US2282986A - Electric controlling apparatus - Google Patents

Description

y 2, 1942. J. D. WOOD 2,282,986

ELECTRIC CONTROLLING APPARATUS Filed June 16, 1939 3 Sheets-Sheet 1 &

ATTORNEY L May- 12, 1942. J. D. WOOD ELECTRIC CONTROLLING APPARATUS 3 Sheets-Sheet 2 Filed June 16, 1938 INVENTOR fis-fiflfl/fao BY K2 2 M ATTORNEY May-12, 1942. J. D. WOOD ELECTRIC CONTROLLING APPARATUS 3 Sheets-Sheet 5 Filed June "16,- 1939 lNVENTOR 55 814 000 BY k 52? M ATTO.RNEY

patented May 12,1942

ELFXJTRIC' CONTROLLING APPARATUS Joseph D. Wood, Bethlehem, Pa., asslgnor, by

mesne assignments, to The Pennsylvania Company for Insurances on Lives and Granting Annuities, Philadelphia, Pa., a corporation of Pennsylvania Application June 1651959, Serial No. 219,431

9 Claims.

diately responsive to very high or excessive lncrease oi the load, or current, beyond a predetermined value. For example, the instantaneous response may be made to occur when the current reaches a value in excess of ten times the normal current, or any other predetermined excessive overload. On the other hand, the apparatus may be made responsive to a comparatively small overload after being continued for say ten or twenty minutes whereas a somewhat greater overload may cause the apparatus to respond after being continued for three or four minutes.

Thatisthe greater theoverload the less the time interval before the apparatus responds to interrupt the controlled circuit breaker or other device. Another object is to provide means for interrupting the supply of energy upon the temperature at a selected location attaining a predetermined value. Another object is to provide a simple form of controlling apparatus which will be dependable and reliable under long continued use. Another object is to provide apparatus which will respond within close limits of the predetermined time intervals depending upon the amount of the overload and also within close limits of the predetermined instantaneous values upon the occurrence of excessive overloads. Another object is to provide simple means for adrjustment oi the apparatus for readily adapting the same to respond at diflerent values accord ing to the setting of the apparatus. Other objects and advantages will be understood from the following description and accompanying z-ldrawings which illustrate various embodiments of the invention.

Fig. 1 is a diagram showing one of the simplest forms or controlling apparatus; Figs. 2 to .10 are diagrams showing various modifications; and Fig. 11 is a graph showing the results obtained with one form of the apparatus under different adjustments or settings.

Referring to Fig. 1 .a source I of alternating current is indicated supplying the lines 2 which lead to the consumption circuit 3 through a circuit breaker 4. This'circuit breaker may be 01' any form or type and is indicated in a conventional simple manner. It is shown in the closed position being restrained by a pivoted latch 8 which is adapted to be automatically tripped when the responsive device comes into playeither instantaneously under an excessive load, or when a fault occurs, or after a time interval depending upon the amount and continuance oi overloads which may be permitted for short intervals without injury to the apparatus connected to the consumption circuit.

A U-shaped magnet i is shown having a vertically movable plunger 1 freely movable upwardly through the end of the lower leg of the magnet and having an upwardly projecting rod 1' which passes freely through the end of the upper leg of the magnet. when the plunger is moved upwardly, it will trip the latch 5 and permit the movable contacts of the breaker to open the line circuit. The magnetic portion 6 of the magnet may be or iron or steel and laminated when desirable. An adjustable screw la engages the bottom of the plunger 1 for adjusting its lower Position.

