US1413239A - Overload protective device - Google Patents

Description

E. W. SEEGER.

OVERLOAD PROTECTIVE DEVICE.

APPLICATION FlLED 1ULY 24,1920.

1,41 3,239. Patented Apr. 18, 1922.

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UNITED STATES PATENT OFFICE.

EDWIN W. SEEGER, OF MILWAUKEE, WISCONSIN, ASSIGNOR. TO THE CUTLER- HAMMER MFG. (10., OF MILWAUKEE, WISCONSIN, A. CORPORATION.OF WIS- CONSIN.

OVERLOAD PROTECTIVE DEVICE.

Application filed July 24,

To all whom it may concern:

Be it known that I, EDWIN W. SEEGER, a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented new and useful Improvements in Overload Protective Devices, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this speclfication.

This invention relates to improvements in overload protective devices and is particularly applicable to those employed in connection with electric motors.

The invention has among its objects to provide simple and efficient overload protective means which may be readily controlled to vary the sensitiveness thereof to meet different requirements as for example starting and running of a motor to be protected thereby. 1 A further object is to provide overload protective means of the aforesaid character responsive to the current conditions of a pol phase alternating current circuit.

arious other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates an embodiment of the invention which will now be described, it being understood that various modifications may be made in the embodiment illustrated without departing from the scope of the appended clalms.

Referring to the drawing, the same illustrates a conventional three phase motor 1, a starting device 2 therefor. and an overload circuit breaker 3 for interrupting the power supply for said motor illustrated-by lines L 2 and La The starting device 2 may be of any desired type, the same being shown schematically with an operating handle movable in opposite directions from an intermediate off position into starting and running positions. The device 2 has a bridging contact 4 associated therewith and in starting position thereof said contact engages stationary contacts 5 and 6 for a purpose hereinafter set forth. Circuit breaker 3 is of 'a three pole type, the same being biased to open position and being adapted to be held in closed position by a latching device 7. Latching device 7 1s provided with overload tripping coils 8 and 9 said tripping coils being sup- Speciflcation of Letters Patent.

position, the paral Patented Apr. 18, 1922.

1920. Serial No. 398,843.

plied with current T and T Current transformers T and T have their prlmary windings respectively connected in lines L and L and the former has its secondary wlnding connected across the terminals of tripping coil 8 while the latter has its secondary winding connected across the terminals of tripping coil 9. The secondarv windings of transformers T and T have one terminal connected together by a conductor 1() while the opposite terminals of said wlndings are respectively connected by conductors 11 and 12 to stationary contacts 5 and 6. 4

With the above described circuit connectlons bridging contact 4 engages contacts 5 and 6 in starting position of the device 2 to connect the secondary windings of the transformers T and T in parallel and to also connect the trip coils-'8 and 9 in parallel with said windings. However, upon movement of the starting device 2 into running el connections between the transformers T and T are interrupted and tripping coil 8 is then connected across the terminals of transformer T while tripping coil 9 is connected across the terminals of transformer T Due to the difference in phase of the current in transformers T and T it is apparent that upon connection of the secondary windings in parallel the resultant current in tripping coils 8 and9 will be less for a given current value in lines L and L than when said transformers are connected independently to said trip coils. Thus it is apparent that when device 2 is in starting by current transformers position .trip coils 8 and 9 will be less sensitive to current conditions in the supply circuit than when said device is in. running position. Accordingly by properly designing the transformers and trip coils, the circuit breaker 3 will permit a relatively high inrush current during starting of the motor while restricting the permissible current to a lower value during running.

While the aforedescribed protective device has been shown and described in connection with a starting device having a single starting position, it is apparent that the same is not limited thereto. If the starting device has a plurality of starting positions the contacts 4, 5 and 6 can be arranged to permit a high inrush of current in any of the starting positions. Also said contacts can be arranged to render the protective device less sensitive during running than during starting.

\Vhat I claim as new and desire to secure by Letters Patent is:

1. A protective controller for polyphase alternating current circuits, comprising current transformers to be connected in different phases of said circuit, means supplied with current from said transformers to act under given current conditions in said circuit and means for establishing parallel connections for certain windings of said trans- .formers to vary the sensitiveness of said means to the current conditions in said circuit.

2. A circuit protective device sensitive to current variations in a polyphase alternating current circuit, comprising current transformers to be connected in diiferent phases of the polyphase circuit, means having separate circuits supplied by said transformers respectively for response of said means under given current conditions in the polyphase circuit and means for interconnecting certain of the windings of said transformers to vary the sensitiveness of said means to the current conditions in the polyphase circuit.

3. A circuit protective device sensitive to variations in current of a polyphase circuit, comprising a plurality of tripping coils, a

plurality of current transformers connected in difierent phases of said circuit and each supplying current to one of said coils to effect response thereof under given current conditions in said circuit and means for paralleling certain of the windings of said transformers for varying the sensitiveness of said coils to the current conditions in said circuit.

4. In a circuit protective device sensitive to variations in current of a polyphase circuit, the combination, with circuit controlling means having a plurality of tripping coils, of a plurality of current transformers to be connected in different phases of the polyphase circuit and each having one of said tripping coils connected across its secondary terminals, and means for establish ing parallel connections for the primary windings of said transformers, said means being operable to make and break such connections to vary the sensitiveness of said tripping coils to the current condition of said circuit.

5. The combination With a polyphase alternating current circuit including a translating device and a controller therefor, of a protective device for said circuit comprising a plurality of tripping coils, current transformers connected in different phases of said circuit to supply current to said coils, and means associated with said controller to establish parallel connections for the primary windings of said transformers under certain conditions and to interrupt said connections under other conditions.

In witness whereof, I have hereunto subscribed my name.

EDWIN W. SEEGER.

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