US1948752A

US1948752A - Automatic torque for gas electric cars

Info

Publication number: US1948752A
Application number: US527270A
Authority: US
Inventors: Newell L Freeman; Norman W Storer
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1931-04-02
Filing date: 1931-04-02
Publication date: 1934-02-27
Anticipated expiration: 1951-02-27

Description

Feb. 27, 1934. N. L. FREEMAN Er AL 1,948,752

AUTOMATIC TORQUE FOR GAS ELECTRIC CARS Filed April 2, 1931 2 Sheets-Sheet l INVENTORS fl ewell L .Freemgn and Alarman W. Szoren ATTORNEY Feb. 27, 1934. FREEMAN ET AL AUTOMATIC TORQUE FOR GAS ELECTRIC CARS Filed April 2, 1931 2 Sheets-Sheet 2 A/orman W. Szorer. BY g; 6 WATTJWEU WITNESSJES Patented Feb. 27, 1934 1,948,752 I AUTOMATIC TORQUE igoa GAS ELECTRIC CAR Newell L. Freeman and Norman W. Storer, Pittsburgh, Pa., assignors to Westinghouse Electric and Manufacturing Company, a corporation of Pennsylvania Application April 2, 1931. Serial No. 527,270

11 Claims.

Our invention relates to electric control means for power systems utilizing internal-combustion engines as prime movers and electric motors as work-performing units.

Electrical transmission for commercial oilelectric or gas-electric railway vehicles includes, in addition to the internal-combustion-engine prime mover, one or more generators and two or more traction motors, usually of the series type. The input to motors of this type is a function of speed and applied voltage. Overloading of an internal-combustion engine, as is well known,

will cause it to run at a. lower speed or stop it entirely. To prevent this undesirable condition, 15 some protective means is necessary.

By one method heretofore known, a diilerential field for reducing the main generator voltage in response to generator load current was used, the differential field being mounted either on the 80 pole pieces of the exciter for the generator or the pole pieces or the generator. This type of equipment is influenced by the condition of the battery, which must necessarily be used on a gas-electric car, is influenced by temperature 26 conditions and is very unsatisfactory for the operation of auxiliaries, such as the auxiliary battery-charging generator, compressor motor, lights, blower motor, etc. Furthermore, this type of equipment does not operate to charge the bat- 30 tery from the main generator during idling.

Such unsatisfactory operation follows, of necessity, from the fact that the auxiliaries are operated from the main generator, their operation thus being dependent upon engine and car speed 86 simultaneously.

It is an object of our invention to eliminate the foregoing defects and to provide for improved operation of auxiliaries and to improve the loading characteristics of the internal-combustion engine, in general, by limiting the torque load impressed on the engine to the torque the engine is capable of delivering for a selected throttle opening.

A more specific object of our invention is to provide for operating the generator of a power system as a motor to start the engine.

Another object of our invention is to provide for utilizing the generator of a power system for charging the battery when the engine is idling.

A further object of our invention is to automatically provide for the most eiTective loading of an internal-combustion engine for a given throttle setting, during variations of tractive effort.

It is an object of our invention to automatically vary the load on an internal-combustion engine to correspond to the torque available, whereby the engine speed will be retained at its rated value for a given throttle setting.

An object of our invention is to vary the load of an internal-combustion engine to correspond to the power the engine is capable of developing at a given speed with the throttle opening set for such speed.

A further object of our invention is to vary the field excitation of a generator driven by a prime mover in response to the speed of the generator, to maintain the speed of the prime mover constant at the speed selected for the prime mover.

It is also an object of our invention, generally stated, to provide a power system that shall be simple and efiicient in operation and readily and economically manufactured.

Other and more detailed objects will become readily apparent from a study of the following specification, when taken in conjunction with the accompanying drawings, in which:

Figure 1 is a schematic diagram of a part of my power system, showing the prime mover, the main generator, the auxiliary generator, the battery, the compressor motor, and some of the control equipment; and

Fig. 2 is a schematic diagram of the remander of the power system, showing the driving motor and further control equipment.

Referring now to the drawings, E designates, generally, an internal-combustion engine of a type suitable to be utilized as the prime mover of a power system. In this particular instance, an engine, having an ignition system I, is illustrated, but it is to be understood that an oil engine or other variable-speed prime mover, which may be operated at low speed when the main load is removed, such, for example, as a Diesel engine, may be substituted.

As will be observed, a generator G and an auxiliary generator or exciter A are mounted on the engine shaft D. As illustrated, the generator G is provided with a series field winding 31, an interpole or commutating field winding 92 and a field winding 35, while the exciter or auxiliary generator A is provided with a shunt field winding 58 and a series field winding 192.

In power systems, particularly power systems utilized for propelling vehicles, it is often desirable to provide auxiliary motors for operating auxiliary apparatus, such as compressors and the like. In this showing of the invention, only one auxiliary motor C is illustrated and thereinafter it will be referred to as the compressor motor.

When the power system is utilized for propelling a vehicle and the like, two

driving motors

1 and 2 are usually provided. The motors l and 2, as illustrated, are of the series type and disposed to be connected in either series circuit relation or parallel circuit relation.

Since, in this particular embodiment of the invention, an internal-combustion engine, provided with an ignition system I, is illustrated, the control means necessarily comprise a spark lever (not shown) and a throttle lever T. As may be readily understood, the spark lever may be disposed for controlling the ignition I in a well known manner, whereas the throttle lever T may be disposed to control the supply of fuel to the engine. The manner of controlling the throttle lever will be discussed more in detail hereinafter.

The electrical control system for such electrical equipment as lights, brakes, the ignition system I, and some other electrical units usually found on gas-electric vehicles, is brought in cooperative relation with the elements of our invention in any desirable manner. Since such additional electrical equipment does not constitute a part of our invention and, if given, would only complicate the present diagram, a detailed description and diagrammatic showing thereof is thought not to be necessary in this disclosure.

In order to start the engine E, the generator G is operated as amotor to turn over the engine. As shown, a storage battery B is provided for operating the generator G as a motor, and the auxiliary apparatus when desired.

