US1789155A - Automatic station control - Google Patents

Description

Jan. 13, 193L A. J. A. PETERSON AUTOMATIC STATTON CONTROL Filed May 27,. 1929 2 sheeisvsheef, 1

Lu T D maf/ INVENTOR AlFIed JAPeifnSfoTl ATTORN EY `lan. 13, 1931. A. J. A. PETERSON AUTOMATIC STATION CONTROL Filed May 27 1929 2 Sheets-Sheet 2 INVENTOR Alfr ed J: APetefsCm ATTORNEY Patented Jan. 13, 1931 UNITED STATES PATENT OFFICE ALFRED J. A. PETERSON, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO` WESTING- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION F PENNSYL- VANIA AUTOMATIC STATION CONTROL Application filed May 27, 1929. Serial No. 366,263.

T his invention rela-tes to automatic stations and, in particular, to automatic stations including a plurality of translating devices, such as transformers, motor-generators, converters or the like. In automatic stations of this type, it is desirable that sufli lent translating capacity shall be connected in circuit to supply the load on the station and it is equally desirable that, When the station load decreases, any unneeded translating apparatus shall be disconnected.

It is the principal obj ect of this invention to improve upon the systems for operating multi-unit stations shown in the Moss Patent No. 1,564,303, the Field and Ross application, Serial No. 199,172 filed June 16, 1927, and the Moss and Peterson application, Serial No. 287,758, filed .lune 23, 1928.

A specific object of this invention is to provide improved means for comparing'the station load and the number of the connected translating devices.

Another object of my invention is to provide load-measuring means which shall not be aii'ected by changes in the voltage of the usual auxiliary supply source.

A further object of my invention is to provide means for varying the order in Which the several units of a multi-unit automatic station are connected in service.

In accordance with my invention, I make use of a plurality of standard over-current relays which are adapted to be energized in accordance with the station load. These relays are set to operate at different values of station-load current 'and serve to initiate the operation of connecting` an additional translrating unit in service when the station load increases, and to disconnect surplus translating units when the station load decreases.

For a complete understanding of my invention, reference should be had to the accompanying drawings in which: i

Figures 1 and 2 illustrate diagrammatically a multi-unit automatic station embodying the novel features of my invention.

Fig. 3 illustrates, diagrammatically, an element necessary in connection with the system shown. in Figs. 1 and 2.

Referring particularly to Figs. land 2, a

high-voltage supply circuit is adapted to supply energy to a relatively low-voltage load circuit 26 through translating devices, such as transformers 27 28 and 29.

The connection of the transformer 27 between the circuits 25 and 26 is controlled by suitable circuit breakers 3() andi 31, in a manner which will become apparent hereinafter. It is to be understood at this point that, although I have illustrated my invention in connection with a transformer station, any other translating devices, such as rotary converters, motor-generators, vapor converters, or the. like may be controlled by meanssimilar to that shown and described herein. It is possible, furthermore, to control nonelectrical processes by the some means. A

As hereinbefore indicated, the operation of the system of my invention is initiated inresponse to an increase in the load on the station in which the transformers 27, 28 and 29 are located. The stationload is measured by the current transformers 32, 33 and 34 connected in corresponding leads of the transformers, in

connection With standard over-current relays 35, 36 and 36. Although I have illustrated my invention in connection with a single- .phase system, it is obvious thatl it may be applied to any polyphase system. In such case, a relay corresponding to relays and 36 Will be provided for each phase, and the front and back contacts thereof will be connected in parallel and in series, respectively, as taught by the VEdmonds Patent No.l 1,67 5,336.

The remaining equipment necessary in the embodiment of my invention hereiny shown will be described in the course of the following explanation of the operation thereof.

It is desirable, in multi-unit automatic stations, that at least one translating device shall be connected between the supply and load circuits at all times. In order to insure this condition, I provide a balance relay37. This relay is arranged to control the operations required to connect an additional translating device between said circuits under the influy windings of the relay are deenergized, as when the apparatus is in the condition illustrated in Figs. 1 and 2, the Contact 38 ot the relay will be closed to complete a circuit from a source of auxiliary control current, such as the automatic bus 39, through the relay arm and the contacts 38. to the winding of an auX- iliary relay and the negative side of the control circuit (represented by a minus sign within a circle). Current is supplied to the automatic bus from any convenient source, as will be explained more fully later. Instead of biasing spring, one of the windings of the relay 37 may be permanently energized, in series with a resistor of appropriate value, to exert a biasing torque on the contact lever of the relay.

