US2095806A

US2095806A - Electric iower plant

Info

Publication number: US2095806A
Application number: US43375A
Authority: US
Inventors: Leo C Frank
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1935-10-03
Filing date: 1935-10-03
Publication date: 1937-10-12
Anticipated expiration: 1954-10-12

Description

Oct. 12, 1937. L. c. FRANK I ELECTRIC POWER PLANT Filed Oct. 5, 1935 INVENTOR L 60 6. Frank.

Patented Oct. 12, 1937 PATENT OFFICE ELECTRIC IOWEB PLANT Leo C. Frank, Irwin, Pa

assimito Westinghouse Electric &' Manufacturing Company,

East Pittsburgh, Pa., syivania Application October 3,

14 Claims.

My invention relates, generally, to electric power plants, and, more particularly, to enginegenerator systems for supplying power to variable loads such, for example, as arc searchlights and 6 the remote control and sound locator apparatus therefor.

In the operation of searchlights and sound-locator control equipment, it is necessary to provide for supplying power to operate the sound- 10 locator equipment and remote control equipment for the searchlight as well as to operate the searchlight. In accordance with the usual custom, the searchlight is not maintained in operation during those periods, commonly referred to as listening periods, when an attempt is being made to detect and locate a sound source such. for example, as an airplane, and, therefore, the only power required is thatnecessary to operate the sound-locator apparatus and the remote control system for the searchlight. Under such conditions, it is extremely important to operate the power plant at a low or idling speed in order to reduce the noise to a minimum so that the sound locator system may function to the greatest advantage. However, during such periods of quiet operation, it is necessary to maintain the voltage of the power source substantially constant at a value somewhere near the value at full load and to provide for automatically maintaining the voltage at the same value, or at some higher value when the load increases as the result of initiating the operation of the searchlight. Furthermore, it is very desirable to maintain the generator voltage substantially constant over its operating range in order that the sound locator and remote control equipment as well as the searchlight will function effectively.

Heretofore it has been the practice to utilize a power plant for operating searchlights and the like in which the engine speed is controlled by means of a mechanical governor only. The low or idling speed is usually obtained by using a load responsive device or relay for rendering the governor ineffective to open the engine throttle for full speed operation and which functions upon a predetermined increase in generator load to release the governor. In some instances voltage regulators, acting upon the generator field winding, have also been used to maintain the generator voltage substantially constant under varying loads and at substantially constant engine speed.

It has been found that power plants of this type possess certain disadvantages when used in connection with an arc searchlight which constia corporation of Penn- 1935, Serial No. 43,315 (Cl. 290-40) tutes a very unsteady load due to the fact that the arcmust be struck in order to start the light,

and the carbons are continually burning away and being fed to the are. In other words the arc tends to lengthen and shorten which produces both current and voltage fluctuations which must be taken care of by the power plant otherwise unsteady operation and flickering of the arc will result. I

When power plants of the type described are used, and especially where a voltage regulator is used to control the excitation of the generator, the engine speed is limited to a predetermined maximum and the regulator tends to maintain the voltage at all times. In nearly all, if not all of the present day are searchlights, the electrode feeding mechanisms operate with a certain amount of time lag or in other words some time is required to reestablish the desired arc condition when it varies. It is desirable, therefore, if the best operation of the light is to be obtained, that the electrode feeding mechanism be pe mitted to function as effectively as possible and that the power plant have such characteristics as to permit this. When a mechanical governor and voltage regulator are used, the power plant actually responds to voltage variations in the arc before the feeding mechanism can respond thereto which only aggravates the condition and makes it more difficult for the feed mechanism to quickly and successfully restore the arc to its proper condition. This results in an unsteady arc and consequently, an inefficient and ineffective light.

In additionto the foregoing disadvantages,

power plants of this type have a limited overload capacity since the engine attempts to maintain a constant speed and can go no higher in order to develop the necessary additional power. When a heavy load is applied, such, for example, as when the arc is struck, the response of the power plant is so rapid that the engine is greatly overloaded and with the voltage regulator attempting to maintain the voltage the overload condition becomes worse which may stall or kill the engine unless a considerable amount of reserve power is provided.

I have found that all of these disadvantages may be successfully overcome by utilizing a power plant in which the voltage is maintained by controlling the engine speed, preferably in accordance with the generator load, and without the use of a mechanical governor except to limit the maximum speed of the engine to a safe value.

