US2006523A - Power generating system - Google Patents

Description

y 1935- c. F. STRONG 2,006,523

POWER GENERATING SYSTEM Filed July 16, 1932 hmn lnnnnmhumml Patented July 2, 1935 UNITED STATES PATENT OFFICE POWER GENERATING SYSTEM Chester F. Strong, Miami, Fla. Application July 16, 1932, Serial No. 622,967

Claims. (01. 290-30) This invention relates generally to power generating equipment utilizing internal combustion engines and has particular reference to improved control equipment for starting or stopping a plu- 5 rality of units either entirely by manual control 'or entirely automatically or by a combination of [the two.

' One object of my invention is to provide an improved control system whereby the various automatic or manual control functions may be effected with equal facility either alone or together and in such a manner that when only a part of their respective functions are selected they will be coordinated without interference from the remaining unused functions. A further object is to provide an improved arrangement for using the generators as motors to start their respective engines which are preferably of the Diesel type and yet reducing to a minimum dangers from a short circuit in case the engines fail to start under predetermined conditions of operation.

Another object is to provide an improved arrangement for insuring, without temporary adjustment, substantially normal voltage when a unit is brought onto the line. If any temporary adjustment is necessary to compensate for briefly existing inherent characteristics it would be particularly troublesome in a. power plant for which my invention is especially adapted, my equipment being used preferably in apartment houses, hotels,

oilice buildings, etc. wherein sudden loads are thrown on the line such as elevator motors, etc. thereby quite often necessitating the starting of a unit and running it only temporarily to carry the elevator load. rary adjustments must be made then if these adjustments are made by an attendant the full value of the economical operation of automatic control is lost because of the cost of the attendants labor. It is an object of my invention to provide improved means for not only taking care of this matter automatically but of simplifying as far as possible the manner in which it is taken care of Specifically it is an object of my invention to eliminate a cause of voltage control diflieulty experienced in automatic apparatus of the kind herein disclosed byproviding a relatively simple arrangement which eliminates the necessity of having automatic devices for compensating for the voltage variations created by the otherwise existing cause. The difficulty referred to is that in a building using my plant, an engine may be idle for a sufficient length of time so that its generator becomes cold whereby when the engine is started the generator will gradually become warm with a consequent variation in voltage over that of the cold generator. In my improved arrangement I have embodied as part of the automatic equipment suitable means whereby It is thus seen that if tempo-.v

the generator at all times will be maintained at or sufficiently near its normal operating temperature to avoid the voltage fluctuations which would otherwise occur A further object is to provide an improved ar rangement for starting the units by motor action of the generator in combination with a battery, battery booster and means whereby starting current for the motors is obtained without current being taken through the armature of the booster, and yet voltage control is effected by the battery booster. v

Other objects and advantages will be more apparent from the following description of the accompanying drawing which is a wiring diagram of my improved system embodying diagrammatic illustrations of the mechanical elements.

In the accompanying drawing, A, B and C represent generating units employing internal combustion engines, preferably of the Diesel type, driving electric generators. A constant source of current supply, such as a supplemental or standby source of current herein specifically shown in the form of an electric storage battery I is connected directly to mains 2 and 3. This source serves not only as an auxiliary source for starting the units but in addition is adapted to supply a certain regular line load. In this regard the source can be a constantly operating engine although a battery is preferable for several reasons including a smoother and more dedendable degree of cooperation between all of the elements. In the case of the battery it is connected directly to mains 2 and 3 through a booster 4 which is driven by a motor 5.

Two methods of starting the generating units are shown herein and these are coordinated in an improved manner. In one, compressed air is stored in a receiver or tank 6 which is supplied by an air compressor 1 adapted automatically to maintain the desired pressure. Air valves 8 are located in pipe lines 6a leading from the tank to supply each engine with compressed air as through distributor valves 9 and pipes III, pipes I0 being omitted from units B and C for clearness. When starting an engine with compressed air, a switch II is closed so that compression relief mechanisms I2 will remain closed and prevent escape of starting air. A lever I3 of a fuel pump I4 is raised from a stop I5 and a latch I6 placed under lever I3 so as to permit fuel pump I4 to inject fuel into the cylinders.

plied to the engine to enable it to maintain the correct speed for the load. The air valve 8 is of course manually closed when the engine starts.

