US2049931A - System of motor control - Google Patents

Description

Aug. 4, 1936. H. L. VAN VALKENB'URG SYSTEM OF MOTOR CONTROL Filed July 9, 1932 Patented Aug. 4, 1936 PATENT OFFICE SYSTEM OF MOTOR CONTROL Hermon L. Van Valkenburg, Wauwatosa, Wis., assignor to Square B Company, Detroit, Mich.

. Application July 9, 1932, Serial No. 621,694

8 Claims.

This invention relates'to a system of motor control.

In the operation of power systems it frequently happens that the service may be interrupted for a very short interval, which, with the ordinary system of motor control in common use, permits the controllers or contactors toopen the motor circuit and thus stop the motor. This type of motor control is secured by momentary contact M push buttons giving what is commonly known as low voltage protection.

However, these systems are not wholly satis- ,factory for two primary reasons.

The first defect is due to the fact that although these interruptions may be very short, nevertheless the motor-circuits remain open in certain types of systems.

The second defect is due to the fact that although some systems may employ a delay device, that nevertheless, when a control station is provided at a remote point, a delay mechanism must be provided. for this control station, and it is obvious, therefore, 'that when it is desired to have a plurality of control stations, that the :5 equipment for each station must be duplicated not only with respect to the push buttons but also with respect to the delay devices, and in addition a relatively large number of wires must be run from each control station to the main w contactor, thus greatly increasing the expense and complication of the system.

This invention is designed to overcome the above noted defects, and objects of this inven tion are to provide a novel motor control system 35 in which the contactor drops open when a momentary overload occurs, but nevertheless a time limit relay or delay device is provided and assooiated with the contactor so that the contactor or controller again closes the motor circuit as 49 soon as the voltage returns to the line, while if the interruption is of longer duration, the contactor or controller remains open, and to so asso= ciate this controller with the individual control stations that each individual control station may be made with the utmost simplicity and the connections from each control station to the main controller or contactor requires a minimum num ber of wires, each control station cooperating with the time limit device of the main contactor 51) without requiring a duplication of the construction for each control station;

Further objects are to provide a system of motor control in which any number of control stations may be employed with the utmost ease 55 and with a very simple iormof wiring, and. in

which each control station is itself of simple construction involving a small number of elements.

A further object of this invention is to provide I a motor control system in which the time ele- 5 ment at the contactor has a diiferent period from the time element of each control station, so that this difference in time is utilized to secure the individual control from each control station, and in addition to secure the closing of the contactor m after momentary interruptions of the service.

The invention permits the momentarydepression of any stop switch or push button at any control station with the assurance that the relative. timing of the delay device at each control 15 station andv of the delay device or time element at the contactor is such that the contactor will open, irrespective of the length of time any of the stop buttons may be held depressed.

Embodiments of the invention are shown in the accompanying drawing, in which:

Figure 1 is a diagrammatic view showing one form of the invention. I

Figure 2 is a similar diagrammatic view -show-. ing a further form of the invention.

Figure 3 is a fragmentary view showing one form of dashpot or delay device.

Referring to Figure 1, it will be seen that the supply lines or mains are indicated by the reference characters 8, 2 and 3, and that connection from these mains to the motor 6 is controlled by means of the contactor indicated generally by the reference character 5. This contactor is biased towards open positioneither by gravity or by means of the spring, the conventional illustration being employed. The contactor is closed by means of a holding coil or magnet 8, one end of which is connected to the main 3 and the other end connected to the conductor l.

The contactor or main controller is also pro videcl with a time limit relay which is depressed or closed by any suitable means, as for instance an when S2 operating simultaneously with the con-- trolley and depressing the small contactor 9 so as to bridge the contacts it and ii. tactor Q may be operated in any suitable manner and is conventionally shown as operated by means of a rod is. It is normally spring urged towards open position, but this opening is resisted by means of a timing device or delay device; such 50 as the deshpot i l, within which a piston it Works. Any other delay device could be used.

A detail of one form of delay device or dashpot is shown in Figure 3, from which it will be seen that the piston it is provided with asmall bleed 5 The conl6 and with an upwardly opening check valve M. This construction permits the ouiclr downward motion of the piston due to the fact that the check valve opens but allows the piston to slowly move upwardly. If desired, the cylinder it may be filled with oil. It is, however, to he distinctly understood that other types of delay devices could be used without departing from. the

spirit of the invention.