Assuming now that it is desired to cause the power system to function to charge the battery. To start the operation of the engine E, switches 3 and 4 are closed and the starting controller segment S, or the starting push-button switch 9, is moved to circuit closing position. Furthermore, the manually operable reversing controller R is moved to the engine only" position, so that the contact fingers on

conductors

5, 7, and 18 are bridged (see Fig. 2) by the segment 6. As a result of these operations, a circuit is established from the positive terminals of the battery B through conductor 5, controller segment 6 of the manually operable reversing controller R, conductor 7, either the starting controller segment 8 or the starting push-button switch 9, conductor 10, the actuating coil of the generator contacter 14, conductor 15, the contact members 16 of the control relay RV, and conductor 17 to the negative terminal of the battery B.

After the operation of the generator contactor 14 a circuit is established from the energized controller segment 6 through conductors l8, l9 and 20, contact members 21 of the generator contactor 14, the actuating coil oi. the field contactor F and conductor 22 to the negative terminal of the battery. The field contactor establishes its own holding circuit from the energized conductor 19 through the contact members 23, and also establishes a circuit for the other generator line contactor 26. This latter circuit may be traced from the energized conductor 10 through the contact members 24 of the field contactor F, conductor 25, the actuating coil of the generator line contactor 26 to the negatively energized conductor 15. After the operation of both the

generator contactors

14 and 26 the battery B is connected across the generator armature terminals and this circuit may be traced from the positive terminal of the battery B through the switch 3, conductors 27 and 28, the contact members 29 of the generator contactor 26, conductor 30, the

armature of the main generator G, the series field 31 conductor 32, the contact members 33 of the generator contactor 14, conductor 34, switch 4 and conductor 22 to the negative terminal of the battery.

The circuit for the field 35 of the generator G is also established by the operation of the field contactor F. This circuit may be traced from the positively energized conductor 27 through the field winding 35 of the main generator G, the conductor 36, either conductor 37 and switch 38 or

resistor sections

39, or 39 and 40, depending on the position of the switch 38, conductor 41, contact members 42 of the dynamic control relay RV, conductor 43, resistor section 44, conductor 45 and contact members 46 of the field contactor F to the negatively energized conductor 34.

The dynamic control relay RV consists of a powerful magnetic circuit, excited by a stationary coil 68, a stationary armature 207, a movable armature 208, and a movable coil 67 connected in series circuit relation to the windings of the stationary coil. The movable coil 67 is disposed in the air gap of the relay, the relay being so constructed that a substantially uniform magnetic field is produced over the entire air gap and the range of movement of the movable coil. Movement of the movable coil, therefore, does not affect the calibration of the relay, since the magnetic field is substantially constant at any position of the movable coil, thereby producing a relay which has a high sensitivity, that is, will pull in and drop out with very small fluctuations of current in the stationary coil and particularly the movable coil. The movable coil is mounted on the movable armature 208 which is pivoted on knife edge bearings 209 and is biased by a long spring 210 to oscillate in a counterclockwise direction. When the dynamic control relay RV is not energized, it will be in the position shown in Fig. 1.

The two coils of the control relay RV are at all times connected across the armature tenninals of the auxiliary generator A, through a variable resistor, the resistance value of which may be varied in a manner discussed more in detail hereinafter. If the coils of the dynamic control relay RV are connected across the armature terminals of the auxiliary generator, it is apparent that for any given excitation of the auxiliary generator, the operation of the relay RV will be in response to the voltage, and in consequence the speed of the auxiliary generator A. With variations of the voltage of the auxiliary generator A, the movable armature 208, pivoted at 209, will move in a clockwise direction, first interrupting the circuit at the contact members 16, then interrupting the circuit at the contact members 42, thereafter moving the contact members 107 to circuit closing position and then moving the contact members 61 to circuit closing position.

The operation of the control relay RV, as influenced by the control circuits hereinafter discussed, is such that

contact members

16 and 42 are either in closed circuit position or open circuit position, whereas contact members 107 when first moved to circuit closing position move relative to each other at a rate of as much as 7 to 10 times a second. When the energization of coil 67 increases above a predetermined amount, vibration at the contact members 107 ceases and these contact members are moved to permanent circuit closing position. With a further increase of the voltage of the auxiliary generator A, the

contact members 61 move to circuit closing position and the control is such that these contact members first vibrate relative to each other at a speed of about 100 times a second. This speed of vibration slowly decreases with further increase of voltage of the auxiliary generator until eventually the contact members 61 are sealed into circuit closing position, whereupon the dynamic control relay RV becomes inoperative to further affect a controlling action on the electrical control system hereinafter described more in detail.

The circuit for the coils 6'7 and 68, assuming that the engine E is idling so that the resistance value of the resistor in series circuit relation with the coils 67 and 68 is a minimum as determined by the position of the throttle mechanisms, may be traced from the positive terminal of the auxiliary generator A, through conductors 2'7, 53 and 62, control segment 63 of throttle mechanism 12,

conductors

155 and 156, contact members 157 of the throttle mechanism 1.1, conductors 156 and 161, contact members 145 of the throttle mechanism 13, conductor 162, resistor section 159, conductor 66, movable coil 6'7 and stationary coil 68 of the control relay RV, conductor 69, resistor section 70 and conductor 71 to the negative terminal of the auxiliary generator A. For a more detailed description of the dynamic control relay RV, reference should be had to the United States patent to W. Schaelchlin No. 1,684,- 151.

The switch 38 may be disposed in the position shown or else connected to shunt either resistor section 39 or both the

resistor sections

39 and 40. It is thus obvious that the rate of charge given to the battery may be manually controlled by the position of the switch 38.

With the starting circuit for the main generator G completed, as above explained, the main generator G will operate as a motor starting the engine E. During the cranking operation the magnetic effect of the series field windings 31 of the main generator G is cumulative with the magnetic effect of the field winding 35, thereby producing the necessary high torque to facilitate the starting of the engine E. After the engine E has started to operate on its own power, the throttle lever T still being in the idling position as above explained, the generator G will supply energy to the storage battery B over the starting circuit above explained. The battery will thus, during the idling operation, be charged from the main generator G. While the machine G is operating as a generator, the magnetic effect of series field windings 31 is differential with respect to the winding .35 and, for any variations in the load current on the main generator G, the voltage of the generator is kept low enough by the series field 31 to prevent an excessive charging of the battery B. The charging rate of the main generator G may be manually controlled by the knife switch 38 controlling the combined resistance value of the

resistor sections

39, 40, 44 and 44.