Assuming that generating unit A has been started by closing its switch H and using starting air through its air valve 8 as just described, then as the engine comes up to speed switch I6 is manually closed causing switching mechanism, to be described, to place the generating unit on the line. This switching mechanism will not permit the generator to be connected with the load line unless the generator voltage is set correctly, the switching mechanism having the further function of opening the connection from the generator to the line and also for automatically shutting down the engine in case the unit becomes out of order.

The control of the switching mechanism is as follows: Closing of switch l6 allows current to flow from line 2 through wires H, H to switch contact I, spring I9, wires 20 and 2|, solenoid coil 23 which closes switch 22, thence through wire 23 and closed contacts 68 of a deenergized solenoid 64 to the other line 3. Closure of switch 22 is then followed by automatic connecting of the unit to the line only if the generator voltage is normal, this being in a manner to be presently described for the full automatic control operation.

After the engine has been started by manual operation and its generator connected to the line, if for any reason the unit becomes inoperative the generator will take current from the line and hence begin to act as a motor. Assuming the unit to be inoperative the motoring of the engine should be stopped only after the motoring action has continued for a predetermined period of time, it being desirable not to stop the unit immediately when it becomes inoperative because the inoperative condition may only be of a temporary character such as air in the fuel lines. However if the cause is of a more permanent nature then at the expiration of the predetermined time the unit is shut down. This is brought about due to an arm I5 of a reverse current time element having been gradually moved upwardduring motoring action until arm I5 engages contact 84' whereupon a circuit is established from wire 32', through arm 15, contact 84', wires 84, 84", solenoid I9 and to the other line 3. Energization of solenoid I9 pulls back catch I6 to allow lever l3 to drop and shut off the fuel. At the same time arm 15 will have opened contact between spring I9 and its contact |8 to break the circuit through wire 20 for solenoid 23 thus causing the opening of switch 22 to stop the motoring of the generator. Switch 22 would normally tend to close when the motoring action starts due to relay 3'l, 38 opening switches 65, 66 all as will be described later.

In the second method of starting wherein the generator is used as a motor to drive the engine until it is started, assume that generating unit A is at rest and that the ,manual con rol i disconnected as by closure of air valve 8 and opening of switch A switch I6 is then closed, thereby energizing solenoid 23 to close switch 22. Upon closure of switch 22 current flows from battery I through series field 25 of battery booster 4 to a bus 24, thence through wire 26, across contacts 28 which have been closed by switch 22, starting resistance 30, protective' resistance 3|, wire 32, compound field 33, armature of generator 34, wire 32', reverse current time element 35, wire 36, current coil 31 of relay 38, wire 39, line 2 and back to battery Closing of switch 6' has also established a circuit from main 2 through wires l1 and 40, field resistance 4|, movable contact arm 42, wire 43, across closed contacts 44, wire 41, shunt field 48 and wire 49 to line 3.

