US2495188A - Liquid rheostat - Google Patents

Description

Jan. 17, 1950 2 Sheets-Sheet 1 Filed July 17, 1948 7 u w 2 ,5. T N6 w o E e W 0 WITNESSES:

G. R. SHAW LIQUID RHEOSTAT Jan. 17, 1950 2 SheetsSheet 2 Filed July 17, 1948 INVENTOR ATTO fiearg' 27 WITNESSES.

Patented Jan. 17, 1950 LIQUID RHEOSTAT George R. Shaw, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 17, 1948, Serial No. 39,319

16 Claims.

My invention relates, generally, to liquid rheostats and it has reference, in particular, to liquid rheostats and slip regulators, and operating systems therefor.

Generally stated, it is an object of my invention to provide an improved liquid rheostat which is simple and inexpensive to manufacture, and is effective in operation.

More specifically, it is an object of my invention to provide for increasing the effective operating range of a liquid rheostat.

Another object of my invention is to provide for reducing the size of liquid rheostats without reducing their effectiveness.

Yet another object of my invention is to provide, in a liquid rheostat, for variably controlling the effective cross-sectional area of the column of electrolyte between the electrode members.

It is an important object of my invention to provide, in a liquid rheostat, for using a flexible liner in the electrolyte container to decrease the effective cross-sectional area of the electrolyte.

An important object of my invention is to provide, in a liquid rheostat, for expanding a flexible liner in an electrolyte container, only when the electrode members are separated by a predetermined amount.

Another important object of my invention is to provide for increasing the resistance of a liquid rheostat after the movable electrode member has reached the limit of its travel without reducing the effective area of either of the electrode members.

It is also an object of my invention to provide, in a liquid rheostat, for expanding a flexible liner in an electrolyte container so as to increase the effective resistance of the rheostat, and for preventing starting of a motor controlled by the rheostat until predetermined pressure conditions are attained between the liner and the inner walls of the container.

Other objects will in part be obvious, and will in part be explained hereinafter.

In practicing my invention in one of its forms, each of the electrolyte containers of a liquid rheostat, which is used for controlling a wound rotor motor, is provided with a flexible rubber liner disposed around the inner side wall of the container. A pump and a reversible valve are utilized in connection with a common header in the main electrolyte tank and individual connections to the containers for normally withdrawing the electrolyte from the space between the cell walls and the liner, and for supplying electrolyte to this space so as to inflate the liner and decrease the effective cross-sectional area of the column of the electrolyte between the stationary and moving electrode members when they are separated the maximum amount. When the pressure in the space between the wall and liner reaches a value indicative of a desired degree of inflation of the liner, a pressure switch is actuated which permits closing the circuit breaker for connecting the wound rotor motor to a source of electrical energy. After a predetermined interval of time, the valve is reversed and the liner is deflated. Operation of the electrode controlling motor is permitted only when the pressure switch indicates that the liner is sufficiently deflated to be clear of the movable electrode member, whereupon the movable electrode member may be lowered to its normal operating or regulating position.

For a more complete understanding of the nature and scope of my invention reference may be made to the following detailed description, which may be read in connection with the accompanying drawings in which:

Fig. l is a side elevational View of a liquid rheostat embodying the invention in one of its forms.

Fig. 2 is an enlarged end elevational view, partly in section of the rheostat of Fig. 1; and

Fig. 3 is a diagrammatic view of a control system showing one form in which the invention may be utilized.

Referring to Fig. 1, the reference numeral lil denotes generally a liquid rheostat or slip regulator which may be used for controlling the operation of a polyphase motor, or the like. The rheostat may comprise a common electrolyte tank 32 from which may be suspended three electrolyte containers I4, I5 and it, wherein may be positioned stationary and movable electrode members.

The tank I2 may be supported in a suitable frame structure ll, on which may be mounted a motor 18 for operating a drive shaft provided with drums 2| and 22 for accommodating ropes or cables 23 and 24 for operating the movable electrode members.

