US1485157A - Overload protective device - Google Patents

Description

Feb. 26, 1924. 1,485,157

C. J. AXTELL QVERLOAD PRoimcTIvE DEVICE Filed July 9, 1920 Invehtor: Y Clinton J. Axtell 9%? Hjs Attorney.

Patented Feb. 26, 1924.

UNITED STATES 1,485,157 PATENT OFFICE.

CLINTON J. AXTELL, 0F SCHENECTADY, NEW YORK, ASSIGNQR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

OVERLOAD PROTECTIVE DEVICE.

Application filed July 9,

To all whom it may concern:

Be it known that I, CLINTON J. AXTELL, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Overload Protective Devices, of which the following is a specification. 7

My invention relates to protective devices for electric circuits whereby an excessive current will insure an opening of the circuit to prevent injury to translating devices connected thereto. More specifically, my invention relates to an overload circuit breaker adapted to operate at any one of a plurality of different values of current, and the invention is particularly useful for operation on a circuit in which the potential of the current differs from time to time. A familiar instance of this kind is an electric railway on which the cars operate at 600 volts on some parts of the line and at 1200 volts on the other parts. In such an equipment, if the cars are provided with four motors, they are connected in parallel when running at full speed on the 600 volt section of the road, and connected in series parallel (two parallel groups of two in series) when the cars are operating on the 1200 volt section of the line. In such an arrangement, the current taken from the 600 volt section will be approximately double that taken from the 1200 volt section for the same speed of operation.

The object of my invention is to provide a circuit breaker which will accommodate itself to the change from operation upon one voltage to operation upon another with the corresponding change in current, and will protect the motors equally well under both conditions.

In carrying my invention into effect, I provide a circuit breaker having an operating electromagnet with a series coil enerized in accordance with the current taken rom the source of supply, and vary the pull of the electromagnet in accordance with the voltage of the supplyse'ction by varying the magnetic reluctance of the operating electromagnet. One embodiment of my invention comprises an operating electromagnet having a series coil and a movable member which is electromagnetically operated to vary the magnetic reluctance of the operating electromagnet and thereby automatically 1920. Serial No. 394,983.

vary the setting at which the overload protective device will disconnect the translating devices from the source of supply. Provision is thus automatically made for accom modating the protective device to the different value of current or the setting of the protective device in accordance with the voltage of the supply circuit.

For a better understanding of my invention, reference is had to the accompanying drawing wherein I have shown an embodiment of my invention for purposes of illustration. Referring to the drawing, the translating devices to be protected, in this case the series wound motors 10, 11, 12 and 13, are adapted to be connected to the source of supply through the operation of the master controller 14 by the closing of the electromagnetic line switch '15. This electromagnetic line switch or contactor 15 is controlled by my improved circuit breaker or overload protective device 16 having a series coil 17 energized responsively to the motor current and a magnetic structure having a movable member or plunger 18 for varying the reluctance of the magnetic circuit in accordance with the value of current at which the overload protective device is to operate. The protective device is also provided with a switch member 19 having contacts in the coil circuit of the line contactor 15. An electromagnet 20, having a shunt coil 21 and a movable plunger 22 mechanically connected with the plunger 18, is adapted to be energized when the motors are connected to the source of supply for parallel operation by throwing the series parallel switch 23 to its lower position. The series parallel switch is shown in the drawing as being thrown in its upper position at which the motors are connected in series parallel across the supply circuit. When the series parallel switch is thrown to its lower position to connect the motors in multiple the movable contact 24 makes engagement with the stationary contacts 25 and thereby connects the shunt coil 21 across the supply circuit. When the overload protective device responds in accordance with the predetermined value of cur-- rent, the switch member 19 is locked in the open position by means of the biased pivoted detent or catch 26. This detent 26 may be released by the energization of the electromagnet 27 when the pilot switch 28 is closed, thereby attracting the detent 26 and perer voltage section of the line. For purposes of explanation, it will be assumed that the higher voltage is 1200 volts. The motors will be accelerated up to ll operating speed by continuing the movement of the master switch 1 which thereby etfects the cutting out of the starting resistor 31 section by section in a well understood manner. The electromagnetic switches tor cutting out the starting resistor and the connections for the same have not been shown, since this an rangement is well understood by those skilled in the art. In case an excessive current. is taken from the source of supply, the series coil 17 will be energized at such a value that. the switch member 19 will open its contacts and thereby decuergize the winding circuit of the line contactor 15, thereby disconnecting the motors from the trolley wire 32 (the source of supply). The detent 26 will prevent the switch member 10 from reclosing its contacts and the operator will then return the master switch 1% to its oif position, thereby reinserting the starting resistor 31 in the motor circuit. In order to reconnect the motors to the supply circuit, the pilot switch 28 is closed, thereby energizing the electromagnet 27 and attracting the pivoted detent 26. .Vhen the switch member 10 has closed its contacts, the pilot switch 28 may be reopened so as to render the detent 2G etlective to lock the switch member 19 in the open position in response to the occurrence another overload. lV hen the series paralleling switch 23 is thrown to its lower position, at which its upper contacts make engagement with the stationary motor terminal contacts, the motors will be connected in parallel across the 5 1 circuit, and the shunt winding 21 will be energized through the contact 2 1:. This will cause the plunger 22 to be drawn upward within the shunt coil 21 and the. plunger 18 to be also moved upwardly, thereby increasing the magnetic reluctance of the magnetic structure or the overload protective device 10. This will change the setting of the overload protective device to accommodate it to the change in potential of the supply circuit, and the overload protective device will not trip open until the current in the series coil 17 is substantially double that at which the protective device previously open ated when the motors were operating on the 1200 volt section of the line. bviously, the protective device may be adjusted or set to operate at any desired value of current when operating on the 1200 or (500 volt section of line by varying the position oi? the plunger it}. in order to simplify the drawing, no means has been shown for holding the plunger in its lower position since the provision of such means obvious and those skilled in the art will readily supply the same.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by any other means.