-It is, therefore, .the object of the invention, generally stated, to provide a power plant especially adapted for use with searchlight equipment and the like, which shall be of simple and reliable nature, eiiicient in operation and which may be economically manufactured and utilized. A more specific object of the invention is to provide for-automatically controlling the speed of an engine-generator set in accordance with both the load and voltage of the generator to maintain constant generator voltage under varying load conditions.

Another object of the invention is to provide for utilizing electro-responsive means controlled in accordance with the generator voltage for controlling the fuel'control valve or throttle ofan internal combustion engine driving the generator.

A still further object of the invention is to a provide for controlling the speed of an engine driving a generator by means of an electricallyoperated throttle control, in addition to a mechanical governor throttle control for limiting the maximum engine speed, which'functions to maintain a low engine speed at light loads and a higher or normal speed range above a predetermined load value and which regulates the enerator set to produce a substantially constant generator voltage at all loads by means of an electrical governor which is responsive to the generator load and which is controlled by a reg-' ulator responsive to generator voltage.

A still further object of the invention is to provide for regulating the speed of an enginegenerator set by means of an electric throttle control which functions to automatically maintain a predetermined generator voltage at low engine speed on light loads and to automatically vary the engine speed inaccordance with load demand.

' Another object of the invention is to provide for controlling the generator voltage of an engine driven generating unit by speed control of the engine in order to provide relatively slow voltage response on suddenly applied and varying load conditions and to provide'maximum overload capacity with minimum engine capacity.

These and other objects of the invention will become apparent from the following description of a preferred embodiment of the invention taken in conjunction with the drawing, in which the single figure is a diagrammatic view of an engine generator system embodying the principal features of the invention.

In practicing the invention in the preferred .form, the power plant comprises a generator having a drooping load characteristic driven by a suitable internal combustion engine. The generator and engine may constitute a unit or the generator may be mounted on a truck and the truck engine utilized to drive it. The engine may be provided with a mechanical governor to control one throttle valve in order to limit its maximum speed and which does not function in any way to control the engine speed in accordance with the generator load. The speed of the engine is controlled to maintain a desiredgenerator voltage by means of an electric throttle control which functions to control a second throttle valve; The second throttle valve is biased toward its open position by means of a spring and its closing movements are controlled by a torque motor or other suitable electro-responsive device which may be responsive to generator load and which may be adjusted by means of suitable resistors to so regulate the engine speed as to main-.

tain any desired voltage. A regulator responsive to the generator voltage is utilized to further control the torque motor. The regulator is controlled by means of a load relay in order to cause the generator to maintain a predetermined voltage under light load conditions and to effect an increase in voltage when the load increases to a predetermined value, such for example, as when the searchlight is turned on. The torque motor or other electro-responsive device when controlled by the generator load current may be utilized alone to maintain approximately constant voltage. When used in conjunction with the regulator the torque motor need not be responsive to the generator load since its operation may be controlled entirely 'by the regulator.

Referring now to the drawing, there is illustrated an engine generator system for supplyingpower to a variable load such, for example, as a searchlight and the remote control and sound locator apparatus therefor. While the system is illustrated and described in connection with searchlight equipment, it is to be understood that the principles of the invention may be applied to power plants for other uses where it is desired to maintain substantially constant voltage operation at widely varying loads and also under conditions where it is desirable to maintain a lownoise level at certain times.

The searchlight load in this instance is illustrated by the carbon electrodes l0 andv II and the auxiliary load l2 which may comprise the remote control system for the light and the necessary data transmitting systems between the sound locator (not shown) and the remote control station or searchlight. Since the load apparatus IO H and I2 is not a part of this invention, it is deemed unnecessary to illustrate or describe them in detail.

The power plant in general comprises a direct-current generator 13 and an internal comfield winding is connected across the generator armature terminals through a fieldrheostat i 9.

It will be readily understood that the use of a generator of this type makes it possible to obtain a substantially constant generator voltage under light load conditions with low engine speeds resulting in a minimum amount of noise and to maintain the same voltage or any other desired voltage substantially constant over the entire load range of the engine and generator by control of the engine speed.

