US793493A - Rheostat. - Google Patents

Description

I PATENTED JUNE 27, 1905. W. 0. YATES & A. M. FENWIGK.

- RHBOSTAT.

APPLICATION FILED SEPT. 26, 1904.

Fi h

I MT ESSESI v UNITED STATES Patented June 27, 1905.

PATENT OFFICE.

WILLIAM C. YATES AND ALEXANDER M. FENWICIQOF SCHENECTADY, NEW YORK, ASSIGNORS TO GENERAL ELECTRIC COMPANY, A COR- PORATION OF NEW YORK.

RHEOSTAT.

SPECIFICATION forming part of Letters Patent N0. 793,493, dated June 27, 1905.

Application filed September 26, 1904. Serial No. 225,877.

To ftZZ whom it may concern;

Be it known that we, WILLIAM C. YATES and ALEXANDER M. FnNwIoK, citizens of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Rheostats, of which the following is a specification.

This invention relates to the control of electric motors; and its object is to provide a rheostatic starting device for a shunt-wound electric motor which shall be simple, compact, and inexpensive and so designed that the parts interlock to make the device foolproof.

Our invention is particularly applicable to devices for starting large shunt-Wound electric motors in which it is not desired to break the motor-circuit at the rheostat-contacts because the contact-surfaces would be pitted by the spark formed when the circuit is broken; but it must be understood that the principles of the invention are applicable to rheostatic controlling devices for motors of all sizes and to speed-regulating rheostats, as well as starting-rheostats.

The novel features of our invention will be definitely indicated in the claims appended hereto.

The details of construction and the mode of operation of our improved rheostatic controller will be better understood by reference to the following description, taken in connection with the accompanying drawings, which show the preferred embodiment of our invention, and in which Figure 1 is a front View of the panel; Fig. 2, an enlarged detail view of one of the circuit-breakers; Fig. 3, an enlargedelevation of the field-switch, and Fig. 4 is a diagram of the circuits.

Referring to the drawings, 1 indicates a panel of soapstone, marble, or other insulating material, preferably supported in an upright position by suitable standards, on which is also secured a subpanel carrying the resistance. Mounted on the panel are two circuitbreakcrs 2 and 8. The breakers shown in the drawings are of a standard type well known to users of electrical apparatus and consist of a pivoted switch-blade cooperating withsuitable contacts and operated by a handle 4 and a latch 5 for holding the blade in the closed position, provided with a handle 6 for tripping the latch. Each breaker is provided with an overload-coil 7 which in response to a predetermined overload draws up'aplunger 8, provided with a projection adapted to en' gage the latch 5 and trip the breaker. One of the breakers is provided with a no-voltage coil 9, suitably incased, which on failure of the line voltage or when the circuit is opened allows its core to drop and rock a pivoted lever 11 to trip the latch 5. Pivotally mounted on the panel is a switch-arm 12, carrying a blade 13, in the path of movement of which is a series of contact-plates 14, arranged in the arc of a circle. Switch-clips 15 are mounted on the panel in position to be cross-connected by the blade 13 when the switch-arm is in the final position to out out of circuit all the resistance. Pivoted in an opening in the panel is a lever 16, which is engaged by the switch-arm when on the first contact-plate of the series 14 to move a rod 17 in guides 17 on the back of the panel to a position in which an opening in the rod (indicated by the dotted circle in Fig. 1) is in alinement with a projecting stud 18, adjustably secured bya set-screw 19 in an opening in the circuit-breaker 2. When the switch-arm 12 is moved away from the first contact-plate 14, a spring 18, having one end attached to rod 17 and the other to a post on the back of the panel, tends to move rod 17 in its guides to carry the opening in rod 17 out of alinement with the projecting stud 18, so that if the blade 13 is out of engagement with the lever 16 and the breaker 2 is open the breaker cannot be closed, as the projection thereon would engage the rod 17, and thus prevent the breaker from being thrown in far enough to close the circuit.

Mounted on the panel below the circuitbreakers 2 and 3 is a switch for the motorfield. This 'switch consists of two parallel blades 20, pivoted in clips 21, mounted on the panel and connected at their ends by a crossbar 23, of wood or other insulating material. Switch-clips 22 are also mounted on the panel in position to be engaged by the blades 20. Secured to or integral with the blades 20 and at right angles thereto are blades 24, which are connected at their ends by across-bar 25, of insulating material, similar to the bar 23. No handle is provided on this switch. Instead it is operated by a switch which interlocks therewith and controls the circuit of the novoltage release-coil 9. Mounted on the panel between the clips 21 is a switch-clip 26, somewhat longer than clips 21, and a switch-blade 27 is pivoted in this clip and extends out between the cross-bars 23 and 25. Mounted on the panel is a switch-clip 28, of about the same length as the clip 26, in position to be engaged by the blade 27, and an operating-handle 29 is provided on the end of blade 27. The armature 30 of the motor is connected to the supply-mains through the breakers 2 and 3 and so much of the resistance connected to the contact-plates 14: as is cut into circuit by the blade 13. The motor-field 2,1 is connected to the switch-clips 21, and the clips 22 are connected to the lines above the breakers 2 and 3. The no-voltage release-coil 9 and a resistance 32 in series therewith are connected across the lines through the blade 27.

