US1354708A - Multivalue overload-relay - Google Patents

Description

G. H. WHITTINGHAM AND W. T. HOLMES.

MULTIVALUE OVERLOAD RELAY.

APPLICATION FILED JULY 25.1917.

Patnted Oct. 5,1920.

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APPLICATION FILED JULY 25,19l7.

1,354,708. Patented Oct. 5,1920.

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GEORGE H. WHITTINGHAM AND WILLIAM ASSIGNORS TO MONITOR CONTROLLER C OF MARYLAND.

Specification of Letters Patent.

T. HOLMES, OF BALTIMORE, MARYLAND,

OMPANY OF BALTIMORE, A CORPORATION MULTIVALUE OVERLOAD-RELAY.

Patented Oct. 5, 1920.

Application filed July 25, 1917. Serial No. 182,698.

To all whom it may concern Be it known that We, Gnonen H. WHIT- TINGHAM and WILLIAM T. HOLMES, citizens of the United States, residing at Baltimore, in the State of Maryland, have invented certain new and useful Improvements in Multivalue Overload-Relays, of which the following is a specification.

This invention relates to protective devices for electric motor circuits, and more particularly to multi-value overload relays of the type covered by our co-pending application, Serial No. 56,011, filed Oct. 15, 1915, on which Patent 1,294,218 issued Feb. 11, 1919.

In such co-pending application, there is shown a relay which is normally set so that it will not be affected by the initial rush of starting current, but which is so assoeiated with the main switch that closing of such switch to complete the motor circuit results in setting the relay to respond to any currents in excess of the normal running load, a suitable time interval being interposed to permit the starting current to subside before such adjustment of the relay to final running condition is complete.

In the present arrangement, the relay is normally set to protect the motor against currents in excess of the running load, and means are provided for temporarily adjusting the relay so as to prevent it from responding to the rush of starting current while such current lasts, and then automatically restoring it to normal condition. It is an important object of the invention to provide not only a device for retarding the restoring action during a definite time interval, but, in addition, manually controlled means for delaying the commencement of the restoring operation as'long as the operator may deem necessary or desirable. In such an arrangement, the motor circuit is not closed until after the temporary. adjustment of the relay has taken place.

IVhile in the system shown in our prior application, it was necessary to set the relay to the desired current value when in its abnormal or starting condition. in the present invention the relay may be accurately set when in its normal or running condition, as it is always in such condition when the circuit is dead. This is another feature of practical importance.

A still further object of the present invention is above described, with starting devices, including one or more sections of resistance in the motor circuit, and to provide means whereby the automatic restoring mechanism also serves to out out such resistance, as the relay approaches running condition.

In order that the invention may be readily understood, reference is had to the accompanying drawings, forming part of this specification, and in which,

Figure 1 is a diagram illustrating our im roved protective device applied to a po yphase motor;

ig. 2 is a similar view, illustrating the application of the device to a direct current motor and showing means for controlling resistances in the motor circuit;

to combine an overload relay, as f Fig. 3 is a sectional front elevation, on I an enlarged scale, showing a portion of the automatic operating and restoring mechanism;

Fig. 4 is a side elevation of the same; and,

Fig. 5 is a fragmentary, sectional elevation, on an enlarged scale, showing one of the overload relays and the adjusting means therefor.

Referring to the drawings in detail, and particularly to Fig. 1, S represents a line switch controlling the supply of three-phase current to the leads 1, 2, and 3. One of the leads, such as 3, is connected directly with an induction motor M, while the other two leads, 1 and 2, are connected to contacts 4 and 5 of a main switch A. This switch comprises the arms 6 and 7, connected by a bar 8 and pivoted as at 9. This switch may be of the usual or any desired construction, the arrangement shown being merely illustrative.

From the pivot points of the arms 6 and 7 of the switch A extend conductors 10 and 12 to the motor M, such conductors including the coils 11 and 13, respectively, of a pair of our improved overload relays.

The operating device for such relays includes a plunger 14, working within a solenoid 15. A wire 16 extends from one of the leads, such as 1, to a. contact 17 of a push button P, the portion 18 thereof, when depressed, being adapted to connect the contact 17 with a similar contact 19. From this contact 19 extends a wire 20 to one side of the solenoid 15, the other side of such solenoid being connected by means of wires 21 contact 24 is connected by means of the wire 23 to the wire 22, while the contact 25 is connected by means of the wire 26 to one side of an electromagnet 27, arranged to operate the switch A, the other side of said electromagnetbeing connected by means of wire" 28 with one contact 29 of a second push button P, the other contact 31 of which is connected by wire 32 with the wire 16, the contacts 29 and 31 being normally bridged by the part 30 of the push button.

