternating current from a direct current source through a regulating means effective to maintain the potential difference across each circuit constant during a wide range of potential variations at the terminals of said source and at a value either above or below the maximum potential available at said terminals.

A still further object is the provision of a selfregulating system of electrical distribution in which a plurality of circuits are supplied with alternating current from a direct current source through a rotary contactor by which each circuit is periodically shunted and then variably connected in series and in parallel with companion circuits; the duration of the shunted, series connected, and parallel connected periods of the circuits being automatically varied by the contactor in such relation to potential variations at the terminal of the direct current sources as to maintain an approximately constant potential across each circuit.

Fig. 1 is a view, in side elevation, of one form of contactor which may be utilized for regulating circuit voltage in accordance with the novel principle of this invention.

Fig. 2 is a sectional view along the line 2-2 of Fig. 1.

Fig. 3 is a view, in elevation, of the rotary element of the contactor. Fig. 4- is a sectional view along the line 44 of Fig. 1, showing the arrangement of the brushes engaging the slip rings on the rotary element of the contactor. In this view certain parts are omitted for the sake of clearness.

Fig. 5 is a detail view showing the bracket which supports the contactor operating motor.

Fig. 6 is a diagrammatic view illustrating the manner in which the contactor is connected between the direct current source and the circuits.

Figs. 7 to 18 inclusive are diagrams illustrating the sequence of circuit connections established by the contactor during one revolution. In this view the illustrated length of the contactor brushes connected to the direct current source represents the minimum span of the brushes.

Figs. 19 to are duplicates of Figs. 7 to 18 except that the illustrated length of the brushes appearing in Figs. 1.9 to 30 represents the maxi- 30 mum span of the brushes.

Fig. 31 is a table showing the manner in which the voltage amperage and wattage of each circuit is varied by the sequence of connections appearing in Figs. '7 to 18.

Fig. 32 is a table showing the manner in which the lengthening of the brushes, as illustrated in Figs. 19 to 80, varies the voltage, amperage and wattage values of the circuits as compared with Fig. 31.

Fig. 33 is a slight modification of the circuits appearing in Fig. 6.

According to the illustrated embodiment of this invention, a plurality of lamp circuits, of equal impedance or resistance, are fed from a direct current source through a rotary contactor which produces an alternating current in each circuit. The contactor also serves to repeatedly transpose the circuit connections that each circuit, between periodic shunting periods preceding the 50 reversal of current flow therein, is variably connected in series and parallel with companion circuits. The contactor is driven by a direct current motor at a speed which varies in direct proportion to potential variations at the terminal of said direct current source to which the motor is connected. The positive and negative brushes of the contactor are automatically adjusted, through the agency of a suitable governor, so that the effective length or span of each brush decreases when the motor speed increases and increases when the motor speed decreases. The circuit connections and the design of the contactor are such that the shortening of the contactor brushes (which occurs when the motor speeds up in response to an increased voltage at the current source) serves to decrease the duration of the shunted and parallel-connected periods of the circuits while increasing the duration of the series-connected periods. Similarly, the lengthening of the contactor brushes (which occurs when the motor speed decreases in response to a voltage drop at the terminals of said source) serves to increase the duration of the shunted and parallel-connected periods of the circuits While decreasing the duration of the series-connected periods. By thus varying the duration of'the shunting periods as well as the relative duration of the parallel and series-connected periods of the circuits, the average potential, current and wattage values of each circuit may be kept approximately constant, within fairly wide limits, irrespective of potential variations at the terminals of the direct current source. As the lamp circuits are periodically shunted and then connected in series and in parallel with each other, in various combinations,

for varying lengths of time, depending on the potential variations at the terminals of the direct current source, there will be, of course, some compensating fluctuation in the voltage, amperage and wattage values of each circuit for each revolution of the contactor but the total effect will be the maintenance of approximately constant average voltage and wattage characteristics for each circuit.