The relay 40, when energized, closes its contacts 41, 42 and 43. The closing of the contact 42 of the relay 40 completes a circuit from the automatic bus 39, through a normally closed contact 44 of a master lockout relay 45, the operation of which will be described further hereinafter, the contact 42 of the relay 40 and the armature 46 of a reversible motor 47, to the negative bus. A circuit is likewise completed at the contact 43 ot the relay 40 for the forward lield'winding 48 of motor `47.

The motor 47 serves to drive a drum switch 49 comprising conducting segments 50 to 56, inclusive, which are adapted to f cooperate with contact lingers 58 to 64, inclusive. When the motor 47 is energized by the completion of the circuits hereinbetore mentioned, the motor starts to rotate in such direction as to cause the contact segments 50 to 56 to engage the lingers 58 to 64. Appropriate gearinginay Y be interposed between the motor 47 and the drum 49 to reduce the speed of the latter. By the operation of the relay 40, a circuit is also completed from the automatic bus39, through the Contact 41 of the relay 40, conductor 58 to the corresponding contacts of a plurality of sequence switches 67, 68 and 69, which determine theorder in whichv the transformers 27, 28 and 29 are connected between the circuits 25 and 26. An extension of the conductor 58 is connected to the contact finger 58 for a purpose to appear subsequently. f

The sequence switch 67 is shown in detail in Fig. 3 and consists et a manually operable drum 70, preferably cylindrical, bearing segments 71 to 76, inclusive, which areV adapted to engage stationary contact lingers 81 to 88, and 92 when the drum isrotated through its various positions A, l5, C and D. A pointer 93 indicates to the operatonthe position of the Contact segments with respect to the contact lingers, and any suitable means (not shown may be provided for rotating the drum 70 past the Contact lingers 81 to 88, 90 and 92 which are fixed to the stationary portion of the switch structure.

elVhen a sequence switch is` actuatedto po sition A, the translating device associated function of which will be described therewith will be the lirst te be connected to the supply and load circuits. The unit having its sequence switch in position B will be connected second in the sequence, and so on. The disconnection of the units will be eected in the reverse order ot their connection, will be described hereinafter.

Assuming that the sequence switch 67 is in position A, the contact lingers 82 and 84 there et will be connected through the segments 71 and 72 in engagement with said lingers, respectively. This being the case, the circuit to the conductor 58 is extended through the Contact fingers 84 and 82 of the sequence switch 67, a current-limiting resistor 95 to the winding of a closing relay 95 associated with the circuit breaker 30 and through an auxiliary switch 96 on said breaker, a switch 97, the position of which is controlled by the manual closing and tripping switches`98 and 99 in such manner that the switch 97 wi l norinally be closed untilithe manual-tripping switch 99 is actuated. rlhe circuit extends to the negative bus through the normally closed contact 100 of a unit lockout relay 101, the

rWhen the relay 95 is energized by tne coinpletion of the circuit which is traced above, it Ycloses its contacts 102 and 103. The closing of the contact 102 completes a locking circuit for the relay95 in parallel with the auX- iliary switch 96. The contact 103 completes a circuit forthe closing coil ot the circuit breaker 30, which is thereupon actuated to its closed position, the source of current 'for the closing coil being indicated by a plus sign within small circle. rlhe consequent opening oi' the switch 96 does not affect the relay 95 but the closing ot another auxiliary sw 104 on the circuit breaker' 30 completes a circuit rom contact 82 of the sequence switch 67 which is connected to the automatic bus, through the drum switch 49, as already described, to the winding ot a cut-cti relay 105. This circuit returns to the negative bus in the saine manner as that described 'for the relay 95. The relay 105 closes its contacts 106 and 107, the former completing a locking circuit for the relay 105 in parallel with its original energizing circuit, and the latter ser g to shunt the winding of the relay 95, which is thereupon deenergized. The relay 1.05 remains energized so long as positive battery is supplied to kconductor 58. "When relay 40 is deenergized, however, as will be p ted out later, relay 105 is likewise deenergized but the circuit breaker 30 remains latched in the closed position.