Between the poles of the magnet is positioned a winding 8 which envelops the upper portion of the plunger Plunger may the winding is shown a bi-metallic strip 9 having one end held in fixed position and carrying a contact 9' at the other end. A similar bi-metallic strip I I has one end held in fixed position and the other end carrying a contact ll which normally engages the contact 9'. The upper terminal oi the winding 8 is connected to a heating coil H which envelops the strip 9 and is connected to the contact 9'. The circuit of the winding is normally completed through the contact ll, strip I 0 and thence by a connection to the lower end of the winding 8. Instead of the heater ll enveloping the strip 9 it may be positioned alongside or the strip 8 in the form 01' a heating coil or resistor, or may be otherwise disposed. When this'strip is sumciently heated the contact 9' will separate from the contact I. and open the circuitoi the winding 8. The strip II is provided for the p p se of compensating for the change in ambient temperatures. That is, it the surrounding temperature should rise or fall appreciably, be afiected equally thereby and will move correspondingly without affecting the separation oi these contacts; 'but when the strip 9 is heated by the heater II at a greater rate than the heat is dissipated therefrom, the temperature of the strip 0 rises relatively to that oi the strip ill and causes the separation of their contacts. In some cases the compensating strip ll may not be used, in which case the connection of the lower terminal oi the winding 8 will be connected directly to the contact ii. In that event the upper terminal oi the winding 8 may sometimes be connected directly to the right-hand end of the strip 9 and cause the current in the local circuit or T and through which winding the pass when raised. At the left of the two strips l and II will this winding to pass through the strip 8 and thereby heat it directly.

The series winding I2 is also located between the poles of the magnet and forms an additional solenoid winding for the plunger I. This winding may be imposed over the winding 8 or wound with it, or adjacent one end of it according to the choice of the designer and the particular characteristics in operation desired. The winding I2 is connected in series in one side of the consumption circuit.

It is apparent that the value of the current passing through the series winding I2 is dependent upon the load current. Under normal conditions this series coil is unable to raise the plunger I and even when overloads occur this winding is likewise inefiective; but under excessive overloads, such as ten times the normal load, or when a short-circuit occurs, the current in the series winding creates a flux sufllciently great to immediately raise the plunger 1 and trip the breaker.

when the load is below that which causes instantaneous tripping of the breaker, a transformer action takes place wherein the winding I2 is the primary winding and the winding 8 the secondary winding. The current induced in the circuit of the secondary winding is dependent upon the current in the primary winding which in turn is dependent upon the load current. The current induced in the secondary winding serves to reduce the flux in the magnetic circuit with the result that the series winding under normal conditions and under permissible overloads is inefiective in raising the plunger and tripping the breaker. Under normal load conditions, the current passing in the circuit of the secondary winding 8 is insuilicient to heat the thermally responsive device 9 sufllciently to separate the contact 9' from the contact ill; but when an overload occurs, the strip 8 will be heated gradually until it finally opens the circuit of the winding 8. If the overload current is say twenty percent and if this overload be continued for say ten minutes, the strip 9 by that time will be heated sumciently to open the circuit of the winding 8. If the overload current is say thirty percent it may continue for seven minutes before the thermally controlled contacts are separated; and the greater the overload the shorter the period it is allowed to continue before separation of the contacts. When, however, the contacts are separated, the opening of this secondary circuit permits the flux in the magnetic circuit to be increased sufficiently to permit the series winding I! to raise the plunger and trip the breaker. Adjustment of the lower position of the plunger I by the screw Ia will determine the value of the current at which the series winding will raise the plunger under excessive overloads but will not materially affect the response under moderate overloads, this being controlled by the opening of the thermally controlled contacts. It is evident that the design of the magnetic circuit, the control windings and the thermally responsive means may be varied as desired to meet particular requirements.

In Fig. 2 the parts which are designated with the same reference characters correspond to similarly designated parts of Fig. 1, Fig. 2 being similar except for the provision of additional controlling means. Here the magnetic circuit includes an extension l3 which passes under the plunger 1 and carries a fixed core I3 on which the plunger i may rest. A non-magnetic adjustable screw I34 passes upwardly through the center of core l8 and engages the bottom of the plunger! and serves as means for adjusting the lower position of the plunger I. A winding [4 envelops the core l8 and is connected in series with the winding 8 and with the thermally responsive device. The winding H is provided with a series of taps, three being indicated, engaged by an adjustable contact arm It for the purpose of including more or less of the turns of the winding ll in the local circuit of the winding 8.

