Патент USA US2125792код для вставки
Aug- 2, 1938- - B. w. JONES 2,125,792 VCONTROL SYSTEM Filed Jan. 50, 1937 Fig. l. 2 Sheets-Sheet 1 ~> Inventor: Benjamin'wdones, by 56/62/16. H ttor-ney. 2 Aug. 2, 1938. B. w. JONES - 2,125,792 CONTROL SYSTEM Filed Jan. 30, 1937 2 Sheets-Sheet 2. Fig.2. // 200 TORQUE 120 8a 150 I ‘\ DYNAMIC BRAKING‘ LOWER/N6 Inventor : 5 eq] amin \Mdo?es, by )émwé/Jwwz Patentet'fAug. 2, 1938v 2,125,792 UNITED ‘STATES PATENT OFFICE 2,125,792 CONTROL SYSTEM _ Benjamin W. Jones, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January 30, 1937, Serial No. 123,217 8 Claims. (Cl. 172—179) This invention relates to control systems, more particularly to systems for controlling the opera motor operation. In other words, it is desirable that all the motor armature resistance shall be tion of electric motors, and it has for an object shunted, thereby to produce the most effective braking and thus, even with increasing load, to the provision of a simple, reliable, and improved 5 system of this character. Still more particularly, the invention relates to motor control systems in which the driving motor is required to drive light loads and also heavy loads which at times may overhaul the motor, 10 and a further object of this invention is the provision of means for safely controlling the motor under these conditions. _ In hoist installations, there has been a demand for‘ ever increasing speeds of lowering an empty 15 hook, together with good safe regulation in brak ing the load for loads that overhaul the motor. For example, there have been demands for empty hook lowering speeds ranging from 150% to 250% of normal running speed, togetherwith safe regu 20 lation for loads that are of such magnitude as to overhaul the motor. Stated in other words, a limit the speed to a safe value. Accordingly, a further object of this invention is the provision of means for producing a moderately steep speed torque characteristic in the power lowering quad rant of motor operation and a fairly ?at speed torque characteristic in the dynamic braking lowering quadrant of motor operation. In carrying the invention into e?ect in one form thereof, a plurality of, resistors are con nected in the motor armature circuit, and means are provided for shunting these resistors, to gether with means for preventing the shunting of one of the resistors during motoring opera tion in one direction, and for shunting this re sistor when the load overhauis the motor. In the case of a motor operating a hoist for driving any load acted upon by gravity, these means also fairly ?at maximum speed-torque curve for the , provide for shunting this resistor when the motor motor is very desirable for this type of installa is hoisting the load, thereby to provide for maxi tion. However, certain difficulties are encoun mum torque output of the motor. g5 tered in obtaining this desired operating char For a better and more complete understanding acteristic. Motor speeds of this order are nat of the invention, reference should now be had to urally obtained with the motor operating with a the following speci?cation and to the accom very weak ?eld. Controllers for such installa panying drawings, in which Fig. 1 is a diagram tions are usually arranged to insert resistance in matical illustration of an embodiment of the 30 the field circuit and to‘ shunt resistance in the invention; Fig. 2 is a simpli?ed diagrammatical armature circuit in predetermined steps. When illustration in “across the line form” of the em a motor is operating'with a ?eld weakened suffi bodiment of Fig. 1; and Fig. 3 is a chart of curves ciently to produce speeds greatly in excess of representing operating characteristics of the mo normal running speed, it is in a very unstable tor, which serve to explain the invention. 3;, operating condition, and shunting the last sec Referring now to the drawings, a motor l0, tion of armature resistance under this condition such for example, as a motor utilized to drive a is very likely to produce bad commutation and hoist, is supplied from a suitable source repre even to produce such a surge of current as to sented by the supply lines il, l2. The motor In result in "?ashover”. 