US1231659A - Electrical protective device. - Google Patents

Description

B. H. SMITH.

ELECTRICAL PROTECTIVE DEVICE.

APPLICATION FILED MAY 4. ISIS.

1,231,659. Patented July 3,1917.

WITNESSES: INVENTOR UNITED STATES PATENT OFFICE.

BENJ MI H. SMITH, or rUn'rLEcnEEK,rnNnsYLvANIA, ASSIGNOB ro wss'rmc- HOUSE ELECTRIC AND MANUFACTURING COMPANY, a conronnrron or PENNSYL- VANIA.

ELECTRICAL PROTECTIVE DEVICE.

Specification of Letters Ilatent;

Patented ul 's, 1917.

To all whom it may concern:

Be it known that I, BENJAMIN H. SMITH, a citizen of the United States, and a resident of Turtle Creek, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Electrical Protective Devices, of which the following is a specification.

My invention relates to electrical-protective devices and particularly to relay mechanisms that are employed for tripping circuit interrupters or other similar devices upon the occurrence of predetermined circuit conditions.

My invention has for its object to provide a device of the above indicated character that shall operate correctly upon any value of overload.

My copendin application Serial No. 850,331, filed Jul 11, 1914, discloses a relay system that comprises a timeelement relay which is adapted to control an auxiliary Winding on a tripping electromagnet for the purpose of permitting the electromagnet tooperate under predetermined conditions. With a device of this type, a circuit interrupter ma be tripped by current derived from the circuit in connection with which it is employed without subjecting the contact members of the relay to any injurious arcing or welding. However, when a device of this type is employed to interrupt very large currents, the tripping electromagnet will frequently operate irrespective of the auxiliary winding that is controlled by the relay. In other words, the tripping electromagnetfrequently operates before the relay functions properly.

In order to cause the tripping electromagnet to operate correctly for any value of current, I provide a main stationary magnetizable core member having substantially the form of a hollow rectangle with an opening in one of its sides, an auxiliary stationary magnetizable member of substantially E-shape and a movable core member having laterally extending projections thereon that are disposed between the stationary core members, and adapted to cooperate with the auxiliary stationary core member under predetermined conditions and with the main stationary core member under other predetermined. conditions. The main and auxiliary core members are adapted to be so separated by a relatively large air gap that, under normal conditions, the magnetic lines of force from one of the core members will not traverse the other core ember. The main and auxiliary. core mem e'rs are severally provided with a main winding that is adapted to be supplied with'current in accordance with the current traversing the circuit to be protected. The main windings are so connected as to normally tend to move the movable core member in opposite direct ons. The auxiliary core member is provided with an auxiliary winding that is adapted to be short circuited a time-interval after the occurrence of an overload upon the circuit to be protected. Thus, when the auxiliary winding on the auxiliary core member is short circuited, it neutralizes the effect of the main winding on the auxiliary core member and permits the movable core member to function properly.

The single figure of the accompanying drawing is a diagrammatic view of a part of a system embodying my invention.

An alternating-current circuit 1 is provided with an interrupter 2 for opening it under predetermined conditions.- In order to trip the circuit interrupter 2, I provide a relay system 3 that derives its energy through a current transformer 4 and a voltage transformer 5.

The relay system 3 comprises a relay 6 that is of the induction type and preferably constructed as set forth in Conrad Patent No. 1,137,840, issued May 4:, 1915, and a tripping electromagnet 7. The secondary winding 8 of the transformer 5 is connected to windings 9 and 10 of the relay 6, and the secondary winding 11 of the transformer 4 is connected in series relation to a winding 12 of'the relay 6 and windings 13 and 14 of the tripping electromagnet 7. The relay 6 is provided with an armature 15 that is mounted on ashaft 16 upon which a contact arm 17 is also mounted. The contact arm 17 cooperates with a stationary contact member 18 for the purpose of controlling the circuit of an auxiliary or controlling winding 19 of the tripping electromagnet 7 The tripping electromagnet 7 comprises a main stationary magnetizable core member 20 in the form of a hollow rectangle having a pole piece ll extending inwardly and downwardly from its upper cross-piece and having a gap in its lower crossacre through which projects a movable core member 22 that is adapted for longitudinal vertical movement. An auxiliary stationary magnetizable core member 23 of substantially E-shape is disposed beneath the main core member 20 and separated therefrom by an air ga 24. The movable core member 22 is provided with laterally extending projections 25 that are disposed in the air gap 24 and normally rest upon the outer and longer legs of the auxiliary core member 23. The movable core member 22 is adapted to cooperate with both magnetizable core members 20 and 23 and is surrounded by the windings 13, 14 and 19. The movable core member 22 is provided with an operating rod 26 that is adapted to trip the latch 27 of the circuit interrupter 2.

As hereinbefore stated, the windings 13 and 14 are supplied with current from the secondary winding 11 of the transformer 4 and are preferably connected in series with the winding 12 of the relay 6, although they may be connected in any other suitable relation with respect thereto. The winding 19 is normally open-circuited but is adapted to be close-circuited by the engagement of contact members 17 and 18 of the relay 6 under predetermined circuit conditions, such, forinstance, as upon the occurrence of an overload or the reversal of the direction of flow of energy in the circuit 1.