`The circuit breaker 30 is provided with auxiliary contacts 108 and 109 which are closed when the circuit breaker is closed. The closing Yof the Contact 108 extends the circuit previously traced to the contact linger 82, through said contact 108V and a currentliiniting resistor 110', to the winding ci a Cil closingrelay 110 associated Withthe circuit breaker 31. This circuit returns to the negative bus through the auxiliary switch 111 of the circuit breaker-31, manual.v switch 97 and thelock-out contact 100. The relay 110 is thereby energizedto close its contacts `112 `and 113. The contact 112 closes a locking circuit for the relay 110 in parallel With thatv including the auxiliary switch 111. The. contact 113 closes an energizing circuit for the clos ing coil of the circuitbreaker 31 which is thereupon actuated to. its closed position; The closing of the circuit breaker 31- Ldoes not allectkthe relay 110 sincethecontact 112 of the latter completes a locking circuit there; for, as described above, but the auxiliary switch 114 of thecircuit breaker 31 completes anenergizing circuit from thecontact linger 82 ofthe sequence switch 67, through theauxiliary contact 108 of the circuit breaker 3() and the resistor 110', tothe Winding ofracutoil relay 115 and the negative Vbus through the auxiliary contact 114. The relay 115 is thus energizedto close its contacts 116 and 117. The contact 116 shuntsl the Winding of the closing relay 110, and the contact 117 locks the relay 1l5-in its energized position, so long as positive batteryV is connected to contact 82 through contact 41 ofi'relay 40.

The circuit vbreakers 30..and 31 are now closed, andthe highvoltage circuit 25 sup.- plies energy to the low-voltage circuit v26 through the .transformer 27. The .highfvoltT age circuit breaker 31, obviously, .may be closed first instead of the low-voltage breaker 30, ifV desired. The circuit breakers are latclied in their closed positions vby latches 118 and 119. These latches .are adapted to be Withdrawn by the tripping coils 120 and 121. The closing of the circuit breakers 30 and 31 also completes one of a plurality of parallel circuits from the automatic bus 39, through the Winding. 122 of the relay 37, to a .balancing7 bus 123, through the auxiliary contacts 124 and` 125 of the circuit breakers 31 and 30, to a resistor andthe negative bus'. Upon theycompetion of this circuit, the coil 122 of the relay 37 is energized,.the latter is thereby restored to balance, andthe circuit for the relay 40 is interrupted, so that further rota-tion of the motor 47 and the drum switch 49 is precluded, leaving the segment 50-in engagement With the finger 5.8 for the time being.

` Conditions in the substation remainunchanged so long as the station loadremains constant. kUpon an increase. in. the station load, however, to a predeterminedvaluathe relay 35Will operate by reasonV of' theincreased load current supplied by the station, to complete'a circuit, at its Contact 126, for a relay 127. The relay 127voperates and is latched in the operated position by the latch 128. The relay 127, through its contact 129, completes. a circuitfrom the-automatic bus 39;l throughthe winding130 of the relay 37 andthecontact 129 ofthe relay 127, to .a resistor and ;the negative bus. When the winding 130 of the relay 37 isthus'e'nergized,

the torque produced thereby count-erbalances l that exerted by coil 122, andthe-.contacts'38 areagain closedv by the biasing spring, with the same results as before. `The relay 40 is energizedto start the motor 47,*and the drum switch. 49 is again rotated.

