US2262558A

US2262558A - Governing apparatus

Info

Publication number: US2262558A
Application number: US353057A
Authority: US
Inventors: Anthony F Schwendner
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1938-08-17
Filing date: 1940-08-17
Publication date: 1941-11-11
Anticipated expiration: 1958-11-11

Description

N0V 11, 1941- A. F. scHwENDNER 2,262,558 GOVERNING' APPARATUS Original Filed Aug. 17, 1938 2 Sheets-Sheet l HNTHourI-T ScHweNausn,

ATTORNEY NOV- 1l, 1941- A. F. scHwENDNER GOVERNING VAPLAR'US Original Filed Aug. l?, 1938 2 Sheets-Sheet 2 my. M. RE H mw -N mww mswm .f-h WSYY EMB `H uw mAH wm Q n 8 E wwd Enr. WN. 4 W

Patented Nov. 11, 1941 GOVERNING APPARATUS Anthony F. Schwendner, Ridley Park, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Original application August 17, 1938, Serial No. 225,272. Divided and this application August 17, 1940, Serial No. 353,057

(Cl. Bil- 67) 6 Claims.

This application is a division of application Serial No. 225,272, filed August 17, 1938, for Governing apparatus and assigned to the Westinghouse Electric & Manufacturing Company, and the invention hereof relates to prime movers, more particularly to steam turbines of the bleeder or extraction type, and it has for an object to provide an improved control system for apparatus of this character.

Where a steam turbine has two or more bleeder points, compensation has heretofore been difficult. With a single bleeder point, the associated pressure regulator may be used directly in connection with the governor for this purpose; however, with two or more bleeder points, this arrangement, Without further additions, cannot be used because too many variables are involved. In one type of bleeder control mechanism for a turbine having a plurality of bleeder points and arranged for speed compensation, the impeller pressure of the governing mechanism is impressed on the admission valve regulating mechanism as well as on the regulating mechanisms of the bleeder valves, but, as the admission valve regulating mechanism is provided with a speed compensator, the impeller pressure would come back to the same value at different loads and, therefore, be useless for the control of the bleeder regulators. Accordingly, it was necessary to incorporate pressure compensation to overcome this diculty. In the control system of the present invention, the regulating pressure may be utilized to operate both the admission valve and bleeder valve regulators for the reason that, with the isochronous arrangement of the system, the regulating pressure does not come back to the same value as in the case of the impeller pressure, but it is maintained at a value determined by the load change. Accordingly, a further object of the invention isv to provide control mechanism for a turbine having one or more bleeder points with means operating to secure a governing pressure which is compensated for load so that such pressure depends upon the load and may be used to operate the various regulators, each bleeder point regulator being also subject to the effect of steam pressure at its bleeder point so that the latter pressure may be maintained at a desired value.

A further object of the invention is to provide a steam turbine having two or more extraction points with a fluid pressure governing system wherein the governing pressure is used both to control the admission of steam to the turbine and to control the valve or valves located in the path of steam flow `of the turbine and at the down-stream side of each extraction point, the effect of the governing pressure being modified by the pressure at each extraction point so as to secure such operation of the associated valve as to maintain the pressure at each extraction point at a predetermined value.

Afurther object of the invention is to provide a steam turbine of the extraction type having admission and extraction point control valves, control means for the valves, and means for modifying the operation of the control means so that the `turbine operates at Substantially a constant speed to provide a desired load-carrying capacity with maintenance of a desired pressure at each extraction point.

A further object of the invention is to provide a steam turbine having two or more extraction points with a fluid pressure governing system wherein the governing pressure directly controls both the admission valve and the extraction or bleeder valves, the latter also being subject to the effect of 4pressure at each extraction or bleeder pointftogether with means responsive to load change to modify the governing pressure.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a view, partly in section and partly in elevation, showing a turbine installation with the improved governing system applied thereto; and

Fig. 2 is a diagrammatical sectional view of the controy system shown in Fig. 1.

