Патент USA US2131607код для вставки
Patented Sept. 274', 1938 2,131,607 'unrrao STATES PATENT OFFICE 2,131,607 CONTROL SYSTEM Allan‘ J. Wade, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application December 15, 1937, Serial No. 179,887 '11 Claims. (Cl. 172-179) This invention reiates to control systems, more particularly to systems for controlling the stop ping of reversiieie alternating current motors, and it has for an object the provision of a simple, reliable and improved system of this character. Heretol’ore, control systems for reversible al ternating current motors have been proposed wherein provision was made for stopping the motor and its load by plugging the motor. A H) motor is plugged when its primary winding'is connected to the power source for rotation in a direction opposite to that in which its rotor is actuallyrotating. This occurs, for example, when a motor is rotating and driving its load in the 15 forward direction, and the connections between the motor and the source are suddenly reversed. When a motor is plugged, a large reverse torque is developed which quickly brakes the motor and its load to rest. After stopping the load, the vention is the provision of a novel arrangement of control apparatus and circuits whereby an alternating current motor may be plugged, i. e. reverse power braking connections established for the motor, and a simple and reliable electro- 5 responsive device provided for interrupting the reverse power braking connections at substan tially zero speed of the motor and'in which pro vision is made for eliminating inaccuracies re- ' sulting from variations in line voltage and from 10 frequency effects. In carrying the invention into effect in one form thereof, means are provided for connecting the motor to a source of alternating voltage for rotation in the forward direction, and means 15 are provided for disconnecting the motor from the source and reconnecting it therewith for rotation in the reverse direction, thereby estab For the purpose of overcoming this difficulty, various forms of control switches operated either frictionally or electromagnetically by the driving lishing reverse power braking connections for the motor.' In addition, means responsive to 20 the voltage of the primary and secondary wind ings are provided for interrupting the reverse power braking connections at substantially zero speed of the motor. In order to eliminate the frequency effects from the voltages supplied to 25 this voltage responsive means, suitable rectify ing means are provided in the connections. In illustrating the invention in one form there gears, have been arranged to disconnect the 30 motor upon initial reverse movement of the load. duction motor suitable for driving a load which 30 90 motor will start to. drive the load in the reverse direction unless disconnected from the source ' at the proper instant. In many industrial and other applications, such a reversal of the load is undesirable and may lead to damage to ex 25 pensive machinery or other serious accidents. Devices of this character require special drive shaft extensions which, in turn, require space which often is not available. Such devices are also subject to vibrations which adversely af 35 fect their operation and produce rapid deteriora tion. Furthermore, such devices are not suit able for vertical motors without a considerable amount of extra gearing and other complications. Electroresponsive devices connected in the of, it is shown as applied to a wound rotor in must be stopped quickly such, for example, as a large sugar centrifugal or ‘the supercalender of a paper-?nishing machine. It will be understood, however, that the invention has other applica tions and may be applied to other types of motors. 35 For a better and more complete understanding of the invention, reference should now be had to the following speci?cation and to the accom panying drawing in which Fig. 1 is a simple, 40 secondary circuit of an alternating current motor diagrammatical representation of an embodiment have also been utilized for this purpose, but the of the invention, and Fig. 2 is a simple, di agrammatical illustration of a modification of accuracy of these devices was adversely ‘affected by variations in the line voltage and by the frequency effect of the variable frequency alter 45 nating voltage supplied by the secondary wind; ings to the actuating coils of such devices. In this connection, the secondary voltage and fre quency vary in direct proportion and as a result the current supplied to the actuating coil of an the system of Fig. 1. ' Referring now to the drawing, a load, such for 45 example as a sugar centrifugal (not shown) is driven by an alternating current motor l0, illus trated as ‘a wound rotor induction motor. Motor I0 is supplied with power from a suitable source, represented by the three supply lines II to which 50 the motor is connected for rotation in the forward quency', thereby rendering ‘the electroresponslve direction by means of .an electromagnetic con-' device insensitive to variations in the speed of tactor [2 under the control of a suitable master "switch ii, The master switch 13 is illustrated the motor. ' 55 Consequently, an important object of this in? as comprising a pair-of stationary contacts Ii. 55 50 electroresponsive device remains substantially constant over a wide range of voltage and fre 2 2,131,607 and a movable contact l3s for bridging the sta resistor 3| is included in the connections 26 for“ tionary contacts. .the purpose of initially