40 ' ‘ _ It is therefore desirable to maintain a section of the armature resistance in circuit when the ‘motor is lowering a load and operating as a motor. This produces a much steeper speed torque curve in the power lowering quadrant of 45 the motor operation, but does eliminate the is illustrated as a series type motor having a series field winding l3 and a commutating ?eld Winding l4. Means are provided for controlling the direc tion of rotation of the motor. These means are illustrated as a multipoint reversing type master switch l5, and a pair of switching devices i6, 11 danger described in the foregoing. ' under the control of the master switch. The However, if the load actually 'overhauls the‘ positions on the right-hand side of the master motor, a steep speed-torque characteristic would ' switch are referred to as the hoistingypositionsr be very undesirable, because the speed might rise and when the master switch is operated to these so quickly to a dangerous value, resulting in dam positions, the switching device l6, referred to as 50 age to the motor and to the apparatus with which the hoisting contactcr, is closed to connect the the motor is associated. Under thiscondition of armature of the motor ill to the source for rota operation, it is desired that the‘maximum speed tion in a direction to hoist the load. Similarly, torque curve of the'motor shall be as ?at as the positions on the left-hand side of the master 55 possible in the dynamic braking quadrant of 'switch are the lowering positions and when the 2 2,125,792 master switch is operated to these positions, the contactor 26, conductor 44 through operating coil lowering contactor I1 is closed to connect the motor ll to the source for rotation in a direc tion to lower the load. Suitable current limiting means illustrated as a plurality of resistors i8, i9, and 20 are included in the armature circuit oi! the motor ior con of contactor 21 to the negative side of the source. Contactor 21 in closing opens its normally closed interlock to interrupt the energizing circuit 0! the contactor 24 previously traced through these interlocks, and, accordingly, contactor 24 is again operated to its open position in which it is illus trated. In the closed position oi the contactor 21, an energizing circuit is completed for con motor. For the purpose of varying the ?eld ex tactor 28 that is traced from the power conductor 10 citation oi the motor, a plurality of resistors ‘M, 10 22, and 23 are included in the field circuit 01' the ' 38 to the conductor 44, as previously, and thence trolling the acceleration and deceleration of the motor, and the shunting of these resistors is under vthrough conductor 44a, segments l5; and ISL oi the control of the electromagnetic contactors 2|, ‘the master switch, conductor 44b, interlock con tacts of contactor 21, normally closed contacts of 2!, and 28, respectively. relay 32, and operating coil of contactor 28 to 15 Contactors 21 and 28 serve to control the shunt 15 ing of resistors I8 and I9, respectively. A resistor the negative side of the supply source. Contactor 29 is at times in the ?eld circuit of the motor and at other times in the armature circuit, de pending upon Whether its controlling contactor Jill 20 is open or closed. ' theA contactor relay 21 provides ‘.21. This counter relay ‘voltage is ordinarily controlcom by a spring or by gravity", to complete nainic braking ci cult for the armatur loop lily‘ of motor terminal it, con» Justed to close its contactav on 25% of nor“ i0 that may he s ‘to extend from in of he motor ti'lrougli trolley W line volts. iii relay 32 having its operating cc“ duc‘tor of dynamic 4?, dynamic braking inciting contactoi' resistor ‘l5 illi, ‘trolley contac "wire 25 connected across the resistors Ill and, it o - operates with interlock contacts 21'; oi" contact-or 21 to control the energization and operation oi 'contactor 28. In order to prevent the relay 32 from energia ing and closing the contactor 28 when the motor 30 i0 is accelerating in the lowering direction, means are provided tor energizing the relay 32 anti causing it to open its contacts when the motor is accelerating in the lowering direction, and for 35 preventing the relay 32 from opening its contact-t it the load should overhaul the motor, These means are illustrated as a recti?er included in therecti?er This circuit may or the he operating of any suitable coil of relay e loot it 40 is preferably of ‘the plate contact t such, for example, as the welldmowo copper hauled by its load in the lowering Clio "t when it is driving the load in the hoist“ ” tion. , With the I‘. descrip this camp‘ eratinga ' from “to of the sol ' on an ant readily‘ Likewise, con \ it and its enei'giringciim L .i tend from the conductor ill 0 75 through segment i512. conductor ‘ it, and thence through series field it and coin mutating field H to the opposite terminal of the motor armature. Thus the apparatus and ele ments are in the positions described in the fore going, and the master switch it”: is in the of‘! posi tion when the pilot switch 3% is closed. Movement of the master switch it: ‘to the ?rst lowering position completes an energizing circuit for the operating coil. oi’ contactor till which ex‘ tenols from the power conductor oi‘ the master , switch ‘through segment I50 and cooperating ?nger, and, thence by conductors iil'ancl t2, and operating coil oi contactoi" Hill to the negative side the source, ?ontactor