In accordance with the present invention, there is provided a prime mover or turbine having one or more extraction or bleeder points and controlled by governing apparatus of the general type disclosed and claimed in Patent No. 2,009,417, July 30, 1935, and in Patent No. 2,224,321, issued December 10, 1940, but which differs from the latter in the respect that the regulating pressure provided by the transformer governor is used directly, not only to control the main admission valve, but also each extraction or bleeder valve, the latter also being subject to the effect of bleeder pressure so that the pressure at each extraction or bleeder point may be maintained at a predetermined value. While an isochronous system of the present type has a load-compensated governing pressure, making the latter peculiarly useful for all of the regulators, yet such a system would not be effective to make the turbine carry a predetermined load in the form of the output of its generator where the latter is tied into an electrical system. Accordingly, a further modification of the present invention contemplates an isochronous governing arrangement for a turbine which kmay be readily changed over to load control so that the electrical output of the generator is maintained substantially constant.

Referring now to the drawings more in detail, there is shown a load or generator 9 driven by a turbine including a high-pressure section I i),` an intermediate-pressure section I I, and a low-pressure section I2, steam being supplied tothe highpressure section I8 through the admission valve I3; and, as shown, bleeder or extraction lines I4 and I 5 are connected at the exhaust lor discharge ends of the turbine sections I0 and II. Valves I6 and I 'I are arranged in the path of steam flow along the turbine at the downstream sides of the extraction or bleeder lines I4 and I5 and serve, with the admission valve I3, to secure such admission and distribution of-steam as to satisfy the power and bleeder demand, these Valves being operated by the improved control system, which will now be described.

The turbine rotor carries an impeller providing oil under suitably high pressure for'the supply passage 2|.vr The system is also provided with an exhaust or drain line indicated generally at 22.

Oil is supplied from the impeller, through an orice 23, to the primary pressure passage 24, the pressure in which is maintained as a function of the turbine speed due to the centrifugal escape passage formed in the turbine rotor, this particular type of pressure developer being disclosed and claimed in the patent to O. N. Bryant, No. 2,035,689, March 31, 1936.

Oil under primary pressure is supplied by the line 24 to the transformer, at 26, to derive oil under regulating pressurefurnished by the line 28 to the servo-motor 21 for the admission valve and to the servo-motors 29 and 38 for the bleeder or extraction valves I6 and I'I.

Oil under regulating pressure supplied from the transformer, at 26, is the only controlling factor for the admission valve servo-motor 21 and it serves as a contributing factor for controlling the servo-motors 29 and 30, the latter also being responsive to pressures of the bleeder lines YI4 and I5, the bleeder line pressures acting on transformers 3| and 32, whose control pressures are impressed, by means of the lines k33 and 34, on the servo-motors 29 and 30. v

While the pressure responsive arrangement or transformer governor, at 26,may be of any suitable type,`one embodying the principlesl disclosed generally in the aforesaid Patent No. 2,009,417 and Patent No. 2,224,321 is preferred. The one illustrated is similar to that disclosed and claimed in saidPatent No. 2,224,321, that. is, it is constructed and arranged to provide for diiTerent types of operation depending upon the requirements peculiar to each installation; but, with bleeder point control, in orderthat the governing or control pressure may be a function of the load, the apparatus is arranged for isochronous operation.

Generally, thev transformer governor, at 26, includes a body structure 35 havingja cylinder 38 provided with an inlet pressure port 3l, an exhaust port 38, and a regulating pressure port 39 arranged between the ports 31 and 38. A spinner piston 4'0 is ydisposed inthe cylinder 36 land it is turned, preferably'by the turbine wheel 4|,

to avoid the effects of static friction. The spinner piston has upper and lower lands 42 and 43 and an intermediate recessed or reduced portion 44 Which cooperates with the interior of the cylinder 36 to provide a regulating pressure chamber 45 continuously in communication with the port 39, the lands 42 and 43 being arranged just to lap the inlet and exhaust ports 3'! and 38 with respect to the chamber 45.

