US1231048A - Electrical relay. - Google Patents

Description

E. 0. MULLER.

ELECTRICAL RELAY.

APPLICATION FILED MAR. 20. I913.

1,231,048. Patented June 26, 1917.

4 56 T T Y4 EGRON OLOF MbLLER, OF BROOKLANDS, ENGLAND.

ELECTRICAL RELAY.

pecification of Letters Patent.

Patented June 26, 1917.

Application filed March 20, 1913. Serial No. 755,777.

To all whom it may concern:

Be it known that I, EGRON OLOF MoLLER, a subject of the King of Sweden, and a resident of Brooklands,-1n the county-of Cheshire, England, have invented a new and useful Improvement in Electrical Relays, of which the following is a specification.

My invention relates to automatic circuit breakers and has for its object to provide improved arrangements for the purpose of insuring that the circuit shall be opened under certain conditions of current or potential.

According to the present invention several resistors of different magnitude and the trip coil of a circuit breaker are connected up 111 a specific manner whereby the circuit breaker is caused to operate with various predetermined conditions of the current or potential. i

In order that the nature of my invention may be fully understood, it will now be de scribed with reference to the accompanying drawings which illustrate diagrammatically several methods by which it may be carried into practical efiect in accordance with the conditions it is desired to fulfil.

Figure 1 shows an arrangement for open ing the circuit when a predetermined overload occurs or when a predetermined current flows in the reverse direction.

Fig. 2 shows an arrangement for protec tion against a predetermined minimum reverse current and' failure of the voltage or against a reverse current, the falling of the current below a certain predetermined minimum and a failure of the voltage.

Fig. 3 shows an arrangement for protecting against a reverse current, failure of the voltage, a rise of the current above a certain predetermined amount with what is commonly known as a time limit effect, and

a fall of the current below a predetermined limit, and Fig. 4c shows an arrangement for attaining similar objects.

Fig. 5 shows an arrangement for opening a circuit when the current fiows in a reverse direction.

Fig. 6 shows an arrangement for opening a circuit at the end of a certain predetermined interval of time when an overload occurs.

The remaining figures illustrate arrangements especially adapted for use in alternating currents.

Fig. 7 shows an arrangement for protecting the circuit against an alteration in the direction of the fall of termined time after an overload occurs, this arrangement being also adapted to open the circuit when the current falls below a certain predetermined limit.-

Fig. 8 shows an arrangement in which in addition the circuit is opened when a failure of the voltage occurs.

Fig. .9 shows an arrangement somewhat similar to Fig. 6 in which transformers are employed.

In all the figures 1 is a generator which supplies current to a circuit of which 2 and 3 are main conductors. 4 indicates the movable member of a circuit breaker for interrupting the circuit under various conditions.

Referring now particularly to Fig. l, 5 is a resistor included in the main circuit, commonly known as a shunt and hereinafter termed the main current shunt. The end of the shunt 5 which is nearest the generator 1 is connected to one terminal of a resistor 6 and the other end of the shunt is connected to the terminal of a coil 7 which is a relay actuating the trip coil 9 of the circuit breaker with the aid of batteries 44. The ends of the resistor 6 and relay 7 are connected together and through a second resistor 8 to the opposite conductor 2 of the circuit. The resistance of resistor 8 is comparatively much larger than the resistance of the resistor 6 or the resistance of the relay coil 7, consequently, the current passing through said resistor 8 is practically constant, and is determined by the amount of resistance in said resistor 8.