When the s egment,51I of the drum switch engages its associatedr contact lingery 59, a circuit iscompleted from the automatic bus 39, through the Contact 41 of vthe, relay 40, the contact finger 58, segments 5() and 51 and finger 59 of the drum switch49, to the finger 86 of the sequence switches 67, 68and 6 9. If it be assumedv that the sequence switch 68 occupies the position B, as indicatedl in Fi 3, the fingers` 82 and 86thereof will be bridged by the segments 71 and 73,v with the resultthat current is supplied from the automatic bus to the closing relay (not shown) for the ,circuit Vbreaker 131, which corresponds to the.V relay 95 shown. in connection WiththeA circuit` breaker 3Q- The necessary, controlv` circuits for the circuit breakers associated with the transformer 28 are not shown in detail. since they. are duplicates of those shown` in connecton `with circuit ` breakers 30 and 31. Y Asdescrihed in connectionwith thelatter, the closing of .the circuit breakers 131 and 132 completes a parallel. circuit from` the balancing busk 123 to a4 resistor and-thenegative bus so that thecoil 122 of the relay 37 is morestrongly energized than before. The result of this operation is torestore the balance of the relay 37, fdeenergize relay 40 and stop .the motor 47.

It is obvious that` another..translatingunin such as the transformer 29, may. be connected to the .load and supply. circuitsthrough suitable circuit breakers 133l and 134, hy. the re` lay 36, which is set to operate at a higher value,of load current than the relay `35, and the. contact segments52 on the drum switch 4 9 similar to the segment 51. Thesequenceswitchl 69 'may be atl its C position toconnect its fingers 81- and 82through segments.. 72 andy 71, whereby the unit 29 is caused to take third place in the operation sequence. v

Alftery all available translating units have beenconnected inservice, it is desirablethat afurther increase in` load be indicated to an attendant.- I, make provision-for such indication in the following manner. If allthe transformers 27, 28 and 29 have been connected; inthe manner hereinbefore described, and a further increase in the station loa-d. occurs. the resulting operation of a relay 36', which is set at the maximum permissible load, will causethe drum switch 49 .to be :actuated again, asfexplained above.

When the segment 53 engages the finger 61, however, a circuit will be completed for the master lockout relay 45. The relay 45 operates, and is latched in itsoperated position by a latch 133. At the contact 134 of the relay 45, the circuit from positive battery through the manual switch 135, the contact`r134 to the automatic bus 39 is interrupted, and all devices drawing current therefrom are deenergized. The driving circuit for the motor 47 is interrupted at the contact 44 of the relay 45 and, at contact 136, a circuit is closed for an'alarm, such as the gong 137. rlhis indicates to an attendant that the station is overloaded and that steps should be taken to reduce the load. rlhe signal device 137 may be located in the station if there are attendants present or it may be placed in any suitable position, such as the oflice of the system Voperator, which may be located at a considerable distance from the station. A Y

Afterthe operation of the master lockout relay 45, it is necessary that an attendant visit the station to reset the lock-out relay by withdrawing the manual latch 133. Until this is done, all automatic operation of the station is, of course, suspended, the translating units remaining connected, so that no interruption in service occurs. Obviously, the relay 36 may control t-he relay 45 directly instead of through the medium of the drum switch, as shown. The time required for the operation of the latter, however, prevents the operation of the master lockout relay 45 upon the occurrence of a temporary overload on the station.

t will be understood from" statements above made that the current relays V35, 36

and 36 are set to operate at different values of current so that they operate'successively, as the station load increases, to cause the second and third'units to be connected and the station to be finally locked out 'as described hereinabove.k

Assuming` now that the station load has increased to such value that the transformvers 27 28 and 29 are connected in service but the master Vlockout relay is not operated, if the station load decreases, the relay 364 .will be so actuated that its back contact will be closed to energize the tripping coil 139 of the relay 138. The latter is thereupon reset and the balance relay 37 operates, because of the opening of one of the plurality of circuits for the left-hand coil thereof at the contact'129 of the relay 138, tov closeits right-hand contacts 140. This result follows because, after the opening of lcontact 129', theY coil 122 is energized more strongly than the coil 130.

The closing of the right-hand contacts of therelay37 completes an obvicusfenergizing circuit for a Arelay 141 which,inr turn, completes a circuit from .the automatic bus 39 through the contact 44 of the relay 45 which, itwas assumed, has been reset manually after locking out, as previously described, a contact 142 of the relay 141 to the armature 46 of the motor 47 L The reverse field winding 143 of the motor is simultaneously energized by the closing of contact 144. rlhe contact of relay 141 sets up a circuit froml the automatic bus 39 to the contact iinger 62 of the drum relay 49.