The inlet pressure port 31 is connected to the high pressure line 2|, the exhaust port is connected to the exhaust line or system 22, and the regulating pressure port 39 at the inner end of the passage 38a, communicates through the latter with the regulating pressure line 28.

If thev spinner piston v4I) is moved axially to place the yinlet pressure port 31 in communication with the regulating pressure chamber 45, then the regulating pressure increases. On the other hand, if the spinner piston moves in the other direction to place the exhaust port 38 in communication with such chamber, then such pressure decreases.

Fluid under primary pressure is supplied by the line 24 to the chamber 46 closed by the bellows 41 and the first pressure abutment 48. A spring 58 exerts its force on the abutment 48 in opposition to theforce of primary pressure exerted thereon. A thrust bearing 5I is arranged between the abutment 48 and the spinner piston 40. With this arrangement, if the primary pressure supplied to the chamber 46 increases, the force thereof exerted on the abutment 48 causes the latter to move upwardly against the force of the spring 58 until such time as the fluid pressure and spring forces are in equilibrium. On the other hand, if the primary pressure decreases, movement occurs in the other direction until equilibrium of forces is established. Movements of the pressure abutment 48, in consequence of changes in primary pressure, are transmitted, through the thrust bearing 5I, to the spinner piston, causing the latterto place the regulating pressure chamber 45 in communication either with the inlet pressure port 3'! or withfthe exhaust port 38, vdepending upon the direction of movement of the spinner piston, to effect change in regulating pressure.

Changes in primary pressure are accompanied by changes in secondary or regulating pressure and the latter are used to restore the spinner piston Valve 48 to neutral position. Accordingly, it isr necessary to apply to the spinner piston valve a secondary or regulating pressure force in opposed relation to the primary pressure force.

To this end, the cylinder 38 extends above the upperpiston portion 42 to provide a pressure chamber 52 closed by the second pressure abutment face 53 at the upper end of the piston portion 42 and fluid is supplied to the pressure chamber 52 from the rsecondary or regulating ressure chamber 45 by a suitable passage, for example, the passage 54. If a change in primary pressure occurs due to change in prime mover speed, then the force applied tothe rst abutment face 48 hanges and the spinner piston moves to bring about a change in secondary or regulating pressure, this operation continuing until the regulating pressure attains such a value that the force thereof applied to the second pressure abutment face 53 balances the resultant of the primary pressure and spring forces applied to the abutment 48 with the spinner piston restored to neutral position, it being apparent that, for .a given change in primary pressure, the change in regulating pressure will depend upon the ratio of the nrst pressure abutment area 48 to the second pressure abutment area 53. To effect a change in speed setting of the governor, it is merely necessary to adjust the force of the spring 50 by means of suitable speed changing apparatus indicated at 55.

While the apparatus so far described would be satisfactory for ordinary `governing operation, the governing or regulating pressure is a function of speed and it would be unsatisfactory for bleeder control unless the total speed change is greatly reduced. This may be readily done with this particular arrangement by the addition of an isochronous connection which causes the primary pressure to be restored to a constant value and the regulating pressure to assume a value dependent on the load.