On gas-electric cars, it is usually very desirable to have available at all times a source of air pressure of a constant value for operating the brakes, the whistle or other signalling device, the throttling mechanism for the internal combustion engine, etc. In our particular invention, a tank K is shown for storing air under pressure and a pump P, driven by a compressor motor C, is used to maintain a given pressure in tank K. To assure a constant pressure in the tank K, a pressure responsive governor 84 is provided for controlling the operation of the compressor motor C.

By our system of control, the compressor motor C may be operated either from the auxiliary generator A or from the main generator G. When the main generator G is not loaded, the gas electric car standing or else coasting down a grade, it may be desirable to operate the pump P by themotor C if the pressure in tank K decreases to a predetermined value. To operate the compressor motor C from the main generator G, the manually operable reversing controller R is moved to bridge the contact finger 75 and the contact fingers on

conductors

18, 5, '72, 98 and 100. During normal operation, if the push button switch 9 was used to start the system, the reversing controller R is usually moved to the positions just stated immediately after the engine drives the generator G because otherwise it would be necessary to hold the push button switch 9 in circuitclosing position to continue any useful operation of the main generator G.

Assuming that the reversing controller R is moved to the full forward position as above explained and that the pressure in the tank K is below a predetermined value, a circuit is then established from the positive terminal of the battery B, through conductor 5, controller segment 6, conductor 18, contact fingers 75 bridged by the controller segment 76, conductors '77 and '18, contact members 79 of the generator contaotor 14, conductor 80, actuating coil 81 of the compressor motor relay CM, conductor 82, contact members 83 on the pressure responsive governor 84, conductors 86 and 87, to the negatively energized conductor 17 leading to the battery 13. It will be noted that the pressure responsive governor 84 is supplied with air under pressure from tank K through the conduit 85.

After operation of the compressor motor relay CM, a circuit is established for the compressor motor C which may be traced from the positive terminal of the generator G, through conductor 36, contact members 29 of the generator contactor 26, the armature of the compressor motor the series field winding 88 of the compressor motor, conductor contact members 90 of the CM, conductor 91, series field winding 92 to th negative terminal of the main generator G. The magnetic effect of the windings 92 is always additive with respect to the magnetic effect of winding 35, thereby increasing the voltage of the main generator G in proportion to the lead added by the o eration of the compressor motor 0.

Movement of the reversing controller R as above explained connects the contact finger on the conductor 72 to the positively energized controllersegment 6, thereby completing a circuit for the generator contactors i4 and 26 which is independent of the position of the push button switch 9, or the position of segment 8 of the starting controller. This circuit may be traced from controller segment 6, through con- 72, T3 of the throttle controller TC, conductor 74 to conductor 25, contact men 24 of the field contactor F and the actuating coil or the generator contactor 14 in parallel circuit relation with the actuating coil of the generator contactor 26, conductor 15, contact member 16 of the dynamic control relay RV to the negatively energized conductor 17. r

If any one, or all, or any combination of the

throttle mechanisms

11, 12 and 13 are operated thereby opening the throttle T to any position other than the idling position, the engine E will adjust its speed to the new throttling opening and in consequence the voltage of the auxiliary generator will build up to some value higher than the value it has during the idling operation, and in consequence, the control relay RV will operate interrupting the circuit for the generator contaotors 14 and 26 at the contact members 16. This operation obviously disconnects the main generator G from the battery B and the main generator is then free to operate the

traction motors

1 and 2 in a manner described more in detail hereinafter. From the operation of the control relay RV, it will be obvious that the battery charging will be shifted from the main generator to the auxiliary generator with a rise of voltage of the auxiliary generator and will also be automatically shifted back from the auxiliary generator A to the main generator G when the voltage of the auxiliary generator, for any given excitation of that generator, decreases below a predetermined value.

If it is desired to start the normal operation of the gas-electric car, it is, of course, necessary to shift the throttle controller from the off position shown in Fig. 2 successively from the first to the sixth positions and thereafter to shift the selector controller S from the off position shown through the first and second positions. To simplify the discussion of the various operations effected by the movement of the throttle controller TC, the selector controller S and the automatic operation of the dynamic control relay RV, let it be assumed that the pressure in tank K is of the desired value so that the compressor motor C will not be operated by the main generator G nor by the auxiliary generator A.

If the-controller TC be moved to the first position, the controller segment 73 disengages the contact fingers on the conductors '72 and 74, thereby disconnecting the main generator from the battery, by interrupting the independent energizing circuit for the

generator contactors

14 and 26 at '73. Movement of the controller TC also establishes a circuit from the positively energized controller segment 6 of the manually operable reversing controller R, through conductor 18, contact fingers 75 bridged by the controller segment 76, conductor 77, controller segment 93, of the throttle controller TC, conductors 94, and 96, actuating coil 97 of the auto matic reversing controller AR, conductor 98, controller segment 99 of the manually operable reversing controller R, conductors 100 and 87 to the negatively energized conductor 17. A circuit is also established from the positively energized controller segment 93, through conductor 101, controller segment 102 of the selector controller S, conductor 103, actuating coil 104 and resistor 105 of the voltage regulating contactor V, in parallel circuit relation, the conductor 106, contact members 107 of the dynamic control relay RV, conductor 17, conductor 22, switch 4, conductor 34, contact members 46 of the field contactor F, charging resistor 52, contact members 51 and series coil 50 of the reverse current relay RC and conductor 49 to the negative terminal of the auxiliary generator A.

The automatic reversing controller AR is shown in an energized position in Fig. 2, and the various controller segments and contact fingers on the automatic reversing controller will be in the position illustrated in Fig. 2 and will remain in that position once coil 97 has been energized, even though coil 97 should subsequently be deenergized; that is, the automatic reversing controller will not change its position until the actuating coil 182, controlling the reverse movement 01' the car, is energized. In the circuits just traced for coil 97, it is, of course, obvious that conductor 95 is positively energized and conductor 98 is negatively energized, and that the controller segment 102 of the selector controller S is positively energized. A circuit is thus established for the series contactor SC which may be traced from the positively energized controller segment 102, through

conductors

127 and 128, back contact members 129 of the series contactor SC, the actuating coil 130, conductor 131, back contact members 132 of the parallel contactor P1, conductor 133, controller segment 134 of the automatic reversing controller AR to the negatively energized conductor 98. Since conductor 95 is positively energized as above explained, a holding circuit is established for the series contactor SC, through the conductor 135 and a pair of contact members on the series contactor SC.

