US2499963A - Phase failure protective device - Google Patents

Description

' March 7, 1950 J. w. M CLAIN PHASE FAILURE PROTECTIVE DEVICE Filed Aug. 5, 1944 Inventor:

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Patented Mar. 7, 1950 PHASE FAILURE PROTECTIVE DEVICE Joseph W. McClain, Schenectady, N. Y., asslgnor to General Electric Company, a corporation of New York Application August 5, 1944, Serial No. 548,225

1 My invention relates to protective devices for three-phase circuits, more particularly to a protective device for three-phase motors, and has for its object a simple and inexpensive means responsive to a fault in one of the three-phase supply lines for the motor for deenergizing the motor.

In carrying out my invention in one form, I provide a relay having two coils arranged at substantially right angles with respect to each other, which coils are connected in two of the three supply lines for the three-phase motor. Under normal conditions, an armature for the two coils is maintained in a predetermined normal position but, in the event of failure of one of the supply lines resulting in single phase operation of the motor, the armature is moved to efieot the deenergization of the motor.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a view in perspective of a protective device embodying my invention; Fig. 2 is a fragmentary sectional view showing details of construction; while Fig. 3 is a diagrammatic representation of a three-phase electric motor circuit provided with protective means embodying my invention.

Referring to the drawing, in carrying out my invention in one form I provide two coils i and 2 which are wound on a suitable supporting spool 3 made of electrically insulating material and supported on the spool with the axes of the coils substantially at right angles with each other and extending at equal angles with respect to the relatively large tubular central portion 4 of the spool. In other words, the two coils are arranged in intersecting relation with each other with the axis or center line of the cylinder 4 substantially bisecting the angle between the two planes of'the coils, a plane of each coil being a plane perpendicular to the axis of the coil in which plane lies one or more turns of the coil.

. Mounted on a pivot 5 carried by a bracket 6 is an armature member 1 made of magnetic material. As shown, the pivot 5 is located intermediate the length of the cylinder 4 and extends at right angles with the center line of the cylinder and parallel with the line of intersection of the It passes through the armature 1 at a point adjacent the lower end of the armature, the armature extending upward through both coils in magnetic flux conducting relation therewith.

Secured to the lower end of the armature I by suitable screws 8 is an arm 9 made of an 1 Claim. (Cl. 175-294) electrically insulating material, such as a hard fibre. At its lower end the arm 9 is provided with a wider portion in which is a central slot i0 whereby the arm 9 constitutes a circuit controlling arm. Thus two stationary contacts ll, mounted respectively on spring arms i2 and I3 and normally biased intoengagement with each other by the spring arms, are located inposition to lie in the slot in when the armature 1 extends, as shown in the drawing, axially or centrally of the cylinder 4. When the armature i is moved in either direction, however, about its pivot 5 by the coils in the event of a fault in the motor circuit, one side or the other of the enlarged portion on the lower end of the arm 9 moves between the two contacts Ii, thus separating them and interrupting a circuit through the contacts whereby the motor is disconnected from its supply lines.

Referring to Fig. 3, I have shown the two coils i and 2 connected respectively in two of the three supply lines of the three-phase motor it which is energized through a switch i5 from supply conductors [8. By closing a push button switch H, the coil i8 for the switch is energized through the contacts i l and the switch it closed, the switch at the same time closing an interlock holding switch 19 for the coil is. The two coils are so connected in the motor supply lines that under normal motor operating conditions, the coils produce a resultant flux which bisects the angle between the coils, i. e., is directed axially of the cylinder i. The armature l is thereby maintained normally in a position parallel with the flux along the axis or center line of the cylinder 4, as shown in the drawing, so that the contacts ii remain in engagement and the switch i5 remains closed.

In the event of the failure of one of the motor supply lines containing one coil, that coil becomes deenergized while the motor continues to operate as a single phase motor. The magnetic flux of I the other coil applies a force to the armature moving it about its pivot 5 in a direction to bring it in line with the flux. This causes the member 9 to separate the contacts Ii whereby the coil I8 is deenergized and the supply switch i5 for the motor opened.

When the fault occurs in the three-phase line which does not contain a coil so that both of the coils remain energized during single phase operation, the current reverses in one of the coils so that the resultant flux then is substantially at right angles with the center line of the cylinder 4. This flux likewise produces a pivotal movement of the armature in one direction or the other and the arm 9 to separate the contacts ii and deenergize the motor.

When the motor is to be restarted after it has been deenergized by separation of the contacts H, as described, the armature I and arm 9 are While I have shown a particular embodiment a of my invention, it will be understood of course that I do not wish to belimited thereto since many modifications may be made and I therefore contemplate by the appended claim 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 01 the United States is:

A single phase failure protective device for a three-phase alternating current circuit having three supply conductors, said device comprising a first flatly disposed coil adapted to be serially connected in one of said supply conductors, a second flatly disposed coil adapted to be serially connected in another of said supply conductors, the current in one of said coils failing entirely or reversing in the event of a failure of one phase of said three-phase circuit, means fixedly mounting said coils in mechanically intersecting relation with the planes-of said coils angularly displaced thereby to produce a resultant pulsating flux having a common portion passing through both said coils, an elongated magnetizable armature extending through both coils and lying generally along the path of said common portion of said flux, and means pivotally mounting said armature on a fixed pivot substantially parallel to the line of intersection of the planes 0! said coils whereby under balanced three-phase conditions said armature is normally held by said resultant flux floating in a central position of alignment with the said common portion of said resultant flux substantially bisecting the angle between the planes of said coils, said armature being rapidly pivoted to another position by the resulting change in direction of said resultant flux upon the failure of one phase of said three-phase circuit.

JOSEPH W. McCLAIN.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 528,268 Armen Oct. 30, 1894 822,234 Andrews June 5, 1906 825,632 Black July 10, 1906 1,269,481 Mathews June 11, 1918 1,620,556 Jones Mar. 8, 1927 1,637,043 Jones July 26, 1927 1,656,116 Hull Jan. 10, 1928 2,161,929 Millikan June 13, 1939 2,169,141 Gille Aug.'8, 1939 2,397,527 Borsum Apr. 2, 1946 2,444,624 Anderson July 6, 1948

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