With isochronous operation, transient speed changes do occur due to changes in load, but the governor operates to restore the speed to a normal value. Accordingly, the spinner piston 40 is arranged so that it effects changes in secondary or regulating pressure but its equilibrium or cut-off position is determined entirely by the opposing forces of the spring 58 and of the primary pressure applied to the first abutment face 48, this being the condition for a constant speed as determined by the setting of the spring 50. If a change in load occurs, there is a concurrent but temporary change in speed, which change results in change in primary pressure supplied to the chamber 46. The change in force of primary pressure causes the spinner piston to move to eifect a change in secondary or regulating pressure, which is applied to the upper or second piston face 53; however, the change in secondary or regulating pressure is applied in a delayed manner to a lower pressure Chamber 51 closed by the third pressure abutment face 58 formed at the lower end of the land 43. To this end, the body 35 is provided with a passage 59 affording communication between the upper and lower chambers 52 and 51, the passage having an orifice 60 and a valve 6|, together with an accumulator or airbell 82 communicating with the pressure chamber 51. With a change in load, the temporary and consequent speed change causes the spinner piston to move, the secondary or regulating pressure exerting its force on the upper or second pressure abutment face 53 and tending to restore the spinner piston to neutral position; however, if such spinner piston were merely restored to neutral` with no additional adjustment, then the speed would be slightly different depending upon the regulation or operating range of the governor. The effect of the passage 59, the orifice 68 and the accumulator is to cause a delayed application of pressure to the lower chamber 51, the pressure in the latter finally coming to equilibrium with that in the upper chamber 52, but, in so doing, the secondary or regulating pressure will be so modified as to effect speed compensation of the turbine at the new load, the speed setting being determined, as already pointed out, by the equilibrium of forces applied to the first pressure abutment 48 with the spinner piston in neutral position, the opposed forces applied to the second and third pressure abutment faces 53 and 58 being in equilibrium.

Fluid under secondary or regulating pressure supplied to the line 28 is used directly, not only to control the admission valve servo-motor 21,

but also the servo-motors 29 and 30 for the bleeder or extraction valves. The servo-

motors

21, 29, and 30 are similar in structure and operation except that the servo-motors 29 and 30 are arranged to be subject to an additional controlling pressure yderived fromdsteam pressure.

Referring to the servo-motor 21, this is shown as comprised by a structure or body 68 having a cylinder 69 for the operating piston 18 and a cylinder 1| for the piston valve 12, the cylinders 69 and 1| being closed by a cover structure 13. The piston valve cooperates with the pressure port 14 supplied by the line 2| and with the exhaust ports 15 and 16 connected to the drain line 22, the pilot valve 12 being moved to place the pressure and exhaust ports in communication with the cylinder ports 11 and 11a.-

The pilot valve 12 is not moved directly by the governing pressure but by an interposed relay device, which, in turn, `is controlled by the governing pressure. To this end, the cover 13 has a pressure chamber 18 closed by the pressure abutment face 19, by the upper bellows 88 andv by the lower and larger bellows 8|, the force of pressure applied to the abutment face 19 being resisted by means of the spring 82.

The abutment 19 is connected to a stern 83 whose lower end carries a cup valve 84 covering the axial bore 86 formed in the pilot valve 12, the cup valve 84 being arranged in the pressure chamber 81 into which the upper end of the pilot valve 12 extends so that its top surface provides a pressure abutment face subject to the pressure therein.

Fluid under pressure is preferably supplied to the chamber 81 from the line 2| by means of an orifice 88, preferably formed in the pilot valve. The downward force of pressure supplied to the chamber 81 and acting on the upper end of the pilot valve is opposed by the spring 98 acting on the lower end thereof.

Assuming a change in output pressure supplied by the line 28, then the first effect thereof is to secure movement of the stern 83 and the cup valve 84, thereby changing the discharge resistance, either by restricting the discharge past the cup valve and through the bore 85 or permitting of greater discharge. With change in pressure brought about in this way in the chamber 81, in consequence of movement of the stem and the cup valve, the pilot valve moves in respense to such change in pressure to follow the motion of the cup valve and the stem. Movement of the pilot valve establishes communication of the cylinder ports 11 and 11a with the pressure and exhaust ports to effect movement of the operating piston 18, and movement of the latter changes the force of the spring 82, this result being effected by means of the lever 9| pivotally connected to the operating piston and providing a support Sla for the upper end of the spring. If there is a change in secondary or regulating pressure followed by movement of the operating piston, it will be apparent that movement of the latter will be in such a direction to change the spring force in such manner as to restore the cup Valve B4 to the position where the pilot valve will be in neutral or cut-off position, whereupon movement of the operating piston ceases.