One embodiment of a motor driven contactor suitable for the purposes of this invention is illustrated in Figs. 1 to 5 inclusive. The motor 5 drives the contactor shaft 6 which is journalled in ball bearings l and 8. The bearing 1 is contained in the motor frame 9 which is fastened to the upper end of a bracket ill rising from the base I l. The bearing 8 is enclosed by the housing H of a bracket 93 mounted on the base at the end remote from the bracket ii).

A sleeve 14, made of insulating material, is fixed on the shaft 6 adjacent the bearing 8. Partially embedded in this sleeve are three insulated slip rings designated l5, l5 and i1. Sleeve l4 also carries three partially embedded commutator segments i8, i9 and 25! which are spaced apart by interposed insulating segments 2!. A stationary brush holder bracket 22, through which sleeve l4 extends, is mounted on the base ll between the three contact segments and the slip ring [5. Bracket 22 carries two diametrically opposite brush holders 23 and 24 containing brushes 23a and 24a (compare Figs. 1 and 2). These brushes are pressed against the contact segments l8, l9 and and the interposed insulating segments 2| by suitable spring devices 25 forming part of the brush holders. The brushes 23a and 24a constitute the fixed positive and negative brushes with which the movable positive and negative brushes 23b and 24b cooperate as hereinafter described. I

- The movable positive brush 232) (shown in full linesin Fig. 1 and by dotted lines in Fig. 2) is a rotatably mounted adjusting ring 21. The movable negative brush 2% is similarly fitted in a brush holder 28 fastened to said ring diametrically opposite the holder 25. Each of the brushes 2% and Zeb is pressed against the contact segments l8, IQ and 25B and the interposed insulating segments 2! by means of a spring device 29.

The adjusting ring 2'! is rotatably supported by anti-friction balls 30 interposed between its outer edge and a surrounding bearing bracket 3|, said balls being confined between two side plates 33 fastened in place as indicated at 34. Ring 2! is also connected to a governor 35 by means of which the ring is rotated in one direction or another in response to a change in the operating speed of the motor 5. As illustrated, the connection between the ring and governor comprises a bell crank 38 having one arm 39 connected to the ring by a universal connecting link 4E and the other arm 4! connected to the movable end member 42 of the governor by a link 43, which works between ball bearings 44 at each of its connected ends. The ring 2'! and bearing bracket (ii are preferably provided with coacting stop members 65 and it to limit rotation of the ring in one direction.

Assuming an increase in the operating speed of the motor, the ring 2i will be turned as indicated by the arrow in Fig. 2 to shift the movable positive and negative brushes toward the cooperating fixed positive and negative brushes to which they are electrically connected as hereinafter explained. This adjustment therefore results in a decrease in the effective length or span of said positive and negative brushes. A decrease in the speed of the motor produces the opposite effect since the ring 2'? is then turned to shift the movable positive and negative brushes away from the fixed positive and negative brushes, thus increasing the effective brush length or span. The turning movement of the ring in the brush shortening direction is limited by the stops 45 .and 46 which may be adjusted to regulate the minimum brush length.

The electrical connection between the fixed and movable positive brushes 23a and 23b comprises a pair of conducting plates 41 and 48 fastened to opposite sides of the stationary brush holder bracket 22. The plate 47 is at the side of bracket 22 opposite the brush holder 23 to which said plate is electrically connected by the brush holder fastening screws 49. The remaining plate 48 is electrically connected to the plate 41 by the fastening screw as and is also engaged by a wiper contact 5! fixed to the brush holder 26 of the movable brush 23a. A similar electrical connection, not shown, is provided between the fixed and movable negative brushes 24a. and 241).

Each of the commutator segments l8, l9 and 20 is connected to one of the slip rings 15,16 and ll. These connections may be made as indicated in Fig. 3 where the segment I8 is shown connected to the ring l5 by a conducting strip 52; the remaining segments 59 and 20 being respectively connected to the rings I6 and I! by the conducting strips 53 and 54.

