2,424,255 Patented July 22, 1947 UNITED STATES PATENT OFFICE 2,424,255 CONTROL SYSTEM FOR ELECTRIC HOISTS Walter Schaelchlin and Kurt Mahnke, Forest Hills, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corpora— tion of Pennsylvania Application August 10, 1945, Serial No. 610,128 '7 Claims. (Cl. 172-152) 1 Our invention relates to electric hoist control systems and especially to systems for controlling the operation of marine winches. Winch controllers are now available in which a load-responsive ?eld ?uttering relay is series-con nected in the armature circuit of the winch motor and controls a resistor in a separately excited mo tor ?eld circuit so as to weaken the ?eld when the the master switch has reached the position 01 highest lowering speed. The motor is thus per mitted to pass from motoring to overhauling con dition if the hook load is su?iciently large. The - current in the load-responsive relay coil may then increase to further maintain the relay in the ?eld strengthening position. The invention is exempli?ed by the embodi ment of a winch control system described here motor load current decreases below a given value. Due to this function of the relay, the motor, 10 inafter in conjunction with the drawing in which: Figure 1 represents a circuit diagram of the when lowering a light or empty hook, will run system; at increased speed which is desirable for fast Fig. 2 is a typical speed torque characteristic cargo handling. as occurring due to the invention when the mas Controllers with such a relay, however, require experienced and cautions handling and may oth 15' ter switch is rapidly placed in the position of erwise cause damage and danger because a mo highest lowering speeds; while , Fig. 3, for comparison, shows a speed—torque mentary overspeed is apt to occur if the operator diagram typical of the condition obtaining in moves the master switch too rapidly to the high control systems with a ?eld ?uttering relay of speed lowering position. This is due to the fact that during the transition from motoring to over 20 the known type referred to in the foregoing. Referring to Figure 1, numeral 1 denotes a hauling the motor load current is low and hence drum for accommodating the hawser of a hoist or the ?eld relay caused to provide a minimum ?eld. winch. A friction brake 2 is provided for stop As a result, the motor has the tendency to accel ping the drum. This brake is mechanically set erate quickly to an extreme lowering speed before by means of a spring and has a magnet core 3 the ?eld relay becomes effective to strengthen the 25 which releases the brake when energized from motor ?eld and to then reduce the speed. the mains LI and L2 of a suitable direct-cur It is an object of our invention to provide a rent source. The hawser drum is geared to the hoist control system, applicable for winches, which armature of a winch motor WM which has a self while being provided with a load-responsive ?eld control relay in order to afford the advantage 30 excited ?eld winding 5 and a separately excited ?eld winding 6. Winding 5 is designed for oper of the above-mentioned known controllers, is free ation either in series of shunt connection depend of the tendency to run temporarily at overspeed ing upon the control condition of the system, when lowering a light hook and thus eliminates while winding 6 is connected to the above-men the danger or the necessity of special skill in 85 tioned mains LI and L2 through a resistor ‘I herent in the known systems. under control by the contact 8 of a load relay According to our invention, a load relay of the LR. Relay LR has a current coil 9 connected in non-?uttering type for controlling the resistance the circuit of armature 4 and is also provided of the separately excited motor ?eld is provided with a voltage coil 10 which acts‘together with with two control coils of which one is series-con the current winding 9 on the same relay armature nected in the armature circuit of the motor while and receives excitation from the mains LI and L2 the other coil is controlled in dependence upon under control by a master switch MS. Relay LR the position of the master switch so that the relay has a delayed dropout. In the illustrated em is caused to maintain a strong motor ?eld in all bodiment, the delay is obtained by means of a lowering positions of the master switch with the short-circuited winding which is magnetically as exception of the position for highest lowering sociated with the relay armature. speed. Consequently, the ?eld remains strong Several resistors denoted by H, l2, I3, M, iii and during the interval of control movement of the I6 are connected with the motor circuits under master switch regardless of the speed with which control by several relays denoted by IM, 2M, the switch is operated and regardless of the mag 3M, 4M, IA, 2A, 3A, 4A, and DB, respectively. nitude of the motor load current flowing during Relay IM has a contact l‘l actuated by a control that interval. Only after the switch has reached coil [8. Relay 2M has its contact [9 controlled the positive of highest lowering speed is the load by a coil 20. Relay 3M has a main contact 2| responsive coil of the relay effective to cause and an interlock contact 22 actuated by a con either the