The engine I4 is provided with a plurality of throttle valves 2| and 22 positioned in the intake passage 23 for controlling the speed of the engine in the usual manner. The throttle valve 2| is controlled by means of a mechanical governor 24, which in this instance functions only to limit the maximum speed of the engine, and does not function in any way to regulate the engine speed to maintain the generator voltage as the load varies. g

The regulation of the engine speed to maintain a desired generator voltage is effected in this embodiment of the invention by means of an electrical throttle control comprising generally an electric governor 25 and a voltageregulator 25. The electric governor 25 may take the form of a torque motor, as shown, having an armature or movable element 21, which is connected to the throttle valve 22 in any suitable manner, such, for example, as by the plate 28 and rod 29. The armature of the torque motor is normally maintained in the position shown by the adjustable springs 3| and 32, and is disposed, when energized, to rotate, through a partial revolution, in a clockwise direction as limited by the stop 33. 'Ihetorque motor is provided with a main field winding 34 and an auxiliary field winding 35, for a purpose to be presently described.

The voltage regulator 25 is of a well-known construction, and is fully described in the United States Patent No. 1,820,712, granted to Walter Schaelchlin, on August 25, 1931. In general, this regulator comprises a magnetic circuit 35 and a movable element 31, which functions in conjunction with the adjustable spring 38 to actuate the movable contact element 39 which vibrates between the adjustable stationary contact elements 4| and 42. The regulator is provided with a movable coil 43, a'stationary main coil 44 and an anti-hunting coil 45.

In this instance, the armature of the torque motor is connected across the generator or load circuit represented by conductors l1 and I5 in series with a torque motor resistor 48, its main field winding 34, the movable and stationary coils 43 and 440i the regulator, a variable resistor 49 and a load resistor 5| The torque motor armature is also connected directly to the load conductor l5 through a variable resistor 52, which is in parallel relation to the main field winding 34, the regulator coils and the resistors 49 and 5|. In order to cause the electric governor 25 to regulate the engine speed in such manner as to maintain the generator voltage, as the generator load varies, its auxiliary field winding 35 is in the nature of a difierential field and is connected across the dlfi'erential series field winding l5 oi the generator through'a variable resistor 53. As will be readily understood, the excitation of the diiferential field 35 is automatically varied in such a manner as the generator load varies as to cause the torque motor armature to adjust itself to the required position to maintain the necessary throttle setting.

The torque motor or electric governor 25, when connected in this manner, is capable 01' functioning alone to maintain the generator voltage at approximately the desired value. However, in this instance, the voltage regulator 25 is utilized to further control the operation of the torque motor to more accurately maintain the desired voltage. As shown, the moving contact element 39 of the regulator is disposed, when in engagement with the stationary contact 4|, to shunt the armature of the torque motor through a variable resistor 54. The vibration of the moving contact element, therefore, regulates the amount of current flowing through the torque motor armature in accordance with the voltage adjustment of the regulator.

anemone The back contact 42 oi the regulator is connected to the shunt field winding l5 oi the generator and when engaged by the moving contact element 33 shunts this field winding through the resistor 54 for the purpose of preventing the overshooting of the generator voltage on removal of load. The anti-hunt coil 45 of the regulator is connected through a suitable resistance 55 across the contact elements 39 and 4| of the regulator and functions in the usual manner.

The setting of the voltageregulator 25 is controlled by the resistors 49 and 5|. The efiectiveness of resistor 5| maybe controlled by the load setting switches 55 and 51 which may be opened or closed in difierent combinations to cause the generator to maintain any desired voltage at different load values. In this particular application, the Searchlight, or other load device, may operate at three difierent ampere ratings, such, for example, as at 150, 200 and 250 amperes. One value of generator voltage for the ampere load may be obtained by closing switches 55 and 51; another value obtained for the 200 ampere load byclosing switch 56 and leaving switch 51 open; and a still further value of voltage obtained for the 250 ampere load by leaving both switches 55 and 51 open.

In this embodiment of the invention, provision is made for causing the generator |3 to maintain one value of voltage under light load operation and a diiierent value of voltage when the load exceeds some predetermined value. This is accomplished by means of the load relay 5| having its operating winding connected across the series field winding |5 of the generator, and its contact members 52 connected to shunt the load resistor 5|. As will be apparent, when the generator load is below the-value for which the load relay 5| is adjusted, a large portion of the resistor 5| is shunted which causes the regulator to maintain a predetermined voltage regardless of the position of the load switches 55 and 51. Upon operation of the load relay, the load switches 55 and 51 become efifective to control the regulator setting The functioning of the torque motor may be controlled or adjusted by the resistors 45 and 52 in its armature circuit, the variable resistor 53 in its field circuit, and the adjustable spring elements 3| and 32 which function to normally bias the throttle 22 toward the open position.