The control stations are duplicates and each may consist of a box or casing within which start and stop buttons or other types of stop and start switches are positioned. Two control stations are shown and indicated by the reference characters ill and it, but it is to be understood that any number of control stations located at remote points from the contactor may be employed. Obviously if desired, one control station could be built in with the contaotor.

Each control station comprises a starting button 2@ provided with a contactor 2i biased to= wards open position and adapted to close the con tacts 22 and 23. The contact 22 is connected in each case to one of the mains, for instance the main 9 by means of the conductor 26.

Each control station is also provided with a stop button 25 provided with a contactor biased towards closecltposition and normally bridging or closing the contacts 2? and 28. This stop button is provided with a dashpot 29 or other time element or delay device which has a longer closing interval than the time element or delay device of the contactor.

A similar numbering has been, employed for the contacts or the control station i9, and it is to be noted that the contacts 22 and oi the starting buttons are connected in parallel, Whereas the stop buttons are connected in series. Each stop button is, as stated, connected in series with every other stop button and is connected with the holding coil or closing coil 6 of the main contactor so that it any one or" the stop buttons is open the circuit of the holding coil o is opened and the contactor drops open.

At this point it is to be noted particularly that although the time element of the contactor holds its portion of the circuit of the holding coil 6 closed, nevertheless this portion of the circuit is open prior to the closing of the stop button switch due to the tact that the closing oi each stop button switch" at each control station re-= quires a longer interval than that required for the opening of the time relay or time element at the main contactor.

@n the other hand if any of the start buttons oi. the control stations are depressed even inornentarily, the main contactor closes and in stantly closes the circuit of its time element de= vice or time relay due to the fact that the closing motion or the time relay of the main controller is substantially instantaneous, but that its opening motionis delayed the requisite length or time, as heretofore described.

It will be seen that a momentary interruption of service or a momentary low voltage would sufi= ciently deenergize the holding coil 6 as to allow the main contactor to drop open. However, it this interruption lasted only a very brief preole tor-mined period, the time element or time relay of the main contactor would not open, so that ii the voltage was again restored, the contactor would again close the motor circuit. However, if the delay was greater than a predetermined value, the main contactor would remain open.

' n theother hand, if any stop button was incaosaoai mentarily depressed at any control station, the contactor would instantly respond to open the motor circuit and the stop button of the particular control station would not close until after the time relay of the contactor had opened. 6

It is also to be noted that the momentary closing or any starting button would instantly close the contactor.

It is to be noted particularly that a single time relayis employed and is associated with the main contactor and does not have to be duplicated for each control station so that each control station may be of very simple construction and also the wiring for each additional control station that it may be desired to add is of the utmost simplicity.

The invention may take other forms, for example as she in Figure 2. The time relay of the main controller Elli may be electrically operated as distinguished from mechanically operated.

In this form of the invention the main contactor to is provided with an auxiliary contactor 3i adapted to bridge or close the contacts 32 and These contacts 32 and are connected in parallel to the contacts 3 3 and 35 of the electricaliy operated time limit relay associated with the controller, although not mechanically operated thereby. This electrically operated limit relay is provided witha magnet 3b which moves its contactor Ell upwardly to close the contacts 34 and 35 with a relatively quick motion. However, the downward or opening motion of the contactor is delayed by means of the dashpot or other delay device 38, the timing being similar to that previously described for the time limit 35 relay associated with the controller of the first form of the invention, the valve, however, being reversed.

The holding coil or holding magnet of the main contactor is connected in parallel with the coil 3B of the time limit relay. These magnets are connected through each stop button or stop switch indicated generally at ill or each control station ll and 12, and connected through the contacts 38 and 32 to the supply mains.

Inasmuch as the contacts 32 and are in parallel with the contacts 36 and it is obvious that the opening oi the auxiliary contactor of the main contactor 39 will not open the circuit of the holding magnet provided the time limit relay is in closed position, and consequently if the voltage is again restored within a predetermined time, the contactor will again close the motor circult, as in the form previously described.

Each starting button indicated generally at 33 5. at each of the substations is adapted. to momentarliy close the circuit of the closing magnet it and the magnet 36 of the time relay, as each starting button is connected in parallel and establishes connection from one side of each of the 6o magnets 36 and ill) to the main i, the other side of each or the magnets 36 and being connected to the main 8.