The operation of these arrangements is as follows: If there is no current passing through the main circuit but the potential between the conductors 2 and 3 is normal, a small current passes through the resistor 6 and relay coil 7 in parallel and through the resistor 8. If the resistance of the relay coil 7 is approximately equal to the resistance of resistor 6, the current passing through the relay coil 7 in this case about half of that which passes through the resistor 8, the resistance of the shunt 5 being generally so small as to be practically negligible in comparison with the other resistors above mentioned. The circuit breaker is arranged so that this current is not suflicient to cause it to open. If a current is flowing potential or a prede- V llO in the main circuit, the potential of that end of the shunt which is nearest the generator 1 will be higher than the potential at the other end of the shunt, consequently, more current will flow through the. resistor 6 than flows through the relay coil 7, and if the main current continues to increase, a point will be reached when all the current which can pass through the resistor 8 passes through the resistor 6. Assuming that the main current increases still further, a current will again pass through the relay coil 7 but in the reverse direction, and, on a further increase in the main current, the current passing through this relay coil 7 continues to increase until it causes the circuit breaker to open.

If the direction of the main current is reversed and reaches a certain predetermined magnitude, a sufiicient amount of the current which passes through the resistor 8 passes through the relay coil 7 thus causing the circuit breaker to open as before, by closing a local circuit from battery 44 through the trip coil 43.

Referring now to Fig. 2, the end 11 of the shunt 5 whichis nearest the generator 1 is connected to the resistor 8 through a relay coil 9 of the circuit breaker, the other end of the shunt being connected to the resistor 8 through the resistor 10. The relay coil is arranged in the ordinary manner to cause the circuit breaker to open through the aid of a trip coil 43 with a battery 44, when the current passing through the relay coil 9 falls below a certain limit.

If the resistance of the relay coil 9 be equal to the resistance of the resistor 10, it will be evident that at no load with full voltage, the current flowing through the resistor 8 will be divided equally between the relay coilv9 and the resistor 10. With normal voltage impressed upon'the conductors 2 and 3 of the circuit, the current through the relay coil 9 is arranged to be sufficient to allow the circuit breaker to remain closed. If, however, the difference of potential be- I tween the conductors 2 and 3 decreases, the

current through the coil 9 decreases and if the potential difference falls below a certain limit, the current passing through said coil is arranged to be insufficient to hold the circuit breaker closed.

With a reverse current, the arrangement operates in the following manner: If a current is flowing in the proper direction from the generator 1 in the direction of the arrow,

the potential at the point 11 of the shunt 5 of potential through the shunt 5 is reversed,

then more current will flow through the resistor 10 and the current through the relay coil 9 will become less as the reverse current in the main circuit becomes greater. Finally when the reverse current in the main circuit reaches a predetermined value the current in saidcoil 9 will have fallen below a predetermined limit and thereby cause the circuit breaker to open.

If the current in the reverse direction in the main circuit is extremely heavy with a corresponding large voltage drop between the points 12 and 11, the current through the relay coil 9 becomes reversed and increases in magnitude in proportion to the increase in the reverse current in the main circuit; For a sudden reversal of the main current therefore itwould seem as if under certain conditions the current in said coil 9 would not fall to a low value for a sufficiently long period of time to cause the circuit breaker to open. In practice however it is found that this is not the case as the reversal of the current through said coil takesplace slowly owing to the impedance of the relay coil 9 being much greater than the resistance of the shunt 5. g

If the arrangement is required to operate when the current in the main circuit in the forward direction becomes less than a certain amount, the relative values of the resistance of the relay coil 9 and the resistance of resistor 10 may be changed by which means the limiting value of the current passing through coil 9 below which the circuit breaker is caused to open, may be chosen in 1 such manner that with full voltage between the conductors 2 and 3 and with no current flowing in the main circuit, the current passing through the coil 9 would not be sufiicient to prevent the circuit breaker from opening, but with forward current flowing in the main circuit and full voltage between the conductors 2 and 3, the current flowing through coil 9 will be sufiicient to permit the breaker to remain closed. If the current in the main circuit should sink below a predetermined value the current through the coil 9 will correspondingly decrease permitting the circuit breaker to open.

