US1152801A - Liquid rheostat. - Google Patents

Description

G. H. DORGELOH.

LIQUID RHEOSTAT.

APPLICATION FILED FEB. 2 1914.

Patented Sept. 7, 1915.

2 SHEETS-SHEETI Inventor:

Witnesses e. H. DORGELOH.

LIQUID RHEOSTAT.

' APPLICATION FILED FEB. 2, 1914. 1,152,801. Patented Sept. 7, 1915.

2 SHEETS-SHEET 2.

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UNITED STATES PATENT OFFICE.

GEORGE H. DORGELOI-I, F SCHENECTADY, NEW YORK, ASSIGNOR '10 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

LIQUID RHEOSTAT.

Specification of Letters Patent.

Patented. Sept/7, 1915.

T 0 all-107mm, it may concern Be it known that I, GEORGE H. DORGELOH, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Liquid Rheostats, of which the following is a specifica- 7 tion.

liquid, condition of the plates, etc.

My invention relates to liquid rheostats for electric circuits and has for its object the provision of a device of this character which will operate to control an electric circuit in a reliable and efiicient manner.

One of the objects of my invention is to provide a liquid rheostat which will have a relatively high resistance ratio, that is, a high ratio between the initial resistance and the final resistance.

Liquid rheostats are now well known and commonly used, especially in the starting of large electric motors. One very common use is in the case of large induction motors of the slip ring type. One point of weakness in all liquid rheostats heretofore devised has been the low range of resistance or the low ratio between the initial resistance and the final resistance value and this defect has resulted in limiting the use of these devices by excluding them from fields of usefulness in which they would otherwise find extensive application. This weakness or defect in prior devices has been due largely to the fact that it was necessary to space the electrodes or plates, as they are commonly called,

such a distance apart in order to avoid flashing over at high voltage that a low resistance could not be obtained; that is, the initial voltage across these plates being high it would be unsafe to have the plates close enough together to give a low final resistance. Attempts have been made to increase the ratio of resistance by arranging for the short circuiting of the plates after the resistance has been reduced to a minimum, but this has been in many cases found to be impracticable and'even dangerous, since it is impossible to determine just what the minimum resistance will be owing to the variable factors, such as the resistance of the Since, therefore, it cannot be determined in advance just how high this minimum resistance will be, and since by reason of the wide spacing of the plates, this minimum cannot be very low, an attempt to short circuit the plates might result in serious damage in case the final resistance should be higher than the short circuit-ing apparatus was or could be designed for.

One of the objects of my invention, therefore, is to overcome this difliculty.

- In carrying out my invention I provide means whereby a low resistance is obtained without dispensing with the wide spacing of the electrodes When the voltage is high. To accomplish this result, I provide-for a wide spacing of the electrodes during initial operation of the device when the voltage is high and less spacing of the electrodes for the final operation when the voltage is low. In

one specific embodiment of my invention I provide main electrodes and auxiliary electrodes, the former being connected in circuit first and the latter being connected afterward, the arrangement being such that when the auxiliary electrodes are in circuit a relatively small spacing of the electrodes results. In the specific embodiment referred to, the auxiliary plates are independent of the main plates and have less spacing than the main plates, although my invention is not limited to this specific arrangement. The auxiliary plates are not immersed during the first stage of the operation and are not connected with the electric circuit. In the final operation of the device, these plates are immersed in the liquid and connected in parallel with the main plates, thereby producing a very low final resistance.

In the accompanying drawing illustrating one embodiment of my invention, Figure 1 is a front elevation partly broken away of the mechanical structure of a liquid rheostat embodying my invention; Fig. 2 is a plan view of the same; Fig. 3 is a side elevation partly broken away; and Fig. 4 is a diagrammatic view showing the circuit connections and general arrangement of parts.

