US2106100A - Circuit controlling means - Google Patents

Description

Jan. 18, 1938.

B. vk'. JONES CIRCUI T CONTROLLING MEANS Filed Oct. 8, 1936 Inventor; Bery'nminjov J n66, I b fl yd' 4 is Attorngy.

Patented Jan. 18, 1938 UNITED STATES PATENT OFFICE CIRCUIT CONTROLLING MEANS of New York Application October 8,

10 Claims.

My invention relates to circuit controlling means, more particularly to control means for circuit controlling switches of the latched closed type and has for an object the provision of improved control means of this character.

Circuit controlling switches of the latched closed type when applied to the control of electrical apparatus, such for example as electric motors, are usually provided with an operating winding for effecting closure of the switch, with latch means for latching the switch in its closed circuit position upon operation thereto, with interlock means for interrupting the energizing circuit of operating winding as soon as the switch is latched closed, and with control means responsive to various electrical conditions of the circuit such as overload or undervoltage conditions for releasing the latch means automatically to open the switch.

In order fully to protect the electrical apparatus against injury due to abnormal circuit conditions, the circuit controlling switch is usually provided not only with undervoltage means and with instantaneously operable electromagnetic means for releasing the latch, but also with thermal overload means responsive to prolonged overloads of less magnitude than are required to operate the electromagnetic overload. Such thermal overload means are ordinarily incapable of exerting a mechanical force of very great magnitude and accordingly the thermal means, being incapable of directly releasing the latch member, may be arranged to control the latch indirectly by controlling the energization of a special trip device or the deenergization of the undervoltage means.

The above arrangement of the thermal overload means is particularly desirable when the circuit controlling switch and its control means are immersed in a body of oil for operation therein, for in such cases it is desirable substantially to isolate the thermal element from the immersing body of oil, as set forth in my Patent 2,051,380 issued August 18, 1936. Various arrangements of the thermal overload means may advantageously be employed when the operating winding of the circuit controlling switch is controlled by means of a momentary-contact type control switch. When, however, it is desired to control. the operating winding by means of a maintaining-contact type switch, for example a float operated or pressure operated switch, con siderable difficulty may arise. Thus, if the overload device is arranged to deenergize the undervoltage means to effect release of the latch, a

1936, Serial No. 104,605

periodic opening and closing of the circuit controlling switch may result due to the fact that the energizing circuit for the operating winding is reestablished through the interlock contacts each time that the switch opens. Since the latch is held in its releasing position by the overload means, the circuit controlling switch will be caused to open and close periodically as the circuit for the operating Winding is made and broken at the interlock contacts.

Furthermore, if the overload means is arranged to energize a special trip coil, difficulties may arise due to the fact that an adequate supply of energy is necessary to effect operation of the tripping device. Thus, the circuit voltage may be too low to eilect operation of the tripping de vice and yet too high to efiect release of the undervoltage means. Accordingly, the switch will remain closed even though a dangerous overload condition exists in the circuit.

It is therefore a further object of my invention to provide control means for a circuit controlling switch of the latched closed type, which control means is simple and inexpensive and which reliably effects release of the switch in response to predetermined overload and undervoltage conditions.

In carrying out my invention in one form, I provide, in connection with a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed position, and means responsive to closure of the switch for deenergizing the operating winding, control means comprising normally energized means operable when deenergized to release the latch means, relay means for controlling the normally energized means, and overload means for energizing the relay means to efiect deenergization of the normal energized means so as to release the latch upon the occurrence of predetermined overload conditions. Connections are also provided by means of which the overload means short-circuits the normally energized device to effect release of the latch, even though the relay means fails to operate.

More specifically, I provide undervoltage means for releasing the latch in response to a predetermined decrease in the voltage of the circuit controlled by the circuit controlling switch and an auxiliary relay is arranged simultaneously to deenergize the undervoltage means and to interrupt the energizing circuit of the operating winding so as to prevent periodic opening and closing of the circuit controlling switch. The relay means and the operating winding have a definite piclnup voltage which is greater than the dropout voltage of the undervoltage means and the additional connections established by the overload means for short-circuiting the undervoltage means ensure release of the latch, even though circuit voltage may be less than the pick-up voltage of the relay and greater than the dropout voltage of the under-voltage means.