till closes in rear: energiaation type its circuit of recti?er. that it passes Rectifier current 33 when so connected motor is driving its lead in the lowering dire n and does not current when it is over" 45 55 28 closes in response to energization and shunts the resistor IQ. The contacts of dynamic brak ing contactor 45 are normally held closed either partially completes the 'tl'ii?'ii ergicing circuit circuit oi‘ motor is conilpleteci iii. coil oi contactor M» the is traced to ma» xncously, the operating an 2,125,792 contactor 28, resistors 29 and 2!! to the negative side of the supply source. Thus it will be noted that themotor is con nected to the line with the resistor 2iiv in the armature circuit and the resistors 20 and 28 in the field circuit. Under these conditions, the motor begins to accelerate, and its performance \_ is represented by the characteristic curve 83 of ‘Fig. 3. ' l 10 ’ It will be understood that it is usual practice ~ 3 terlocks of contactor 25 (in the closed position thereof), and operating coil of contactor 30 to the opposite side of the supply source. Contactor 30 closes its contacts in response to energization and connects the resistor 29 in parallel with re sistor 20, and at the same time, it connects the ?eld winding i3 to the negative sides l2 of the supply source through the resistors 23 and 22 without passing through resistor 20, so that the motor is now connected to the line in a straight 10 for the operator to throw the master switch quicklyfrom the off position to the maximum shunt connection, and the motor performances speed position. However, this operation is de Contactor 30 in closing completes an energizing circuit for accelerating relay 3|. This circuit is traced from the terminals ills of the motor arma 15 ture through conductors 46 and 41, resistor 48, conductor ‘Ii , operating coil of relay 3|, conductor scribed as taking place step by step so that the 15 operation may be more readily visualized and understood. 0n the second point, of the master switch, the energizing circuit of contactor 28 is interrupted at the segments l 51, P51. of the master switch, and 20 the contactor opens its contact and inserts the re will be in accordance with the curve ‘iii of Fig. 3. 12, interlock contacts of relay 30, and thence by conductors 13 and 14 to the common terminal of resistors 22 and 23, and thence through resistor sistor IS in the armature circuit of the motor. 23 to the opposite motor terminal. Relay 3i 20 Under this condition, the performance of the mo closes its contact under the in?uence of the coun tor, that is to say, its speed-torque characteristic, ter voltage of .the motor to complete an energiz is represented by the curve 64 of Fig. 3. When 'ing circuit for contactor 21, provided that the 25 resistor is is inserted in the motor circuit, a volt motor speed has become sufficiently high. The 25 age dro‘p appears across this resistor which causes energizing ‘circuit for contactor 21 is readily current to flow through the operating coil of re traced from‘ power conductor 36 of the master lay 32. This voltage drop is oi such a polarity switch through segment l5g and co-operating that current will ?ow through the recti?er ‘33. ?nger, thence through conductor 15 and contacts 30 The circuit is traced from the right-hand or posi of relay 3i, and thence through conductor 44 tive side of the resistor i 9 through the contacts and the coil of contactor 2'! to the negative side 30 of contactor 2?, thence through conductor 65, op 7 of the supply source. As a result, contactor 21 erating coil of relay 32 and conductor 66, recti?er closes its main contacts and shunts the resistor 33 to the left-hand or negative terminal of the IS in the armature circuit of the motor, thereby 35 resistor. As a result of its energization, relay 32 vcausing it to increase its speed. Under this‘ con opens its contacts and further interrupts the en dition, the motor performance will be in accord 35 ergizing circuit of contactor 28 so that it cannot be reclosed as long as current flows through the resistor IS in the direction from right to left; or 40 in‘ other words, as long as the motor is operating ‘ as a motor in the lowering direction. ance with the speed-torque curve ‘iii of Fig. 3. In the closed position of contactor 21, its in terlock contact 21s interrupts the energizing cir cuit of contactor 24. The coil of contactor 22 is short-circuited by a resistance 11, and accord ingly, this contact will open its contacts with a On the third point of the master switch, the energizing circuit for the'operating coil of con Y slight time delay. Contactor 2i in opening its tactor 21 is interrupted. This energizing circuit contacts inserts the resistor 2i in the ?eld cir 45 was previously traced through the segment i5: cuit oi’ the motor and this produces further accel of the master switch and the interlock contacts eration of the motor in accordance with the char of contactor 26.