In practice, the circuit breaker is very easily adjusted to operate at a predetermined value of the current in coil 9 by'adjusting the magnetic core which the coil 9 is arranged to actuate.

p Referring now to Fig. 3, the arrangement therein shown is substantially the same as that shown in Fig. 2,.but a switch 13 is included in the circuit of the relay coil 9 adapted to be opened if the current passing through an expansive conductor 14 connected between the points 11 and 12 increases beyond a certain predetermined limit. These expansive conductor relay devices for controlling switches are well known and their construction need not be further described. It will be readily seen that in the arrangement shown, as the current passing through the conductor 3 increases, the current through the expansive conductor 14 also increases and if an overload occurs, the current through the expansive conductor will rise beyond the predetermined limit and the expansion of such wire will permit the switch 13 to open and the consequent cessation of current through the coil 9 will cause thecircuit breaker to open with the aid of trip coil 43 and battery 44. As is well known, with the expansive conductor relays,

L the time within which the switch 13 will be opened depends on the strength of the current passing through the expansive conduc tor 14 and the greater the overload, the more quickly will the device operate.

The operation of the arrangements under the conditions of reverse current failure of voltage or fall of current below a predetermined limit are, of course, the same as hereinbefore described with referenceto Fig. 2 of the drawings.

It will be readily understood by those skilled in the art that with the arrangements shown in Figs. 2 and 3, when the circuit breaker is being closed, the magnetic core upon which the relay coil is arranged to act has to be moved from its releasing position to its normal position against an opposing force,- which is usually gravity, and it will be necessary for considerably more current to flow through the coil 9 for this purpose than is required for merely holding said core in its normal position, showing reason for using an external source of energy. In order, therefore, to assist the relay coil 9 in picking up its magnetic core without the ad dition of an external source of power, an

additional coil 15 is provided, as shown in- Fig. 4c. This additional coil, however, is included in an auxiliary circuit controlled by a switch 16 operated by the circuit breaker in such a manner that when the circuit breaker is closed, the auxiliary circuit through coil 15 wilLbe opened. At the moment of closing the circuit breaker, it will be seen that the current will flow from point 11 through the relay coil 9, the trip coil 15, switch 16, a portion of the resistor 8 to the conductor 2, consequently, both coils 9 and 15 are energized and move the magnetic core from its release position to its normal position. When the circuit breaker is fully closed however, the switch 16 is opened, thereby breaking the auxiliary cir cuit through the coil '15, in which case current willfiow through the coil 9 only, and the apparatus will operate in the manner hereinbefore described. It will be understood that the coil 15 when in' circuit with switch 16, attached to the main breaker, is

arranged to shunt a portion of the resistance of resistor 8. The circuit breaker is included in the conductor 1 so that suflicient current will pass through coil 15 to allow the core to be readily picked up.

Referring now to Fig. 5, the arrangements herein shown are applicable to circuit breakers which are provided with a series or trip coil included in the main circuit, a shunt coil and a relay or retaining coil, the relation of the coils to the magnetic circuits being such that the current in the shunt coil opposes the magnetic effect of the current in the series coil on the movable or releasing member of the circuit breaker, and the flux due to the current in the retaining coil is adapted to retain said movable or releas ing member in its normal position when the circuit breaker is closed. Circuit breakers of this description are well known in the art. As shown in Fig. 5, the series trip coil 17 of the circuit breaker is included in the conductor 3, the retaining coil 18 is connected between the point 11 of the main shunt 5 which is nearest the generator, and the moving coil 19 is connected in series with said'resistor 8.

The operation of these arrangements is as follows: With a forward direction of the main current, that is to say, in the direction of the arrow, the direction of the current in the retaining coil 18 and shunt coil 19 will be such that the movable or releasing portion of the circuit breaker will be held in a position to permit the circuit breaker to remain closed, notwithstanding the flow of current in the series trip coil 17. If now the direction of flow of the main current becomes reversed, the polarity of that portion of the magnetic circuit of the circuit breaker which is energized by the series coil 17 also becomes reversed and this will tend to operate the movable portion to open or release the circuit breaker. Furthermore, the current through the retaining coil 18 becomes less or re'versed,-depending upon the magnitude of the reverse current in the main conductor 3 and shunt 5, so that the action 'of this retaining coil either becomes lessened or even becomes reversed in its effect and so permits or assists in causing the circuit breaker to open. The coil 19 may also be arranged to energize that portion of the magnetic circuit energized by the series coil only in the arrangement described above, without diverting from the spirit of the invention.