The rings l5, l6 and I! are respectively engaged by brushes 55, 55 and 51 mounted in suitable brush holders 58, 59 and 60 provided with spring devices fit for holding the brushes to the rings, said brush holders being also provided with terminals $2, 53 and 64.

The manner in which the contactor is connected between the direct current source and the lamp circuits is diagrammatically illustrated in Fig. 6. As here shown the two electrically connected positive brushes 23a and 23b are connected, by way of conductor 66 and switch 61 with the positive terminal 68 of the direct current source represented by the battery 69 and the shunt wound charging generator III. The electrically connected negative brushes 24a and 241) are connected, by way of conductor II and switch 6! with the negative terminal 12 of the direct current source. The commutator segments I8, I9 and 20 are respectively connected, by way of the conductors 52, 53 and 54, with the slip rings I5, I6 and IT.

We come now to the connection of the lamp circuits indicated at A, B and C.

One side of circuit A is connected to commutator segment I8 by way of conductor I3, slip ring brush 55, slip ring I and conductor 52; the other side of said circuit being connected to the commutator segment I9 by way of conductor I4, slip ring brush 56, slip ring I6 and conductor 53.

One side of circuit B is also connected with commutator segment I9 by way of conductor I4, slip ring brush 56, slip ring I6 and conductor 53; the other side being connected to commutator segment 29 by way of conductor I5, slip ring brush 51, slip ring I! and conductor 54.

One side of the remaining circuit C is connected to commutator segment I8 by way of conductor "I3, slip ring brush 55, slip ring I5, and conductor 52; the other side being connected to commutator segment 29 by way of conductor I5, slip ring brush 51, slip ring I1 and conductor 54.

The motor 5, which operates the contactor shaft 6, is also connected to the terminals of the direct current source by the conductors appearing at 5a and 5b in Fig. 6.

The voltage regulation obtained by adjusting the span of the positive and negative brushes engaging the commutator segments to which the circuits A, B and C are connected is best explained by reference to the diagrams of Figs. '7 to 30 and the tabulations of Figs. 31 and 32. For the purpose of this explanation it is to be understood:

1. That the resistance of each of the circuits A, B and C is 5 ohms.

2. That a constant E. M. F. of volts is impressed on the said positive and negative brushes by the direct current source which, in order to avoid unnecessary duplication, is shown only in Fig. 7.

3. That the minimum span of said positive and negative brushes is represented in Figs. '7 to 18 while the maximum span is represented in Figs. 19 to 30.

4. That the appearance of the mark 0 in association with a circuit indicates shunting of said circuit.

5. That the appearance of the mark in association with a circuit indicates that said circuit is connected in series with one of the companion circuits which is similarly identified, the direction of flow being toward the arrow head.

6. That the appearance of the mark in association with a circuit indicates that said circuit is connected, in parallel, with one or both of the companion circuits.

'7. That, for convenient illustration, the commutator segments I 8, I9 and are represented as being stationary while the engaging positive and negative brushes are represented as traveling relatively to said segments.