Closing of switch 22 as described above allows current to flow through armature of generator 34 which thus acts as a motor to rotate the engine E of generating unit A. As the speed of rotation of the motor or generator 34 increases, the voltage across same also increases until when it reaches a certain value more current is passed to the motor. The effect of this is to insure that the rotating parts of the engine generator have accumulated sufficient momentum before fuel is injected into the cylinder, otherwise if fuel was injected before this momentum was acquired the engine would not be able to carry over dead center against the explosion which occurs ahead of dead center. The compression reliefs will also remain open until this momentum is obtained thereby rendering it easier for the engine to come up to speed. To control this action a coil 5| is connected across the armature of generator 34 as by wires 32, 50, 52, 39, 36 and 32'. Hence the increasing motor voltage upon reaching a predetermined value causes solenoid 5| to close its contacts 5| and thus short circuit resistance 30 to permit more current to pass through generator 34, again increasing its speed. In practice this speed is brought up to about half that when running at generating speed. Resistance 3| remains in circuit with the generator whenever contacts 28 and 5| are closed. Closing of contacts 5| also closes contacts 53. This permits additional current to flow from line 2 (adjacent the battery) through wire I1, switch l6, wire spring |9, wire 20, across contacts 53 to wire 54, oil pressure cut out 55, fuel control solenoid 56 and thermal cut out 51, which is closed whenever normal temperatures exist either in the cooling water or bearings, the circuit continuing down through wire 58 to line 3. When lubricating oil pressure is sufiicient to close oil pressure cut out device 55, coil 56 is energized and arm l3'on the fuel pump control is raised against the tension of a spring 59 to engage a stop 60, the latch I6 having been previously pushed back manually so as to not interfere with automatic operation. Fuel then enters the cylinders whereupon engine of unit A starts and comes up to speed which will cause generator 34 to equal the voltage across busses- 2 and 3 providing rheostat 4| is set to permit suflicient current to pass to the shunt fields 48 of generator 34. If a small amount of current is flowing through series field 33 in a direction normal for machine 34 to act as a generatorfcoil 31 of relay 38 will assist a shunt coil 6| to raise armature 62 and close its contacts. If, however, machine 34 does not come up to a speed sufiicient to cause this actioncurrent will be flowing in the opposite direction through coil 31 and armature 62 will not raise. Closing of these armature. contacts establishes a circuit through wire 64 to energize coils of switches 65 and 66 and close the same. Closing of switch 65 opens contacts 68 and deenergizes coil 23 of switch 22. This disconnects generator 34 from starting line 24, but at the same time the generator is connected with service bus 3 through wire 32 and switch 65.

Should engine of unit A at any time fail to operate, relay 38 permits its armature contacts to open because machine 34 will now act as a motor from constant potential mains 2 and 3. This causes switches 65 and 66 to open, dic'sonnecting machine 34 from main 3. Contacts 68 also close atv this same time, causing switch 22 to close, whereupon machine 34 receives current again through resistance 3|. This resistance is thus always in circuit with machine 34 when it is motoring or tending to motor. Should anything happen to generating unit A, such that it is suddenly stopped due for instance to seizure of a bearing, piston sticking, etc. resistance 3| prevents the armature of machine 34 from acting as a short circuit from main 2 to startingmain 24. Relay 38 thus acts to control proper operation of the switching mechanism when machine 34 is acting as a generator and comes on the line but it also causes the generator to be discon- 'nected if it is not operating properly to supply current to mains 2 and 3. The ballast resistance 3| is therefore a very essential feature as it limits the current that machine 34 can take when,

under any conditions, it is taking current from mains 2 and 3 and it also prevents a short across armature of booster 4 if there is any overlapping in the actions of switches 22 and 65.

When switch 22 is closed a resistance 69 is shorted out of the shunt field circuit of machine 34. If rheostat 42 is set for the correct voltage when machine 34 is in parallel with the other machines B or Cor batteryl through booster 4, then when the machine is disconnected and allowed to motor as before the generator field will not build up to permit quite suificient voltage to stabilize machine 34 and cause it to develop suflicient voltage to come in on the line. By shunting out resistance 69, machine 34 is permitted to develop sufiicient voltage to start a slight current flowing through series field 33 and back to bus.3 when being driven at the proper speed by engine 3 and with switch 65 open. This action causes relay 38 to close the contacts of its armature 62"whereuponswitch 55 raises to cause switch 22 tofall open. With load current established through series field 33, generator 34 stabilizes its voltage and resistance isin circuit when switch 22 opens. Machine 34 then develops the correct voltage over its normal Motorzor generator 34 is usually a' so range; called fiat compound machine for the given variation in engine speed from no load to full load and generator 34 usually functions from about one-quarter load to full load or over load.