- Contaotor 21 opens its contacts acteristic curve 18 of Fig. 3. and inserts the resistor i8 in the armature circuit When contactor 2'! closed its contacts, its upper of the motor, and the motor continues to accel-' interlock contacts» also closed, thereby partially to 50 erate its load in accordance with the speed-torque complete an energizing circuitfor the operating characteristic represented by the curve 81' of Fig. coil of contactor 28. However, since the energiz 3. Contactor 21 in opening, recloses its lower ing circuit for contactor 28 is maintained open at interlock contacts 21a to re-establish the ener the contacts of relay 32 as long as the motor is gizing circuit for the operating coil of contactor driving its load in the lowering direction, con 56 24. Contactor 24 closes in response to energize tactor 28 remains open and the resistor i9 re tion. mains in the armature circuit of the motor. At On the fourth point of the master switch, the this time the motor i0 is operating with a very energizing circuit for the operating coil of con- ' weak ?eld because the resistors 2!, 22, and 23 are tactor 26 is interrupted. at the segment [5b of all connected in series in the ?eld circuit. If the 60 the master switch, and the contactor opens its . resistor is in the armature circuit of the motor contacts and inserts the resistor 23 in the field cir could he short-circuited at this time, the motor suit of the motor. This causes the motor to ac performance would be in accordance with the celerate further in accordance with the char speed-torque curve 19 of Fig. 3. It may now be acteristic represented by the curve 68 of Fig. 4. assumed that at the present point in the opera As the master switch passes to its ?fth posi 65 tion, the speed and torque of the motor are repre tion, the energizing circuit for the operating coil sented bythe point 80 on the speed-torque char of contactor 25 is interrupted at the segment I51 acteristic 18. Now it will be observed that if the oi’ the master switch, and as a result, contactor resistor IS in the armature circuit of the motor 25 opens its contacts and inserts resistor 22 in should be short-circuited at this point in the op 70 the field circuit/of the motor._ At ‘the same time eration, the performance of the motor would be an energizing circuit is completed for the operat— suddenly transferred from the point 80 on the ing coil of contactor 30. This circuit is readily characteristic curve 18 to a point 8| on the char traced from the power conductor 36 of the master acteristic curve 19. The point 8| on the curve 19 switch through segments iEd and co-operating 75 ?ngers, thence by conductor 69 through upper in is readily seen to represent» a torque speed of ap proximately 200%, and since torque and current 50 55 60 65 2,120,702 5 8. A motor control system for hoists and the to shunt said resistor during motoring operation > like in which the motor drives the load and at and to provide for operation of said contactor to times is overhauled thereby comprising a plu shunt said resistor when the motor load becomes rality of resistors in the motor armature circuit, prevent said relay from actuating said contactor a plurality of contactors each for shunting a overhauling. 7. A motor control system for hoists and the like in which the motor drives the load and at times is overhauled thereby comprising a reversi 4 in ble type masterlswitch operable to hoisting and to lowering positions for controlling the direction of rotation of said motor, a plurality of resistors in the armature circuit of said motor, a corre sponding plurality of contactors controlled by said master switch for shunting said resistors in succession, and means responsive to motoring operation of said motor in the lowering direction for preventing one of said contactors from shunt ing its corresponding resistor and responsive to overhauling operation and to motoring opera tion in the hoisting direction for effecting opera_ tion of said contac'tor to shunt said correspond ing resistor. - corresponding one of said resistors, a multi-posi tion reversing type master switch for controlling the operation of said contactors in sequence to shunt said resistors, and means responsive to the direction of current flow in the armature cir 10 cuit of said motor for preventing operation of one of said contactors from shunting its correspond ing resistor during motoring operation in the lowering direction and providing for shunting said resistor when said motor is overhauled by its load and during motoring operation in the hoist ing direction said means comprising a rectifier connected across a portion of said armature re sistors. 20 BENJAMIN‘ W. JONES.