Referring now to Fig. 6, the circuit breaker in this arrangement is designed to open the circuit on the occurrence of an overload at the end of predetermined intervals of time, dependent upon the strength of the overload current. The circuit breaker is of the type which has a series or trip coil and a retaining coil, the current in which acts to prevent the opening of the circuit breaker due to the flow of current 1n the series coil. In the arrangement shown, the

series coil is included in circuit with the main conductor 3, and the retaining coil 1s connected between the points 11 and 12 of the main current shunt 5, the circuit through said retaining coil 21 being controlled by a switch 22 operated by an expansive conductor relay 23 of the kind herein above mentioned with reference to Fig. 3.

The operation of this arrangement is as follows:

Vhen the current passing through the main shunt 5 has reached a predetermined value, the expansion of the expansive conductor 23 causes the auxiliary switch 22 to open, thereby breaking the circuit through the retaining coil 21. This coil is mounted on a part of the magnetic circuit of the circuit breaker which maintains the movable or releasing portion of the circuit breaker in a position to prevent the circuit breaker from opening. As soon as said retaining coil is deenergized, the movable or releasing portion of the circuit breaker is actuated by the magnetic flux, due to the current in the series or trip coil 20, to cause the circuit breaker to open the circuit.

It will be noted that the current through the auxiliary switch 22 is of a very low potential, as the potential drop is only due to' the resistance of the main shunt 5. The switch 22 will, therefore, open without any appreciable sparking, and the contacts, being normally closed, will remain clean for a very long time.

The remaining figures of the drawings show arrangements for operating with alternating current circuits, although the arrangements hereinbefore described and shown in the earlier figures of the drawings, may be used with alternating current circuits operating at a low tension, provided that the parts of the circuit breakers are adapted to be actuated by alternating currents.

Referring now to Fig. 7, the generator 1 is arranged to supply the circuit 2, 3 with alternating currents, and the main shunt 5, instead of being included in the conductor 3, has its terminals connected to the secondary winding 2 1 of a series transformer, the primary winding 25 of which is included 1n the conductor 3. 26 is a resistor connected to the point 27 of the main shunt 5 and to one terminal of a resistor 28, the other term nal of which is connected to the secondary WlIldIIlg 29 on a transformer, the primary winding 30 of which is joined across conductors 2 and 3 of the main circuit. The free terminal of the secondary winding 29' is connected to the point 27 of the main shunt 5. Joined in parallel with the resistor 26 is the expansive conductor 31 of a relay which governs a switch 32'in the circuit of the coil 33 which is the tripping coil of a circuit breaker. Said coil is connected in shunt to a portion of the resistor 28 as shown. The expansive conductor relay 31 is arranged to maintain the switch 32 open so long as the current passing through the expansive conductor does not exceed a certain predetermined limit. But when an excess current passes through the expansive conductor its expansion permits the switch 32 to close and coil 33 is thereby energized and opens the circuit breaker. The coil 33 may, of course, be included in a separate circuit and be supplied with energy from any suitable source when the switch 32 is closed in place of being connected as shown.