The servo-motors 29 and 38 are similar to the servo-motor 21 except that the lower bellows elements 8| provide pressure chambers supplied by the

transformer lines

33 and 34, so that the associated cup valves assume positions wherein the difference in forces of pressures supplied to the chambers `18 and 18a must be in equilibrium with the force of the spring 82 when the pilot valveis restored to neutral position incident to termination of movement of the operating piston, whereby these servo-motors respond both to the regulating pressure and to control pressures dependent upon the respective bleeder line pressures.

Referring now to the transformers, at 3| and 32, these devices are similar to that disclosed and claimed in Patent No. 2,009,418, July 30, 1935. Each of these transformers has a steam line 92 connected to its bleeder line, the steam line supplying steam to a pressure chamber 93 closed by an abutment 94 and a bellows 95, the abutment bearing on a stern 96 connected to the cup 91 having a ange 98 abutting the upper end of a spring 99, the lower end of the latter bearing against the abutment face of the structure |0I.

control pressure line

33 or 34.

The secondary or control pressure chamber |08 also communicates, by way of passage H0, with the lower pressure chamber closed by the piston abutment face ||2 provid'ed by the lower end of the land |05. The spinner piston |03 is given spinning motion by means of the turbine element ||3. The lower end of the spinner piston engages with an abutment I 4 through the intermediary of a thrust bearing H5, the abutment being sustained'by a spring IIB with which cooperates an adjustable abutment ||1.

In operation, each transformer 3| and 32, therefore, receives steam pressure through its line 92 from the bleeder line and such pressure is transformed into a controlling fluid pressure dependent thereon, the controlling pressure being supplied to the pressure chambers 18a of the servo-motors 29 and 30 and the transformers, at 3l and 32, serving to bring about such control as to maintain the bleeder line pressure at a predetermined value.

With the apparatus so far described, it will be apparent that the governor mechanism not only serves to control the admission and distribution of steam in such manner as to maintain the pressure at each bleeder point at a predetermined value with variation in bleeder demand, but also serves to maintain the power developing capacity of the turbine at a point determined by the load, that is, the governing system assures that the turbine may operate both to meet variations in bleeder and power demand.

With the present isochronous arrangement, the primary and secondary or regulating pressures are not maintained in proportionate relation as in the case of ordinary transformer governor operation, for the reason that the primary pressure is constant, the turbine operating at the same speed at all loads. However, when there is a change in load, a temporary speed change occurs, the extent of speed change being a measure of the changein load, and the governor mechanism operates to secure such admission and dis'- tribution of steam as will meet the new load condition with the turbine operating at the normal speed. Since, in this way, the governing mechanism is compensated for speed change due to load change, it will be apparent that the secondary or regulating pressure is dependent upon load and may, therefore, be used for controlling all of the regulators.v

If it is desired to have the power output of the turbine held at a substantially constant value, as may be the case where the generator of the turbine is tied into an electrical system and it is desired to have the generator /carry a denite part of the system load, then the isochronous control arrangement would be ineffective; and, for this reason, provision is made, as more particularly disclosed and claimed in the Patent No. 2,224,321 aforesaid, for changing the governing system from the speed compensation type to the load compensation type. To this end, a load responsive device is associated with the turbine and it exerts its effect on the governing system in such mann-er that the latter causes steam to be admitted to the turbine to cause the latter to deliver a desired power. Accordingly, the generator 9 driven by the turbine has its supply line ||5 loperating a device, at H6, which responds to ther power of the generator, the device being associated with the transformerVat H1, so as to provide a secondary or load-responsive control pressure supplied by the line ||8 to the transformer, at 26, to secure modification of the operation thereof, as will be immediately pointed out. Therefore, the transformer, at ||1, responds to a change in electrical output of the generator in such manner as to oppose the change, whereby the electrical output is maintained at substantially a constant value.