adjusting the balance ofv the coils Us and 2h. A lockout relay 32 is provided to prevent re starting the motor l? until the master switch I3 has been operated to the off position after a , For the purpose of plugging the motor, i. e. establishing reverse power braking connections therefor, and electromagnetic contactor I4 is provided for connecting the primary winding of motor Hi to the source H for rotation in the reverse direction. For the plugging operation, 'both contactors i2 and M are under the ‘control 10 of a control relay l5 which, in turn, is under the control of a. suitable “stop” push button type switch 15. A plugging resistor i1 is included in the second ary circuit oi’ the motor W for limiting the cur 15 rent inrush to the motor during the plugging operation. An electromagnetic contactor it is provided for short~circuiting this resistor when ‘the motor is started from rest. A resistor it known as an accelerating resistor 23 is ‘also including in the secondary circuit of the motor, providedand for an‘ short-siren electromegn he centactor acceleratin sister it during the starting operation 0; ’ motor. For the purpose of controlling the reverse cone tactor M to interrupt the reverse power liveli ing connections at substantially zero speed plugging operation. _ With the foregoing understanding of the ele ments and apparatus and their organization in the system, the operation of the system itself will readily be understood from the following detailed description. To start the motor ill, the master switch I3 is actuated to its closed position in which a circuit is established for the actuating coil of the for ward contactor Hi. This circuit is traced from the lower supply line H, through conductor 33, i contacts of master switch I3, conductors 34 and Elli, lower contacts of lockout relay 32 and control relay i5, conductor 36, actuating coil of contactcr iii to the upperslde oi‘ the supply source ii. In. response to energization, oontactor it‘ closes its contacts to connect the primary winding or"; motor iii to the supply source H for rotation in the forward direction. Simultaneously, an energiz~~ ing circuit is established for the actuating coils of This circuit is the same as previously traced for contactor it. as for as the . ; lugging contactor i8. ' motor, provided, having asuitable core These member electrorespcnsive meanstie areupon iilustrated which means as twoa cctun 30 conductor 35 thence through conductors ST and 38, actuating coil of plugging contactcr i8 and conductor 39 to the upper side of the supply shown ating coils as provided Us and with ale are a pair wound. of stationary relay torr tacts ii in and an armature member Zia carrying a cooperating movable contact member H; which is biased to the open position by a spring Us. In order to eliminate any inaccuracies in the operation of the electroresponsive 2! re" sulting from variations in the line voltage, one of ‘the actuating coils is connected to the primary winding of the motor Hi and the other of the actu“ source ii. Plugging contactor Iii closes ‘its c0n~ tacts in response to energization and short-sin cults the plugging section ll of the secondary resistor. At the same time the actuating coil of a time delay relay 40 which is connected in par allel with the actuating coil of contactor I8 is energized, and after an interval of time deter- eludes connection to a special small secondary the conductor 31 as before and thence through the contacts of time delay relay 40 and actuating coil of accelerating contactor 2D to the upper side of the supply source ii. In response to en“ erg’ization, accelerating contactor ‘20 closes its contacts to short~clrcuit the accelerating resist-0r it, as a result of which'the speed of the motor mined by the setting of the time delay device 40s, the time delay relay 40 closes its contacts to es ating coils is connected to the secondary winding tablish an energizing circuit for the actuating Obviously, this connection oi’ the actuating coil coil of the accelerating cont-actor 20. This circuit to the secondary winding oi the motor also in~ is readily traced from the lower supply line i l to 45 winding on motors such as squirrel-cage motors ‘which do not have secondary working windings, The actuating coils 2h, and Me are so connected that their magnetomotive forces oppose each other. Since any variation in the line voltage is re?ected in the secondary voltage of the motor, any inaccuracy or the relay as a result or" varia“ tion in the line voltage is balanced out the connections described. As the1 * actuating cell We is connected through it open in~ tcrlocks M. on the reverse contact iii to one phase of the secondary terminals . he motor i3. Similarly the actuating coil ‘its ‘ relay 2! connected by means of conducts 25 and and the normallyy open contacts is or relay motor 60 to the primary winding terminals is 2E ‘26 or to the source as shown. In order to eliminate the effects oi‘ ‘varying fre quency of the variable frequency voltage supplied to the actuating coil 2%, suitable full wave recti 65 fying means 21 are included in the connections between the actuating coil and the secondary winding of the motor iii, and a similar rectifying, means 28 is included in the connections between the actuating coil Ric and the source. Although any suitable rectifying means may be employed, the rectifying devices 2'! and are iiiustrateti as copper oxide type recti?ers connected. in‘ Bridge circuit connections to provide full wave recti?ca tion. Suitable resistors 29 3B are included in