While in this instance the electric governor 25 is rendered responsive to the generator load current by means of its differential field winding 35, it will be apparent that such is not necessary since the regulator 25 may be utilized to control its operation independently oi the generator load if desired. The connections shown,

however, are such as to impose a lighter duty on the regulator since the electric governor 25 inherently functions to approximately maintain a desired generator voltage under all load conditions and the regulator 25 is only required to correct the setting of the electric governor to more accurately maintain the generator voltage at the desired value.

In order to reduce the noise level of the plant to as low a value as possible, provision is also made for driving the cooling fan 53 for the radia tor 54, when such is used, by means of a seperate motor 55, the speed of which may be controlled in accordance with the engine or generator load to give the desired amount of cooling under both light and heavy load operation.

In this instance, the fan motor 55 is connected across thegenerator load conductors l1 and I8 in series with a resistor '66 which functions to control the fan motor speed. The efiectiveness of the resistor 66 may be conveniently controlled I by the load relay iii, the contact members 61 thereof being disposed to shunt the resistor 66 and increase the motor speed when the relay operates at the predetermined load value.

With this arrangement the fan motor 65 operates at a low speed during light load operation, or during the listening period, when the power plant is being used with searchlight apparatus. Aside from the reduction in noise the engine 14 is maintained at its normal operating temperature, providing smoother operation and a warmed up engine which is always in a condition to assume full load. Furthermore, since the engine is always operated at normal temperature, it stays in better operating condition,

and consequently, may be operated on light loads over long periods oftime without mechanical attention.

In view of the foregoing description, it is apparent that the invention provides a greatly improved form of throttle control for internal combustion engines which is of extremely simple and rugged nature and which is capable of functioning to so regulate the engine speed that the generator voltage will be maintained substantially constant regardless of load variations over the entire operating range of the machine. The electric throttle control functions independently of the mechanical governor, and thus requires no readjustment or resetting as the generator load increases. It functions also to maintain a low idling speed of the engine, and consequently a low noise level when the generator load is small, and performs without further adjustment to take care of increased generator load.

It is further apparent that this power plant embodies highly desirable features and advantages not present in power plants now in use. The principle of controlling the generator voltage by speed control of the engine is highly desirable, since it provides a relatively slow voltage response which is a distinct advantage where the power plant is subjected to widely varying and suddenly applied loads and also when the load device is of such nature that it must be permitted to function property without interference on the part of the power plant operation, such, for example, as in the case of an arc searchlight. Control of the generator voltage by controlling the engine speed, as distinguished from a form of control wherein the generator voltage is controlled by a regulator acting upon its field winding, enables the engine to readily pick up a suddenly applied load, such as results when the arc is struck, and furthermore, enables the generator voltage to follow the operation of the arc controlling mechanism and not precede it. The are control mechanism is thus permitted to perform its function without interference from the generator which results in a marked increase in the steadiness of the operation of the searchlight.

illustrated example constitutes a practical embodiment of my invention, I do not wish to limit myself strictly to the exact details herein illustrated, since modifications of the same may be made without departing from the spirit of the invention defined in the appended claims.

I claim as my invention:

1. In combination, a generator, an engine for driving the generator, electro-responsive means for controlling the speed of the engine in accordance with the generator load, and a separate regulator device responsive to the generator voltage for controlling the energization of said electro-responsive means in accordance with the voltage of the generator to maintain substantially constant generator voltage regardless of varia tions in generator load.

2. In combination, a generator, an engine having a fuel control valve for driving the generator, a torque motor connected to actuate the fuel valve and responsive to generator load for controlling the speed of the engine, and a vibratory regulator for further controlling the operation of the torque motor to cause the generator to develop substantially constant voltage as the generator load varies.

3. In combination, a generator, an engine for driving the generator, electro-responsive means for controlling the speed of the engine, voltage regulator means responsive to the generator voltage for controlling said electro-responsive means to maintain a substantially constant generator voltage, and means responsive to a predetermined increase in generator load for causing said voltage regulator means to efiect an increase in the generator voltage.

4. In a power plant, in combination, a generator, an engine for driving the generator, means including a torque-motor for controlling the speed of the engine, and means responsive to a predetermined generator load for rendering said means including the torque-motor efiective to produce a predetermined increase in the generator voltage.

a regulator responsive to generator voltage for controlling the flow of current through the torque-motor, thereby to maintain a substantially constant generator voltage.