To eliminate the cause of voltage variation due to a cold machine, warming current flows from main 2 through wires 52 and 52', resistance I0, rheostat 4|, arm 42, wire 43, resistance 59 and wire 41 to generator field 48 providing switchltl' is open so as to avoid shunting current around resistance 4|. The amount of this warming current is less than that used when the generator is operating with switch IE or its equivalent closed. This current keeps the fields of generator 34 Warm so that when the unit is started generator 34 develops about the correct voltage without adjustment of rheostat 4| to allow for changed temperature. of fields and consequent change of resistance from hot to-cold.

In place of manual operation of switches I6 for each unit, relays 12 and 13 placed in the load line may be adjusted to start units A, B or C progressively as line load demands. Switches 14, 14B and 14C would be closed for this method of operation. Thus if the load demand should increase above a certain small amount which is normally carried by the battery alone, then relay will be sufliciently energized and closed to establish a circuit through wire 80, switch 14 and contact spring l9 to wire 20 whereupon solenoid 23 is energized to close switch 22 after which the operations are the same as those previously described when starting the unit by motor action of the generator. If load demand increases beyond the capacity which it is desired to take from unit A, then relay "will become sufliciently energized to close and establish a circuit through wire 8| and switch 14B to the starting elements of unit B corresponding to those of unit A. Further increase in load demand similarly closes relay I3 and establishes a circuit through wire 82. If for any reason unit A should not start after a given length of time, hand 15 of reverse current time element 35 would, at expiration of that time and due to the motoring of the generator, have moved up into engagement with contact spring l9 and broken the circuit through wire 2|], contacts 53 and wire 54, thereby breaking the circuit through oil pressure device 55 and solenoid 56 whereby fuel control arm I3 is pulled to its shut off position by spring 59. However, arm 15 upon breaking this circuit would establish a-new circuit through wires 84 and 85, 82 and switch 14C to start unit C. Similarly if unit B fails to start, hand 15 of its reverse current time element will establish a circuit through wires 85, 81 and 82 to start unit C, assuming this unit is idle as it would be if unit A was in normal operative condition.

If desired switch l6 on the first unit can be left closed retaining this unit in service at all times and allowing units B and C to be brought on the line by relays 12 and 13 as load demand requires. This method obviates battery or any other suitable source of standbycurrent from carrying load except starting current or momentary fluctuations. Any unit may thus be selected to operate continuously, merely by closing its switch "5'.

Compressed air tank 6 is maintained auto- I matically at proper pressure by air pump l which is operated by any usual pressure device on an electric controller 88. This may be of the usual standard construction for; such compressors and regulators.-'. It will beseen that by operating the.

1 when its voltage is too low. Should the operator wish to leave the plant, switches I4, 1413 and "C can be closed and switches II, B and NC opened. Switch l6 may be left closed but the corresponding switches of the other units can be left open. A load beyond capacity of unit A will be taken care of by units B and C and failure of unit A compensated for" by starting of C or B.

Booster 5 is shown with one of my improved forms of control for its shunt fields, the charging field being controlled by vibrating relay 89 and the field for maintaining correct line voltage on battery discharge by vibrating relay 90 although it will be understood that my improved booster controlcan also be used, such being shown in my co-pending application, Serial No. 434,281. The starting current passing through the series field of the booster assists it in maintaining the linev voltage and compensates for the resistance drop of the battery when it is discharging during starting of a unit. When the generator has reached normal voltage and has been placed on the line .then battery booster functions to charge the battery on normal line voltage and causes battery to discharge into the line when line voltage becomes slightly below normal due to the generators being unable to meet the sudden momentary increase in current demand or a demand in excess of the generator capacity.