Referring first to Fig. 4 for a general understanding of the principles of my invention, M represents an induction motor of the slip ring type which is to be controlled. The slip rings of this motor are connected to the electrodes of the liquid rheostat, which, as an entirety, is designated by R. The mechanical construction of this rheo- I movable weir type,

, stat are as follows:

detail, in connection with the other figures of the drawing, but the principle of operation will be clearly understood from the diagrammatic view shown in Fig. 4. This rheostat is of the type commonly known as the in which the height to which the liquid will rise in the chamber will depend upon the position of the weir. Rheostats of this general character are well known. In the illustration shown in Fig. 4. the fluid chamber is indicated'at 10 and the weir for varying the possible height to which the liquid can rise in the chamber is indicated at 11. This weir, which is pivoted at 12 and counterbalanced by a counterweight 13, closes an opening 14 in the chamber, more or less, depending upon its position, as is well understood. The position of the weir is adjusted by an operating handle 15, which handle also operates the controller C, the arrangement being such that the weir is always operated when the handle is moved in either direction while the controller is moved to either forward or reverse direction, depending upon the direction of movement of the handle. Within the chamber 10 are located the electrodes or plates comprising the main electrodes 16 and the auxiliary electrodes 17 The main electrodes extend nearly to the bottom of the chamber and are spaced farther apart than theauxiliary electrodes which extend about half way to the bottom of the chamber. The fluid is forcedinto the bottom of the chamber by a pump 18 driven by the electric motor 19. The overflow from the chamber enters the outer casing 20 from which the pump takes its supply.- As the liquid therefore rises in the chamber 10 the plates 16 will first be immersed and if the weir 11. is set high enough, the liquid will afterward engage the plates 17 The electrical apparatus and connections used for-controlling Two line contactors 21 and 22 are provided, one for each direction of'rotation. These contactors are each of the double pole type provided with interlocks 23 and'24, respectively, which prevent the operation-of the two contactors at the same time. These two contactors and their connections constitute the reversing mechanism for the motor M under the control of the master controller C. The plates or electrodes 17 of the liquid rheostat are connected in circuit by the double pole contactor 25. These plates are not connected in circuit until the liquid rises in the chamber to a considerable extent, so that there will be no danger of arcing across between the auxiliary electrodes 17, which are closely spaced together, or between the auxiliary electrodes 17 and the main electrodes 16. The voltage being high at first, there is danger of arcing across, especially where the atmosphere may motor M, and since there is lever corresponding the current to this rheo-' ther movement of be charged with steam and other vapors. In order to prevent this, I rovide means whereby, when the liquid rises to a point just below the lower ends of the electrodes 17, the electrodes will be connected in the circuit in parallel with the main electrodes. This is accomplished by means of the tube 26 connected with the main chamber and having located within it contacts 27 and 27', the former being connected with the contactor 28, while the latter is connected with the line so that when the liquid rises so as to immerse the contacts, the contactor 28 will be energized through transformer 29. The closing of contactor 28 energizes the contactor 25 which in closing connects the electrodes 17 in circuit in parallel with themain electrodes.

The arrangement of circuits and the mode of operation are as follows: When the controller C is moved to the first forward position, marked f, and the switch S is closed, the contactor 21 will be energized from phase a of the three phase circuit, through the contacts on the controller, and through the interlock 24 on contactor 22 to the winding of contactor 21, and back to phase b. This will close the primary circuit of the liquid in the bottom of the chamber, the secondary circuit will be completed through a high resistance and the motor will start. At the same time that the controller is moved, the weir 11 will be operated. The closing of the switch S also causes the motor 19 to drive the pump and force liquid into the chamber 10. As the liquid rises in the chamber, the resistance in the secondary circuit of the motor will decrease in a wel understood manner, the liquid rising to a height corresponding to the position of the weir. The first movement of the operating to the position 7 on the controller will, in the present instance, move the weir to such a position that the liquid will only rise to a point somewhat below the lower end of the auxiliary plates 17. Furthe operating handle will move the controller to the position f and will raise the weir to such a point that the liquid will rise and immerse the auxiliary plates 17. Just before the liquid reaches the bottom of the plates 17, the contactor 28 will be energized by the rising of the water in the tube 26 and the closing of the contacts 27 and 27, the circuit of the contactor 28 extending through the controller C in its second position. The closing of the contactor 28 energizes the contactor 25 to connect the auxiliary electrodes 17 which are spaced closer together than the main electrodes 16, in parallel with the main electrodes. The voltage being now much lower, there is no danger of arcing across between the electrodes. The connecting of the closely ing, above the bottom plate.