the coil connections, and a suitable adjustable is increased to full operating speed. If it is desired to stop the motor and. to bring it rapidly to rest, the push button 46 depressed to complete an energizing circuit for the actuating coil of the control relay iii. In response to en ergization, control relay l5 closes its upper and intermediate normally open contacts and opens its lower normally closed contacts thereby to in terrupt the circuit for the actuating coil of for ward contactor i2, and also to interrupt the energizing circuit for contactors I8 and 20, and the time delay relay 40 previously traced through these contacts. As a result forward contactor I2 opens its contacts and vdisconnects the motor In from the supply source I l. Simultaneously con tactor i8 opens its contacts and inserts the plug ging resistor I1 in the secondary circuit of motor iii, and accelerating contactor 20 opens its con tacts and inserts the accelerating resistor IS in the secondary circuit of motor to. In the closed position of the control relay IS, a circuit is established for the actuating coil of the reverse contactor I4 which is traced from the a lower side of the supply source H through the contacts of the master switch I3, conductors 34, 3 2,131,007 35, and H, intermediate contacts of control relay I5, conductor 42, normally closed interlocks on circuit independent of the upper contacts of con trol relay I5 so that when the upper contacts of control relay I5 were subsequently opened in re sponse to deenergization of the relay 2 I, the lock out relay 32 remained closed. In its closed posi the forward contactor I2, actuating coil of re verse contactor I4 to the upper side of the- supply source I I. In response to energization, contactor I4 closes its main contacts to connect the motor ' tion, lockout relay 32 maintains its lower contacts ' III to the supply source II for rotation in the re verse direction while its armature is still rotating in the forward direction. As a result of the es 10 tablishment of these reverse power braking con open and thereby prevents reenergization of the forward contactor I2 until the lockout relay 32 is deenergized by actuating the master switch I3 to its open position in which it is illustrated. 10 In the modi?cation of Fig. 2, the single core type relay 2I is replaced by a balanced voltage nections, a large braking torque is produced which tends to bring the motor III rapidly to rest. The magnitude of the current inrush to the motor and ' type relay 43 illustrated as comprising a pivoted the magnitude of this braking torque are limited arm member ‘3a to which two core members 43s 15 to safe values by means of the plugging resistor and 43¢ in turn are pivoted as illustrated. The 15 l1 and the accelerating resistor I9, both of which coils 43d and ‘3e are similar respectively to the are now included in the secondary circuit of the coils 2Ib and 2I¢ of Fig. 1 and are similarly con nected through recti?ers 44 and 45 to the sec In the closed position of the reverse contactor ondary and primary terminals of the motor. The 20 l4, the interlock I4- is also closed to connect contacts 43: correspond to the contacts 2Id and the actuating coil 2Ib of relay 2I to one phase of 2I1 of the relay 2I of Fig. 1. The coils 43d and the secondary winding of the motor I0. ‘3e and resistors in the balanced voltage relay are At the instant the motor is plugged, the secon so proportioned that at the instant of plugging, dary voltage and frequency of motor III become the contacts 43: will close, and not until the volt age generated across the slip rings of the motor 25' 25 double the locked rotor values and since the fre quency effect of the voltage supplied to coil 2Is, has decreased to one-half of the locked rotor is eliminated by means of the recti?er 21, the voltage, will the contacts of the relay open. magnetomotive force of coil 2Ib is also doubled. The operation of the modi?cation of Fig. 2 is As a result a ?ux is set up through the core and identical with the operation of the system of Fig. ‘ motor. 30 armature member 2'1: of the relay, which causes the armature member to move the movable con tact member 2|: to bridge the stationary contact 2 Id and the movable contact member 2 I j to bridge the stationary contact members 2h. of the relay 1 described in the foregoing. . ‘ able contact member 2I1, a. circuit is completed thepatent statutes the principle of this inven tion has been explained ‘and the structure de scribed and explained which embodies the best mode in which it is contemplated applying the principle of the invention, it will be understood that the apparatus and elements and connections in parallel with the contents of the push button ' switch I 6 which may now be released. The that the invention is not limited thereto, since 35 against the tension of the spring Zlg. When the stationary contacts 2| 4 are bridged by the mov 40 closing of contacts 2h; completes the connection 80 Although in accordance with the provisions of shown and desscribed are merely illustrative and alterations and modifications‘; will readily suggest 40 of coil 2Ic to the primary winding of motor Ill. themselves to persons skilled in the art without As the speed of the motor III is reduced, the , departing from the true spirit of this invention or magnitude of the secondary voltage and the from the scope of the annexed claims. magnitude ofv the magnetomotive force of the What I claim as new and desire to secure by 45 coil 2h, are correspondingly reduced. At sub stantially zero speed