For a more complete understanding of my invention, reference should now be had to the drawin in which the single figure is a somewhat diagrammatic representation of a circuit controlling switch provided with control means embodying my invention.

Referring now to the drawing, I have shown my invention as applied to a circuit controlling swite 5c of the latched closed type provided with circuit controlling contacts H arranged to control the connection of a load circuit represented by a pair of conductors I 2 and a supply circuit represented by a pair of conductors i3. Although I have shown single phase circuits in order to simplify the drawing, my invention is obviously applicable as well to three phase supply and load circuits. As shown, the circuit con trolling switch i8 is provided with an operating winding 1'4- arranged when energized to effect movement of the circuit controlling contacts H to their closed circuit position, with a pivoted latch l5 normally biased to its latching position by a spring 56 and with suitable interlock contacts which comprise a movable contact member '5 connected to the switch it by means of a resilient connection it and arranged to engage a plurality of stationary contacts 19, 20, and 2|. The movable contact H is also connected, as shown, to suitable time delay means 22 represented as a conventional dash-pot for delaying operation of the contact I out of engagement with the stationary contacts 19, 26 and 2! for a predetermined time after the switch i8 is operated to its closed circuit position.

In order to control the latch in response to predetermined undervoltage conditions, I provide undervoltage means of the type disclosed in my Patent 2,001,494, issued May 14, 1935, which undervoltage means may be described for the purposes of the present invention as comprising a full wave rectifier 23 which includes a plurality of asymmetric conducting units 24 for supplying direct cnrrent energy to an energizing winding 2? of an electromagnetic relay which includes a magnetizable core 28 and a pivoted magnetizable armature 2i! biased by gravity to its unattracted position, in which position it effects the release of the latch 15. As more fully described in my above referred to Patent 2,001,494, the armature 2Q, when in its closed circuit position, provides in conjunction with the magnetizable frame :28 a substantially closed magnetic circuit and the full wave rectifier provides a closed local circuit winding 21', so that upon a decrease in the voltage supplied to the terminals of the rectifier, an induced current will flow through the closed local circuit comprising the winding 27 and the legs of the full wave rectifier, which current tends to prevent decay of flux in the closed magnetic circuit and thus retains the armature in its attracted position for a predetermined time after the voltage has decreased.

Adjacent the pivoted latch 15 I also provide an electromagnetic overload device which comprises winding for moving a magnetizable plunger l, the upper end of which carries a projecting finger 32 arranged to engage the pivote latch l5 and operate it to its releasing posit-ion against the bias of the spring it": upon a predetermined degree of energization of the winding 30. The winding is energized from a current transformer 33 so as to be responsive to overload conditions in the circuit represented by the conductors l3 and a heating winding 34 of a suitable thermal overload device 35 is connected in series with the current transformer 33 the winding 36 of the electromagnetic overload device.

As shown, the thermal overload device 35 comprises in addition to the heating winding 34 a bi-metallic element 36, the free end of which carries contact 31 arranged to engage a stationary contact 38.

In addition to the above described apparatus, my improved control means includes a pair of normally closed push-button switches 31 and 38, a control switch 39, which is of the maintaining contact type, and which may be either manually operated or float operated switch for example, and an auxiliary relay 4!) having a pair of normally open contacts 4! and a pair of normally closed contacts 42. Furthermore, in order to energize the Lmdervoltage means in accordance with the voltage of the circuit controlled by the switch If I provide a potential transformer having a pri mary winding 43 connected across the supply circuit represented by the conductors 23 and a secondary winding 44 which supplies energy to the undervoltage means, and likewise supplies control energy for the operating winding It and the auxiliary relay 40.