The tank [2 may be provided with a sump or drain pipe 26 through which the heated'electrolyte flows to a sump tank 2'! and a heat exchanger 28. A pump 30 may be provided for forcing the electrolyte through the heat exchanger and returning the cooled electrolyte to the tank 52 through a pipe 3|.

Referring to Fig. 2, it may be seen that each of the containers, and in particular, the container I4, may comprise a cylindrical body member 34 of a suitable insulating material such as one of the cement bonded asbestos compositions Well known in the art. The body member 34 may be secured to the tank I2 in any suitable manner being, for example, secured to the bottom of the tank I2 by means of clamp means 35, in

alinement with an opening 31 in the bottom of the tank, through which the electrolyte 38 may have access to the interior of the container. The body member 34 may be closed at the lower end by means of an end member or plate 40 secured thereto by means of clamp means 42. The stationary electrode member 44 may be mounted on the end member 49 by means of studs 46, through which electrical connection may be made to the electrode member 44 by means of conductors 47. The movable electrode member 49 may be suitably secured to a lift rod 50, which is suspended from a common connecting channel member 52, to which the cable 23 may be attached.

The tank I2 may be provided with a cover 53 having an opening 54 through which the rod 50 passes. A partition 55 may be provided adjacent the right-hand edge of the tank so as to furnish a common duct or manifold. 55 through which the electrolyte may be returned from the pipe 3 I. Each of the electrode cells or containers may be provided with an inlet such as the pipe or conduit 58 which connects into the manifold 55 and through the bottom or end member 40 of the container.

In order to provide for extending the oper ating range of the liquid rheostat and increasing the effective resistance thereof, each of the containers may be provided with a flexible diaphragm, sleeve or liner, such as for example the cylindrical rubber liner 60, which may be secured around the inside wall of the container by means of clamp rings 62 and 63 at the top and bottom, respectively. The liner 6!! may be disposed to provide a substantially annular space or chamber 65 between itself and the inner surface of the container.

In order to vary the effective cross-sectional area of the column of electrolyte between the stationary and moving electrode members 44 and 49, fluid pressure means such as the pump 61 may be provided for varying the pressure in the chamber 65. v The pump maybe provided with an inlet pipe 68 positioned in the electrolyte 38, and an outlet condult 7D. A partition I2 may be provided adjacent the left-hand side of the tank I2 so as to provide a pressure chamber 14 into which the outlet 19 of the pump may be connected. Individual connections may be made from the pressure chamber 14 to each of the containers by means such as the conduit 75, which may extend from the pressure chamber 14, through the side wall of the container I4 into the chamber 65. The partition 12 may be provided with suitable valve means for relieving the pressure therein, so as to limit the pressure which may be built up by the pump 61. For example, the partition 12 may be provided with a suitable orifice 16, through which the electrolyte in the pressure chamber may escape back to the tank I2. Means such as the reversing valve 18 may be in connection with the pump 6'! for reversing the direction of flow of the electrolyte in the pipe for the purpose of regulating the volume of the annular chamber 65.

A pressure switch I9 responsive to the pressure in the chamber 65 may be connected to the pressure chamber I4.

Referring to Fig. 3, it will be seen that the movable electrode member 43 may be controlled by means of the electrode motor I8, which comprises an armature BB and a field winding M. The motor I8 may be of the shunt type with the field Winding 8| connected in shunt circuit relation with the armature 8d. Suitable reversing means, represented schematically by the reversing switch 82, may be provided for controlling the direction of rotation of the motor !8 for the purpose of raising or lowering the movable electrode members in a manner well known in the art.

The liquid rheostat I0 is herein designated as connected in the rotor circuit of a wound rotor motor 84, though for the purposes of simplification, the connections of only one phase of the secondary winding are shown, the connections being made as illustrated to the stationary electrode member 44 through the conductor 47 whereby the circuit will be completed through the electrolyte in the container I4. Operation of the wound rotor motor 84 may be efiected by means of a circuit breaker 85 having an operating winding 31 and provided with a suitable latch device 83 for maintaining it in the operated position.