The magnitude of the current through the expansive conductor 31 depends partly upon the shunt current in the secondary winding 29 and partly upon the relative magnitude and phase angle of the current in the secondary winding 24. To fully understand the action of the device, let it be as-. sumed that the current in the primary 30 at a certain moment is passing from conductor 3 to conductor 2 in the direction of the arrow. The secondary current in coil 29 passes around the circuit in the direction of the arrow through the resistor 28 to point 34 where it divides into two branches, one of which passes through the resistor 26 to point 27 of the main shunt 5, and the other passes through the expansive conductor 31 to point 35 of the main shunt 5 andthrough said shunt to point 27 whence the combined currents pass back to the secondary winding 29. When there is a voltage between points 36 and 37 at the terminals of the primary 30 and no current is flowing through the primary winding 25 of the series transformer, the current flowing from point 34 divides equally between the resistor 26 and the expansive wire 31, the resistance of the latter being approximately equal to the resistance of resistor 26, and the resistance of the main shunt 5 being practically negligible in comparison. If, now, a current passes through the conductor 3 in what may be assumed is the forward direction bf the current from the generator, a current will be induced in the secondary winding 24 which passes in the direction shown from point 35 to point 27 through the main shunt 5. Owing to the resistance of the main shunt 5, point 35 will be of higher potential than point 27 when the current is flowing in the direction given, the potential drop will therefore be greater between points 34 and 27 than that betweenpoints 34: and 35, and, consequently, the current passing through the resistor 26 will be larger than that passlng through the expansive conductor 31. The conductor 31 will therefore be mai1i-' tained cool and the circuit breaker will not open. If, however, a very heavy current passes through the main conductor 3, the secondary current 24 may be so large as to overpower the current from the secondary Winding 29 which passes from point 34 through wire 31 to point 35 and cause a reversal of the current in said wire 31 which, if the main current is suificiently great, will heat the wire to such an extent as will cause the switch- 32 to close and thereby energize coil trip 33 and so open'the circuit breaker.

If a reversal of the current in the main circuit takes place, that is to say, of the phase angle between the current flowing in conductors 2 and 3 and the voltage between said conductors alters by 180 degrees, the direction of current flow in the primary winding 30 and the secondary winding 29 of the shunt transformer remains the same as before, while the current in the conductor 3 flows in the opposite direction. The current in the secondary winding 24 will reverse in direction and the potential of point 27 will be higher than that of point 35, consequently, more current will flow through the wire 31 than through the resistor 26 and the said wire will expand, and, on the reverse current through the series transformer exceeding a predetermined limit, the expansion of the expansive conductor 31 permits the switch 32 to close, the 0011 33 is energized and opens the circuit breaker.

It will be clear that the device operates both on a large forward current and on a small reverse current, and this'is generally desired in practice. By adjusting the relative values of the resistances of the expansive conductor 31 and the resistor 26, the values of the currents passing through the series transformer 25 at which the device operates may be so determinedthat the circuit breaker may be caused to operate either with a large reverse current or a small reverse current or even when the forward current reaches a predetermined minimum value, as well as operate when the forward current exceeds a predetermined value.

Referring now to Fig. 8, the arrangements shown are very similar to those shown in Fig. 3, with the exception that current is supplied to the main shunt 5 from the secondary 24 of a series transformer, the primary 25 of which is included in the conductor 3 and the current through the resistors 8 and 10 and tri coil 9 on the circuit breaker is supplied from the secondary winding 29 of a shunt transformer, the primary 30 of which is connected across the conductors 2, 3. The expansive conductor 38 which controls the switch 13 in circuit with the trip coil 9 is included in series with the resistors 10 in place of being connected as a shunt in the main shunt 5. The resistor 10 is constituted by a reactor, the impedance of conductor 38 and coil 10 being approximately the same as the impedance of coil 9 and switch 13. The operation of the arrangement is as follows:

WVith a forward current in the conductors 2 and 3, as indicated by the arrow, a current will flow through secondary 24 and from point 39 through the main shunt 5 to point 40. The current from the secondary 29 of the shunt transformer will flow in the direction of the arrows through resistor 8 to point 41 and through trip coil 9, switch 13, to point 40 and thence back to the other end of the secondary 29. A shunt current will also tend to fiow from point 41through the resistor 10 and expansive wire 38 to point 39 and thence through shunt 5 to point 40 and back to the other end of the sec ondary 29. The potential of point 39 due to the current from secondary 24 being higher than that of point 40, less current will tend to fiow through the expansive conductor'38 and resistor 10 than through the trip coil 9, thereby tending to hold the breaker in still firmer. If the main current increases beyond a predetermined limit, the current through the expansive conductor 38 will become reversed and finally reach such magnitude that the expansive conductor relay operates switch 13, opening the breaker. Obviously, if the voltage of the main circuit falls below a predetermined limit, the current in the trip coil 9 will be reduced to such an extent as will cause the circuit breaker to open.