.spaced electrodes in parallel with the main electrodes lowers the resistance, and, as the Water continues to rise, the result will be a very low resistance in the final position, much lower than would be possible with the main electrodes alone. In like manner, if the controller is thrown to the opposite position r, the contactor 22 will be energized to reverse the motor, and in the second position r of the controller the auxiliary electrodes 17 will be thrown in parallel as before.

- In Figs. 1, 2 and 3 I have shown the mechanical construction of a liquid rheostat of the type just described. The structural features of this rheostat are of no importance so far as the broad aspects of my invention are concerned, the invention may be more fully comprehended, I have shown the details of construction. Referring to Figs. 1, 2 and 3, it will be seen that the movable weir 11 is pivoted in the upper part of the casing and that the pump 18, as well as the motor 19 by which it is driven, are located at the bottom of the casing and discharge into the chamber 10. The opening of this chamber 10 is so arranged that liquid will always stand above the lower ends of the main electrodes 16 with the weir in its lowermost position. This is accomplished by having the sill 30, forming the lower edge of the openof the electrodes. In the structure shown in the drawings the main electrodes 16 are formed of pipes 31, as shown in Fig. 2, the pipes being connected together so as to give the effect of a By the use of pipes in this way a larger area is obtained than would be the case if flat surfaces were employed. It will be noted by reference to Figs. 1 and 3 that the main electrodes are of different lengths. The purpose of this arrangement is to cause a gradual decrease in resistance as the liquid rise's, this being well understood in the art. he auxiliary electrodes 17 are formed of plates, the lower ends of which are beveled, as shown in Fig. 1, to gradually decrease the resistance as the liquid rises. The contacts 27 and 27 are located in the pipe 26 connected with the chamber 10. Handle 15 operates the weir 11 through the link 32, and arm 33 on shaft 34. Handle 15 also operates shaft 35, which operates the controller 36 through segmental rack 37 and pinion 38.

In the normal operation of my device, in

controlling the slip ring induction motor for driving, for instance, a hoist, the motor 19 driving the pump 18 will be operating continuously so that the water will be always circulating between the chamber 10 and the lower casing 20. In operation, therefore, it is only necessary to move the handle 15 in 7 one direction or the other to eflect either the forward or reverse starting of the motor. The movement of the arm 15 moves the but in order that controller and at the same time sets the weir at the ,proper position.- voltage has dropped sufliciently by the rising of the liquid in the chamber 11 to permit a less spacing of the electrodes the auxiliary electrodes 17 which have a less spacing than the main electrodes are connected in circuit in parallel with the main electrodes. The arrangement is such that the connecting of the auxiliary electrodes in circuit causes only a gradual lowering of the resistance, and as the liquid rises further the resistance is further lowered. The result is that the final resistance is verylow. I have found that with a rheostat of this type it is possible to obtain a resistance range or ratio of 1 to 180 or even greater. This is very much greater than has ever been obtained in a device of the prior art so far as I am aware. By the use of this device, therefore, the resistance which is left in circuit with the motor is reduced to almost m7, and the loss due to the slip is similarly reduced.

While I have described my invention as embodied in concrete form and as operating in a specific manner for purposes of illustration, it should be understood that I do not it my ,invention thereto, since various modifications thereof will suggest them selves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new, and desire to secure by Letters Patent of the United States is z 1. A liquid rheostat for electric circuits comprising main electrodes and auxiliary electrodes arranged to be successively immersed in the liquid, said auxiliary electrodes being normally disconnected from the said circuit, and means for automatically connecting said auxiliary electrodes in circuit when they are immersed.