The contact 25 is also connected by means of a Wire 33 with one ofa pair of contacts 34, the other one of which is connected by means of a wire 35 with one of a similar pair of contacts 34, the other of which is connected by a wire 39 with an auxiliary contact 40, adapted to be engaged by the switch arm 7. The contacts 34 are normally bridged by a plate 35 loosely supported on a vertical rod 36, slidably mounted in a fixed guide 37, secured to the switchboard. A light helical spring 38 is interposed between the plate 35 and guide 37, so as to resiliently hold the plate 35 in engagement with the contacts 34. h

The contacts 34 are bridged by a similar plate 35, supported by a rod 36', sliding freely through a guide bracket 37, in all respects similar to the correspondingly numbered parts just described.

The improved operating devices for the overload relays will now be described. Projecting downwardly from the plunger 14 of the solenoid 15 is a rod41, the end of which is adapted to bear against a movable frame comprising top and bottom members 42 .and 43, respectively, united by a pair of spaced vertical rods 44 and 45. These rods pass a bracket 47, secured to thepanel, and the frame is normally supported in the position shown in Figs. 1 and 3, by means of helical springs 48, which surround the rods 44 and 45 and are interposed between the top member 42 and the shelf 46. Attached to the bracket 47 within the frame is a dashpot D, the piston rod 49 of which is secured to the top bar 42. To the lower end of the rod 49 is secured a piston 50, having ports 51 therethrough, closed by an upwardly opening flap or valve 52. The dashpot cyl nder contains a liquid such as oil orglycerin, and by virtue of the construction described, downward movement of the piston is permitted with comparative freedom, owing to the passage of the liquid through the ports 51, but upward movement of the piston is strongly retarded.

To the lower bar 43 is secured a downwardly extending rod 53, on which is loosely mounted a plate or disk 54, supported by a cross pin 55, and resiliently held against such in by means of a light helical spring 56. he plate 54 is adapted to en age and bridge the contacts 24 and 25 when t e frame is depressed, as will be described.

The rods 36 and 36' are mounted immediately above the solenoids 11 and 13 of the overload relays, respectively. The solenoids 11 and 13 are provided with freely movable cores 58 and 57, respectively, and these cores have projecting upwardly therefrom rods 64 and 63, adapted toabut against the ends of the rods 36 and 36, respectively.

Each of the cores 57 and 58 is provided with a scale 62, as shown in Fig. 5, such scale having a series of numbers indicating current values in amperes and being read in connection with the lower edge of the solenoid. The cores 57 and 58 are supported on the ends of adjusting screws 59 and 60, respectively, set into the cross bar 43. The screws 59 and 60 are preferably provided with lock nuts 61, to maintain them in adjusted position.

In operation, the cores 57 and 58 normally occupy the positions shown in the drawing,

the screws 59 and .60 being adjusted so as to set the cores at any desired scale division corresponding to the current value of the maximum load which it is desired that the motor shall carry under running conditions. This position of the cores will be referred to as their normal position, and when the cores are in this position the relays are in a condition of maximum sensitiveness.

When it is desired to start the motor, the push button P is pressed, thus bridging the contacts 17 and 19 and closing a'circuit from the line through solenoid 15, as will be obvious. The energization of .this solenoid pulls the core 14 downward, and the rod 41,