maintenance of the strong ?eld or a trol coil 23. Relay 4M has also a main contact 55 reduction in ?eld strength depending upon the 24 and an interlock contact 25, both actuated by value of the load current. a coil 26. Relays IM, 2M, 3M and 4M control According to another feature of our invention, the direction of current flow through the arma we provide the load-responsive‘?eld relay with ture 4 of the winch motor and also the connec timing means in order to delay the weakening tion of ?eld winding 5 as regards its series or of the motor ?eld for a short interval of time after 60 2,424,255 3 parallel arrangement relative to the armature 4. Relays IA, 2A, 3A and 4A control the acceler ation characteristic of the motor by shorting the resistors I3 through 55 sequentially, thereby in creasing the current in the motor armature 4. Associated with the control coils 34 and 36 of the relays 3A and 4A are two timing relays IT 4 contact I9. Relay DB picks up because its coil 42 lies in parallel to coil 23 of relay 3M. Hence, contact 4| opens and disconnects the dynamic braking resistor I2. Relay |A picks up in cir cuit LI, 5|, 50, 49, etc. The closure of contact 2| in relay 3M causes coil 3 to release the friction brake 2. Armature 4 and ?eld winding 5 of mo tor WM are now energized in series connection and ET. Relay IT has two contacts 3'1 and 51 controlled by a coil and relay 2T has two in the circuit LI, 2|, 21, I4, I5, I6, 5, 4, I1, L2, contacts 39 and 58 controlled by a coil 49. 10 with resistor II connected at I9 in shunt rela Relay DB has a contact 4| which, when closed, tion to the armature 4. In other words, the re connects resistor I2 across armature 4 for dy sistors I4, I5 and I6 are now effective in series namic braking. Coil 42 of relay DB is excited connection with ?eld winding 5 and armature 4 in all positions of the master switch MS with and the voltage across the armature 4 is lowered the exception of the off position so that the brak~ by resistor II. As a result, the motor is ener ing resistor I2 is effective only when the control 15 gized for operation in the hoisting direction and system is set for stopping the winch. An inter lock contact 43- in relay DB is disposed in the coil circuit of relay 4M and prevents relay 4M for development of lowest hoisting effort. On second point hoisting of switch MS, the above-mentioned control conditions are main from being energized in the off position of the 20 tained with the exception that relay 2M drops out master switch. due to the interruption of its coil circuit. Con All above-mentioned relays of the control sys tact I9 opens and disconnects the shunt resistor tem receive excitation from mains LI and L2 un II for operation at increased speed or torque. der control by the master switch MS and through On third point hoist, relay 2A picks up through a connection which extends through the contacts 25 LI, 3|, 5|, 54, 49, etc., and short~circuits the re 44 and 45 of a low voltage relay LV whose con= trol coil is denoted by 46. > The coil circuits of the above-mentioned relays sistor I4 at contact 29 while opening the inter lock contact 30. Timing relay IT drops out with are connected to the contact ?ngers, such as those delay and closes its contact 51, thereby preparing denoted by 41, of the master switch MS. The switch has a number of contact segments denoted by 48 through 55, respectively, and in the illus a circuit for coil 34 of relay 3A. 2T picks up through LI, 33, 31, 49, 49 etc. The tem is in operative condition and the ?eld wind at 32 for a further increase in hoisting speed or Timing relay closure of contact 29 in relay 2A completes a short circuit for resistor I4 and hence causes a trated example has ?ve selective hoisting posi~ further increase in hoisting speed or torque. tions and five selective lowering positions. On point four hoist, relay 3A comes in through When the mains LI and L2 are excited by the 35 circuit LI, 34, 51, 5|, etc., and shorts resistor I5 closure of a main switch (not illustrated) , the sys torque. Time relay 2T drops out due to the in terruption of its coil circuit at 33, and closes contact 58 with delay, thereby preparing the coil as the master switch is in the illustrated o? po sition due to the fact that contact 2| of relay 3M, 40. circuit for relay 4A. On point ?ve hoist, relay 4A picks up through which controls the supply of load current and LI, 3B, 58, 55, 5|, etc., and shorts resistor I6 at ?eld current to the motor, is in the open posi contact 35 for maximum hoisting speed. tion. Since the excitation of the brake releasing When returning the master switch to the oil’ coil 3 is also controlled by contact 2| of relay 3M, - position, the above-mentioned control steps are the brake remains set. The closure of the main performed substantially in the reverse sequence. switch, however, has the effect of energizing coil The performance of the control system during 46 of relay LV in the circuit LI, 45, 48, L2 and lowering operations is as follows: closes a self-holding circuit at contact 44. Con Starting with the illustrated off position, the sequently, when thereafter the master switch is 50. positioning of switch MS on point one lower has turned out of the off position, relay LV stays the e?ect of energizing