US848915A - Trip-coil for circuit-breakers. - Google Patents

Description

PATENTED APR. .2; 1907.

Y 3.3. MEBRIAM. TRIP COIL FOR 01120011 BREAKERS.

. APPLIOATIONFILED, FEB. 16,' 1905.

Inventor Ezra BMerrianH b witnssz/qp vinu'rir n srnrns regrnnr orifice.

EZRA B. MERRIAM, OF SCHENEOTADY, NEW YORK, ASSEGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

rein-con. on ciacliar sssaness.

Specification of Letters Patent.

Patented ril a, 1907.

Application filed February 15, 1905. Serial No- 245,648.

& Breakers, of which the following is a specification.

This invention relates to automatic oircuitinterruptin means, and has for its object the provision of improved means for varying at will the load undef'which the trip device will be automatically operated to break the circ'uit.

In the starting of electric motors considerable annoyance is often caused by the tripping of the circuit-breaker at the first rush of current upon the closing of the circuit. This is most particularly annoying in the'case of induction-motors, wherc an excessive alternating current flows in starting and an oilswitch is set to normally trip at a certain overload. In this case the excessive starting-current will immediately trip the circuitbreaker. This is undesirable, since the armature of the motor will usually stand heavy current for such a time as is necessary for it to reach normal speed.

It has been the standard practice when the tripping-coil is excited from a current-trans former to-short-cirouit the coil. This overcomes the objectionable feature of the circuit-breaker tripping out; but it does not protect the apparatus until the shunt pr short circuit is removed.

In carrying out my invention I make .use of a special feature for the tripping mechanism by providing means whereby a change in the calibration of the mechanism may be effpcted temporarily and'at the will of the operator. I am aware that it has been proposed to change the calibration by varying the tension of the tripping spring, and likewise by providing two springs of different tensions, to-

gether with means'for shifting them so thatthe tension of the trip may be instantaneously changed. These devices, while to a certain extent overcoming the difficulties above noted, are still open toobjections. They necessitate the use of a circuit-breaker inwhich thev trip is spring-pressed and will not be-ca pable of use employed Moreover. 111 many forms of aircuit-breake'rs the construction is such that Where a gravity-operated trip is where a s ring-trip is used it is not accessible, and considerable modification in structure of calibration in this way. i In addition to this it is necessary in devices of this character that the change in calibration be effected at the circuit-ln'eaker instead of at a remote point, as is often desirable. v

The means which I employ to vary the caliproviding a trip-coil with differential windings, whichmay he joined or opposed by means of a switch to vary the pull of the mag net-coil. Y

I have-illustrated my invention in connection with a particular type of circuitbreaker'L. a, the oilswitch type for alternating currents; but it is to be under,- stood that I do not limit myself as to the type of switch or the nature of the current used and formmga part of this specification.

Referring a circuit-breaker provided with my improved trip-coil, and Fig. 2 shows a diagram of the circuits.

Referring to Fig. 2, l, 2, and 3 represent the leads of a three-phase circuit, two legs of formers 4 5. The circuit extends horn the generator-leads A, B, and O through the oilswitch and the leads 1, 2, and to an induc: "tion or similar motor M. As the mechanism which these two transformers operate is the though it is to be understood that a similar trip-c 'iland-means for changing its calihration maynbe used in connection with transformer instead of connecting both trans formers to the coil in the manner shown in Fig. 1.. 6 and '7 represent" two companion windings of a trip coil which are 'sim ly shown(diagrammatically inthis figure, ut which in ractice will both be wound on one s 001 and rovided with a core. 8 is a doub e-pole dbublathrow switch, the middle contacts of'which are connected with the ter-. minals of coil 7. The coil 6,Lis in series with the secondary of transformer 4 and has one terminal connected to the upper contact 9 of the switch, while the terminal ofthe secondany is connected with contact 10. 9 and 10 are oross-connected, as-shown in dotted lines, with the lower contacts 11 and would be necessary to bring about a change" beyond the scope of the claims appended to' same, 1 shall only describe one of them, al

bration is very simple and consists merel r in to the drawings, Figure 1 shows which are provided with the current-trans- Contacts 7 12. From this it will be seen that when the switch-bladesare in the position shown the 7 current from the transformer will pass through the coils 6 and. 7 in the direction shown by the heavy arrows, while when the switch is thrown so as to make contacts at 11 and 12 the direction of the; current through. these coils is indicated by the dotted arrows. Thus when the switch is in its 11 er position the windings, and. therefore t e uxes of the" coils 6 and 7, will be joined,

while with the switch in the lower position they are opposed. For instance, suppose the Y or when three am eres is the normaltrip ping-current it won d require fifteen amperes to trip the same device when the switch is reversed and the ratio changed ,1

In Fig. 1 I have shown conventionally an oil-switch for three-phase current provided with a trippingmechanism which includes the differential trip-coil above described.

'As my invention does not relate to the specific switch mechanism, and, moreover,- as switches of this characterare. old and Well known, a description thereof is unnecessary. Let it therefore suflice to say that when thedifferential coil 13 is energized the trip 14 is .drawn down, and the. springs-15 and 16 opthe switch to the erate to break the circuit in a well-known manner. It will be understood that the tripcoil will be arranged to-trip at a certain overload-current; but upon starting in order to prevent the circuit-breaker from tripping out, due to the first rush of current which the motor can stand for a short time, the switch 8 is thrown into engagement with the contacts 11 and 12, connecting the windings of the tripcoil in opposition to each other, so that a current greater than normal will be required breaker. i

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

1'. The combination with an automatic circuit-brtaker, of mechanism for tripping the same comprising a trip-lever, an electromagnethaving differential windings for actuating the same, and' a circuit-changer for varying at will the relative directions of a current through said windings.

2. The combination with an automatic circuit-breaker, of mechanism for tripping the same comprising a trip-lever, an electromagnet having differential windings for actuat 'ing the same, and means whereby the fluxes due to a current through the windings may be joined or opposed at will.

In Witness whereof I have hereunto set my hand this 13th day of February, 1905.

v v EZRA B. MERRIAM.

.Witnesses:

BEN AMIN B. HULL,

HELEN ORroRn.

.to cause thetrip-coil to actuate the circuit

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