The flux due to the winding ll in its magnetic circuit is substantially independent or the flux due to the windings 8 and I2 and serves as a holding coil tending to restrain the plunger I in its lowest position. The presence or this holding coil causes the flux of the load current through the series winding l2 to be greater for an instantaneous responsive action than would be the case it it were not present because the lifting effect of the series winding is additionally opposed by the holding effect or the winding Is. The value or the load current at which the instantaneous response occurs may be adjusted'by means of the screw Ila, the raising of the plunger 1 by the screw reducing the value at which the response occurs, while lowering the position of the plunger 1 by the screw increases the value at which the response occurs.

The adjustment of the number of turns of the winding ll in series in the secondary circuit by the movable contact ll serves to change the responsive action as regards overload currents for permissible periods. When all of the turns of the winding M are included in this circuit, as in the position shown in Fig. 2, the impedance of this circuit is at its highest value thereby reducing the value of the current induced in the secondary circuit and correspondingly increasing the time interval before the thermally controlled contacts are separated for opening the breaker. Moving the contact M to the next contact reduces the impedance of this secondary circuit and thereby shortens the time interval of the permissible overload before the separation of the contacts and the opening of the breaker. Further adjustment of the contact I4 produces a corresponding eiIect without materially changing the instantaneous response upon excessive overloads, provided there are a suflicient number of turns of the winding l4 remaining in the local secondary circuit for exerting suflicient holding effect upon the plunger I. An adjustable impedance device l5 may, if desired, be included in series in the secondary circuit as additional means for adjusting the impedance of this circuit and thereby change the time intervals for continuance of overloads before the breaker is opened by itjhe separation of the thermally controlled conacts.

Fig. 11 shows the results obtained from apparatus corresponding to Fig. 2. In Fig. 11 the abscissas represent the percent rating of the load or device controlled by the circuit breaker and the ordinates indicate the time in minutes. The curve corresponding to #3 setting represents the results obtained when all of the turns of the winding [4 were included in the local secondary circuit, as indicated in Fig. 2. The curve marked #2 setting corresponds to the results obtained when the switch M was shifted to the next tap and the curve marked #l setting shows the results when connection was made to the next tap. As shown by Fig. 11, the instantaneous trip octhe curve oi'Lthe #3 setting, the breaker westripped alter twice the normal load continued about 75 minutes; was tripped after three times the normal load continued five minutes: was tripped alter five times the normal load continued .7 or a minute: and was tripped after eight times the normal load continued for .3 oi a minute. The curve marked #2 setting showed that after twicethe normal load had continued seven minutes the breaker was tripped; after three times the normal load had continued for 1.3 minutes the breaker was tripped; and alter five times the normal, load had continued .37 minute the breaker was tripped. The curve corresponding to setting #i showed that after twice the normal load had continued 1.4 minutes the breaker was tripped; after three times the normal load had continued .5 minute the breaker was tripped; and after five times the normal load had continued .23 minute the breaker was tripped. Thus Fig. 10 shows an example of the results which may be accomplished by the structure indicated in Fig. 2 and by adjustment of the turns of the holding coil. Adjustment oi the impedance device i could likewise secure various results, as above explained.

Fig. 3 shows a modification wherein the closing of the thermally controlled contacts causes the breaker to be tripped. Here a terminal of the heater ii instead of being connected to the contact 8' is connected directly to a terminal of the winding M. This forms ,a local secondary circuit containing the winding 8, heater Ii and winding. The joint connection of the windings i4 and I is connected to the thermal strip I. Upon the occurrence of permissible overloads for predetermined intervals, the current induced in the secondary circuit increases the heating of the thermal strip 9 and upon attaining the predetermined interval for the then exciting overload, the contact 9' will engage the contact I. and short-circuit the holding coil and likewise place the winding 8 on a local circuit including the heater II. This action eliminates the eflect of the holding coil with the result the current in the series winding i2 is sufilcient to cause the tripping of the circuit breaker. I

Fig. 4 shows a construction wherein a resistance of a metal having a high positive temperature co-eflicient, such as iron or nickel, is inserted in series with the windings 8 and H. In this case the continuation of a permissible overload will cause the resistive element, It to gradually increase in temperature and thereby reduce the current in the secondary circuit. When the reduction of this current has reached a predetermined value at the end of the permissible interval for the then existing overload, the reduction of current in the holding winding together with the increase in fiux in the magnetic circuit due to the reduction of current in the secondary winding 8, permits the series winding I! to have a predominating eilect and trip the breaker.