Since it was assumed that the units 27, 23 and 29, were in service, it is obvious that the drum switch 49 will be so positioned that segment 52 engages the finger 60. Such be* ing the case nothing will happen until the reverse movementof the drum switch causes segment 56 to engage finger' 64, whereupon the circuit to the linger 62 will be extended, through segments 54 and 56, to a tripping conductor 146 which is connected to a finger 35 of the sequence switches 67, 63 and 69. lt will be assumed that the sequence switches 67, 63 and 69 are so adjusted, as before stated, that transformer 27 is the lead-o5 unit, and transformers 28 and 29 thesecond and third units. tion, the sequence 'switch 67 should be placed in position A, sequence switch 63 in position B Vand switch 69 in position C. The circuit traced to the conductor 146 and contact finV gers 35 of the sequence switches, therefore, extends from linger 35of thesequence switch 69 to segment 74,'segment 76 and finger' 92 of said sequence switch.

Since the complete closing and tripping` circuits for the circuits breakers 131-134 have not been shown, the tripping of the circuit breakers 133 and 134 will be described in connection with circuit breakers 30 and 31, it being remembered that circuit breakers 133 and134 are tripped by thel first decrease in the station load sufficient to cause the relay 36 to close its back contact. From the finger 92, the circuit extends to the tripping coils for the circuit'breakers 133 and 134 corresponding to those illustrated'at 120 and 121 for the circuit breakers 30 and 31. rEhe tripping coils withdraw the latches which maintain the circuit breakers closed, and the breakers are tripped in the usual manner. f

The tripping` of the circuit breakers 133 and 134, at the auxiliary contacts thereof, opens one of the parallel circuits to the balancing bus 123. IThe lenergization of the coil 122 of the relay 37 is thereby d1 ninished,

To arrange this4 sequence of operaf and the relay 37 is restored'to balance. The

opening of the contactsV 146Y Vthereof Kile-V energizes the relay 141 and stops the motor 7. i

l desire to emphasize, at'this'point, the advantage resulting from the staggering of the segments 55 and 56 with respect to segments 51and 52. rlhis arrangement of contact segments requires that a movement of the switch 49 be effected before anyk unit is tripped, and thus introduces a'slight time delay between the decrease in the station load and the reduction in the member of translating units connected. If this time delay were not. provided, a rapidly fluctuating load on the station might cause repeated closing and tripping ofthe circuit breakers 133 and 134. This repetition of needless operations is avoided by properly staggering the contact segments 51, 52 and 55, 56 so that no change in the number of connected translating devices will be eil'eeted until a substantial change in load conditions occurs, of sufficient duration to permit the required movement of the switch 49.

Further decrease in the station load will cause the relay 35 kto `close its back contact to repeat the tripping impulse through the relays 127 and 37. Segment 55 of the switch 49 subsequently engages finger 63 to extend a tripping circuit for the circuit breakers 131 and 132 through lingers 90 and 92 bridged by segments and 76 of sequence switch 68 which is in position B. The translating units are thus disconnected from the load and supply circuits until the station load is balanced, with the capacity of the translating devices connected in circuit, or until only one unitremains in service.

In addition to the automatic operation described hereinbefore, I provide manual means for controlling the operation ofthe circuit breakers which connect the translating units between their load and supply circuits. Examples of these means are the closing and tripping switches illustrated at 98 and 99. The manual switch 98 is adapted to complete a circuit :for relay 95 from the non-automatic bus 147, which may be connected to the auxiliary source of current by actuating the manual switch 135 to the non-automatic position. As a result of the operation of the relay 95, the circuit breakers are closed, as described above. The manual switch 99 is for the purpose of tripping the circuit breakers 30 and 31 and, when operated, completes an energizing circuit for the trip coils 120 and 121.