coil 20 of relay 2M in the picked up through contact 44 as long as the volt circuit LI, 20, 53, 52, 45, 44, L2. Contact I9 is age between mains LI and L2 remains su?iciently closed so that the shunt resistor II is effective. high. In the case of voltage failure, relay LV Relay 3M is energized through LI, 23, 53, 52, etc., drops out and can be reset only by returning ~ so that the brake 2 is released. Relay DB picks switch MS to the off position. With relay LV in up and opens its contact 4| because its coil 42 the picked up condition, the current for energiz is energized in parallel to coil 23 of relay 3M. ing all other relays is supplied from main LI Relay 4M comes in through LI, 26, 42, 53, etc., and through contacts 44 and 45 and thence through opens contact 4|. Relay 2A picks up in circuit either segment 49 or 52 of switch MS, provided 60 LI, 3|, 53, etc., and short resistor I4 at contact the switch is in any of its hoisting or lowering ing 6 of motor WM is energized, while armature 4 and ?eld winding 5 remain deenergized as long positions. Consequently, when during the oper ation of the winch the relay LV drops out due to voltage failure, all other relays are deenergized so that the motor is stopped and the brake 2 put in operation. When, starting from the illustrated off posi tion, the master switch MS is turned into the first hoisting position, the following operations take place. Relay 3M picks up in circuit LI, 23, 59, 49, 45, 44, L2, and closes contacts 2| and 22. Relay IM picks up in circuit LI, 22, 25, I8, 49, 45, 44, L2, and closes contact I1. Timing relay IT picks up in circuit LI, 30, 38, 49, etc. Relay 2M picks up through L2, 29, 50, 49, etc., and closes 29. Relay 3A picks up through LI, 34, 39, 54, 53, etc., and shorts resistor I5. Relay 4A comes in over LI, 35, 58, 55, 54, 53, etc., and shorts re sistor I6. The armature circuit of motor WM is now closed through LI, 2 I, 24, 9, 4, ||, I9, L2, and the ?eld winding 5 is connected in parallel to the armature 4 through contacts 35 and 24. The mo tor is now energized for low speed lowering op eration with resistors I4, I5 and I6 short-cir cuited and the armature energized in series con nection with resistors II and I3 by a current Whose direction is opposite to that effective dur ing the above-mentioned hoisting operations. The armature current flows through coil 9 of the load relay LR, However, this coil is rendered in 2,424,255 effective due to the fact that coil II) of the same relay is energized in all lowering positions except the ?fth and causes relay LR to close contact 8. thus placing increased excitation on the sepa rately excited ?eld winding 6 in order to reduce the motor speed accordingly. One second point lower, relay 4A drops out teristic with the diagram according to Fig. 3 will elucidate the new performance and advantages of the present invention. According to Fig. 3, which it will be remembered refers to a load-responsive ?eld weakening relay that is not dependent on the position of the master switch, the speed torque characteristic F’ for point 5 lowering under transient acceleration conditions extend from and opens contact 35. Resistor I6 is inserted point QI through points Q2 and Q3 to the ?nal in the circuit of ?eld winding 5 and weakens the 10 load point Q4. Due to the fact that the motor ?eld in order to increase the lower speed. load current is low during the transition between On third point lower, relay IA picks up in cir motoring and overhauling, the load-responsive re cuit LI, 28, 53, etc., and closes contact 21, lay does not respond, so that the separately ex thereby short-circuiting the resistor I3. Relay cited motor ?eld remains weak and causes the 3A drops out and opens contact 32, thereby in serting the resistor I5 in the circuit of ?eld wind 15 motor to accelerate rapidly to a temporary over speed which is reduced only after the load cur ing 5 for a further weakening of the ?eld excita rent reaches a su?icient magnitude. This re tion. duction occurs at point Q3 in Fig. 3. The re On the fourth'point lower, relay 2A ‘drops out sponse of the relay has the effect of causing the and. increases the resistance in the motor ?eld circuit by adding the resistor I4. As mentioned, 20 motor to thereafter run at a lower speed in ac cordance with point Q4. It thus will be seen that, the relay LR stays in during all above-mentioned when the master controller is turned from off to lowering operations. ?fth point lower at excessive speed, the motor On ?fth point lower, relay IA drops out and may develop a temporary overspeed which leads adds resistor IS in series with ?eld winding 5 of the motor. At the same time, the circuit of coil 25 to overstress, jerky operation and may entail clan~ ger to the operating crew. In systems according I0 is interrupted at contact 48 so that relay LR to the invention, these disadvantages are fully is now free to respond to the condition of coil eliminated and the motor condition remains al 9. However, the effect of coil I0 vanishes with ways under safe control regardless of the speed delay. Hence, contact 8 remains closed for an additional interval of time and maintains full 30 with which the master switch is actuated. For the sake of completness, Figs. 2 and 3 indicate also excitation