Each of the stop buttons is provided with a time limit device, such as the dashpot indicated by the reference character ill, which permits a quick opening motion but a delayed closing motion, the timing of the closing being greater than the timing of the opening of the element St of the time limit relay.

in this form of the invention it is preferable to build the time limit relay in with the main contactor, as previously described, although obviously it could be located at a separate point it tor any cause such-construction was desired. 75

obtains with .this form of the invention as that previously described,inthat any number of control stations may be added without duplicating the time relay and without complicating the wiring.

It will be seen that a novel form of motor control system has been provided in which any number of control stations may be employed with a very simple form of wiring and without undue oomplicationin the wiring system, irrespective of the number of control stations employed.

It will be seen further that although low voltage protection is secured through a time relay or time element adapted torestore service for momentary interruptions which exist for a limited, predetermined time, that nevertheless it is not necessary to duplicate this time relay as additional control stations are provided, as each control station cooperates with the single time limit relay employed with the main contactor or main controller.

Although this invention has been described in considerable detail it is to be undertood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed. I claim:

1. In a motor control system, a main contactor, a delayed action time relay, a holding circuit for said main contactor controlled by said time relay, said time relay being biased towards contactor-open position, a plurality of control stations, each control station having a starting switch and a stop switch, each stop switch cooperating with said time relay for controlling the holding circuit and means for each stop switch for positively closing said stop switch at a rate less than the rated action of said time relay.

2. In a motor control system, a main contactor, a delayed action time relay, a holding circuit for said main contactor controlled by said time relay, said time relay being biased towards contactor-open position,.a plurality of control stations, each control station having a starting switch and a stop switch, each stop switch cooperating with said time relay for controlling the holding circuit, and means for each stop switch for positively closing said stop switch at a rate less than the rate of action of said time relay, the opening of any stop switch or .of said time relay serving to open said holding circuit, said starting switches operating in parallel to said time relay.

3. In a motor control system, a main contactor, holding means for said main contactor responsive to circuit conditions, said holding means including a delayed action device, and a delayed action stop switch cooperating with said holding means. said stop switch except for the delayed action being free to move towards closed position, a spring urging said stop switch towards closed position, said stop switch having a greater delay in returning to its closed position than said delayed action device. has in moving to its open position.

e. In a motor control system, a main contactor, holding means responsive to circuit conditions for normally holding said main contactor closed,

said holding means including a delayed action device biased toward open position, and a push button stop switch for opening saidmain contactor, said push button stop switch being permanently biased towards closed position and having delayed action means retarding its return to closed position for an interval of time greater than that of said delayed action device has in moving to its open position.

5. In a motor control system, a main contactor, a delayed action time relay biased toward open position, a holding circuit for said main contactor controlled by said delay actiontime relay, a stop switch in said holding circuit permanently biased towards closed position, and delay means for delaying the closing motion of said stop switch for a longer interval than that of said delayed action time relay in moving to open position.

6. In a motor control system, a main contactor, a delayed action time relay biasedtowards open position, a holding circuit for said main contactor controlled by said delay action time relay, a starting switch for initially closing said holding circuit, a stop switch in said holding circuit permanently biased towards closed position, and delay means for delaying the closing motion of said stop switch for a longer interval than that oi! said delayed action time relay in moving to its open position.

7. In a motor control system, a main contactor, a delayed action time relay biased towards open position, a holding circuit for said main contactor controlled by said time relay, a plurality of control stations, each control station having a starting switch and a stop switch, each stop switch cooperating with said time relay for controlling the holding circuit, the opening of any stop switch serving to open said holding circuit, a spring biasing each stop switch towards closed position, each stop switch having a delayed closing action slower than the delay of the time relay in moving towards open position.

3. In a motor control system: a main contactor; a delayed action time relay biased to-- wards open position; a holding circuit for said main contactor controlled by said delayed action time relay; and a plurality of control stations, each control station having a push button starting switch biased towards open position for initially closing said holding circuit, and a push button stop switch permanently biased towards closed position and having delay means delaying its closing motion for a greater interval of time than that of said delayed action time,relay in moving towards open position, each of said stop switches being connected in series in said holding circuit.

. HERMON L. VAN VALMNBURG.

Images