When the turbine operates independently of an outside power system, two variables are encountered, first load demand, and, second, steam' ilow demand at the extraction points. Load changes are cared for with no changes in speed, the governing valve and the extraction valves moving in order to maintain the extraction'pres'- sures with practically no corrections from the extraction point regulators. Flow changes `at either of the extraction points will change the pressure at that particular point which will position the control valve, through the action of the regulator at that point, and the change in steam iiow will change the load-carrying capacity of the turbine and consequently its speed. The governor, with its isochronous device, will posi-` tion, not only the governor valve, but also the extraction valves to correct the kload capacity and also the speed without a secondary correction required from the extraction regulator.

When the installation is connected to an outside power system or to other` units in the same plant when the turbine speed is controlled by a characteristic of the system such as a synchronous electrical correction, changes in extraction flow would change the load carried by the turbine. The load regulating device then changes the position of all the valves to enable the unit to carry the same load as before without a secondary resetting action from the extraction pressure regulator.

When the load regulator is used, the pressure responsive to speed changes is constant due to the reasonably constant frequency of a power system. Transformed pressure variations then depend on the pressure from the load-responsive device. An increased load-responsive control pressure will increase the regulating pressure the sam-e amount and move the valves in the closing direction. Therefore, if the steam demand, for example, in the high-pressure extraction line, decreases, the pressure in that line will increase and open the extraction valve and the steam will flow through that part of the turbine and it will pick up load. The low-pressure extraction point will receive more steam, and, due to the increase in its pressure, will open the grid valve, thereby further increasing the turbine load. The increase in load will increase the load-responsive control pressure of the load regulator and the resultant regulating pressure will close all of the valves until the load is reduced almost to its previous value. A certain amount of load change, due to extraction steam changes, will have to be allowed in order to increase the stability of the system.

The transformer, at ||1, is comprised by a body structure ||9 having a cylinder |20 within which is arranged the spinner piston |2| turned by means of a turbine element |22. The cylinder |20 has a pressure port |23 connected to the pressure supply line 2|, an exhaust port |24, and a secondary or control pressure port |25 arranged between the ports |23 and |24. The spinner piston has lands |26 and |21 which just lap the pressure and exhaust ports |23 and |24 with respect to the secondary or control pressure chamber |28 formed by the reduced portion |29 and the interior of the cylinder |20, the chamber |28 being continuously in communication with the control pressure port |25. The upper land |26 has a top pressure abutment face |30 exposed to pressure in the chamber |3| supplied by the branch passage |32 from the control pressure chamber |28. The force of the spring |34 is exerted on the lower end of the spinner piston, the spring force being varied by the mechanism, at |35. The watt-meter device, at ||6, exerts a magnetic force on the core |36 connected to the spinner piston.

Thus, it will be seen that the spinner piston is subject to opposing forces, an increase in output or power results in increase in the upward force or pull of the core |36 resisted by the spring |34 and the consequent upward movement of the spinner piston causes increase in secondary or control pressure and consequently of the force thereof acting on the piston face |30. This increase in control pressure continues until such time as the force thereof acting on the piston face |30 is sufficient to permit the spring |34 to restore the spinner piston valve to its neutral position. In the event of decrease in magnetic pull, the spring |34 causes the spinner piston to move downwardly bringing about a decrease in load-responsive control pressure and the latter will decrease until the force thereof acting on the abutment face |30 is sufficient to compensate for the change in magnetic force and to restore the spinner piston to neutral or cut-off position.