By the operations above discussed, the main generator G is connected across the

traction motors

1 and 2 connected in series circuit rela-' tion, and this circuit may be traced from the positive terminal of the main generator G, through conductor 30, conductor 108, the armature of the traction motor 1, conductor 109, controller segment 110 of the controller AR, conductor 111, series field winding 112 of the traction motor 1,

conductors

113 and 114, controller segment 115 of the controller AR, conductors 116 and 117, main contact members 118 on the series contactor SC,

conductors

119 and 120, the armature of the traction motor 2, conductor 121, controller segment 122 of the controller AR, conductor 123, series field winding 124 of the traction motor 2, conductor 125, controller segment 126 of the controller AR and conductor 91, commutating pole field windings 92 to the negative terminal of the main generator G. The gas-electric car will thus start operating at a reduced speed.

The

throttle mechanisms

11, 12 and 13 are electrically controlled by the throttle controller TC. As previously explained, the controller segment 6 is positively energized. A control circuit for the throttle mechanism 13 may thus be traced from the controller segment 6, through

conductors

18, 19 and 135, controller segment 136, conductor 137, actuating coil 203 of the pneumatic throttle control mechanism 13, conductor 139, back contact members of the compressor motor relay CM to the negatively energized conductor 87.

The pneumatic throttle control mechanism 13 is, in every particular, like the throttle control mechanism 11 shown in section in Fig. 1. The throttle mechanism includes a pair of oppositely disposed valves 199 mounted on a valve stem 196, spring biased to a given position by a spring 194. To operate the throttle lever T, the

throttle mechanisms

11, 12 and 13 are provided with

air engines

141, 142 and 143, respectively. Each of these air engines is provided with a piston 198, spring biased to a lowermost position by a spring 197. These air engines are provided with apertures 193 for discharging the air above the piston, thereby preventing interference with the operation of the throttle T when any one, some,

or all of the

coils

201, 202 and 203 are energized. Furthermore, the chambers of each of the

pneumatic throttle mechanisms

11, 12 and 13 are provided with apertures 195 for discharging the air from the air engines when the throttle mechanisms are in their inoperative position.

As coil 203 is energized, air is admitted from the tank K through the conduit 140 to the air engine 143, and in consequence, the piston in that engine moves upwardly, breaking the circuits at the contact members 144 and 145 and also moving the lever 146 about a pivot 147. The lever 148 is similarly pivotally mounted at 147 and the U -shape member 149 is pivotally mounted on levers 146 and 148 at 150 and 151, respectively It is thus obvious that by a proper selection of the position of the pivot points 150 and 151 and by a proper selection of the lengths of lever arms 146 and 148, the angular movement of the throttle lever T may be varied in successive stages by the successive selective operation of the air engines.

During the movement of the throttle controller TC from the first to the sixth position, the

air engines

143, 141, 141 and 143, 142 and 143, 141 and 142, and. 141, 142 and 143, respectively, are caused to operate, thereby opening the throttle in six successively larger steps. Since the engine will have a given speed for each throttle opening, the voltage of the auxiliary generator will have a fixed value for each speed. Any slight variations of speed will cause a variation of the voltage of the auxiliary generator A and such variations in voltage will cause the control relay RV to effect its successive control operation.

It should be noted that the excitation of the shunt field 58 of the auxiliary generator A takes place through the resistor segment 56. This circuit may be traced from the positively energized conductor 27, through conductor 53, either conductor 62, controller segment 63 of the throttle mechanism 12 to conductor 154 or conductor 152, contact members 153 of throttle mechanism 11 to conductor 154, through resistor section 56, conductor 57, shunt field windings 58, conductor 59,

contact members 51 and series winding 50 of the reverse current relay RC and conductor 49 to the negative terminal of the auxiliary generator A. From the circuit just traced, it will be apparent that as long as either the air engine 141 or the air engine 142 is in inoperative position, the resistance value in series with the shunt field of the generator A will not be affected. It is only after the controller TC has been moved to the fifth and sixth positions that a variation of the resistance value in series with the shunt field winding takes place.

The operation of the air engine 143, however,

does decrease the. resistance value of the combined resistors in series with the field winding 35 of the main generator G. This is accomplished by the operation of the dynamic control relay RV. The circuit for the dynamic control relay RV may be traced from the positively energized conductor 27, through conductor 53, conductor 62, controller segment 63 of the throttle mechanism 12, conductor 155, conductor 156, contact members 157 operated by the piston of the air engine 141, conductor 156, resistor section 158, resistor section 159, conductor 66, the movable coil 67, and the stationary coil 68, respectively, of the control relay RV, conductor 69, resistor section and .conductor 71 to the negative terminal of the generator A. It is thus obvious that if the voltage of the generator A exceeds a predetermined amount, the relay RV will be caused to operate despite the fact that resistor sections 158 and 159 are connected in series circuit relation to the coils 67 and 68. The initial movement of the armature 208 causes the interruption of the circuits for

contactors

14 and 26 as above explained.

To provide for the proper charging of the battery B by the auxiliary generator A a shunt coil 48 of the reverse current relay RC is connected across the terminals of the auxiliary generator A. As the voltage of the auxiliary generator A builds up, the reverse current relay RC is actuated, closing the contact members 51. The circuit for this relay may be traced from the positively energized conductor 27, through conductor 47, shunt coil 48 of the reverse current relay RC and conductor 49 to the negative terminal of the auxiliary generator A. Operation of the reverse current relay RC establishes a circuit from the positive terminal of the auxiliary generator A, through conductor 27, switch 3, battery B, conductor 22, switch 4, con-.- ductor 34, contact members 46 of the field contactor F, charging resistor 52, contact members 51 of the reverse current relay RC, series coil 50, and conductor 49 to the negative terminal of the auxiliary generator A. While the battery is being charged, the magnetic effect of

coils

48 and 50 is additive. Before the operation of the reverse current relay, the shunt field windings 58 of the auxiliary generator A are energized from the battery by a circuit which may be traced from the positive terminal of the battery, through switch 3, conductors 27, '53 and 152, contact members 153 of the throttle mechanism 11, conductor 154, resistor section 56, conductor 57, shunt field windings 58, conductor 59, charging resistor 52 and contact members 46 of the field contactor F to the negatively energized conductor 34.