In Fig. 7 the positive brush is bridging the commutator segments I8 and I9 while the negative brush is engaging the segment 20. Circuit A is thus shunted while circuits B and C are connected in parallel with each other. As indicated in column D of Figure 31 this condition persists for a length of time corresponding to 4 degrees of a 5 complete revolution of the brushes. (In actual practice this would correspond to 4 degrees of a complete revolution of the rotatably mounted commutator segments appearing in Figs. 1 to 6 inclusive.) It therefore follows that, as indi- 10 cated in columns D and E of Fig. 31, the potential diiierence across each of the circuits B and C is 10 volts, producing a current fiow of two amperes and a wattage value of 80. The next position of the brushes is represented in Fig. 8, the circuit connections noW established persisting for a period of time corresponding to 56 degrees of a complete revolution of the brushes. In this case the circuits A and B are connected in series with each other and in parallel with circuit C, the resulting go change in the voltage, amperage, and wattage values of the circuits being indicated in the aforesaid columns D and E of Fig. 31. The circuit connections subsequently established by the brushes as they complete one revolution, being clearly indicated in Figs. 9 to 18 inclusive, will be briefly referred to as fol1ows:In Fig. 9 circuit B is shunted while circuits A and C are connected in parallel with each other; in Fig. 10 circuits B and C are connected in series with each other and in parallel with circuit A; in Fig. 11, circuit C is shunted while circuits A and B are connected in parallel with each other; in Fig. 12 circuits A and C are connected in series with each other and in parallel with circuit B; in Fig. 13 circuit A is again shunted while circuits B and C are connected in parallel with each other; in Fig. 14 circuits A and B are again connected in series with each other and in parallel with circuit C; in Fig. 15 circuit B is again shunted While circuits A and C are connected in parallel with each other; in Fig. 16 circuits B and C are again connected in series with each other and in parallel with circuit A; in Fig. 17, circuit C is again shunted while circuits A and B are connected in series with each other; and in Fig. 18 circuits A and C are again connected in series with each other and in parallel with circuit B. The manner and extent to which the voltage, amperage and wattage values of the circuits are varied by the last mentioned sequence of connections is indicated under the appropriate headings in columns D and C of Fig. 31. By studying the figures in these columns, in conjunction with the showing of Figs. 7 to 18 inclusive, it will be seen that, for each complete revolution of the brushes, each circuit is shunted for a total period of time corresponding to 8 degrees of brush revolution; is connected in parallel for a total period of time corresponding to 128 and is connected in series for a total period of time corresponding to 224. Since a constant E. M. F. of 10 volts is impressed on the brushes and since the resistance of each circuit is 5 ohms it follows that the potential difference across each circuit will be zero for 8; five volts for 224 and ten volts for 128 and that the Wattage will vary accordingly. When the positive and negative brushes are lengthened to their maximum span as represented in Figs. 19 to 30 the sequence of circuit connections remains the same as in Figs. 7 to 18 but the duration of the series-connected periods of each circuit is decreased while the duration of the shunted and parallel-connected periods is increased. The efiect of this with respect to varying the voltage and wattage characteristics of the circuits will be apparent from a comparison of the tabulations in Fig. 32 with those in Fig. 1, which clearly shows that, with the voltage impressed on the brush terminals remaining constant, the voltage and wattage values of the circuit may be varied approximately 30 per cent by full range adjustment of the span of said brushes.

In accordance with the purpose of the present invention, the aforesaid circuit regulating effect of the brush-span adjustment is utilized to maintain the voltage and wattage characteristics of the circuits approximately constant throughout a Wide range of potential variations to be eX- pected across the terminals of the direct current source under actual service conditions. This is accomplished through the agency of the previously described motor operated governor mechanism which automatically shifts the movable brush members so that the duration of the shunted, series-connected and parallel connected periods of the circuits is varied in such relation to the potential changes of the direct current source as to maintain the voltage of each circuit at a predetermined constant value which may be substantially above or substantially below the maximum value of the fluctuating direct current source voltage. It will thus be seen that the voltage regulating means of the present invention is adapted to take care of a wide range of variations either above or below the normal voltage of said source.

In regard to the structural design of the contactor it will be understood that the length or" the commutator segments l8, l9 and 2t) and the interposed insulating segments 2 I, as well as the minimum and maximum span of the engaging adjustable brushes, are variable factors which may be predetermined to suit particular installations, it being important however that the minimum span of the brushes should be somewhat greater than the spacing of adjacent segments. It will also be understood that, in applying the principles of this invention, the number of contactor segments and the number of circuits controlled by the contactor may be varied.

In Fig. 33 there is shown a slight modification in which auto transformers, appearing at T, T and T", are respectively included in the lamp circuits A, B and C, to step up the voltages of said circuits with respect to the voltage impressed on the brushes. Transformers comprising separate primary and secondary windings with the usual interlinking alternating magnetic flux can also be used in place of the transformers illustrated herein.