With the above description of the principal elements in mind, it is believed that a complete understanding of my invention may now be had from a description of the operation. Upon closure of the control switch 39, either manually or in response to a predetermined condition if the switch is float operated or pressure operated, an energizing circuit is established for the operating winding M of the switch H), which circuit may be traced from one side of the secondary winding 44 of the potential transformer through the conductors 45 and 46, the push-button switch 37, the conductors 4'! and 48, the control switch 39, the conductors 43 and 58, the operating winding- 14, a conductor 5!, a pair of interlock contacts 52 carried by the plunger 3| of the electromagnetic overload device, the conductor 53, the cooperating contacts l9, II, and 23, the conductors 5 and 55, the normally closed contacts 42 of the auxiliary relay 4G and by way of the conductors 56 and 5! to the opposite side of the secondary winding 44.

Immediately upon cnergization of the operating winding 14, the contacts l l of the circuit controlling switch it! are operated to their closed circuit position and an energizing circuit is established for the undervoltage means to attract the pivoted armature 29 and release the latch l5 for movement to its latching position. This energizing circuit for the undervoltage means extends from the previously energized conductor 49 through a conductor 53, a pair of interlock contacts 59 on the switch ID, a conductor 5c, the rectifier 23, a conductor 8!, a current limiting resistor 62, the conductors 63 and 64, the cooperating interlock contacts 2i, l1, and 20, the conductors 54 and 55, the normally closed contacts 42 of the auxiliary relay 4!), and by Way of the conduotors 56 and 5'! to the secondary winding M of the potential transformer.

Operation of the switch I!) to its closed circuit (Ill position is also effective to stress the resilient means 58 and accordingly the movable contact ll tends to move out of engagement with the fixed contacts is, so, and 2!. The time delay means 22, however, prevents movement of the contact ll until after the under-voltage means has been energized and the latch l5 has moved to its latching position. As soon as the contact ll is disengaged from the contacts it), 28, and 2!, the energizing circuit for the operating winding Hi is interrupted and accordingly the switch is thereafter maintained in its closed circuit position solely by the latch iii. Likewise, dis engagement of the contact il from the contacts Eli and ii is effective to insert a second resistor $5 in the energizing circuit or" the undervoltage cans so as to reduce the energisation of the rectifier and the winding 2; of the undervoltage relay a predetermined amount. The energizing circuit for the undervoltage means new extends from the conductor through a conductor 6t; and the current limiting resistor 65 to the conductor 55 rather than through the conductors ti l and and the contacts ll, 20, and 2!,

So long as normal current conditions exist in the circuit represented by the conductors i2 and it, the switch it will remain in its closed circuit position under the control the switches 37 and 39. Whenever the switch Sal is open, the energizing circuit for the undervoltage means will be interrupted and accordingly the armature of the undervoltage relay will be released to move the latch 5 to its releasing position and open the switch Ill. If the control switch 38 is a pressure operated or float operated switch, the pushbutton switch 3? may be used to open the switch it at will.

It will now be assumed that with the switch 40 in its closed circuit position, a predetermined decrease in the voltage or" the circuit represented by the conductors l2 and i3 occurs. Consequently, the magnetic flux in the frame 28 and the armature 29 of the undervoltage device tends to decrease, but is maintained for a predetermined time by the induced current flowing in the winding 2'? and. the rectifier 23. If the voltage does not return to its normal value within a predetermined time, the armature 229 will be released and will move to the position shown in the drawing to release the latch and open the switch ill. Although the energizing circuit for the operating winding Hl will be reestablished as soon as the movable contact ll reengages the contacts l9 and 28, the switch it will not be operated to its closed circuit position until the voltage returns to normal, because the pick-up voltage of the switch it is considerably greater than the drop-out voltage of the undervoltage device. As soon as the voltage returns to normal, however, the switch will again be closed and the undervoltage device energized to attract its armature 29 and permit the latch id to move to its latching position.