The reverse current relay prevents discharging of the battery through the auxiliary generator. If at any time during the operation of the system the voltage of the auxiliary generator decreases below a predetermined value so that the battery begins to discharge through the armature of the generator A, the series coil acts differentially with respect to the voltage coil. When the discharge current is at some low predetermined value, the contact members 51 are caused to open, thus disconnecting the battery from the power system.

After operation of the reverse current relay RC, the shunt field windings 58 are energized from the auxiliary generator A by a circuit extending from the positively energized conductor 27, through

conductors

53 and 152, contact members 153 of the throttle mechanism 11, conductor 154, resistor section 56, conductor 57, shunt field windings 58, conductor 59, contact members 51 and series coil 50 of the relay RC and conductor 49, to the negative terminals of the generator A.

The charging resistor is of a very low resistance value,--a fraction of an ohm. By connecting the switch elements 51 of the reverse current relay RC between the charging resistor and the auxiliary generator, and the shunt field across the battery through the resistor as shown in Fig.

1, the shunt field windings 58 are battery excited of the generator A rises, causing an interruption of a circuit for the generator field 35 at the contact members 42. One of the excitation circuits for the field 35 may, therefore, be traced from the conductor 27, through the field winding 35, conductor 36,

resistor sections

39, 40, 44 and 44, conductor 45, charging resistor 52, contact members 51 and series coil 50 on the reverse current relay RC and conductor 49 to the negative terminal of the generator A. The other circuit for the field Winding 35 extends from conductor 27, through the field winding 35, conductor 36, resistor section 16-, to the negative terminal of the generator A.

With a further rise of the engine speed to conform to the throttle opening, a circuit for the regulating contactor V is closed at the contact members 107. This circuit may be traced from the positively energized controller segment 102 of the selector controller S, through conductor 103, actuating coil 104 of the contactor and resistor section 105 in parallel circuit relation, conductor 106, contact members 107, conductor 17, conductor 22, switch 4, conductor 34, contact members 46 of the field contactor F, charging resistor 52 through the reverse current relay RC to the negative terminal of the generator A. It will be noted that the operation of the regulator contactor V establishes a shunt circuit for the resistor section 164, thereby decreasing the resistance value in series with the field 35 of the main generator G.

With increased excitation of the field winding 35 of the main generator G, the main generator loads the engine and, since the throttle opening remains fixed, the speed of the engine decreases and the voltage of the auxiliary generator decreases. The total result of this variation is that the circuit at the contact members 107 for the regulator contactor V is interrupted and the resistor section 164 alone is again inserted in series with the field winding 35. It should be noted in this connection that the resistance value of the resistor section 44 is large relative to the resistance value of the resistor section 164, so that the repeated operation of the regulating contactor V provides the main control of the excita tion of the field winding 35. When the resistor section 164 is in series circuit relation with the field winding 35, the generator G, being less heavily excited, is unloaded and, in consequence, the speed of the engine immediately increases. Since the regulator contactor V controls the excitation of the field of the main generator G while the dynamic control relay RV controlling the operation of the contactor V is responsive to the voltage of the auxiliary generator A, it is obvious that the control system might be subject to hunting unless some provision be made to anticipate the change. Hunting is to be expected because a speed change affects only the voltage of the auxiliary generator. This voltage then operates the sensitive dynamic control relay RV; next the regulator contactor V opens or closes and the field excitation of the main generator begins to change. Eventually, the field value is changed suificiently to reverse the initial speed change. In all, considerable time elapses between the registering of the chosen speed and the final reversing of the initial speed change causing it. It is thus apparent that the time lag needs to be overcome by anticipating it and such is accomplished by changing the setting of the relay RV, as soon as the regulator contactor V closes or opens. The resistance value of any one of the resistor sections of the resistor O is relatively high and in consequence, does not materially aflect the excitation of the field 35 as has been previously explained, but the resistance value of the resistor section 164 ranges from about an ohmand-a-half to two-and-one-half ohms, while the resistance value of the resistor sections and 163 ranges from about two-tenths of an ohm to about four-tenths of an ohm. The important feature about these values is not their absolute values, but rather their relative values. I do not wish to be limited to resistors having the stated resistance values. The conductor 69 is connected to the resistor section 163 at such a point that hunting will be prevented. In the particular embodiment shown, representing an actual installation, the resistance value of the resistor section 70 is about .05 of an ohm. If for a given throttle opening and main generator excitation the speed of the engine rises as above explained, the voltage of the auxiliary generator rises, causing. the operation of the sensitive control relay RV, and in consequence, the regulator contactor V operates to shunt the resistor section 164. Since the resistance value of the resistors 163 and 70 combined is only about one-fourth that of the resistance value of the resistor 164, most of the current traversing the field windings 35 passes through the resistor section 70. The resistance drop in the resistor section 70 will thus be several volts, depending upon the size and character of the field windings of the main generator G, and in consequence, the voltage across the coils 67 and 68 will be immediately decreased. The immediate effect of this is as though some of the'reduction in engine speed which is expected to take place has already taken place, that is, the use of the resistor section 70 of a low resistance value in circuit relation with both the field winding 35 and the operating coils of the relay RV in conjunction with the operation of the regulator contactor V, anticipates the speed change. By a proper selection of the resistance value of the resistor 70, the control can be quickened to a point where it is entirely self-energized and there are in fact no speed pulsations. For its source of energy, the control relay RV and in consequence the regulator contactor V, depends on speed although it originates its own impulses.

The relation between the proper time of the closing of the switch elements 165 or of the opening of these switch elements (main generator field strength), and the load of the main generator, would appear to have no connection with the regulating system. Such, however, is not the case, for if the average field strength of the main generator is too low to cause adequate loading, the engine speed will increase. A slight increase in engine speed increases the voltage of the auxiliary generator A. The pulsating operation of the regulating contactor V then takes place between two slightly higher voltage values of the generator A. The ultimate result is that the switch members 165 stay closed a longer interval of time and open a smaller percentage of the time. This will raise the average value of the field excitation for the main generator. A rise in the field value of the main generator will thus increase the loading and hold the engine to a speed slightly higher than before.