. Fig. 5 shows a modification wherein an additional leg I! is added to the magnetic circuit on which is positioned the secondary winding Ia.

The terminals or this winding are connected to the thermal strips 9 and III, the contacts oi which are normally open. A heating element i8 is shown encircling the strip 9 and is connected in series with the load winding l2. Under norcause suilicient heating'oi the strip I to eiiect theclosingoi thethermallycontrolledcontacts and under-this condition the flux due to the load winding i2 finds a return path through the leg ii for the major portion 01' the ilux. when, how-' ever, a permissible overload occurs, the heater ll raisesthe temperature or the strip I and alter a predetermined interval for the then existing overload, causes the closing of the thermally controlled contacts which short-circuits the secondarywinding la. Thisreduce's thefiuxintheleg i1 and causes a transfer 01' a suiiicient amount oi fiux in a path through the plunger 1 to raise the same and trip the breaker.

Fig. 8 shows a structure similar to Fig. 5 except the series winding indicated as its envelops the middle leg of the magnetic circuit and also the portion including the plunger I; and the secondary winding 8b is located on the middle leg. Under normal load conditions the heater ll is not heated sufiiciently to cause the closing of the contacts; and the major portion or the flux passes through the legs 6 and II of the magnetic circuit. When an overload occurs, the heater It carries the local circuit oi the winding 8b to be short-circuited after a predetermined interval depending upon the amount or the overload, with the result that the fiux in the inner leg 8 is greatly reduced and causes a large in-. crease of fiux to be passed through the-portion.

of the magnetic circuit including the plunger 1 with a return path through the leg II. This increase in flux of the plunger causes it to be drawn upwardly and trip the breaker.

Fig. 7 shows a magnetic structure and windings similar to those shown in Fig. 2. However, instead of the secondary circuit completed through a'pair oi thermal strips, one of which is heated in accordance with the amount 01' over load current, the local circuit or these windings is normally completed through a thermal strip mal operating conditions, the heater it does not It, the contact of which engages a fixed contact 1|. The thermal strip it is located adjacent to any portion of a device, or within any device,-

in which it is desired to prevent the temperature from exceeding a predetermined value. For example, the thermal strip I9 may be embedded in or adjacent to any form of electro-magnetic device supplied from the consumptioncircuit 3, such as a transformer, motor, windings, or in or near the bearings of any device or at any part of the machine which it is desired to protect from overheating. Such a device is generally indicated by the character 2! in Fig. '7. In operation, the current passing in the local secondary circuit prevents the series winding I! from being efleciive; but when the device II has attained a,, temperature which will cause the thermally responsive strip is to open this local circuit, the

holding coil is rendered ineffective and the flux is permitted to increase through the magnetic circuit of the plunger 1 sumciently to permit the flux created by the winding [2 to trip the breaker and discontinue the supply of energy to the device 2i.

Fig. 8 shows an embodiment of the invention,

wherein the responsive device functions as a re'-. lay to close an auxiliary circuit which may variously be used, such as for tripping a circuit breaker. This figure shows an application of the, invention to a three-phase system wherein the;

three-phase source 22 supplies the lines 23a, 23b

and 280 of a three-phase distribution system/ The three-phase circuit breaker 24 is shown as adapted to be opened by a trip coil 25 having a plunger 26. A current transformer He is shown related to the line 230 for supplying current to the series winding l2 of a responsive device similar to that shown in Fig, 2, the secondary winding 8 being connected in a local circuit including the holding coil II and the thermal strips 9 and ID. Similarly a current transformer 21a is shown related to the supply line 23a and is connected to the series winding I! of another responsive device like that shown at the left of the figure. The trip coil 25 is adapted to be supplied with energy from an auxiliary source 28, one terminal of which is connected to a pair of fixed contacts 29, 29a. A terminal of the trip coil 25 is connected to a pair of movable contacts 30, 300:. These movable contacts are located respectively above the rods I of the plungers of the responsive devices. It is apparent from the explanations already made that upon the occurrence of an overload in any phase of the system which may be permitted for predetermined intervals according to the amount of the overload, either one or both of the responsive devices will respond to cause either one or both of the movable contacts 30, 38a to engage the fixed contacts 29, 29a and close the local circuit of the trip coil and thereby open the breaker Z i.

