US1989485A - Rectifier protective system - Google Patents

Description

Jan. 29, 1935. 0. K. MARTI 1,989,485

RECTIFIER PROTECTIVE SYSTEM Filed Oct. 6, 1932 Illlll Patented Jan. 29, 1935 UNITED STATES 1,989,485 RECTIFIER PROTECTIVE SYSTEM Othmar K. Marti,

Wauwatosa,

Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis, a corporation of Delaware Application October 6, 1932, Serial No. 636,431

5 Claims.

This invention relates to improvements in protective systems and more particularly to improvements in protective systems for electron discharge devices.

Electrical systems comprising electron discharge devices are usually provided with protective means for the purpose of disconnecting the device from its associated circuits upon the occurrence of an overload or of a short circuit in the output circuit thereof, or in case of a disturbance such as a backfire within the device itself. Such protective means usually comprise circuit breakers which must interrupt the entire current carried by the device and must, therefore, be of considerable capacity. The current in the device may also be interrupted by suitable energization of control electrodes but the action of such control electrodes is not always fully effective, in addition to which it is usually desirable to provide a physical opening of the circuits of the device. By interrupting the current in the device by the action of the control electrodes and thereupon opening the circuit by means of a circuit breaker, the circuit may be opened by the circuit breaker without interruption of current or with interruption only of a materially reduced amount of current, so that the circuit breaker may be of a. reduced capacity and, therefore, less expensive.

It is accordingly one object of the present invention to provide a protective system for electron discharge devices in which the device is automatically made inoperative upon occurrence of a disturbance in the circuits thereof.

Another object of the present invention is to provide a protective system for electron discharge devices in which the circuits of the device are opened only after the device has been made inoperative.

Another object of the present invention is to provide a. protective system for electron discharge devices in which the circuits of the device are physically opened by a circuit breaker without interruption of current or with interruption of only a reduced amount of current.

Objects and advantages other than those above set forth will be apparent from the following description when read in connection with the accompanying drawing which diagrammatically illustrates one embodiment of the invention applied to an electron discharge device used as an electric current rectifier.

Referring more particularly to the drawing by characters of reference, reference numeral 1 designates an electron discharge device operable for the conversion of electrical energy between an alternating current line 2 and a direct cur--v rent line 3, 4. Device 1 is connected with line 2 by means of a transformer having a primary winding 6 and a secondary winding 7, comprising a plurality of star connected portions severally connected with the anodes 8 of the device. Transformer winding 6 is connected with line 2 through fuses 9 and a disconnecting switch 11.

Device 1 is provided with control electrodes 12 which may be energized from the secondary winding 14 of a control transformer having a primary winding 13, the secondary winding 14 being connected with a battery 16. The positive terminal of battery 16 is connected with the cathode 17 of the device and. the negative terminal thereof is connected with the neutral point of winding 14. Current limiting resistances 18 are inserted betweenwinding 14 and control electrodes 12. The circuit of the device may be interrupted by means of a circuit breaker 19 provided with a latch 20 and with a strip coil 21 which may be energized from a battery 22. Winding 13 of the control transformer is energized from winding 7 through a circuit breaker 23 provided with a latch 24, a trip coil 26 and auxiliary contacts 28. Trip coil 26 is energized from a current transformer 27 provided with two primary windings inserted in the circuits of two portions of windings 7 supplying currents displaced in phase with respect to each other by degrees.

In operation, the system being connected as shown in the drawing, transformers 6, 7 and 13, 14 are energized from line 2. Control electrodes 12 are generally maintained at a negative potential by battery 16 and are sequentially energized at a positive potential by the portions of winding14 connected therewith. Positive energization of control electrodes 12 permits operation of the associated anodes 8 as is well known in the process of electric current electrification. In normal operation, the current supplied to trip coil 6 by current transformer 27 is not of sufficient magnitude to operate latch 24.

Upon occurrence however of a disturbance in line 3, 4 or in device 1, excessive currents will flow in the several portions of winding '7 and current transformer 27 will supply a current of sufficient magnitude to trip coil 26 to operate latch 24. Circuit breaker 23 then opens thereby disconnecting winding 13 from winding "I. Winding 14 is thus no longer energized from winding 13 and all control electrodes are maintained at the negative potential of battery 16. After a period of one cycle of the alternating current voltage of line 2, each of anodes 8 will have received an alternating negative potential from transformer winding 7 during which period the anode ceases to carry current and will thereafter be incapable of carrying current because of the energization of the associated control electrodes at a negative potential. During the occurrence of such negative potential, circuit breaker 23 has fully opened thereby closing its contacts 28 and permitting energization of trip coil 21 from battery 22.