In Figs. '7 to 32 it has been shown that, when using a constant voltage direct current source, the energy input may be decreased or increased by shortening and lengthening the effective span of the positive and negative brushes. It will therefore be seen that by regulating the span of the brushes independently of the voltage across the terminals of the supply source, a. wide range of control may be exercised with respect to the energy input to the lamp circuits.

In order to eliminate or diminish sparking between the commutator segments and the engaging brushes of the circuit controller when dealing with currents of high amperage, it is proposed to enclose the assembly appearing in Fig. l within a gas-tight casing Ha filled with air or gas under appreciable pressure. In this case the battery and circuit leads will be connected through the agency of pressure-tight terminals passing through the base I I.

Having thus described my invention, what I claim is:-

1. A system'oi electrical distribution comprising, in combination, a direct current source, a plurality of circuits, and circuit connecting means through which all of said circuits are connected to said source, said connecting means acting automatically to repeatedly transpose the circuit connections to produce an alternating current in each circuit and to connect each circuit in varying series and parallel relation with companion circuits between shunting periods of said circuit preceding a reversal of the current flow therein, and meansfor automatically regulating the action of said connecting means to vary the duration of the shunted, series-connected, and parallel-connected periods of each circuit in such relation to voltage variations at the terminals of said source as to maintain the voltage characteristics of each circuit approximately constant.

2. A system of electrical distribution comprising, in combination, a direct current source, a

plurality of circuits, and circuit connecting means through which all of said circuits are connected to said source, said connecting means acting automatically to repeatedly transpose the circuit connections to produce an alternating current in each circuit and to connect each circuit in varying series and parallel relation with companion circuits between shunting periods of said circuit preceding a reversal of the current flow therein, and means for automatically regulating the action of said connecting means to vary the duration of the shunted, series-connected, and parallel-connected periods of each circuit in, such relation to voltage variations as the terminals of said source as to maintain the voltage characteristics of each circuit approximately constant at a predeter mined value which may be either substantially above or substantially below the maximum voltage delivered by the direct current source.

3. A system of electrical distribution comprising, in combination, a direct current source, a plurality of circuits, and a rotary contactor connected between said source and said circuits, said contactor functioning to produce an alternating current in each circuit; to periodically shunt each circuit; and, between shunting periods, to connect each circuit in series and parallel with companion circuits; and means for adjusting said contactor to shorten and lengthen the shunted, series-connected and parallel-connected periods of said circuits in response to potential variations at the terminals of said source and in such relation to said variations as to maintain an approximately constant voltage across each circuit.

4. A system of electrical distribution comprising, in combination, a direct current source, a contactor including a series of rotary contact segments and engaging positive and negative brushes, said brushes being respectively connected to the corresponding terminals of said source, a plurality of circuits connected to said segments so that, during rotation of the segments relative to the brushes, each circuit is periodically shunted and, between shunted periods, is variably connected in series and in parallel with the companion circuits, and means for adjusting the efiective span of said brushes to vary the duration of the shunted, series-connected and parallel-connected periods of said circuits.

5. A system of electrical distribution comprising, in combination, a source of direct current, a plurality of circuits, 2. contactor connected between said source and said circuits, said contactor functioning to produce an alternating current in each circuit; to periodically shunt each, circuit; and to variably connect each circuit, between its shunted periods, in series and in parallel with companion circuits, and means for adjusting said contactor to vary the duration of the shunted, series-connected and parallel-connected periods of each circuit and thereby step up or stepdown the potential across each circuit with respect to the potential across the terminals of the direct current source.

6. A system of electrical distribution comprising, in combination, a direct current source, a plurality of circuits, a circuit controller through which all of said circuits are connected to said source so that, during operation of the controller, each circuit is periodically shunted and, between shunted periods, is connected in varying series and parallel relation with companion circuits, a motor driving said controller and connected so that the speed of the motor varies in direct proportion to potential variations at the terminals of said source and controller adjusting means acting automatically, in response to changes in the operating speed of the motor, to vary the duration of the shunted, series-connected, and parallel relation of the circuits in such relation to the potential changes at the terminals of the direct source as to maintain an approximately constant voltage across each circuit.