It will be understood that in each of the Figures 1 to 8 the series load winding will respond immediately to open the breaker upon the occurrence of an excessive overload or current, independently of the action particularly described which trips the breaker after permissible overloads have continued for predetermined time intervals. It will be understood that the movable plungers of the electromagnets already described will pass through sleeves of brass'or other non-magnetic material in order to avoid direct contact between the plunger and the frame of the magnet; and that the rod 71" may be of nonmagnetic material and that if made of magnetic material, a non-magnetic sleeve will be provided in the magnetic frame as a spacer and guide. Aithough the magnetic frame has been described as of U and E forms, they may be supplemented by similar additional portions on the opposite side of the plunger and may be made of various forms and shapes to suit the preference of the designer. It will also be understood that where the bi-metallic thermal element controls a normally open contact, it will be reversed with reference to the cases where it controls a normally closed contact; and although a bi-metallic strip has been particularly referred to as the heated element, any other suitable form of thermally responsive device may be used for controlling the contacts.

Fig. 9 shows another form of the invention applied to a three-phase circuit and circuit interrupter. The current transformer Z'lc applied to one of the lines is connected to another transformer 3| having a secondary winding. the number of turns of which are indicated adjustable. This secondary winding is connected in series with the heater H of the thermal strip 9, the circuit continuing through a winding 33 of a relay controlling the movable contact 36 and to the other terminal of the secondary winding of transformer 3i. A pair of normally closed thermal strips 9 and It? are connected in series with each other and with a comparatively low resistance 32 in shunt to the winding 33. Another line of the three-phase circuit is provided with a current transformer winding 21a which supplies energy to responsive apparatus similar to that Just described and indicated by corresponding reference characters. Either or both of the contacts 34 when attracted by their windings 33 will close the circuit of the trip coil 25 and cause the circuit interrupter to be opened.

In operation, the occurrence of any permissible overloads continued sufliciently long will cause one or the other of the thermally controlled pair of contacts to be separated and open the circuit through the resistor or resistors 32 and thereby cause one or both of the windings 33 to be sufficiently energized to close the circuit of the trip coil 25 and open the breaker. If an excessive overload should occur, such as due to a fault, then one or both of the windings 33 will receive suflicient current to close the circuit of the trip coil 25, even though both pair of thermally controlled contacts remain closed.

Fig. 10 is similar to Fig. 1 except a single controlling winding is utilized in the magnet. In Fig. 10 a current transformer 35 supplies current to a winding 36 of the magnet having a frame 31. Taps from this winding complete a circuit through the heater II to contact 9 and through strip Ill, This causes the thermal responsive device to be subjected to a current which is dependent upon the current passing in winding 36 which is proportional to the load current. In operation, the winding 36 will respond instantly to trip the breaker upon the occurrence of an excessive overload. When a permissible overload has continued for a time sufficient to cause the contacts of the thermal device to separate, the increase in current in winding 36 is sufiicient to cause a tripping of the breaker, because the shunting of current from the winding by the thermal device is then discontinued.

It will be understood that in each of the foregoing described figures after the circuit inter rupter has been opened, the thermal responsive devices will return to normal temperatures and bring their contacts to their normally closed or normally open positions and thus be prepared to operate upon the reclosing of the supply circuit.

Although certain embodiments of the invention have been particularly described, it will be understood that various modifications may be made in the form. and relationship of the parts without departing from the scope of the invention.

1 claim:

1. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element and a winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current of said circuit, said magnet also having a winding subjected to the fiux of said first named winding and having a current induced therein, a thermally responsive device affected by said induced current and having contacts normally engaged and closing the circuit of said second named winding and the opening of said contacts effecting the movement of said element, and means controlled by said element for opening said circuit interrupter.