6. In a power plant for supplying electrical power to a variable load comprising a direct-current generator, an internal combustion engine for driving the generator, an electrical governor having field. and armature windings for controlling the engine speed to cause the generator to maintain approximately a desired voltage, said field winding being excited in accordance with the generator load and a voltage regulator for controlling the. armature current of the electrical governor, whereby the generator voltage is maintained at a substantially constant value regardless of load variation.

'7. In a power plant for supplying electrical power to a variable load comprising a direct-current generator, an internal combustion engine for driving the generator, an electrical governor responsive to generator load current for controlling the engine speed to cause the generator to maintain approximately a desired voltage, a voltage regulator for further controlling the operation of the electrical governor to provide substantially constant generator voltage, and means responsive to a predetermined increase in generator load for changing the adjustment of the regulator to produce a higher generator voltage, whereby the speed of the engine is so regulated as to cause the generator voltage to be maintained substantially constant at different values over different load ranges.

8. An engine-generator unit for supplying power to a varying load at constant voltage, comprising a generator having a drooping characteristic, an engine for driving the generator, means including a torque motor for controlling the speed 01' the engine, said torque motor being responsive to variations in the generator load to vary the engine speed in accordance with load variation of the generator to approximately ,maintain a desired voltage, and a separate regulator device responsive to generator voltage for controlling the armature current-of the torque motor, thereby to cause the engine speed to be ad- Justed to maintain substantially constant generator voltage under varying load conditions.

9. A power plantfor' supplying power to a variable load comprising a generator, an internalcombustion engine for driving the generator, said engine being provided with a plurality of fuel control valves,a speed-responsive governor for controlling one of said valves to limit the maximum speed of the engine, electro-responsive means jointly responsive to the generator load current and voltage for controlling the other valve, and means for adjusting said electro-responsive means to cause the generator to maintain different predetermined voltages regardless of load variation.

10. A power plant for supplying power to a variable load comprising a diilEerentially-compounded generator, an internal-combustion engine for driving the generator, said engine being provided with a plurality of fuel control valves, 9. speed-responsive governor for controlling one of said valves to limit the maximum speed of the engine, electro-responsive means jointly responsive to the generator load current and voltage for controlling the other valve, means for adjusting said electro-responsive means to cause the generator to maintain different predetermined voltages regardless of load variation, and load responsive means for controlling the functioning oi the electro-responsive means, thereby to cause the generator to maintain one voltage below a predetermined load and another voltage above said predetermined load.

11. A power plant for supplying power to a.

variable load comprising, a generatorhaving a drooping characteristic, an engine for driving the generator, electro-responsive means Jointly responsive to the voltage for controlling the speed of the engine to maintain a desired generator voltage, and means responsive to a predetermined generator load for causing said electro-responsive means to function to increase and maintain a difl'erent generator voltage.

12. A power variable load comprising a diil'erentially-compounded generator, an engine for driving the generator, an electro-responsive device ior controlling the speed of the engine in accordance with the generator load, regulator meansresponsive to the generator voltage for controlling the electroresponsive device, resistor means for varying the calibration oi the electro-responsive device and regulator means to determine the generator voltage, and relay means for controlling the eil'ectiveness of the resistor means, said relay means being disposed to normally render the electro-responsive device and regulator means effective to maintain one predetermined generator voltage and operable at a predetermined generator load for rendering saidelectro-responsive device operable to maintain another predetermined generator voltage.

13. A power plant for supplying power to a variable load comprising a generator, an engine for driving the generator, a torque motor for controlling the speed having difl'erentially-related field windings one of which is responsive to the generator load current to increase the engine speed as the load increases, a regulator operable to shunt the armature oi the torque motor and having an operating coil connected in series with the torque motor, and variable resistance means for controlling the functioning or the regulator to determine the generator voltage. 1

14. A power plant for supplying power to a variable load comprising a generator, an engine for driving the generator, a torque motor for controlling the speed of the engine, said torque motor having dlflerentially-related field windings one 01 which is responsive to the generator load current to increase the engine speed as the load increases, a regulator operable to shunt the armature or the torque motor and having an operating coil connected in series with the torque motor, variable resistance means for controlling the functioning oi the ulator to determine the generator voltage, and means responsive to generator load current for varying the effectiveness of the resistor means, whereby the generator maintains difi'erent voltages dependent upon the load.

LEO C. FRANK.

or the engine, said torque motor generator load current and plant for supplying power to a