Trip coil 21 operates latch 20 which releases circuit breaker 18,.thereby physically opening the tripping of circuit breaker 19, circuit breaker 19 will open its contacts without interrupting any current.

In the event of line 3, 4 being energized by other converting means or by a direct current generator or upon occurrence of a backfirein device 1, a direct current will flow from line 4 through device l, contacts of circuit breaker 19' and winding 7 to line 3. Such current cannot be interrupted by application of a negative potential to control electrodes 12 and must, therefore, be interrupted by circuit breaker 19. Because circuit breaker 19 need not interrupt the alternating current supplied to device 1 by winding -7 as described above, it will be under-' stood that, even in-the event of external energization of line 3, 4'or of disturbances, the current interrupted by such circuit breaker is much less than would be the case in the absence of negative energization of control electrodes 12.

Ifa disturbance such as a short circuit occurs in either of winding 6 or '7, a large current will be drawn from line 2 which will cause fuses 9 to blow and will disconnect winding 6 from line 2. In such case no disturbance occurs in the circuit of device 1 and circuit breaker 19 will not operate.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit-of the invention or from the scope of the appended claims. I

It is claimed and desired to secure by Letters Patent: v

1. In a protective system for electron discharge devices, an alternatingcurrentsupply line, an electron discharge device having anodes with associated control electrodes, a transformer arranged for connection with said line and with the anodes of said device, a circuit breaker controlling the connection of the anodes with said transformer, a transformer arranged for connection with the first said transformer and with the control electrodes, a circuit breaker controlling the connection of the said transformers, and a current transformer associated with the first said transformer to control the operation of the second said circuit breaker, the second said circuit breaker controlling the operation of the first said circuit breaker.

2. In an electric current converting system, a source'of current supply, an electron discharge device comprising a casing having electrodes disposed therein forming terminals for the fiow of current therebetween, means operable to establish and to interrupt connection of said source of current with said electrodes, means supported within said casing operable to control the initiation of flow of current from said source by way of said electrodes, and means operable to-'control the said operation ofthe second said means and to thereup n control the operation of the first said means to interrupt connection of said source with said electrodes.

3. In an electric current converting system, a source of current supply, an electron discharge device comprising a closed casing having electrodes supported therein forming terminals for the flow of current therebetween, means operable to establish and to interrupt the connection of said source of current with said electrodes, means supported within said casing operable to control the initiation of flow of current from said source by way of said electrodes, and means operable responsive to and upon the occurrence of flow of current of predetermined magnitude between said electrodes to control operation of the second said means and to thereupon control the operation of the first said means to interrupt connection of said source-oi current with said electrodes.

' 4. Inan electric current converting system, a source of current supply, an electron discharge device comprising a casing having electrodes therein forming terminals for the flow of current therebetween, circuit breaker means oper able to establish and interrupt the connection I of said source of current with said electrodes, means comprising control electrodes supported within said device operable to prevent and to con trol the initiation of' flow of current from said source byway of the first said electrodes, and

electromagnetically actuated means operable responsive to and upon the occurrence of flow of current of predtermined magnitude from said sourceby way of the first said electrodes to'cause operation of the second said means to prevent said initiation of fiow of current and to thereupon establish connections to cause operation of said circuit breaker means to interrupt connection of said source of current with the first said electrodes.

5, In an electric current converting system, a source of alternating current, an electron discharge device comprising a casing having there'- in a cathode, a plurality of anodes, and'a plurality of control electrodes, a transformer connected with said source of current and having a winding dividedinto a plurality of phase displaced sections, a circuit breaker operable to establish and interrupt connection of said phase sections severally with said anodes, a second transformer having a primary winding connected with said source of current and a secondary wind-. ing divided into a plurality of phase displaced sections severally connected with said control electrodes operable. to. impress potential supplied from said source of current on said control electrodes of such sign and magnitude and at such recurring periods as to facilitate the initiation of flow of current from said source through said device sequentially by way of said anodes to said cathode, means actuated responsive to flow of current from said source to said anodes of abnormal magnitude operable to interrupt the connection of said source of current with said primary winding and to thereupon cause operation of said circuit breaker to interrupt connection of the first said transformer with said anodes, and a source of direct current connected with and continuously impressing potential on said control electrodes of such. sign and magnitude as to prevent said initiation of flow of current by way of said anodes.

OTHMAR K. MAR'II.

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