While the control for the motor 84 is being generally represented sch matically by the circuit breaker 86, it is to be understood that the usual control apparatus for the starting and operating of such a motor may be provided, but since it forms no part of the present invention, it is being omitted for the purpose of simplification. In this connection, for example, shunt trip means (not shown) ma be provided for tripping the circuit breaker either manually or in connection, with suitable overload devices (not shown) in a manner well known in the art.

In order to provide for controlling operation of the reversing valve 78, magnetic control means 99 may be provided comprising an inflate solenoid 9I having an operating winding 92 and a deflate solenoid 94 having an operating winding 95. A start relay 97 having an operating winding 98, may be provided in conjunction with a start push button switch 99 and a stop push button switch I80 for controlling the op-- eration of the control means 99. The pump 6? may be provided with a suitable motor N32 for operating it in response to operation of the start relay. While the motor has been shown as a direct current motor, it will be obvious that an alternating current motor may be used if desired.

In order to prevent inflation of the cell liner 65 before the moving electrode 49 reaches its uppermost position, in which it will be entirely clear of the liner, a limit switch I84 may be provided, which normally provides for energizing the deflate Winding and only permits energization of the inflate operating winding 82 when extension I95 on the connecting channel 52 actuates the limit switch to indicate that the moving electrode 49 is in its uppermost position.

A time delay relay I66 having an operating winding Iii! may be provided for deenergizing the inflate winding 92 and energizing the deflate Winding 95 after the circuit breaker 86 has been closed a suilicient length of time to permit the starting current of the wound rotor motor 84 to drop to a relatively low operating Value.

The pressure switch I9 may be utilized for controlling the operation of the electrode motor 18 and the wound rotor motor circuit breaker 86, so as to prevent operation of the electrode motor when the pressure in the chamber 65 between the liner and the container side wall is above a predetermined value, and prevent closing of the circuit breaker unless the liner 60 is in the expanded position. The pressure switch may be of any suitable type comprising, for example, .apiston I I I normally biased in one direction by a spring i l2 and actuated in the opposite direction by means of fluid pressure in the pressure chamber 14 through a conduit H4.

When it is desired to start the wound rotor motor 84, the electrode motor 1-8 may be operated by closing a control switch H5 which connects the motor to a source of electrical energy represented by the conductors H6 and H1, through the reversing switch 82 and normally closed contact members 1% on the pressure switch. When the moving electrode 49 reaches its uppermost position, the extension I05 on the connecting channel 52 actuates the limit switch I04 and sets up a starting circuit for the start relay 91 through contact member I040. When the start push button switch 99 is actuated, the start relay 91 operates, and provides a holding circuit for itself through contact member 91b. An energizing circuit for the pump motor I62 is provided through contact member 910.. When the conductors H6 and H! are energized, the time delay relay 106 is energized through contact member 86a of the circuit breaker. An energizing circuit is thereupon provided for the inflate operating winding 92 which actuates the reversing valve 18 to the position shown. Fluid pressure will thereupon be supplied by the pump 6] to the chamber 65 so as to expand the liner 66 and decrease the effective cross-sectional area of the column of electrolyte between the stationary electrode member 44 and the movable electrode member 49.

When the pressure in the chamber 65 reaches a predetermined value, which indicates that the resistance of the column of electrolyte between the stationary and movable electrode members is sufficiently high, the pressure switch 19 operates. An energizing circuit thereupon provided for the operating winding 8'! of the circuit breaker 86, extending from the conductor H6 through conductor H9, contact member 91c, operating winding 81, contact member 19a, conductor I20, conductor I21, and contact member 1 040, to conductor Ill. The circuit breaker 86 thereupon closes and connects the wound rotor motor 84 to a source of alternating current electrical energy represented by the conductors I23 for the purpose of starting the motor.

As soon as the circuit breaker 8.6 closes, the energizing circuit for the operating winding 10'! of the time delay relay )6 is interrupted at contact member 86a. After a predetermined interval of time the relay I06 returns to the deenergized position and the energizing circuit for the deflate operating winding 95 will be completed through contact member 106a, while that for the inflate winding 95 will be interrupted at contact member "36b. Accordingly, the valve 18 will be operated to the reverse position, whereupon the pump 61 withdraws the electrolyte from the chamber 65 and returns it to the tank [2.