The regulating contactor is provided with a condenser 166 connected in parallel circuit relation to the contact members or switch elements 165. The capacity of the condenser 166 is of a small value, being just sufficient. to store some 80- coils of the relay RV may then be traced from y ductor 53, conductor 62, controller segment 63 tion,

air engines

142 and 143 are caused to operconsiderably higher than the sum of the resisttroller segment 63 of the throttle mechanism 12,

- l and 160, 158, 159 and 160, and 65, respectively, in

electrical energy, thereby permitting the separation of the contact members 165 without sparking. When the full surge of the interrupted field circuit would tend to take effect at the contact members 165, these contact members have separated a sufficient distance that arcing can no longer take place across them. During normal operation, the switching operations at the contact members 107 and 165 take place at the rate of about 7 to 10 times a second.

The control operations of the control relay RV above discussed take place for all the positions selected for the throttle controller TC. To accelerate the car to full speed, the throttle controller must be shifted from its first to its sixth position. If the throttle controller be shifted to the second position, a circuit is established for the throttling device 11. This circuit may be traced from the positively energized controller segment 136, through conductor 200, actuating coil 201 of the throttling device 11, conductor 139, back contact members of the compressor motor relay CM to the negatively energized conductor 87. The instant the air engine 141 operates the contact members 157 and 153 are moved to open circuit position and in consequence the resistance value of the circuit including coils 67 and 68 is increased by the insertion of the

resistor sections

160 and 159 in series circuit relation with the coils of the relay RV. The circuit for the the positively energized conductor 53, conductor 62, controller segment 63 of the throttle mechanism 12, conductor 155, resistor section 160, conductor 161, contact members of the throttle mechanism 13, conductor 162, resistor section a and 143 and in consequence the resistance value of the circuit including the coils of relay RV is further increased. The resistorsections now in series circuit relation with the relay RV are 160, 158 and 159, that is, the circuit for the coils 67 and 68 extends from the positively energized conof the throttle mechanism 12, conductor 155,

resistor sections

160, 158 and 159 to conductor 66 leading to the operating coils of the relay RV. When the controller is moved to the fourth posiate. These operations remove the resistor sections 158 and 159 and from the circuit of the relay RV and instead of these resistor sections, the resistor section 65 having a resistance value ance values of the resistors mentioned, is inserted in series with the coils of the relay RV. This circuit may be traced from the positively energized conductor 53, through conductor 62, conconductor 64 and resistor 65 to the conductor 66.

Briefly stated, the operation of the controller TC from the first to the fourth position causes the insertion of

resistor sections

158 and 159, 159

series with the operating coils of the relay RV. Since the resistance value of successive combinations of resistors selected is progressively larger a progressively higher voltage of the auxiliary generator A is required to cause the operation of the dynamic control relay RV. From the foregoing discussion, it is obvious that for each of the throttle positions selected, as determined by the throttle controller TC, a definite voltage of the auxiliary generator is necessary to cause operation of the relay RV. For each controller position, the relay RV, therefore, controls the loading of the main generator G in exactly the same manner as above discussed in connection with the first position function of the speed of the engine, it is obvious that the voltage of generator A for the fifth and sixth position of the throttle controller may exceed that required for proper charging of the battery. Furthermore, because of the higher speed of the auxiliary generator A, and in consequence the higher voltage of this generator, the contact members 107 permanently close, and in consequence the beneficial controlling action of the control relay RV may not be realized for the last two positions of the controller TC. To prevent the voltage of generator A to rise above a predetermined value, and also to provide for a wider range of operation for the relay RV, the resistance value series with the shunt field windings of the auxiliary generator A maybe varied with each new position of the throttle controller.

If the throttle controller be moved to the fifth position,

air engines

141 and 142 are caused to operate, thereby inserting the

resistor sections

55 and 56 in series with the shunt field windings 58. This circuit may be traced from the positive conductor 53, through the contact members 144, of the throttle mechanism 13, conductor 144, re-. sistor

sections

55 and 56 and conductor 57 to the shunt field windings 58. For this fifth position of the controller TO, the relay RV again goes through its cycle of control, fixing the loading of the main generator G to fit exactly the power which the engine E is capable of delivering at such throttle opening.

For the fifth and sixth position of the throttle controller TC the resistance value of the circuit for field windings 58 is increased, as just explained, and in consequence the voltage of the auxiliary generator decreases with the result that the speed control of the relay RV is accomplished by a variation of the voltage of generator A and not by an increase of the resistance value of the circuit for the coils 67 and 68 of the relay RV. If the engine speed changes for a given position of controller TC, the voltage of generator A changes with the result that the percent of time the contactor V is closed changes, either increasing or decreasing, depending on the rate and sign of the speed change.

It is a known fact that the output of an internal combustion engine is dependent upon the fuel, its mechanical condition and atmospheric conditions. But the beneficial effect of our control scheme is not impaired by this varying characteristic of an internal combustion engine. If, for any given operating condition, the fuel be bad, or some of the spark plugs do not operate, or the humidity or barometric pressure be such as to impair the output of an internal combustion engine, then it is still true that the engine E will have some definite speed for a given throt tle opening. Since the relay RV is responsive to speed only. the main generator G can in no case be loaded to stall the engine E, but the engine E will always run at a constant speed and will be at the most efiective loading for a given throttle opening.

Movement of the controller to the sixth and last position causes the operation of all of the air engines, and in consequence, the resistance value in series with the shunt field windings 58 of the generator A is increased to a maximum. The circuit for the shunt field windings extends, in this case, from the positive conductor 53, through resistor sections 54, and 56, through conductor 57 to the shunt field windings 58. The control relay RV for the sixth controller position goes through the cycle of control previously discussed, and if the generator G is further unloaded, as would be the case when the vehicle being driven is coasting down a grade, the speed of the engine E will increase. As the voltage of the generator A continues to rise, the contact members 107 move to permanently closed position and the movable armature 208 moving in a clockwise direction causes the contact members 61 to make contact.

When the contact members 61 move to circuit closing position, a shunt circuit is established for the shunt field windings 58. This circuit may be traced from the energized conductor 57, through conductor 60, contact members 61, of the relay RV, conductor 43, resistor section 44, conductor 45, charging resistor 52, contact members 51 and series coil 50 of the reverse current relay RC and conductor 49 to the negative terminal of the auxiliary generator A. Each shunting of the field windings 58 causes a rapid variation in the voltage of the generator A, and in consequence, the contact members 61 move to open circuit position. After having moved to open circuit position, the voltage of generator A again rises and in consequence the contact members 61 again move to circuit closing position. This cycle of operation is repeated at the rate of about 100 times a second, and as the speed rises, the speed of vibration of the armature 208 gradually decreases. At some predetermined speed of the generator A, the shunt field windings 58 are completely shunted by the movement of the contact members 61 to a permanent circuit closing position. Any further rise of speed can, therefore, not raise the voltage of generator A to injure the battery B or any constant voltage auxiliaries that may be operating from the generator A.