on ?eld winding 6. This permits the the speed torque characteristic occurring at motor to pass from motoring to overhauling con steady state operation, i. e., under steady condi dition in cases where the load on the hook is tions, the characteristics extend also along curves su?iciently high. In such cases, the current in coil 9 will increase and maintain the relay 35 F or F’ except that they then follow the lines G or G’ between points P2, P3 and points Q2, Q3 LR closed before the latter has time todrop out respectively. and to produce a weak ?eld condition. If the load It will be understood by those skilled in the on the hook is insufficient to cause an overhaul art that control systems according to the inven ing condition, the current in coil 9 remains too tion may be modi?ed as to details without de low for closing the contact 8 upon the expiration parting from the principal and essential features of the above-mentioned timing interval. Conse of the invention. For instance, while we have quently, relay LR will then drop out and insert shown an embodiment in which the voltage coil the resistor ‘I in the circuit of ?eld winding 6, of the load-responsive relay is energized directly thereby weakening the ?eld excitation of the mo— through a contact of the master switch, it is tor in order to increase the lowering speed. readily possible to tie this voltage coil up with The performance of the load relay will be more one of the other relays of the system. For in fully understood from the following reference to stance, the relay IA, as illustrated in the draw the schematic diagrams in Figs. 2 and 3. Both ing, can be made to pick up during points one diagrams show a typical speed torque character ' through four lower of the master switch, and istic as occurring when moving the master switch the coil ID of the load relay LR can be energized set rapidly from off to ?fth point lowering. The together with the coil of relay IA or it may be diagram, according to Fig. 2, exempli?es condi energized by a contact actuated by relay IA. tions obtaining in a system which is designed and These and other possibilities of modifying the operative in accordance with the invention and as described in the foregoing in conjunction with 55 invention are not illustrated in the drawing be cause they will be obvious to those skilled in the Fig. 1. The diagram of Fig. 3, in comparison, rep art. resents a typical speed torque characteristic as We claim as our invention: occurring in a system of the known type men 1. A hoist control system, comprising a hoist tioned previously in this speci?cation, The transient speed torque conditions occurring 60 motor, control means connected to said motor and including a master switch having a plurality during the acceleration of the winch motor in a of hoisting and lowering positions for causing system according to Fig. 1 when a load is low said motor to operate at different speeds in the ered with the master controller quickly moved to hoisting and lowering directions respectively, cir point 5, lower, are typi?ed by the curve F in Fig. cuit means for providing controllable ?eld excita 2. Starting at point PI, the lowering speed in tion for said motor, a relay disposed for con creases at a declining motor torque. When the trolling said circuit means to increase and de hook load is sufficient to produce overhauling crease said ?eld excitation and having two con torque, the load relay LR will stay in, as men trol coils, one of said coils being connected to tioned previously, so that the ?eld winding 8 of said motor so as to respond to the load current 70 the motor continues to receive full excitation. In of said motor in order to provide increased ?eld this case, the characteristic will continue steadily excitation when said current exceeds a given through points P2 and P3 to the ?nal operating point P4 depending upon the magnitude of the load. magnitude, said other coil being connected with said control means so as to provide increased A comparison of the above-described charac 75 ?eld excitation when said master switch is in 2,424,255 7 position for lowering speeds and decreased ?eld excitation when said switch is in a position for high lowering speed. 8 5. A hoist control system, comprising a hoist motor having an armature circuit and a shunt ?eld circuit, control means connected to said ar mature circuit and including a master switch hav 2. A hoist control system, comprising a hoist motor having armature circuit and a shunt Cl ing a plurality of hoisting and lowering posi ?eld circuit, control means connected to said tions for causing said motor to operate at differ armature circuit and including a master switch ent speeds in the hoisting and lowering directions having a plurality of hoisting and lowering po sitions for causing said motor to operate at dif ferent speeds in the hoisting and lowering direc tions respectively, resistance means disposed in said ?eld circuit, an electromagnetic relay having contact means connected with said resistance means for controlling the ?eld excitation of said respectively, resistance means disposed in said ?eld circuit, an electromagnetic relay having con tact means connected with said resistance means for controlling the ?eld excitation of