From the foregoing disclosure, it is seen that my improved arrangement is adapted to control the engines individually through manual operation in combination with automatic paralleling of the units or by a simple manipulation the complete automatic control can be brought into operation with manual means for disconnecting any one unit even though the automatic control should be set for a contrary action, there being the further advantage that no matter how the controls may be manipulated no danger exists as to short circuiting a unit across the line nor is excessive voltage variation created when a unit is started or stopped due to the current supply to the motor being shunted around the booster while yet obtaining all advantages of the booster.

Briefly summarized, the following are certain of the features of operation of my improved system.

Manual operation 1. Starting engine by opening air valve 8, and closing of switch H 'to close compression relief valves, and latching fuel lever I3 in its upper open position.

2. When engine comes up to speed switch 46 is closed, thereby closing switch 22, the speed governor controlling fuel supply.

3. Unit automatically connected to line only if generator voltage is normal.

4. If unit fails to start, then operator does not close switch l6.

5. If unit becomes inoperative after being con nected to line, generator acts as motor and arm 15 of reverse time element subsequently opens switch 22 to break current supply to motor, also pulling latch Hi from under fuel lever I?) to shut off fuel. I

Semi-automatic operation 1. Switch I6 is closed, to supply current from battery to generator armature as though resistance 3| but without going through booster, current also beinz suppliedto shunt field 48 across contacts 44, the motor thus rotating engine.

2. As generator speed increases more currentis passed thereto due to relay 38 causing closure of contacts 5| to shunt resistance 30, protective resistance 3| remaining in circuit.

3. Engine speed increases until lubricating oil pressure is sufiicient to close oil pressure device 55 whereupon coil 56 is energized and fuel arm l3 raised to start engine.

4. If engine comes up to speed, relay 38 will respond to corresponding increase of generator voltage which when normal will permit automatic connection of unit to line the same as in manual operation.

5. Failure of unit to start causes reverse current time element to open switch 22.

6. Ballast resistance 3| limits amount of current generator can take as for instance if engine abnormally stops when running.

7. Warming current for cold generator.

1. Line load relays H, 12 and l3'substituted for manual operation of switches l6 for each unit by closing switches 14, 14B and "C.

2. Automatic operations previously described then take place. I

3. A unit can be kept on line by closure of its switch l6, allowing remaining units to be controlled by relays I2 and 13 assuming the first unit to be.continuously operated.

It will of course be understood by those skilled in the art that from the foregoing disclosure various changes may be made without departing from the spirit of my invention as set forth in the appended claims.

I claim:

1. The combination in a generating system for supplying a main line, comprising a plurality of units each having a generator driven by a Diesel engine, means for starting the engine of each unit by compressed air, a manually operable switch for each unit, the switch of a unit that is started being actuated by the operator when the unit approaches normal speed, and means for automatically connecting the generator of said unit to the line after said switch is actuated and the generator voltage is normal.

2. The combination in an electric generating system for supplying a main line, comprising a plurality of units each having a generator driven by a Diesel engine, means for starting the engines, means whereby during starting of an engine its generator is substantially disconnected from the line but after the engine is started the generator is connected to the line to supply generated current thereto, and means for automatically disconnecting a unit from the line in case the unit gets out of order.

3. The combination in an electric generating system for supplying a main line, comprising a plurality of units each having a generator driven by :1. Diesel engine, means for starting the engines, means whereby during starting of an engine its generator is disconnected from the line but after the engine is started the generator is connected to the line, and means whereby a unit which is connected to the line and subsequently becomes inoperative is disconnected automatically after the inoperative condition has existed for a'predetermined time interval.

4. The combination in an electric generating system for supplying a main line, comprising a plurality of units each having a generator driven by a Diesel engine, means for starting the engines, means whereby during starting of an engine its generator is disconnected from the .line but after the engine is started the generator is connected to the line, and means whereby upon subsequent failure of unit its generator receives current from the line to act as a motor to drive the engine for a given length of time whereupon the unit is automatically disconnected from the line and stopped.

5. The combination set forth in claim 4 further provided with a fuel supply control for the engines, and means whereby the automatic disconnecting means also stops the fuel supply to the engine.

' CHESTER F. STRQNG.

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