As soon as the pressure in the chamber 65 reaches a predetermined minimum value, which indicates that the liner is substantially withdrawn against the inner side walls of the container, the pressure switch 19 operates, and a circuit is thereupon completed .for the electrode motor l8 through contact member 19b, whereupon operation of the motor I8 to regulate the rotor current of the motor 84 may be efiected by the usual control means (not shown).

From the above description it will be apparent that I have provided in a simple and eifective manner for increasing the effective resistance of rheostats and slip regulators of a liquid containing type. By utilizing a flexible .or elastic liner within the usual electrolyte container, a simple, durable and effective means of control may be provided. Since the pressure in the chamber between the liner and the side walls of the container is substantially in accordance with the position of the liner, interference between the liner and the movable electrode is readily prevented by using a pressure switch to control the electrode motor circuit. Since the pump is normally utilized to maintain the liner in a deflated condition, in substantially close contact with the inner wall of the container and this is substantially the natural position of the liner, no interference between the liner and the moving electrode is possible.

By utilizing the features of my invention, the effective resistance of existing liquid rheostats may be greatly increased, while the size of rheostats to be built may be greatly reduced while yet maintaining a high eifective value of resistance for controlling motors of the wound motor type and the like. Moreover, in practicing my invention the full area of the electrode members is retained in the circuit, thereby minimizing boiling or foaming of the electrolyte at the contact members under peak current conditions such as exist during starting of wound rotor motors.

Since certain changes may be made in the above described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the material contained in the above description and shown in the accompanying drawings shall be considered as illustrative and not in a limiting sense.

I claim as my invention:

1. A liquid rheostat comprising, a container for an electrolyte, fixed and movable electrodes disposed within the container, and a flexible liner within the container disposable to reduce the effective cross-sectional area of the electrolyte in the container.

2. In a liquid rheostat, a container for an electrolyte having a side wall, relatively movable electrode members positioned in the container, a flexible liner disposed adjacent the side wall, and conduit means providing a connection to between the liner and the side wall.

3. A liquid rheostat comprising, a container of an insulating material for an electrolyte, a fixed metallic electrode at one end of the container, a movable electrode positioned within the container, a flexible liner secured in the container to provide an enclosure between the liner and the inside surface of the container, and duct means connecting with said enclosure to vary the fluid content thereof.

4. In a liquid rheostat, in combination, an elongated container of an insulating material having relatively movable electrode members therein, a flexible liner disposed within the container and arranged to be secured adjacent the ends thereof to provide a variable volume annular chamber, and fluid means including a conduit connected into the chamber to vary the volume thereof.

5. In a liquid rheostat, a container for an electrolyte comprising a substantially cylindrical member of an insulating material closed at one end, a fixed metallic electrode positioned within the container adjacent said one end, a movable electrode movable axially within the container, a rubber liner positioned about the inner surface of the container and secured to the container adjacent its ends to provide an annular chamber, and fluid means including a conduit through a side of the container for supplying electrolyte to said chamber.

6. In a liquid rheostat, an elongated container for an electrolyte having one end closed, a fixed electrode positioned adjacent the closed end, a movable electrode movable longitudinally of the container, a flexible liner within the container disposed to be positioned adjacent an inner longitudinal surface of the container to provide an expandable chamber therebetween, and fluid means including a conduit extending into said chamber for expanding said chamber to reduce the effective cross-sectional area of the electrolyte in the container.

7. A rheostat comprising, a common tank having a plurality of openings in the bottom thereof, an electrolyte container having an upper end secured to the tank about each opening and having a fixed electrode member positioned therein adjacent the lower end, a movable electrode member positioned in each container, a flexible liner positioned within each container and secured thereto adjacent the ends, and fluid means including a common manifold and a separate conduit connection to each container disposed to supply electrolyte to a space between the liner and the inner wall of the container.