If a severe overload occurs in the circuit represented by the conductors l2 and i3, a current will be induced in the current transformer 33 which will energize the winding 36 of the electro magnetic overload device suificiently to move the plunger 3! upwardly and operate the latch [5 to its releasing position. Since the energizing circuit for the operating winding N3 of the switch it is interrupted at the contacts 52 upon operation of the plunger ill, the switch iii will not be reclosed, even though the contact i7 reengages the contacts Ill and 29 until the plunger 3| of the overload device returns to its normal position. In order to prevent the plunger 3! of the overload device 25 from returning to its normal posi-- tion as soon as the switch It opens, and thereby reestablishing an energizing circuit for the switch ill, the overload device 25 is preferably provided with suitable latch means, shown as a pivoted spring pressed latch 31a for retaining the plungor (ii in its uppermost position upon operation thereto. The latch Ma may be withdrawn by pressing a button 3H) to release the plunger 3i and permit it to drop and close the circuit through the contacts 52.

It will now be assumed that an overloaded condition exists in the circuit represented by the conductors l2 and 53 which induces in the current transformer 33 a current which is insufficient to operate the plunger 3! of the overload device but which is suirlciently large to cause the heating winding 34 of the thermal overload relay 35 to generate considerable heat. If this overload continues for a predetermined time, the bimetallic element 36 of the thermal relay 35 will flex in adirection to efiect engagement of the contacts 3i and 38 and establish an energizing circuit for the energizing winding of the auxiliary relay 40.

This energizing circuit may be traced from the secondary winding oi the potential transformor through the conductors to and it, the pushbutton switch 31, the conductors and. the contacts 3? and 38, the conductors .38 and lit, the winding of the auxiliary relay 4E, and. by way of the conductors "5E? and 5? to the other side of the secondary winding i l. If the voltage existing on the circuit represented by the conductors i2 and i3 is sufiiciently high to induce in the secondary winding i l of the potential transformer a control voltage which is above the pick-up voltage of the relay lil, the relay will immediately be operated to interrupt at the contacts both the energizing circuit for the undervoltage means and the energizing circuit for the operating winding l4. Consequently, the armature 29 of the undervoltage relay will oper ate with a slight time delay to the position. shown in the drawing to release the latch l5, whereupon the circuit controlling switch M is immediately opened. As hereinbefore mentioned, the energizing circuit for the operating winding M is 11126-- wise interrupted at the relay contacts 42 and accordingly the circuit controlling switch it does not reclose.

Consequent to operation of the relay 49 to its uppermost position, a holding circuit is established for the en rgizing winding of the relay is, which circuit may be traced from the secondary winding 45 of the potential teansforrner through conductors t5 and ii, the push-button switch 38, a conductor T2, the contacts M of relay M, a conductor 13, and by way of the energizing winding for the relay M and the con ductors ill and 5? to the secondary winding Thus, it will be seen that the relay 4e will be maintained in its operating position to prevent reestablishment of an energizing circuit for the operating winding i until such time as the pushbutton switch 33 is operated to decnergize the relay at and reestablish energizing circuits for the operating winding l and the means.

As will be well understood by those skilled in the art, certain types of overloads may cause a considerable decrease in the voltage of the circult and I have found in actual practice that overundervoltagc load conditions will often arise in which the voltage of the circuit represented by the conductors l2 and 13 may be of such a value that the control voltage induced in the secondary winding 44 of the potential transformer will be less than the pick-up value of the relay and greater than the drop-out value of the undervoltage lieans. Under such voltage conditions, closure of the contacts 3'! and 38 does not effect operation of the auxiliary relay 4!! and since the control voltage is of sufficient magnitude to maintain the undervoltage device in its energized position, the circuit controlling switch in will not be opened, even though a dangerous overload con dition exists in the circuit represented by the conductors l2 and i3.

In order to provide for operation of the switch its open circuit position under such conditions, the contacts 3'! and 38 controlled by the overload relay 35 are arranged upon closure to short-circuit the undervoltage means and thereby ensure release of the latch l5, even though the auxiliary relay 43 does not pick up. This short-circuit extends from the conductor 4'! in the energizing circuit of the undervoltage means through the conductor 2, the contacts 31 and and the conductors 6B and 14 to a midpoint on the current limiting resistor 65. As soon as this short-circuit is completed, the undervoltage means will be substantially deenergized and the latch it will be released to open the switch ll Under these conditions, it is not necessary to interrupt the energizing circuit of the operating winding M since the control voltage available is below the pick-up voltage of the switch 10 and accordingly a periodic opening and closing of the switch 153 cannot occur.