bearing upon the bar 42, depresses the entire freely through the horlzontal portion 46 of frame composed of the bars 42 and 43 and the rods 44 and 45, compressing the springs 48 and placing the same under tension. The lowering of the bar 43 permits the cores 57 and 58 to move downwardl by gravity so that they project farther below their respective solenoids. It is evident that when they are so lowered, they are in a less effective position and so long as the bar 23 remains depressed, the relays are less sensitive to current flow. As the frame approaches the lower limits of its travel, the plate 54 bridges the contacts 24 and 25, thus closing a circuit through magnet 27 as follows: Beginning at lead 2, the current flows through wire 22, wire 23, contacts 2425, wlre 26, magnet 27, wire 28, push button P and wires 32 and 16 back to the lead 1. This energizes the magnet 27 which immedlately closes the switch A, thus com leting the motor circuit. As the switch closes, it establishes another circuit through magnet 27 by means of the auxiliary contact 40, such circuit extending from contact 40, through wire 39, contacts 34, wire 35*, contacts 34, wire 33, and thence over wire 26 and magnet 27, as before. This is the holding circuit and serves to maintain the switch A closed after the circuit through contacts 24-25 has been broken. Owing to the fact that the cores 57 and 58 have been withdrawn from their respective solenoids before the switch A closes, the relays do not respond to the normal starting current. If, however, by reason of a short circuit or other defect, the current at starting should become excessive, one or the other of the cores 57 or 58 will be drawn upwardly so as to cause its respective rod 63 or 64 to strike the corresponding rod 36' or 36, and thus lift the plate 35 or 35 from the contacts 34' or 34 thereby interrupting the holding c1rcuit through the magnet 27 and permitting the switch A to open. The construction described, therefore, does not result in rendering the relays wholly inoperative at starting, but results in rendering them responsive only to currents in excess of the normal starting current, so that, while such normal starting current is permitted to pass, the system is protected from dangerous or abnormal flow.

\Vhen the solenoid 15 becomes deenerized, due to the release of the push button F, the springs 48 automatically return the frame 42-43 to its normal position. Such return movement is, however, retarded by the dashpot D, so that, even though the push button P be only momentarily depressed, a time interval is interposed between the release of such button and the restoration of the relays to normal running condition. This time interval is usually sufficient to permit the initial rush of starting current to subside.

It will be observed, however, that as long as the button P is held down, the solenoid 15 remains energized, the frame 42-43 is maintained in its depressed position, and the relays remain in their starting or least sensitive condition. t is therefore apparent that by holding down the button P, the operator is enabled to delay the operation of the spring-actuated restoring mechanism as long as desired. In other words, the apparatus described not only provides means for producing a pre-determined amount of retardation of the automatic restoring tion by means of springs 72 means, but also provides manual means for.

delaying at will the commencement of the restoring movement.

After the relay parts have been restored to the position shown in the drawings, which is their normal running position, the motor is protected against overloads. If the current should rise above the point indicated by the scale division to which the cores 57 and 58 have been set, one of these cores will be drawn up and will break the holding circuit of the switch A at contacts 34 or 34', as above described, thus .ning the motor circuit. 7

If it is desired to stop the motor by hand, the button P is depressed. This breaks the holding circuit through magnet 27 at the contacts 29-31, thus opening the motor circuit in the same manner as if an overload had occurred.

In Fig. 2, we have shown one of our improved relays used in connection with a direct current motor having the usual startin resistance. In this figure, S designates the line switch and A the automatic main switch, the other reference characters being as nearly as possible the same as those used in connection with Fig. 1 to designate corresponding parts; therefore, only the respects in which Fig. 2 differs from Fig. 1 will be described.

In the system shown in Fig. 2, we employ but a single overload relay as there is but a single motor circuit. The coil of this relay is designated at 11. The automatic restoring device is the same as that described in Fig. 1, except that the bars 42 and 43 are extended as indicated at 42 and 43, so as to control the starting resistance. F represents the shunt field of the motor which is connected by Wires 83 and 84 with the leads 2 and 10, while M designates the armature, in circuit with which are arranged two sections of resistances'R' and R Resistance is arranged to be sh ort-circuited b means of a switch 65, operated by an electromagnet 66, which is included in a conductor 67, extending from the lead 2 to a contact 68.

This contact is normally engaged by a lever 69, pivoted at 70, and provided with a tailpiece in which is set an adjusting screw 71, so located as to be in the path of movement of the extended end 42 of the bar 42.

The switch 75 is arranged to be operated by an electromagnet 76, included in a con ductor 77, extending from the lead 2 to a contact 78 normally engaged by a lever 79, pivoted at 80, and provided with a tailpiece in which is set an adjusting screw 81, arranged to lie in the path of movement of the extended end 43 of the bar 43. The levers 69 and'7 9 are moved to normal posiand 82, respectively, and are connected with the line 1 by means of Wires 73 and 39 through contact 40.