en a reversal of the current in the main circuit occurs as described with reference to Fig. 7, the direction of the fall of potential through the main shunt 5 is reversed and with a sufficiently heavy current, the decrease of current in coil 9 will open the main circuit breaker as hereinabove described. For a very heavy and sudden reversal of the current, suflicient current would pass through expansive wire 38 to operate switch 13, which again would open the circuit breaker.

Fig. 9 shows an arrangement for opening an alternating current circuit a predetermined length of time after an overload occurs. The apparatus is similar to that shown in Fig. 6 with the exception that the series trip coil 20 of the circuit breaker and retaining coil 21 with switch 22 and expansive conductor 23 are included in the circuit of the secondary winding 41 of a transformer, the primary winding 42 of which is included in series with the main conductor 3. The operation of this device is as follows:

So long as the current through the pri mary winding 42 of the transformer does not exceed a predetermined limit, the current through the conductor 23 of the relay will be sufficiently small to enable the switch 22 to remain closed and the current through the retaining coil 21 will not permit the circuit breaker to open. If, however, the current in the conductors 2 or 3 increases beyond a certain predetermined limit, a corresponding increase in the current through the expansive conductor 23 will occur and expansion thereof will result in the opening the series trip coil 20. In the same way, the arrangement shown in Fig. 5 could easily be adopted for high tension alternating current circuits by introducing the necessary shunt and series transformers. I j

' The relative position of trip coils, relay coils, expansive conductor relays or other types of relays, in the diagram as shown in Fig. 1 or 4 may be varied to form many more difierent combinations than described above, without departing from the spirit of this invention. It will be understood that the type of circuit breaker and nature of the mechanical.

and electro-magnetic connections between the circuit breaker and the trip coil are not material to the present invention, as any suitable circuit breaker which can be operated either direct or through the medium of a relay, may be employed with the apparatus. The selection of a suitable circuit breaker can readily be made by any person skilled in the art, in accordance with the conditions it is desired to vfulfil. The construction of the resistances and of the shunt may also be of any suitable description.

I claim as my invention:

1. The combination with an electrical cir cuit, of a relatively low-resistance resistor supplied with current proportional to the current traversing the said electric circuit,

a second relatively low-resistance resistor,

a relatively low resistance electromagnet winding, corresponding terminals of said second resistor and said winding, at one end, being connected together and the corresponding terminals, at the other end, being connected to the respective terminals of the relatively low-resistance resistor, and a relatively high-resistance resistor connected to the first named terminals to receive current proportional to the difierence in potential between the conductors of the said electric circuit.

2 Th'eco'mbination with an electrical circuit, of aresistor supplied with current pro- .portional to the current traversing the said circuit, a second resistor, an electromagnet winding, and a third resistor having one ter-' min-a1 connected to one terminal of the said second resistor and to one terminal of the said electromagnet winding and having its other terminal 'so connected that the said the remaining terminals of the second resistorand the electromagnet winding being connected to the respective terminals of the first resistor.

3. The combination with an electrical circuit, of a relatively low-resistance resistor, a relatively low -resistance electromagnet winding having the same impedance as the said resistor under all conditions, and means for so connecting the .said resistor and the said winding that the same current traverses the two under predetermined conditions of operation and a relatively different current traverses each under other predetermined conditions of operation.

4. The combination with an electrical circuit, of a resistor, an electromagnet winding of substantially the same resistance as the 7 said resistor, and means for so connecting the, said resistor and the said winding that diiTerent currents traverse the same when the current reverses in the circuit.