If, during the loaded operation of the generator G, the pressure in tank K drops below a predetermined value, it may be desirable to operate the compressor motor C from the auxiliary generator A. This is accomplished by the relay CA. The circuit for this relay may be traced from the positively energized controller segment 6, through conductor 18, contact fingers bridged by the controller segment '76, conductors '77 and '78, back contact members 188, of the contactor 14, conductor 189, actuating con 190 of the relay CA, conductor 82, contact members 83 on the pressure responsive governor 84 and conductor 86 to the negatively energized conductor 87. Operation of the relay CA establishes a circuit for the compressor motor C which may be traced from the positive terminal of the auxiliary generator A, conductors 27 and 28, the armature of the compressor motor C, the series field windings 88 of the compressor motor, conductor 89, contact members 191, of the relay CA,

series field windings 192 of the auxiliary generator A to the negative terminal of the generator. The series field winding 192, when connected in circuit, is cumulative in action with the shunt field winding 58. It is, therefore, obvious that the operation of the relay CA, in addition to establishing a circuit for the compressor motor C, establishes a circuit for the series field 192 which then automatically compensates for the voltage drop caused by the additional load on generator A.

When the compressor motor C is operated from the main generator G the field windings 35 should be subject to a corresponding increase of excitation. This is accomplished by the relay CM and particularly the contact members 205. Operation of the relay CM causes a shunting of the

resistor sections

39 and 40 by a circuit extending through conductor 204, contact members 205 and conductor 206.

With all the operations heretofore discussed, the

traction motors

1 and 2 at all times remained connected in series to the generator G. Transition may take place at any position of controller TC. To operate the vehicle at a higher speed, the traction motors l and 2 must be connected in parallel. This is accomplished by the independently operable selector controller S. Movement of the selector controller segment 102 to a position to engage the contact finger on conductor 16'? and to disengage the contact finger on conductor 103 causes the interruption of the circuit for the regulator contactor V and also the interruption of the circuit for the actuating coil of the series contactor SC. At the same instant these circuit interruptions just stated take place, a circuit is established for parallel contactor P1. This circuit may be traced from the controller segment 102, through conductor 167, actuating coil 168 of parallel contactor P1, to the negatively energized conductor 133. Operation of the parallel contactor P1 causes the opening of the circuit for the actuating coil 130 of the series contactor SC at the contact members 132. The series connection for the

traction motors

1 and 2 is broken an instant after the single traction motor 1 is connected across the terminals of the main generator G. During transition, it is obviously desirable that the traction motor connected in parallel be not subjected at once to twice the generator voltage. This is accomplished by the regulator contactor V which is deenergized the instant the transition is to take place. Movement of the contact members 165 to open circuit position increases the resistance in series with the shunt field windings 35 of the main generator G, thereby reducing the voltage of the main generator.

The instant the series contactor SC moves to open circuit position a circuit is established from the positively energized conductor 95, through the back contact members 169 of series contactor SC, conductor 1'70, actuating coil 171 of parallel contactor P2 and conductor 172 to the negatively energized conductor 133. When the transition from the series to the parallel connection has been completed, the contact members 128 have moved to circuit closing position and in consequence the circuit for the regulator contactor V is again re-established, the circuit extending from the positively energized conductor 95, through the contact members 128,

conductors

128, 127 and 103 to the actuating coil 104 of the regulator contactor V. The controlling operation of the dynamic control relay RV and 3 proper speed conditions.

the regulator contactor V may thus proceed exactly as heretofore discussed in connection with the parallel operation of the

traction motors

1 and 2! If it be desired to further increase the speed of the vehicle being propelled, the selector controller is moved to its third and last position, thereby establishing a circuit from the positively energized controller segment 102, through conductor 178, actuating coils 1'79 and 180 in multiple of the accelerating relays and conductor 181 to the positively energized conductor 133. Operation of the accelerating relays obviously establishes a shunt across the series field windings r12 and 124 of traction motors l and 2, respectively.

The speed of these motors is thus increased to some new speed.

When it is desired to decrease the engine speed the controller is moved from the position it occupies to some lower speed position. Should the controller TC be moved to the off position the engine will slow down to the idling speed, but the

contactors

14 and 26 do not connect the battery to the main generator prior to the time of As the engine slows down the voltage impressed on coils 67 and 68 decreases. It should be noted that only the resistor section 159 is in series with coils 67 and 68 during speed reduction by the controller TC with the result that

contact members

107 and 61 are firmly closed. When the engine speed is actually down to an idling speed the voltage impressed on coils 67 and 68 is suificiently low to permit closing contact members 16 by the actuation of the spring 210. With the closing of the contact members 16 the

contactors

14 and 26 are energized, as previously explained, and the main generator is connected to the battery to charge the battery.

If it be desired to operate the vehicle in reverse direction, the manually operable reversing controller is moved to its second position, thereby establishing a circuit from the positively energized conductor 95, through conductor 96, actuating coil 182, of the controller AR. conductor 183, controller segment 99 of the controller R to the negatively energized conductor 100. The automatic reversing controller AR will thus move the segments to the right, thereby establishing the desired circuits through bridging members 184 and 185 and the controller segments 186 and 187.

Briefly stated, our invention provides an electrical control system for the electrical and mechanical equipment on a gas or oil-electric vehicle, whereby the main generator may be utilized during idling operation to charge the battery and supply the electrical energy to all auxiliary equipment, and where the main generator maybe disconnected from all auxiliaries and the battery during the running operation and be connected to the traction motor. During running operation, the battery charging is accomplished in a desirable and approved manner by an auxiliary generator connected to the shaft of the main generator, and the auxiliary equipment, such as the compressor motor, lights and signals, are operated by the auxiliary generator. Furthermore, our in vention provides a torque control responsive to the speed of the engine so that the load on the generator never exceeds the power available at the crank shaft of the engine. The control means being provided with special circuit arrangements to prevent hunting despite the fact that the speed of the engine is controlled in response to the speed of the engine.

We do not wish to be restricted to the specific structural details, arrangement of parts or circuit connections herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of our invention. We desire, therefore, that only such limitations shall be imposed as are indicated in the appended claims.