2. A liquid rheostat for electric circuits comprising main electrodes spaced apart, auxiliary electrodes spaced apart by a less distance than the main electrodes and arranged to be immersed in the liquid after the main electrodes, and means for causing the auxiliary electrodes to be connected in the electric circuit when they are immersed.

3. A liquid rheostat for electric circuits comprising main electrodes and auxiliary electrodes, means for causing the auxiliary electrodes to be connected in the electric circuit after the main electrodes have been immersed a predetermined amount, the minimum spacing between electrodes being less when the auxiliary electrodes are connected in circuit than when the main electrodes are connected in circuit.

4. A liquid rheostat for electric circuits comprising a liquid chamber, means for causing the liquid to gradually rise in said chamber, main and auxiliary electrodes When the spaced apart and mounted to be successively immersed as the liquid rises in the chamber, means for causing the auxiliary electrodes to be connected in the electric circuit when they are immersed, the minimum spacing of the electrodes in the liquid being less when the auxiliary electrodes are connected.

5. A liquid rheostat for electric circuits comprising main and auxiliary electrodes, a liquid chamber, means for causing first the main electrodes and then the main and auxiliary electrodes to be successively and gradually immersed in the liquid as the latter rises in the chamber, and means whereby the auxiliary electrodes are connected in circuit when they are immersed, the minimum spacing of the electrodes being less when the auxiliary electrodes are connected in circuit than before they are so connected.

6. A liquid rheostat for electric circuits comprising main electrodes and auxiliary electrodes spaced apart, means whereby said electrodes are gradually and successively immersed in the liquid, and means for causing the auxiliary electrodes to be connected in said circuit in parallel with the main electrodes when the latter are immersed a predetermined amount, said electrodes being so arranged with reference to each other that the minimum spacing of the electrodes will be less when the auxiliary electrodes are connected in circuit than before they are so connected.

7. A liquid r eostat for electric circuits comprising main electrodes spaced apart, auxiliary electrodes spaced apart by a less distance than the main electrodes, and means for causing the main electrodes to be first immersed and connected in the electric circuit and then the auxiliary electrodes.

8. A liquid rheostat for electric circuits comprising main electrodes spaced apart and connected in the electric circuit, auxiliary electrodes spaced apart by a less distance than the main electrodes, and means for causing the auxiliary electrodes to be connected in the circuit in' parallel with the main electrodes when the latter are immersed a predetermined amount.

9. A liquid rheostat for electric circuits comprising main electrodes spaced apart, auxiliary electrodes spaced apart by a less distance than the whereby the main electrodes and the auxiliary electrodes are successively immersed in the liquid, connections whereby the main electrodes are first connected in circuit, and

main electrodes, means electromagnetic means whereby the aux- I iliary electrodes are connected in a parallel circuit with the main electrodes when they are immersed in the liquid.

10. A liquid rheostat for electric circuits comprising a liquid chamber, means for causing the liquid to gradually rise in said chamber, main electrodes spaced apart, auxiliary electrodes spaced apart by a less distance than the main electrodes, said electrodes being mounted to be successively immersed in the liquid as the latter rises in the chamber, and connections whereby the main electrodes are first connected in circuit, and then the auxiliary electrodes are connected in parallel circuit with the main electrodes.

11. A liquid rheostat for electric circuits comprising a liquid chamber, means causing the liquid to gradually rise in said for chamber, main electrodes spaced apart, au xiliary electrodes spaced apart by a less distance than the main electrodes, said electrodes being mounted to be successively immersed in t e liquid as the latter rises in the chamber, connections whereby the main elec, trodes are first connected in circuit, and electromagnetic means whereby the auxiliary electrodes are connected in a parallel circuit with the main electrodes when they are immersed in the liquid.

In witness whereof, I have hereunto set mv hand this 31st day of January, 1914.

GEORGE H. DORGELOH.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

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