2. A circuit interrupter, an'alternating current circuit controlled thereby, an electromagnet having a movable element and a primary winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current of said circuit for actuating said element, said magnet also having a secondary wind ing subjected to the flux of said primary winding; said magnet also having a winding for opposing the actuation of said element connected in series with said secondary winding, a thermally responsive device for affecting the circuit of said last two named windings to permit said primary winding to actuate said element after said thermally responsive device has attained a predetermined temperature, and means controlled by the actuation of said element for opening said circuit interrupter.

3. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element and a primary winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current of said circuit for actuating said element upon the occurrence of excessive overload current in said alternating circuit, said magnet also having a secondary winding subjected to the flux of said primary winding; said magnet also having a winding for opposing the actuation of said element connected in series with said secondary winding, a thermally responsive device for affecting the circuit of said last two named windings to permit said primary winding to actuate said element after said thermally responsive device has attained a predetermined temperature, and means controlled by the actuation of said element for opening said circuit interrupter.

4. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element and a winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current of said circuit, said magnet also having a winding subjected to the flux oi said first named winding and having a current induced therein, a thermally responsive device aflected by said induced current and having normally open contacts in the circuit of said second named winding and the closing of said contacts effecting the movement of said element, and means controlled by said element for opening said circuit interrupter.

5. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element and a winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current of said circuit for actuating said element, said magnet also having a winding in a local circuit subjected to the flux of said first named winding and having a current induced therein variable with the value of the current in said first named winding, a thermally responsive device controlled by said induced current for ail'ecting said local circuit to affect the flux of said electromagnet and thereby cause said first named winding to become effective to actuate said element, and means controlled by said element for opening said circuit breaker.

6. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element, said magnet having a primary winding connected in series in said circuit and subjected to the load current in said circuit for actuating said element, and having a secondary winding in a local circuit subjected to the flux of the primary winding and having a current induced therein variable with the value of the current in said primary winding,

and thermally responsive means controlled by said induced current for aflecting the local circuit of said secondary winding to affect the flux of said electromagnet and thereby cause said primary winding to actuate said movable ele ment after a predetermined interval of overload current in said alternating circuit, and means controlled by the actuation of said element for opening said circuit interrupter.

7. A circuit interrupter, an alternating current circuit controlled thereby, an electromagnet having a movable element, said magnet having a primary winding connected in series in said cir cuit and subjected to the load current of said circuit for actuating said element, and having a secondary winding in a local circuit subjected to the flux of the primary winding and having a current induced therein variable with the value of the current in said primary winding, and thermally responsive means controlled by said induced current for aifecting the local circuit of said secondary winding to affect the flux of said electromagnet and thereby cause said primary winding to actuate said movable element after a predetermined interval of overload current in said alternating current circuit, and means controlled by the actuation of said element for opening said circuit interrupter, said primary winding being related to said movable element to cause its actuation and opening or the circuit interrupter immediately upon the occurrence of excessive overload current in said alternating circuit.

8. A circuit interrupter, an alternating current load circuit controlled thereby, an electromagnet for controlling the opening of said circuit breaker, said electromagnet having two windings,

means for connecting one of said windings in relation to said circuit for subjecting the winding to a current corresponding in value to the current in said load circuit, the other oi said windings being connected in a local closed circuit and subjected to the flux of the other winding and having a current induced therein variable with the value of the current in said first named winding, a thermally responsive time delay device, and means for subjecting said device to the heating effect of said induced current for opening said local closed circuit to ailect the flux of said electromagnet for controlling the opening of said circuit breaker upon the temperature of said device attaining a predetermined value.

9. A circuit interrupter, an alternating current load circuit controlled thereby, an electromagnet having a movable element and a winding, means for connecting said winding in relation to said circuit for subjecting said winding to a current corresponding in value to the load current 01' said circuit, said magnet also having a winding subjected to the flux of said first named winding, a thermally responsive device having normally open contacts, means for subjecting said device to the heating effect of a current corresponding to the value of the load current in said circuit for closing said contacts upon said device being heated to a certain temperature and thereby affecting the circuit oi. said second named winding and the flux of said magnet for causing the movement of said element, and means controlled by the movement of said element for opening said circuit breaker.

/ JOSEPH D. WOOD.

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