It will thus be seen that I have provided improved control means which will reliably effect operation of the switch ill to its open circuit position under all dangerous conditions of overload or undervoltage.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

1. Control means for a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto a. d means responsive to closure of the switch for deenergizing the operating winding, said control means comprising normally energized means operable upon deenergization thereof to release said latch means, relay means for controlling said normally energized means, overload means for energizing said relay means to effect deenergization of said normally energized means and thereby release said latch means upon the occurrence of predetermined overload conditions, and con nections controlled by said overload lncans for short-circuiting said normally energized means to effect release of said latch means upon the occurrence of said overload conditions even though said relay means fails to operate.

2. Control means for a circuit controlling switch having an Operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto and means responsive to closure of the switch for deenergizing the operating winding, said control means comprising means normally energized from the circuit controlled by said switch and operable when deenergized to release said latch means, relay means energizable from said circuit for controlling the energization of said normally energized means, overload means responsive to predetermined overload conditions for energizing said relay means to effect deenergization of said normally energized means and thereby release said latch means, and connections controlled by said overload means for short-circuiting said normally energized means to effect release of said latch means even though the voltage of said circuit is insufficient to effect operation of said relay means.

3. Control means for a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto and means responsive to closure of the switch for deenergizing the operating winding, said control means comprising means normally energized from the circuit controlled by said switch and operable when deenergized to release said latch means, relay means energizable from said circuit for controlling the energization of said normally energized means, overload means responsive to prcdet rrnined overload conditions for energizing said relay means to efi'ect deenergization of said normally energized means and thereby release said latch means, means controlled by said relay means for preventing reenerglzation of said operating winding upon movement of said switch means to its open circuit position, and connections established by said overload means for short-circuiting said normally energized means to effect release of said latch means even though the voltage of said circuit is insufiicient to operate said relay means.

4-. Control means for a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto and means responsive to closure of the switch for decnergizlng the operating winding, said control means comprising undervoltage means energizable from the circuit controlled by said switch for releasing said latch means upon a predetermined decrease in the voltage of said circuit, an auxil ary relay energizable from said circuit, means responsive to predetermined overload conditions for establishing an energizing circuit for said relay, means responsive to operation of said relay for cleenergizing said undervoltage means to release said latch means and for preventing reenergization of said operating winding upon operation of said switch to its open circuit position, and connections established said overload means for short-circuiting said undervoltage means to release said latch means even though the voltage of said circuit is insunicicnt to operate said relay.

5. Control means for a circuit controlling switch havin an operating winding energizable to close the switch, means for latching the switch in its closed circuit 1 osition upon operation thereto and means responsive to closure of the switch for deenergizing the operating winding, said control means comprising undervoltage means onrgizable from the circuit controlled by said switch for rel-easing said latch means upon a pre determined decrease in the voltage of said circuit, an auxiliary relay energizab-le from said circuit, overload means responsive to predetermined overload conditions for establishing an energizing circuit for said auxiliary relay, means responsive to operation of said relay for deenergizing said undervoltage means to release said latch means and for preventing recnergization of said operating winding upon operation of said switch to its open circuit position, said switch and said relay having a pick-up voltage greater than the drop-out voltage of said underroltage means, and connections established by said overload means for short-circuiting said undervoltage means t release said latch even though the voltage of said circuit is greater than said drop-out voltage and less than said pick-up voltage.

6. Control means for uit controlling switch having an operating energizablc to close the switch, means for latching the switch in its closed circuit position upon o1 ration. thercto and means responsive to closure oi. the switch for deenergizing the operating winding, said con. trol means comprising means for deriving from the circuit controlled by said switch a control voltage proportional to the voltage of said circuit, undervoitage means energizablc in accordance with said control voltage for releasing latch Inca upon a predetermined decrease in the voltage of said circuit, an auxiliary relay, over-- load means i sponsive to predetermined overload conditions for one wing said auxiliary iron; said volts deriving means, means respons' to operation of said relay for deenergizing said ruidervoltage means to release said latch means and [or preve r-oonergization of opupon operation of said switch ting vindl to its open circuit position, switch and said relay hav' pick up voltage greater than the dropo t c of said undervoltage means, and blished by said overload means for s.=: iii-lg undervoltage m t. to release said atch means even though control voltage i greater than. said drop-out voltage and less Ji'litll said pick -up voltage.