hat I claim as new, and desire to secure by Letters Patent 01. the United States, is

1. An overload circuit breaker adapted to open at a plurality of predetermined different values of current in the circuit controlled thereby, comprising a coil energized responsivcly to the current in the controlled circuit, a magnet structure therefor, a switch ieinber controlled thereby for controlling the controlled circuit and electromagnetic m ans for changing the magnetic reluctance ot the said magnetic structure to change the value of current at which the circuit breaker is to open.

2. An overload circuit breaker adapted to open at a plurality of predetermined different values of current in the circuit controlled thereby, comprising an operating electromagnet having a coil energized responsively to the current in the controlled circuit, a switch member controlled thereby for controlling the controlled circuit. and electromagnetic means for varying the pull of the operating electromagnet to change the value of current at which the circuit breaker is to open.

3. An overload circuit breaker adapted to open at either of two different values of current in the circuit controlled thereby, comprising an electrom'agnet having a coil energized responsively to the current in the controlled circuit, a magnet structure there- "for having a movable member for varying the magnetic reluctance of the structure, a switch member controlled by the electromagnet for controlling the controlled circuit, electromagnetic means for varying the position of the said movable member, and means for controlling the said electromagnetic means to vary the value of current at which the circuit breaker is to open.

4. An overload circuit breaker adapted to open at one value of current when the translating device controlled by the circuit breaker is connected to a source of supply of one voltage and to open at a hi her value of current when the translating evice is con nected to a source of supply of lower voltage, comprising a coil energized by the our rent in the circuit of the translating device, a magnet structure therefor, a switch member controlled thereby for controlling the circuit of the translating device, and electromagnetic means energized from the source of supply of lower potential for increasing the magnetic reluctance of the said magnetic structure to increase the value of current necessary to open the circuit breaker.

5. An overload circuit breaker adapted to open at one value of current when the translating device controlled by the breaker is connected to a source of supply of one voltage and to open at a higher value of current when the translating device is connected to a source of supply of lower voltage, comprising a coil energized by the current, a magnet structure therefor, a switch member controlled thereby, the said magnet structure having a magnetic movable member, and an electromagnet energized from the source of lower potential for moving the said movable member to vary the magnetic reluctance of the said magnet structure to vary the value of current at which the circuit breaker is to open.

In witness whereof, I have hereunto set my hand this 8th day of July, 1920.

CLINTON J. AXTELL.

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