of motor ID the magnetomo tive force of coil 2Ib‘becomes equal to and bal anced by the magnetomotive force of coil 2|c thereby reducing the ?ux in the core and arma 50 ture of the relay to zero and allowing the spring 2|; to open the contacts 2Ie and 2Ih. Since the push button switch I6 has been released, relay 2I in its open position interrupts the energizing circuit for the control relay I5. As the result of 55 deenergization, control relay I5 closes its lower contact and opens its upper and intermediate contacts to interrupt the energizing circuit for Letters Patent of the United States is: 1. A control system 'for alternating current 60 ~ , 70 motors having primary and secondary windings comprising means for establishing reverse power connections to brake said motor, and means con trolled in response to the voltage supplied to the primary winding and the voltage 01' said. second ary winding for interrupting said reverse power connections at substantially zero speed of said motor. 2. A control system for an alternating current motor having a primary winding and a secondary winding comprising means for establishing 're verse power braking connections to the primary the reverse contactor I4. As a result of its de energization, contactor I4 opens its main contacts ' winding of said motor, and means responsive to the voltage of said secondary winding and the 60 to interrupt the reverse power braking connec tions for the motor III, and also opens its inter-, voltage supplied to said primary winding for in lock contact I 4! to interrupt the connections for terrupting said reverse power connections com the actuating coil 2h, of relay 2I. The circuit of prising an electromagnetic switching device hav ing electrical connections to both said windings. coil 2 Ic is interrupted at contacts 2 lb 3. A control system for an alternating current 65 When control relay I5 was actuated to the closed position in response to closure of the push motor having a primary winding and a secondary winding, comprising means for establishing re button switch I6, a'circuit was established for the verse power braking connections from a source actuating coil of the lookout relay 82 which cir cuit is traced from the lower side of the supply of power to said primary winding, and means re source II through the contacts of the master sponsive to the voltage supplied to said primary switch I3, conductors 34, 35 and 4|, upper con- ‘ winding and the voltage‘of said secondary wind tact of control relay I5 and actuating coil of lock out relay 32 to the upper side of supply source I I. In response to energization, the lookout relay closed its upper contacts to complete a locking ‘ ing for interrupting said connections at substan tially zero speed of said motor comprising an electromagnetic switching device having electri cal connections to both said windings and recti 75 4 2,181,607 tying means included in said electrical connec tions. - 4. A control system for alternating current motors having a primary winding and a second ary winding comprising means for connecting said motor to a supply source, means for estab lishing reverse power braking connections for said motor, and means responsive to the voltage of said secondary winding and the voltage sup plied to said primary winding for interrupting said reverse power connections at substantially zero speed of said motor’comprising an electro magnetic switching device having a core member and a pair of coils arranged in opposition there on, electrical connections from one of said coils to the primary winding of said motor and from the other of said coils to said secondary winding and rectifying means included in said connections for eliminating the effect of the frequency of said voltages. -‘ 5. A control system for an alternating current motor having a primary winding and a second ary winding comprising a contactor for connect ing the primary winding to a supply source for rotation in a forward direction, a second con tactor for‘ connecting said primary winding to said source for rotation in the reverse connec tion, means for actuating said first contactor to disconnect said primary winding from said source 30 and for actuating said second contactor to con nect said primary winding to said source to estab lish reverse power braking connections for said motor, and means for actuating said second con tactor to interrupt said braking connections at substantially zero speed of said ' motor com prising an electromagnetic switching device hav ing a core member and a pair of coils, each connected to one of said windings and arranged on said core so that their magnetic fluxes are in opposition. 6. A control system for alternating current motors having a primary winding and a second ary winding, reversing switching mechanism for said motor comprising forward and reverse elec 45 tromagnetic contactors, means for actuating said forward contactor to connect said primary wind ing to a source, a switching device for deener gizing said forward contactor thereby to discon contactor to establish reverse power braking con nections for said motor, and means for inter rupting said reverse power braking connections at substantially zero speed of said motor com prising a balanced type relay having a pivoted member provided with a pair of cores connected to said member on opposite sides of the pivot and a coil surrounding each of said cores, and electricalyconnections from one of said coils to said primary winding and from the other of said 10 coils to said secondary winding. 