A partcular feature ofthe manual switch .is that, when the tripping switch 99 is actuated, the normally-closed back contact97 associated therewith is opened and latched to prevent functioning of the automatic circuit-breaker-controlv equipment. `The latch is released when the manual closing switch 98 is actuated. This feature provides for a suspension of the automatic operation during a period of manual operation which may be necessary for any reason. Duplicates of the manual switches 98 and 99'will, obviously, also be provided for each of the units 28 and 29. An alternative means for manually closing the various circuit breakers for connecting the translating units 27, 28 and 29 in service is afforded by the connection of the 'automatic bus 39 to contact fingers 83 ofthe sequence switches 67, 68 and 69. Thus, when the sequence switches are shifted to the D position, in which fingers 82 and 83 are engaged by segments 71 and 73, current is supplied to the relays corresponding to for closing the circuit breakers. This manual operation, obviously, maybe effected even when the switch'135 is in the automatic position. The tripping of the breakers might be similarly accomplished should this bel desirable but, of courseboth closing andftripping by the sequence switches could not be controlled except by adding other contacts to the sequence switches.

The unit llockout relay 101 may be controlled by any number of suitable protective devices each of which is adapted to control contacts, such as those shown at 148. `These contacts are connected in parallel and serve to energize the lockout relay upon the occurrence of any `condition which it is desired to guard against, such as excess load on any unit, excess temperature thereof, or the like. Although only a single lockout relay is illustrated, it is desirable that one such relay be provided for each unit in the station. When any one of the contacts 148 is closed, the circuit for the relay 101 is completed and its f operation closes a circuit at contact 149 for the tripping coils 120 and 121 of the circuit breakers 30 and 31. The unit lockout relay, furthermore, by opening the automatic control circuit at contact 100, prevents continued operation of the transformer 27 in the automatic sequence. Upon the occurrence of such condition, the balance relay 37 is so actuated as to cause another unit, if available, -to be substituted for that disconnected by the protective equipment. The relay 101 is of the manually reset, latching type.

A push-button switch 150 or its equivalent is provided to enable an attendant to reset the motor relay ll7-49 when the station has been locked out automatically. As above stated, after a station lockout, it is necessary for an attendant to reset the lockout relay 45. It is also necessary for the motorrelay l17-49 to be reset and this is accomplished by actuating the switch 150 which completes a circuit for the reverse winding of the motor 47. Vhen the relay 47-49 has been reset, the relay 37 operates automatically, as described above, to connect the first unit in service and additional units are required.

It will be apparent that the system of my invention provides means whereby the aggregate connected translatingcapacity-of an automatic station may be made to correspond to the station load. This system obviates certain diliculties experienced in similar systems known heretofore. vThe principal of these ris that, in the present case, the loadindicating relays respond lonly at a definite value of station load. Exact balancing of the load-indicating relay, therefore, is easily possible, whereas, in previous systems, the load-indicating coil of the balance relay was continually subject to changes in its energizetion, in accordance with stationload, so that maintenance of an exact balance ot the relay was exceedingly diilicult. In this system also, I am able to vary the sequence in which the units are connected by a simple adjustment of the sequence switch. Upon the lockout of any unit, furthermore, another unit is automatically substituted. .Excess translating capacity, also, is automatically disconnected as soon as the station load decreases to a predetermined value. i

Various changes, modiiications, substitutions, additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention:

l. An automatic station comprising a plurality of transformers, circuit breakers for connecting the windings ot said transformers to load and supply circuits, closing and tripping means for said circuit-breakers, a drum switch adapted to successively energize said closing means when rotated in one `direction and said tripping moans when rotated in the other direction, a motor for driving said switch in both directions, and a balanced relay for controlling said motor, said rela-y having opposing windings, one of which is energized in proportion to the numbery of connected translating devices, and the other of which is energized by a plurality of over-current relays responsive to successively increasing values of the current in the supply circuit and relays controlled by said balance relay for causing either the closing or the tripping means to be energized by said drum switch. y

2. The combination with a plurality oi translating devices, circuit-breakers for connecting said devices to load and supply circuits, closing and tripping coils for said circuit breakers, of a controller load-responsiverelay means for energizing said closing coils when operated in one direction and said tripping coils when operated in the reverse direction, means for operating said controller in both directions, a relay for controlling said operatine' means, said relay having two opposing windings, one controlled by auxiliary switches on said circuit-breakers and the other controlled by over-current relays responsive to successively increasing values of current in said supply circuit.