We claim as our invention:

1. In a power system, in combination, a battery, a dynamo electric machine, an internalcombustion engine, means for connecting the battery to the dynamo electric machine to start the engine, said dynamo electric machine having main field windings and series field windings, said series field windings during cranking of the engine acting additively and during operation of the engine when the dynamo electric machine operates as a generator acting differentially to prevent excessive charging of the battery, an auxiliary generator having a voltage characteristic such that the voltage is directly proportional to the speed of the engine, means responsive to the voltage of the auxiliary generator for transferring the battery connection from the dynamoelectric machine to the auxiliary generator, a ballast resistor for controlling the charging rate of the battery by the auxiliary generator and means responsive to the voltage of the auxiliary generator for varying the excitation of the auxiliary generator to prevent excessive charging of the battery for the higher speeds of the engine.

2. In a power system, in combination, an internal-combustion engine, a throttle mechanism adapted to be operated to a plurality of positions to secure a plurality of engine speeds, a main generator coupled to the engine, a field winding for said generator, a separately excited auxiliary generator coupled to the engine and disposed to energize the field winding of the main generator, a regulating relay responsive to the speed of the engine and disposed to vary the field current of the main generator to vary its load, and a plurality of circuits disposed to be selectively interconnected with the regulating relay to control its operation, whereby the engine speed is maintained substantially constant at the speed selected by the throttle.

3. In a power system, in combination, an internal-combustion engine, selecting control means for effecting the operation of the engine at a plurality of speeds, a main generator coupled to the engine, a field winding for said generator, a separately excited auxiliary generator coupled to the engine and disposed to energize the field winding of the main generator, control means for controlling the excitation of the field winding of the main generator to vary its load, a regulating relay responsive to the speed of the auxiliary generator and associated with said load control means to vary the load over a substantially definite range on the generator to maintain the speed of the engine constant at the speed selected by the selecting control means, and means for automatically changing the range of said load control means and speed responsive means for each position 01 said selecting control means.

4. In a power system, in combination, an internal-combustion engine, a throttle adapted to be operated to a plurality of positions to secure a plurality of engine speeds, a main generator coupled to the engine, a field winding for the main generator, 2, separately excited auxiliary generator coupled to the engine and disposed to energize the field winding of the main generator,

a vibrating contactor disposed to control the field current of the main generator to vary its load, a control relay responsive to the voltage of the auxiliary generator for controlling the operation or the vibrating contactor, a plurality of circuits disposed to be selectively interconnected with said relay by the throttle to control its operation to maintain the engine speed substantially constant at the speed selected by the throttle, and means including resistors in the field circuit of the main generator associated with the control relay and the vibrating contactor to prevent hunting of the engine.

5. In a power system, in combination, an internal-combustion engine, a throttle adapted to be operated to a plurality of positions to secure a plurality of engine speeds, a main generator coupled to the engine, a field winding for the main generator, a separately excited auxiliary generator coupled to the engine and disposed to energize the field winding of the main generator, a vibrating contactor disposed to control the field current of the main generator to vary its load, a control relay responsive to the voltage of the auxiliary generator for controlling the operation of the vibrating contactor, a plurality of circuits disposed to be selectively interconnected with said relay by the throttle to control its operation to maintain the engine speed substantially constant at the speed selected by the throttle, and means including resistors of predetermined relative values disposed in parallel circuit relation in the field circuit of the main generator and associated with the control relay and the vibrating contactor to prevent hunting of the engine.

6. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, a main generator driven by the engine and having a separately excited field winding, an auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, said auxiliary generator having a straight line speedvoltage characteristic, and regulating means responsive to the voltage of the auxiliary generator for controlling the excitation current of the main generator to vary the output of said generator thereby maintaining the speed of the engine substantially constant at the selected load speed.

7. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, a main generator driven by the engine and having a separately excited field winding, a separately excited auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, the voltage of said auxiliary generator being directly proportional to the speed of the engine, and regulating means responsive to the voltage of the auxiliary generator for controlling the excitation current of the main generator to vary the load on the engine to maintain the speed thereof substantially constant at the selected load speed.

8. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, a throttle mechanism for controlling the supply of fuel to the engine, a main generator driven by the engine and having a separately excited field winding, an auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, a source of constant potential for exciting the auxiliary generator to cause it to generate a. voltage directly proportional to the speed of the engine. and regulating means responsive to the voltage of the auxiliary generator for controlling the excitation current of thmain generator to vary the load on the engine to maintain the speed thereof substantially constant at the selected load speed.

9. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, an electro-pneumatic throttle mechanism for controlling the supply of fuel to the engine, a main generator driven by the engine and having a separately excited field winding, an auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, a source of constant potential for exciting the auxiliary generator to cause it to generate a voltage directly proportional to the speed of the engine, regulating means responsive to the voltage of the auxiliary generator for controlling the excitation current of the main generator to vary the load on the engine, and means associated with the throttle mechanism for controlling the operation of the regulating means, whereby the speed of the engine is maintained substantially constant at the selected load speed.

10. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, an electro-pneumatic throttle mechanism for controlling the supply of fuel to the engine, a main generator driven by the engine and having a separately excited field winding, an auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, a source of constant potential for exciting the auxiliary generator to cause it to generate a voltage directly proportional to the speed of the engine, a regulator having an actuating coil connected across the armature winding of the auxiliary generator to be responsive to the voltage of the auxiliary generator, and means controlled by said regulator for varying the excitation current of the main generator to vary the load on the engine, whereby the speed of the engine is maintained substantially constant at the selected load speed.

11. In a power system, in combination, an internal-combustion engine adapted to be operated at several selectable load speeds, an electropneumatic throttle mechanism for controlling the supply of fuel to the engine, a main generator driven by the engine and having a separately excited field winding, an auxiliary generator driven by the engine to supply excitation current to the field winding of the main generator, a source of constant potential for exciting the auxiliary generator to cause it to generate a voltage directly proportional to the speed of the engine. a regulator having an actuating coil connected across the armature winding of the auxiliary generator to be responsive to the voltage of the auxiliary generator, means controlled by said regulator for varying the excitation current of the main generator to vary the load on the engine, and means associated with the throttle mechanism for varying the potential applied to the coil of the regulator to control its operation, whereby the speed of the engine is maintained substantially constant at the selected load speed.

NEWELL L. FREEMAN. NORMAN W. STORER.