The operation of the device will be readily understood from the foregoing description. Then the motor is not in operation, the breakers 2 and 3 are open and the switch-blades 20 and 27 are out of clips 22 and 28, respectively. In starting, the circuit of the motor-field should be closed first. If it is attempted to close the armatu re-circuit without first closing the field, the breaker 3 may be thrown in and will be held by its latch 55, thus closing one side of the armature-circuit. The other side, however, cannot be permanently closed, for if breaker 2 is thrown in the latch 5 will not catch, as the circuit of the no-voltage releasecoil 9 is open and the lever 11 will beheld by the core 10 of the no-voltage release in a position to prevent latch 5 from holding the breaker in, and the switch 27 for the no-voltage release-circuit cannot be closed without closing the field-circuit. Thus the armaturecircuit cannot be closed before the field-circui t except by the operator intentionally closing the field-switch otherwise than by handle 29 and blade 27 or by holding the breaker 2 in. To properly start the motor, blade 27 is turned on its pivot by the handle 29 and engages crossbar 23, thus pushing the blades 20 into clips 22 and closing the field-circuit. On further movement of the handle 29 blade 27 enters the clip 28 and closes the circuit of the no-voltage release-coil 9, which raises its plunger, and thus permits lever 11 to move out of engagement with the end ol latch 5. The armature-circuit should then be closed by the breakers 2 and 3. 'When the armature-circuit is closed, the switch-arm 13 for regulating the resistance should be on the first contact-plate 14, so that all of the resistance is included in circuit to cut down the cur rent admitted to the motor-armature immediately at starting. If the blade 13 is not onv the first contact, the rod 17 is drawn to such a position by spring 18 that the opening therein is out of alinement with the projection carried by the breaker 2, and the breaker cannot be closed. WVith the field-circuit of the motor closed and blade 13 on the first contactplate 14 the breaker 2 can be closed, thus starting the motor. Switch-arm 12 is then turned on its pivot, moving blade 13 over the contactplates 14 to cut resistance out of the armature-circuit. and thus bring the motor up to speed until it reaches its final position, where it engages clips 15 and connects the armature directly across the lines. In event of an overload, coils 7 on the breakers draw up the plungers 8 and open the breakers to open the armature-circuit. .ln event of an under-load or of an opening of the circuit core 10 falls, rocking lever 11 and latch 5, and thus opening the circuit at the ln'eaker 2. In either case the spring 18 moves rod 17 in its guides to prevent the armature-circuit from being closed again without first bringing the rheostat-arm 13 around to the first position. The armature-circuitmay beintentionally opened by pressing the handle 6 on latch 5 of either of the breakers. The field-circuit of the motor, however, cannot be opened while the armature circuit is closed. It switch-blade 27 is pulled out by means of handle 29, circuit through the no-voltage releasecoil 9 is opened as soon as the blade leaves clip 28, and the release-coil opens breaker 2 immediately. Further movement of blade 27 brings it into engagement with cross-bar 25, and thus forces the blades 20 out of the clips 22 to open the field-circuit. Thus the armature-circuit of the motor cannot be permanently closed before the field-circuit is closed, the field-circuit cannot be opened until after the armature-circuit is opened, and the armature-circuit cannot be closed except when the switch-arm I3 is on the first contact-plate let, in which position all of the resistance is cut into the armature-circuit.

It will be evident that many modifications can be made in the design and construction of our improved rheostat without departing from the spirit of the invention.

Such modifications of the controlling-device illustrated and described herein we consider within the scope of our invention, and we aim to cover them in the claims appended hereto.

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

1. The combination of a motor, a switch for closing the armature-circuit thereof, an adjustable resistance in the armaturecircuit,

ITO

means preventing closure of said switch unless all the resistance is in circuit, means for closing the fieldcircuit of the motor, and means preventing opening the field-circuit before the armature-circuit isopened.

2. The combination with an electric motor, of a circuit-breaker for closing the armaturecircuit thereof, a low-voltage release device therefor, means for closing the circuit of the low-voltage release device, and means for closing the field-circuit of the motor arranged to insure closure of the field-circuit before the circuit of the low-voltage release device is, closed.

3. The combination with an electric motor, of a circuit-breaker for closing the armaturecircuit thereof, a low-voltage release device therefor, means for closing the circuit of said device, and means for closing the field-circuit of the motor arranged to insure opening the circuit of said release device before the fieldcircuit is opened.

4:. The combination with an electric motor, acircuitbreaker for closing the armatu re-circuit thereof, and a low-voltage release device for the breaker, of a switch for closing the field-circuit of the motor, and a switch -interlocked therewith for closing the circuit of said low-voltage release device.

5. The combination with an-electric motor, a circuit-breaker for closing the armature-circuit thereof, and a low-voltage release device for the breaker, of a switch for closing the field-circuit of the motor, and a switch for 7 closing the circuit of said low-voltage release device interlocked to insure closure of the field-circuit before the circuit of the low-voltage release device is closed.

6. The combination with an electric motor, a circuit-breaker for closing the armature-circuit thereof, and a low-voltage release device for the breaker, of a switch for closing the field-circuit of the motor, and a switch for closing the circuit of said low-voltage release device interlocked to prevent opening the fieldcircuit before the circuit of the low-voltage release device is opened.

7. The combination with a motor, of a circuit-breaker for closing the armature-circuit thereof, a low-voltage release device for said circuit-breaker, an adjustable resistance in the armature-circuit, means preventing closure of the breaker unless all the resistance is in c1rcuit, a switch for closing the field-circuit, and

Images