said motor, said relay having two coils for controlling said contact means, one of said coils being connected with said armature circuit in order to respond to motor, said relay having two coils for controlling 15 the load current of said motor so as to provide in said contact means, one of said coils being con nected with said armature circuit in order to re spond to the load current of said motor so as to creased ?eld excitation when said current exceeds a given magnitude, said other coil being con nected to said control means in order to be ener provide increased ?eld excitation when said cur“ gized in dependence upon the position of said rent exceeds a given magnitude, said other coil 20 master switch so as to provide increased ?eld ex being connected with said control means so as citation in all lowering positions of said switch to provide increased ?eld excitation when said except the position for highest lowering speed, master switch is in position for low lowering and timing means associated with said relay for speeds and decreased ?eld excitation when said delaying the change from increased to decreased switch is in a position for high lowering speed. 3. A hoist control system, comprising a com pound hoist motor having an armature circuit and a shunt ?eld circuit, control means connected to said armature circuit and including a master ?eld excitation a given interval of time after said switch is placed into said position for highest low ering speed. 6. A hoist control system, comprising a hoist motor having an armature circuit and a sepa switch having a. plurality of hoisting and lowering 30 rately excited ?eld circuit, means disposed for controlling the excitation of said ?eld circuit and different speeds in the hoisting and lowering di connected with said armature circuit to strength rections respectively, resistance means disposed positions for causing said motor to operate at in said shunt ?eld circuit, a relay having two con en said excitation when the load current in said trol coils and being disposed for controlling said 35 armature circuit exceeds a given magnitude, op erator-actuated master control means connected resistance means to vary the ?eld excitation of to said motor for causing it to selectively operate said motor, one of said coils being connected with at different hoisting and lowering speeds, and said armature circuit in order to respond to the means under control by said master control means to render said load responsive control means in 40 effective when said master controller is set for ceeds a given magnitude, said other coil being lowering with the exception of the setting for connected to said control means in order to be highest lowering speed. load current of said motor so as to provide in creased ?eld excitation when said current ex energized in dependence upon the position of said 7. A control system for wi ches, comprising a master switch so as to provide increased ?eld winch motor having an armature circuit and a excitation in all lowering positions of said switch 45 Li. A hoist control system, comprising a motor, separately excited ?eld circuit, resistance means disposed in said ?eld circuit, an electromagnetic magnitude, said other coil being connected with switch contacts and said armature circuit for position for high lowering speed, and timing highest lowering speed in order to permit said except the position for highest lowering speed. relay disposed for controlling said resistance control means connected to said motor and hav means and having two control coils, one of said ing a master switch with a plurality of positions for controlling said motor to operate at different 50 coils being connected with said armature circuit in: order to respond to the load current of said speeds for hoisting and lowering respectively, cir motor so as to provide increased ?eld excitation cuit means for providing adjustable ?eld excita when said current exceeds a given magnitude, tion for said motor, a relay having two coils for control means comprising a selective multi-posi controlling said circuit means, one of said coils being connected with said motor so as to respond 65 tion master switch having contacts adjustable into a plurality of hoisting and lowering posi to the motor load current in order to provide high tions and relay means disposed between said ?eld excitation when said current exceeds a given causing said motor to operate at different selec said control means in order to be energized in de pendence upon the position of said master switch 60 tive hoisting and lowering speeds, said other coil of said relay being also connected to said switch so as to provide high ?eld excitation when said contacts so as to be energized when said switch is switch is in a position for low lowering speeds placed in any lowering position except the one .for and low ?eld excitation when said switch is in a means associated with said relay for delaying the 65 load-responsive coil to cause an increase in ?eld excitation during lowering operations only in said change from high to low ?eld excitation for a highest speed lowering position of said switch. given interval after said switch is placed into said position for high lowering speed. WALTER SCI-IAELCHLIN. KURT MAHNKE.