If the turbine is being operated in a speed compensated manner, without the load-responsive device, at ||6, being effective, any changes in load being rst manifested as speed changes and these bringing about readjustments in steam admission and distribution to secure isochronous operation, and, if it is desired to render the loadresponsive device, at IIS, effective, the spring |34 is varied until such time as the pressure in the line I8, and indicated by the pressure gauge |31, is the same as the regulating pressure indicated by the gauge |38, at which time the valve |39 in the line ||8 is opened and the valve 6| is closed so that the lower pressure face 58 of the transformer governor is subject to a fluid pressure, which is a function of the setting of the load control device.

To slow up the motion of any of the operating

mechanisms

21, 29 and 30 in relation to each other or to the transformer governor, at 26, there are shown needle valves |4I providing restricted communication of the regulating pressure line or header 28 with the pressure chambers 18 of the operating mechanisms, air bells or accumulators |42 being in communication with the chambers 18. Likewise, if desired, a similar arrangement of needle valves |43 and accumulatcrs |44 may be used with the steam pressure responsive regulators 3| and 32 and the pressure chambers 18a. of the operating mechanisms 29 and 30, the air bells or accumulators communicating with the chambers 18a. Any or all of these delay devices may be rendered ineffective by suitable opening of the needle Valves |4| and |43, or relative retarding effects thereof may be secured by appropriate adjustment o-f the needle valves.

The improved controlling arrangement for a turbine having one or more extraction points operates as follows: Where the turbine is isolated, it is operated isochronously, or with very little speed change due to load change, the regulating pressure or effect from the governor being applied to the admission valve as well as to each extraction point control valve with the result that load changes are cared for with no changes in turbine speed, all of the valves being adjusted by the regulating pressure furnished by the governor with Whatever adjustment may be required by such pressure to maintain the predetermined extraction point pressure. A change in flow at an extraction point will change the steam pressure thereat, thereby resulting in operation of the associated regulator to adjust its control valve and the resulting change in steam flow will change the load-carrying capacity of the turbine and consequently speed with the result that the governor response will adjust all of the valves to correct the load-carrying capacity and the speed.

The control system contemplates a multiplicity of fluid pressures. Primary pressure, which is a function of turbine speed,is supplied to the governor transformer, at 26, and the latter delivers a regulating pressure to the servo-motors, at 21, 29 and 30. 'I'he bleeder line transformers, at 3| and 32, each delivers a control pressure, dependent upon bleeder line steam pressure to the servo-motors, at 29 or 30. The load control transformer, at Ill, delivers a load-responsive fiuid pressure. As already pointed out, when operating isochronously with the load control transformer, at I I1, isolated from the main governing transformer, the regulating pressure is not a proportional amplification of first or primary pressure but it depends upon load. If there is a change in load, there immediately follows a temporary change in speed and in primary pressure, the change in primary pressure bringing about a change in regulating pressure and the latter change is used to secure such further change or modification of regulating pressure that the admission and extraction valves will be positioned to secure such admission and distribution of steam at the new load condition as to restore the turbine speed toits normal value. When the turbine. drives a. generator tied into an electrical. systemand is subjected to load control, a change in turbine power is accompaniedr by a change in load-responsive control. pressure and thejlatter change .acts on the governing apparatus with the result that changes in. extraction flowy are accompanied by a narrow range of variation in turbine loading capacity; and, as already pointed out, the load capacity .may be altered by suitable adjustment. of the .spring |34 of the load regulator.

- While the invention has been shown in but one form, it will be obvious to those skilled in the artthat it isy not so limited,y but is susceptible of various changesfand modifications without departing fromthe spiritthereof, and it is desired therefore, that only. suchlim'itationsl shall be placed thereupon asare specifically set forth in appended claims.

What is claimed is:

l'. In a steam-operated prime mover having one or more extraction points, an admission valve, a valve for controlling the. flow of steam along the prime mover at each extraction point, aforce-responsive device for controlling each of said valves, and means providing a variable force andy for applying the latter to each of said devices and including means responsive to departure of speed of the prime mover from a predetermined speed incidentto load change for effecting change in said variable force to effect operation of said valves until the predetermined speed is restored at the new load.