7. Control means for a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto and means responsive to closure of the switch for rcenergizing the operating winding, said control means comprising undervoltage means energizable from the circuit controlled by said switch for releasing said latch means upon a predetermined decrease in the voltage of said circuit, electroi i'netic means for releasing said latch substantially instantaneously in response to overload currents of predetermined magnitude, an auxiliary relay energizable from said circuit, thermal overload means responsive to prolonged overload currents of less than said predetermined r. enitudc for controlling the encrgizatlon of said relay, means responsive to operation of relay for deenergizing said on voltage means to release said latch and for preventing reenergization of said operating winding upon operation of said switch to its open circuit position, and connections established upon operation of said thermal overload means for short-circuiting said undervoltage means to release said latch independently of said auxiliary relay.

Control means for a circuit controlling ch having an operating winding energizable its closed circuit position upon operation in thereto and means responsive to closure of the switch for deenergizing the operating winding,

said control means comprising means for dcriving from the circuit controlled by said switch a control voltage proportional to the voltage of said circuit, undervoltage means energizable in accordance with said control voltage for releasing said latch means upon a predetermined decrease in the voltage of said circuit, electromagnetic overload means for releasing said latch means substantially instantaneously in response to overload currents of predetermined magnitude, an auxiliary relay, thermal overload means relsponsive to prolonged overload currents of less than said predetermined magnitude for energiz'ng said auxiliary relay from said current deriving means responsive to operation of said relay for deenergizing said undervoltage means to release said latch means and for preventing reenergization of said operating winding upon operation of said switch to its open circuit position, said switch and said relay having an eiiective pick-up voltage greater than the dropout voltage of said undervolt means, connections established upon operation or said thenmal overload means for short-circuiting said undervoltage means to insure release of latch means even though said control voltage is less than said pick-up voltage and greater than said drop-out voltage.

9. Control means a circuit controlling switch having an operating winding energizable to close the switch, means for latching the switch in its closed circuit position upon operation thereto and means respcrsive to closure the switch for deenergizing the winding, said control means comprising undervclt means energizable from the circuit controlle said switch for releasing latch mean; in. a predetermined decrease in the voltage of circuit, an auxiliary relay ener able fr m said circuit, overload means respcn e to mined overload conditions for completing an on ergizing circuit for said relay, means responsive to operation of said relay for deenergizing said undervoltage mea release said latch means and for prover f 12 of said operating winding upon operat'co of said switch to its open circuit position, additional means responsive to operation of said relay for completing a hold ing circuit therefor, manual means for interrupting said holding circuit to deenergize relay to permit reenergization of said operating winding and said undervoltage means, and connections established upon operation of said overload means for short-circuiting said undervoltage means to release said latch means even though the voltage of said circuit is insuflicient to effect operation of said relay.

10. Control means for a circuit controlling switch having an operating windi energizable to close the switch, means for latching the switch in its closed circuit position upon peration thereto and responsive to closure of the switch for deenergizing the operating winding, said control comprising for deriving from the circuit controlled by said switch a control voltage proportional to the voltage of said circuit, means for energizing said operating winding from said voltage deriving means, undervoltage means energizable in accordance with said control voltage for releasing said latch means upon a predetermined decrease in the voltage oi": said circuit, electromagnetic overload means for releasing said latch means substantially instantaneously in response to overload currents of predetermined magnitude, a relay,

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said relay to permit reenergization of said operating winding and said undervoltage means, said switch and said relay having an effective pick-up voltage greater than the drop-out voltage of said undervoltage means, and connections established upon operation of said thermal overload means for short-circuiting said undervoltage means to insure release of said latch means even though said control voltage is less than said pick-up voltage and greater than said drop-out 10 voltage.

BENJAMIN W. JONES.

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