Under normal c'ircuit conditions, the current in the winding 12 of the relay 6 is insufficient to cause the switch 1718 to close, and, consequently, the winding 19 remains open-circuited and is not affected. However, the windings 13 and 14 are continuously energized so long as the circuit interrupter 2 remains closed, but, being adapted to cooperate with independent magnetic circuits, they exert opposing forces upon the movable core member 22. The magnetic circuit of the winding 14 being substantially closed under normal conditions, the movable core member 22 remains stationary in the position shown. Also, since the magnetic circuit of the winding 14 is normally closed, whereas a considerable air gap exists in the magnetic circuit of the winding 13 at the upper end of the movable core member 22, it is obvious that the winding 14 may, and preferably does, have a smaller number of convolutions than the winding 13.

When an overload or other abnormal condition occurs upon the circuit 1. an increased current is induced in the winding 11 of the transformer 4 that is sufficient to cause the relay 6 to close the switch 17-18 the closing of which may be delayed or not, as desired. When the switch 1'7-18 is closed, the winding 19 is close-circuited and an electromotive force is induced by it in the winding 14, thereby decreasing the magnetizing effect of the winding 14 because of the counter-flux produced by the winding 19. When the magnetizing efl'ect of the winding 14 is reduced, the pull exerted by the winding 13 is permitted to predominate over that of the winding 14, and the movable core member 22 will rise in its entirety, thereby tripping the circuit interrupter 2. When the overload or other abnormal circuit condition disappears or the circuit interrupter is closed, the switch 17-18 is opened, and the movable core member 22 is returned by gravity to its normal position.

The auxiliary stationary core member is disposed such a distance from the main core member 20 that the winding 13 will normally not have any efi'ect upon the projections 25 of the movable core member 22, and the projections 25 and the auxiliary core member 23 are of such dimensions that, under shortcircuit conditions in the circuit 1, they will not become saturated before the stationary core member 20. Thus, no matter what load traverses the circuit 1, the movable core member 22 will not be moved upwardly until the relay 6 has functioned.

An adjusting screw 28 is provided for adjusting the position of av spring 29 that is disposed in an opening 30 in the shorter leg of the stationary core member 23. By adjusting the position of the spring, the amount of efi'ecti e Weight of the movable core member 22 may be so varied that the device can be set to operate at any predetermined minimum value of operating current.

While I have shown and described my invention in the preferred form it may obviously be variously modified within the scope of the appended claims.

I claim as my invention:

1. An electromagnetic device comprising two stationary magnetizable core members separated by an air gap, a common movable core member therefor, a winding for each of the stationary core members normally tending to move the movable core member in opposite directions, and an auxiliary winding for neutralizing the efiect of one of the windings.

2. An electromagnet comprising a main magnetizable core member having substantially the foam of a hollow rectangle having an opening in one of its sides, an armature extending through the opening and having an enlarged portion intermediate its ends, and an auxiliary core member having legs that are adapted to engage the enlarged portion of the said armature.

3. An electromagnet comprising a main magnetizable core member having substantially the form of a hollow rectangle having an opening in one of its sides, an armature extending through the opening and having an enlarged portion intermediate its ends, and an auxiliary core member of substantially E-shape the outer legs of which are adapted to normally engage the enlarged portion of the said armature.

4. An electromagnetic device comprising a main stationary magnetizable core member, a movable core member having an enlarged portion intermediate its ends and an auxiliary stationary magnetizable core member having legs that are adapted to normally engage the enlarged portion of the movable core member.

5. An electromagnetic device comprising a main stationary magnetizable core mem her having substantially the form of a 1101- low rectangle having an opening in one of its sides, a movable core member extending through the opening and having laterally extending portions thereon, and an auxiliary magnetizable core member having legs terminating adjacent the laterally extending portions of the movable core member.

6. An electromagnetic device comprising a main stationary magnetizable core member having substantially the form of a hollow rectangle having an opening in one of its sides, a movable core member extending through the opening and having laterally extending portions thereon, and an auxiliary magnetizable core member of a substantially E-shape the outer legs of which are adapted to normally engage the laterally extending portion and the central leg of which is adapted to normally engage one end of the movable core member.

7. An electromagnetic device comprising two stationary magnetizable members, and a common movable core member therefor having laterally extending projections thereon that are disposed between the stationary magnetizable members, said laterally extending projections being adapted to normally coiiperate with only one stationary magnetizable member.

8. An electromagnetic device comprising two stationary magnetizable core members, and a common movable core member therefor having laterally extending projections thereon disposed between the two core mem bers, said laterally extending projections being adapted to cooperate with one core member under predetermined conditions and with the other under other predetermined conditions.

In testimony whereof, I have hereunto subscribed my name this 29th day of April 1916.

BENJAMIN H. SMITH.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G.

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