5. The combination with an electrical circuit, of a resistor, an electromagnet winding. of substantially the same resistance asv the said'resistor, and" means for so connecting the said resistor and the said electromagnet winding that a relatively difi'erent value of current traverses the electromagnet winding than traverses the resistor when the current reversesin the said circuit and when an overload traverses the said circuit.

6. The combination with an electrical circuit, of a relatively low-resistance resistor connected in series relation to one conductor of the said circuit, a second relatively sistor, the said second resistor and the said electromagnet winding having correspondin terminals at o e'end connected together and having corresponding terminals, at the other end, connected to the respective terminals of the said first resistor, said relatively high-resistance resistor being connected to the first named terminals and to one conductor of thesaid circuit.

7. Thecombination with an electrical circuit, of a relatively low-resistance resistor connected-in series relationto one conductor of the said circuit, a second relatively lowresistance resistor, an electromagnet winding, and arelatively high-resistance resistor, the said second resistor andthe said electromagnet winding having corresponding terminals, at one end, connected together and corresponding terminals, at the other end,

connected to the respective terminals of the said first resistor, said relatively high-resistance resistor being connected to the first named terminals and to the conductor of the circuit other than the onein which the said first resistor is connected.

8. In an electric circuit, the combination with a circuit interrupter and a trip coil 'therefor, of a resistor, an electromagnet Winding of substantially the same resistance as the said resistor, means for so connecting the said resistor and the said electr'omagnet winding that a relatively different value of current traverses the electromagnet winding than traverses the resistor when the current reverses in the said circuit and when an overload traverses the said circuit, and means controlled by said electromagnet Winding for operating the said trip coil.

9. In an electric circuit, the combination With a circuit interrupter and a trip coil therefor, of a relatively low-resistance resistor that is supplied with current proportional to the current traversing the said circuit, a second relatively low-resistance resistor, a relatively low-resistance electromagnet winding, and a relatively high-resistance resistor, corresponding terminals of the said second low-resistance resistor and the said electromagnet Winding, at one end, being connected together and the other terminals thereof being connected to the terminals of the said first low-resistance resistor, said high-resistance resistor being connected to the first named terminals to receix e current proportional to the voltage of the said circuit.

10. The combination with an electrical circuit, of a resistor, an electromagnet Winding connected in parallel with the resistor and having substantially the same resistance, and means for so connecting the said resistor and winding to the circuit that different currents traverse the same when the current in the electrical circuit reverses and when an overload traverses the circuit.

'11. The combination With an electrical circuit, of two energy-consuming devices having the same resistance under all conditions and means for so connecting the said devices to the circuit that different currents traverse the same when the current in the electrical circuit reverses.

12. The combination With an electrical circuit, of a resistor, an electromagnet winding having the same resistance and normally subjected to the same potential as the resistor and means for so connecting the said resistor and the said Winding that different potentials are impressed thereon under predetermined conditions.

13. The combination with an electrical circuit, of a resistor, an electromagnet winding having the same resistance and normally subjected to the same potential as the resistor and means for so connecting the said resistor and the said winding that different potentials are impressed thereon when the current reverses in the circuit.

14. The combination with an electrical circuit, of a resistor, an electromagnet winding having the same resistance and normally subjected to the same potential as the resistor and means for so connecting the said resistor and the said winding that different potentials are impressed thereon when the current reverses in the circuit and when an overload traverses the circuit. 15. The combination With an electrical circuit, of a resistor, an electromagnet winding normally subjected to the same potential as the resistor and means for so connecting the said resistor and the said Winding that different potentials are impressed thereon under predetermined conditions.

16. The combination with an electrical circuit, of a resistor, an electromagnet winding normally subjected to the same potential as the resistor, and means for so connecting the said resistor and the said winding to the electric circuit that different potentials are impressed thereon when the current reverses in the electric circuit.

Intestimony whereof, I have hereunto subscribed my name this twenty-sixth day of February 1913.

EGRON OLOF MOLLER. Witnesses:

N. W. BOWMAN, JAs. STEWART BROADFOOT.

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