2. The combination with a steam turbine having one or more extraction points and provided with an admission valve and ya control valve at each extraction point; of pressure responsive devices for controlling the admission and extraction point valves, a governor providing a reguklating pressure for application to each of the pressure responsive devices, means responsive to load change to effect adjustment of said regulating pressure to adjust the. regulatingpressure to reiect speed correction with changes in load, and means responsive to steam pressures at each extraction `point for securing operation of the associated fluid pressure responsive device to adjust the valve so as to maintain the extraction point pressure substantially constant.

3. In a steam-operated prime mover having one or more extraction points, an' vadmission valve, a valve controllingthe flow of steam along the flow path of the4 primemover at each extraction point, ay force-responsive'device for controlling each valve, means providing a rst, force which varies as a functionof the, prime mover speed, means utilizing said first force for develop-I ing a second force, means for subjectingv all of saidforce-responsive devices to the influence .of said secondforce, said second force developing Ymeans including means for `varying said second -force in response to departure of said first force from a predetermined value and for continuing to vary the second force until said rst force is restored to its predetermined value, means providing a force for each extraction point and dependent upon the steam pressure thereat, and means for applying each last-named force to the device of the associated extraction point valve.

4. In a steam-operated prime mover having one or more extraction points, an admission valve, a valve controlling the flow of steam along the flow path of the prime mover at each extraction point,` a pressureresponsive device-for controlling each valve, means; providing a: force which varies-as a function. of theprime mover speed, means utilizing said, forcev for developing fluidl under pressure, means for subjectingall of said pressure-responsive devices to the; influence ofl said fluidpressure; said fluid pressure developing means` includingVA means for varying said fluidA pressure in response to` departure of said force froma predetermined. value and for continuing` to vary said fluid pressure until said force; is restored to said predetermined value, means providing a fluid pressure for each extraction point and which is dependent uponthe steam pressure thereat, and means forapplying each last-namediluid pressure to the device of the associated extraction point valve.- n

5. In a steam turbine having one or more extraction points;an admission valve;`a valve-for controlling the flowof steam along the turbine at each extraction point; means operated by the turbine for developing fluid under rst pressure varying as afunction of vits speed; means providing; ajsecond pressure and including avalve movable in response to change in firsty pressure to change the second pressure; a device responsive to ,secondi pressure for controlling the admission valve; means providing a fluid pressure dependent upon steam pressure at eachextraction point; a device responsive to the joint effect of the last-named pressure `and second pressure for controlling the corresponding extraction point valve; and means responsive to departure. of first pressure fromf a predeterminedlvalue. in going from one load condition to another to ef,- fect further change in second pressure to an extent sullicient to secure admission of steam to the turbine such that its. speed and theirst pressure are restored .to their first load condition values. 6. In a steam operated prime mover having one; or more extraction points; an admission valve; a valve for controlling the flow of steam alongthe flow pathof the prime mover at'each extraction point; Ymeans operated by vtheprime mover and providing fluid under first pressure which varies as a .function of the prime mover speed; means providing a second fluid pressure and including a valve movable in one direction to increasethe second pressure and in the other direction to decrease the second pressure; means for moving the valve including first, second. and third pressure abutments and a spring; said spring being so disposed that its forcev opposes theforce of pressure applied to` the first abut-` mentand the second andy third abutments being of equal area andarranged in opposed. relation; means. for supplying fluid under first pressure for action on the first abutment; means for supplying fluid under second pressure for'action on the second abutment; means for supplying fluid under second pressure-,for action on thethird abutment and including a passage provided with an orifice; an accumulator communicating with said passage between the. orifice and the third abutment; a device responsive to second pressure for controlling said admission valve; means for developing fluid under pressure dependent upon the steam pressure at each extraction point; `and a device responsive both to the last-named pressureV and said second pressure for controlling the corresponding extraction point valve.

ANTHONY F. SCHWENDNR.