When the main switchA is open, the switches 65-and 7 5 are also open, and the resist'ances R and R are both included in the motor circuit, As the frame 42- 13- moves downwardly, the levers 69 and 7 9 are swung about their pivots so as to disengage the contacts 68 and 7 8 before plate 54 reaches the contacts 24: and 25, so that when the main switch A closes, the circuits of magnets 66 and 76 are open at the contacts 68 and 78. -As the frame 4243-rises under the influence of the springs 48 and is retarded by the dashpot, the lever 7 9 is first permitted to engage its contact 78, thus energizing the magnet 76 and closing the switch 75, and afterward lever 69 is permitted to engage its contact 68, thus energizing the magnet 66 and closing the switch 65. The resistance sections R and R are therefore successively cut out of circuit as the relay is restored to normal or running position. The time interval between the closure of switches 7 5 and 65 can be regulated as desired by adjusting the screws 71 and 81 so that the frame 42-43 disengages them in proper sequence.

What we claim is: j

1. In a motor control system, the combination with the main motor circuit, of an overload relay in said circuit, said relay being normally set to respond to a predetermined current value, manually controlled means for temporarily adjusting said relay to respond only to a greater current value, and for then closing the motor circuit, and means for automatically restoring said relay to initial condition while said circuit is closed.

2. In a motor control system, the combination with the main motor circuit, of an overload relay in said circuit, said rela being normally set to respond to a pre etermined current value, manually controlled means for temporarily adjusting said relay to respond only to a greater current value, and for then closing the motor circuit, automatic means for restoring the relay to initial condition, while said circuit is closed, and means for retarding the action of said automatic restoring means.

3. In a motor control system, the combination with a main motor circuit, of an overload relay in said circuit, said relay being set to respond to, a predetermined current value, manually controlled means serving by an initial movement to adjust said relay to respond only to a greater current value, and by a further movement to close the motor circuit, said manually controlled means being arranged to maintain such adjustment of the relay as long as desired, andautomatic means for restoring said relay to initial condition after the release of said manually controlled means.

4:. In a motor control system, the combination with a switch controlling the main circuit of the motor, of anoverload relay in said circuit, electromagnetic operating means for said switch controlled by said relay, the parts of said relay being normally in a position of relatively great sensitiveness, manually controlled means for shifting a part of said relay to decrease its sensitiveness and for subsequently closing,

the circuit of the said electromagnetic means, and automatic means for restoring shifting a part of said relay to decrease its sensitiveness and for subsequently closing the circuit of the said electromagnetic means, and automatic means for restoring said relay to normal condition a predetermined time after said manually controlled means has been released.

6. In a motor control system, the combination with the main motor circuit and a normally open switch for controlling the same, of an overload relay having a coil in said circuit and normally set to respond to current of predetermined value, means, including an electromagnetic device, for adjusting said relay to respond only to currents in excess of said predetermined-value and for then causing the. closure of said switch, a manually operable switch, an energizing circuit for said device adapted to remain closed as lon as said latter switch is closed, and means or restoring said relay to normal condition when said electromagnetic device is denergized while said main circuit is closed.

7. In a motor protective apparatus, the combination with the main motor circuit, of an overload relay having a coil in said'circuit, a vertically arranged core loose in said coil, a spring-sustained member on which said core is supported, the core being normally within the coil in such position as to respond to predetermined current values, manually controlled means for temporarily depressing said memberso as to withdraw said core to a position where it responds only to current value in excess of said predetermined value, and means operated by such downward movement of said member for closing the-main motor circuit.

8. In a motor control system, the combination with the main motor circuit, of an overload relay and a resistance in said circuit, said relay being set to respond to cur.- rents of a value no greater than the usual starting current, manually controlled means for temporarily adjusting said relay to respond only to currents in excess of the norrents of a predetermined value less than the usual starting current, means for first ad justing saidrelay torespond only to currents in excess of the normal starting-current, and then closing said motor circuit, automatic means for restoring said relay to normal condition, and for simultaneously short clrcu tmg said resistance, and manual means controlling the actuation of said first mentioned means, for delaying at will the time at which said'automatic means hegins to act.

10. In a motor control'system, the combination with the main motor circuit, of a reslstance thereln, a movable member, means for movlng said member to close the motor circuit, means for maintaining the motor circu t closed, a sprlng for returning said member to initialposition, manual means for delaying at will the beginnin of the return movement, means for retar ing such movement, and means operated by-said member on its return movement for short circuiting said resistance.

In testimony whereof we have aflixed our signatures.

GEORGE H. WHITTINGHAM. WILLIAM T. HOLMES,

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