8. A control system for an alternating current motor, having a primary winding and a second ary winding, comprising in combination, revers ing switching mechanism for said motor com 15 prising forward and reverse electromagnetic con tactors, means for actuating said forward con tactor to connect said primary winding to a source, means for actuating said forward con tactor to disconnect said primary from said 20 source and for actuating said reverse contactor to connect said primary, winding to said source to establish reverse power braking connections for said motor, and means for actuating said re-' verse contactor to interrupt said connections at substantially zero speed of said motor compris ing an electromagnetic switching device for con trolling the energization of said reverse contactor having electrical connections to said windings, interlock contacts controlled by said reversing switching mechanism for establishing said elec trical connections only when said braking con nections are established,- and rectifying means in said electrical connections. 9. A control systemfor an alternating current motor having a primary winding and a secondary winding comprising forward and reverse con tactors, means for actuating said forward con tactor to connect said primary winding to a source for rotation in the forward direction, means for actuating said forward contactor to disconnect said motor from said source and for actuating said reverse contactor to establish re verse power braking connections from said pri mary winding to said source, and a balanced volt age type relay for effecting the actuation of said 25 30' 85 40 45 reverse contactor at substantially zero speed of said motor, said relay having a pivoted arm mem ber, a pair of cores attached thereto on opposite sides of said pivot, a coil surounding each of 50 said cores, contacts actuated by the movement of nect said primary winding from said source and for establishing an energizing circuit for said 50 reverse contactor thereby to actuate said Creverse contactor to establish reverse power braking , said pivoted member/and electrical connections from one of said coils to said primary winding connections for said motor, and means for deen ergizing said reverse contactor to interrupt said and from the'other of said coils to said second ary winding, said coils being so proportioned that 55 reverse power braking connections at substan tially zero speed of said motor comprising an their magnetomotive forces are substantially equal at zero speed of said motor whereby said electroresponsive device having a first coil con nected to be responsive to the voltage supplied to contacts are actuated to deenergize said reverse the primary winding of said motor, an opposing contactor. 60 coil connected to be responsive to the voltage of said secondary winding and contacts controlled by said coils for maintainingsaid energizing cir cuit for said reverse contactor upon establish ment of said reverse power connections and for interrupting said energizing circuit when the magnetization of said opposing coil becomes equal to the magnetization of said ?rst coil. '7. A control system for an alternating current motor having a primary winding and‘ a second ary winding comprising in combination a forward contactor and a reverse contactor, means for ac-r tuating ~said forward contactor to connect said primary winding to a source, means for actuating ‘said forward contactor to disconnect said winding 75 from said source and for actuating said reverse 10. A control system for alternating current motors having a primary winding and a second ary winding comprising reversing switching mechanism for said motor, means for actuating said switching mechanism to connect said pri mary winding to a source for rotation in the 65 forward direction, means for actuating said mechanism to disconnect said motor from said source and for establishing reverse power brak ing connections for said motor, and means for controlilng said switching mechanism to inter 70 rupt said reverse power braking connections at substantially zero speed of said motor compris ing an electroresponsive device having electri cal connections to said secondary winding and rectifying means included in said connections 76 9,181,607 5 for eliminating frequency effects from the volt age supplied to said electroresponsive device. connections comprising an electroresponsive re lay having an actuating coil and a pair of nor 11. A control system for an alternating cur rent motor having a primary winding and a sec mally open contacts in parallel with said stop control switch, auxiliary interlock contacts ac tuated by said reversing contactors for connect ing said coil to said secondary winding so that said device closes said normally open contacts ondary winding comprising a forward contactor and a reverse contactor, means for actuating said forward contactor to connect said primary wind ing to a source for rotation in the forward di rection, a stop control switch for actuating said 10 forward contactor to disconnect said primary winding from said source and for actuating said reverse contactor to establish reverse power brak ing connections for said motor, and means for actuating said reverse contactor to interrupt said when said braking connections are established and opens said contacts at a predetermined mo tor speed, and rectifying means included in the connections between said coil and said secondary winding for eliminating frequency effects from the voltage supplied to said coll. ALLAN J. WADE.