8. In a liquid rheostat, a common electrolyte tank having a plurality of spaced openings therein, a plurality of electrolyte containers having side walls with the upper ends maintained in alinement with said opening and having closed lower ends with stationary electrode members positioned therein, a moving electrode member in each container, elastic liners secured to inner surfaces of the side walls of the containers to provide chambers of variable volume, and fluid means including conduit means connecting to said chambers and pump means operable to apply fluid pressure to said chambers to decrease the effective cross-sectional area of the electrolyte in said containers.

9. A liquid containing rheostat comprising, a relatively shallow elongated pan having a plurality of centrally disposed openings in the bottom thereof, said pan having partitions adjacent opposite edges providing enclosures extending 1ongitudinally of the pan, a container of an insulating material for an electrolyte depending in alinement with each of said openings, said container being enclosed at the lower ends and provided with a fixed electrode member adjacent said end, a movable electrode member in each container, a flexible sleeve disposed about the inner periphery of each container to provide a variable volume chamber between the sleeve and an inner wall of the container, fluid means including a conduit connecting from one of said enclosures to each of said chambers and pump means connected to said enclosure to build up a pressure within said chambers, and additional fluid means connected to the other enclosure disposed to supply electrolyte to said containers.

10. In a liquid containing rheostat, an elongated container of an insulating material for an electrolyte, said container having a stationary electrode member adjacent its lower end, a movable electrode member positioned in the container, a rubber sleeve disposed within the container to provide a variable volume annular chamber, and fluid means including a pump and conduit means connected to said chamber to supply electrolyte thereto.

11. A liquid rheostat comprising, a container for an electrolyte having a stationary electrode member adjacent one end, a movable electrode member positioned within the container, fluid means supplying electrolyte to the container, a flexible liner secured Within the container to provide a variable volume chamber about the inner surface of the container between the electrode members, and additional fluid means disposed to supply electrolyte to said chamber.

12. A liquid rheostat comprising, a container for an electrolyte having relatively movable electrode members therein, a flexible liner within the container disposed to provide a substantially annular chamber of variable volume, and fluid means responsive to predetermined positioning of the electrode members controlling the supply of electrolyte to said chamber.

13. A liquid rheostat comprising, a container for an electrolyte, said container having a fixed electrode member at one end and a movable electrode member, a diaphragm disposed about an inner wall of the container to provide a variable volume chamber therebetween, pump means, conduit means including a reversible valve connecting the pump means to said chamber, and control means responsive to predetermined movement of the movable electrode member for controlling operation of the valve means.

14. In a liquid containing rheostat, a container for an electrolyte, said container having relatively movable electrode members therein, a flexible liner disposed within the container to provide a substantially annular chamber therewith, fluid means operable to control the amount of electrolyte in said chamber, control means responsive to predetermined separation of the electrode members controlling the fluid means to provide fluid pressure to said chamber, and time delay means operable after a predetermined time interval to effect operation of the fluid means to remove fluid pressure from the chamber.

15. A liquid rheostat comprising, a container for an electrolyte, fixed and movable electrode members in said container, a motor connected in driving relation with the movable electrode member, a flexible liner disposed within the container to provide an annular chamber, fluid means controlling the pressure in said annular chamber, switch means responsive to the pressure in said chamber connected to control the operation of the electrode motor, and control means responsive to the position of the movable electrode member disposed to control operation of the fluid means.

16. In a control system for a main motor, a circuit breaker operable to supply electrical energy to the main motor, a rheostat including a container for an electrolyte and fixed and movable electrode members therein connected in circuit relation with the motor, an auxiliary motor operable to actuate the movable electrode member, a flexible liner in the container disposed to provide a variable chamber between the liner and the sides of the container, fluid means including a pump and conduit means connected to control the sup- 9 ply of electrolyte in the chamber, valve means REFERENCES CITED operable to reverse the flow of electrolyte in the conduit means, switch means responsive to the electrolyte pressure in the chamber for controlling The following references are of record in the file of this patent:

the operation of the main motor breaker and the 5 UNITED T S PATENTS auxiliary motor, and. switch means responsive to Number Name Date h p si ion of he movable electrode member dis- 1,166 157 Simmons 28, 1915 posed to control the operation of the valve means. FOREIGN PA s GEORGE SHAW- 10 Number Country Date 70,025 Germany July 28, 1893

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