3. ln a multi-unit automatic translating station, a plurality of translating' devices, switches for connecting said devices to load and supply circuits, operating and releasing means for said switches, a controller for successively energizing said'means, a motor for driving said controller and a two-winding differential relay Jfor controlling said motor, auxiliary contacts on said switches for controlling the energization or" one winding of said relay, and a plurality of relays responsive to the current in said supply circuit for controlling the energization or' the other winding of said ditterential relay.

l. An automatic station comprising a plurality of translating units, means for connecting said units between load and supply circuits, and means for successively operating said connecting means, including a balance relay normally biased to effect the connection of one of said units between `said circuits, means controlled by said connecting means for restoring said relay to neutral, and a plurality of over-current relays responsive to predetermined different values of current in said supply circuit ror again biasing said balance relay to effect the connection of an additional unit when the station load exceeds the capacity of the unit previously connected.

5. An automatic. station comprising a plurality of translatingunits, means Jfor connecting said units to a supply circuit and to a load circuit, and means for successively operating said connecting means, including a balancerelay effective in one position to cause thesuccessive closing of said connecting means to connect said units to said load and supply circuits, and in the other position to cause the successive opening of said connecting means to disconnect said units, means normally biasing said relay to said first-mentioned position, a solenoid controlled by a plurality of relays responsive to the station load for assisting said biasing means and a solenoid controlled by said connecting means for opposing said biasing means, whereby an additional unit is connected `between said circuits whenever the station load exceeds a certain relation to 'the number of connected units, and a unit is disconnected whenever the station load has a certainother relation to the capacity ci the connected units by a predetermined a iount.

6. ln a multi-unit automatic station, supply and load circuits, a plurality of translating units, means for successively connecting said units therebetween and disconnecting said units therefromV inthe reverse order of their connection, a relay for controlling said means and a plurality of over-current relays responsive to different predetermined values of current in said supply circuit for controlling` said first-mentioned relay.

7. In an automatic station, a plurality of translating devices, meansy for connecting them between load and supply circuits for transferring energy therebetween, load relays responsive to the total station load, a balance relay having two opposing windings, means whereby said load relays control the energization of one of said windings, means controlled by said balance relay for controlling the operation of said connecting means and means for controlling the energization of the other winding of said balance relay in response to said operation.

8. In an automatic station having a plurality of translating units andvmeans including a motor-operated switch for connecting them to load and supply circuits, a balance `relay for controlling the operation of said connecting means, said relay having opposing windings adapted to be energized from a common source, and means responsive to the station load ,and to the number of said units connected to said circuits respectively, for controlling the energization of said windings.

9. An automatic station including a plurality of translating devices, means includin a balance relay responsive to the station loa and the number of translating devices in service for varying the number of said devices in service, and means for delaying the initiation of the operation of said devices for a predetermined time after the occurrence of a predetermined change in the station load comprising a drum switch having spaced contacts, adapted to be controlled by said loadresponsive means.

l0. In an automatic station, apparatus units, means for rendering said units elfective including a balance relay adapted to be controlled in accordance with the station load and the number of said units connected in f service, means for biasing said balance relay to maintain at least one of said units in service at all times, and means including a motoroperated timing device controlled by said re lay for causing other units to become effective after a time delay, upon an increase in the station load.

11. In an automatic station, apparatus units, means for renderingsaid units effective including a balance relay adapted to be energized from a common source and controlled in accordance with the station load and the number of said units connected in service, and means for biasing said relay to maintain at least one of said units in service at all times.

l2. In a control system for a plurality of apparatus units adapted to supply a common load, means for eifecting the initiation and cessation of the operation of said units, a balance relay having opposing electro-magnetic operating means for controlling said iirst-mentioned means, and means for controlling the energization of said operating means from a single energy source in accordance with the common load and the number of units connected whereby the effects of Vation of said devices, and control means comprising a balance relay for said first-mentioned means responsive only to definite, predetermined changes in the station load.

In testimony whereof, I have hereunto subscribedmy name this 20th day of May-1929. 70

ALFRED J. A. PETERSON.

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