'7. A system of electrical distribution comprising, in combination, a direct current source, a circuit controller comprising a commutator and engaging variable-span positive and negative brushes, said brushes being respectively connected to the corresponding terminals of said source, a plurality of circuits connected to said commutator so that, during relative movement between the commutator and brushes, each circuit is periodically shunted and, between shunted periods, is connected in series and in parallel with companion circuits, and means responsive to potential changes at the terminals of said source for adjusting the span of said brush to vary the duration of the shunted, series-connected and parallel-connected periods of the circuits, in such relation to said potential changes as to maintain an approximately constant voltage across each circuit.

8. A system of electrical distribution comprising, in combination, a direct current source, a motor connected to said source to operate at a speed directly proportional to the potential across the terminals of said source, a circuit controller, driven by said motor, comprising a commutator and engaging variable-span positive and negative brushes, said brushes being connected to the corresponding terminals of said source, a plurality of circuits connected to the segments of said commutator so that each circuit is periodically shunted and then variably connected to said source in series and parallel relation with companion circuits, and a governor operating, in response to changes in the speed of said motor, to adjust the span of said brushes to vary the duration of the shunted, series connected, and parallel connected periods of said circuits, in a manner compensating for the changes in potential producing the aforesaid changes in the speed of the motor.

9. A system of electrical distribution as claimed in claim 3 including a casing enclosing said rotary contactor and containing a gaseous medium under pressure.

10. A system of electrical distribution comprising, in combination, a direct current source, a plurality of circuits, and circuit connecting means 5 through which all of said circuits are connected to said source, said connecting means including an interrupter mechanism functioning to repeatedly transpose the circuit connections to produce an alternating current in each circuit and to connect each circuit in varying series and parallel relation with companion circuits, and means for adjusting said interrupter mechanism to vary the duration of the series-connected and parallelconnectcd periods of each of said circuits.

11. A system of electrical distribution comprising, in combination, a direct current source, a plurality of circuits and an adjustable rotary contactor connected between said source and said circuits, said contactor functioning to produce an alternating current in each circuit and to connect each circuit in series and parallel with companion circuits and means for adjusting said contactor to shorten and lengthen the series-connected and parallel-connected periods of said circuits.

12. A system of electrical distribution comprising, in combination, a direct current source, a plurality of circuits, a circuit controller through which all of said circuits are connected to said source so that, during operation of the controller, each circuit is connected in varying series and parallel relation with companion circuits, a motor driving said controller and controller adjusting means acting automatically in response to changes in the operating speed of the motor to vary the duration of the series-connected and parallelconnected periods of said circuits.

13. Electrical apparatus for supplying alternating current of approximately constant potential to each of a plurality of load circuits comprising, in combination, a direct current source,

a contactor including a series of contact segments and engaging positive and negative brushes, said brushes being respectively connected to the corresponding terminals of said source, means including an electric motor for efiecting relative movement between said contact segments and said brushes and means for adjusting the eiTective span of said brushes in response to changes in the speed of the motor.

14. Apparatus as claimed in claim 13 in which the motor is connected to the direct current source so that its operating speed varies in direct proportion to potential variations at the terminals of said source.

15. Apparatus for use in supplying alternating current of approximately constant potential to each of a plurality of load circuits comprising, in combination, a direct current source, a plurality of transformers and circuit connecting means through which the primary circuits of all of said transformers are connected to said source, said connecting means including an interrupter mechanism functioning to repeatedly transpose the circuit connections to connect each of said primary circuits in vary series and parallel relation with companion primary circuits and means for automatically adjusting said interrupter mechanism to vary the duration of the seriesconnected and parallel-connected periods of said circuits.

ALFRED C. TURTLE.

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