US2018235A - Protective system for discharge devices - Google Patents

Description

Oct. 22, 1935. F. SOCHER ET AL ,0

PROTECTIVE SYSTEM FOR DISCHARGE DEVICES Filed Sept. 26,- 1954 2 Sheets-Sheet 1 Z j E WITNESSES: INVENTORS ATTORNEY Oct. 22, 1935. F. SOCHER r-rr AL PROTECTIVE SYSTEM FOR DISCHARGE DEVICES Filed Sept. 26, 1934 2 Sheets-Sheet 2 "Ill 5 WITNESSES: IgyENbTOR 5 fa Z 06 f' 00 g; J u

ATTORNEY Patented Oct. 22, 1935 UNITED STATES PROTECTIVE SYSTEM FOR DISCHARGE DEVICES Franz Socher, Finkenkrug,

Clemens Hofmann,

near Berlin, and

Berlin- Spandau, Germany, assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 26, 1934, Serial No. 745,540 In Germany October 20, 1933 10 Claims.

Our invention relates to a vapor electric converter and particularly to a protective system for such a converter.

In the operation of vapor electric converters, it

has become customary to utilize control electrodes such as grids for controlling the initiation of the current carrying arc in the device and in the event of are back in the rectifier to utilize the same control electrodes for extinguishing the 1) backfire arc.

In the systems heretofore proposed for quenching the backfire arc, it has been customary to 'interrupt the positive impulses to the control electrodes while leaving a normal negative bias 15 connected to the grids for interrupting the arcs.

In the converting system according to our invention, the negative bias is increased to such magnitude that the usual positive impulses have no effect to start a current carrying arc in the device.

In the apparatus according to our invention, each of the arc paths of the converter is provided with a control electrode and. means provided for impressing negative potential on the 25 electrode normally maintaining the arc paths inoperative. However, suitable distributing means are utilized for impressing positive potentials suflicient to momentarily counteract the normal blocking potential and permit the formation of a current carrying arc at the desired time instant in the converter.

Normally, the negative potential for all of the control electrodes is provided from the same source and suitable resistors acting between the source and each of the electrodes so that the negative potential of the source is materially reduced before being applied to the electrodes. Also, the resistors serve a further purpose in that they prevent cross application of the control potentials applied to the electrodes. For instance, if a positive potential is applied to one of the control electrodes, this potential would have to pass through two resistors in series before it could reach another of the electrodes. This effectively prevents cross excitation by a potential applied to one electrode.

Suitable switching means are provided for shorting out the resistors and applying the full negative potential to the control electrodes in the event of a backfire or other abnormal operation of the converter.

In order to be effective to protect the converter, each path of the converter must be blocked at high speed after the occurrence of a fault. Relays for closing a plurality of contacts have a decided drawback in that they have a rebounding characteristic, that is, the relay does not move into final positionat once but requires a definite time to reach its final position.

However, it is possible to produce relays capable 5 of closing a single pair of contacts which are free of this objectionable characteristic.

Since it is necessary to bridge a plurality of voltage consuming means, we have provided switching means controlled by a high speed relay having only a single pair of contacts for effecting the bridging of a plurality of paths without otherwise interconnecting the paths.

It is an object of our invention to provide a high speed relay device capable of short circuiting the resistors in a sufficiently short interval of time to prevent damage to the converter because of abnormal operation.

Other objects and advantages of our invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a schematic illustration of a converter embodying our invention.

Fig. 2 is a similar view embodying improved means for controlling the short circuiting device, and

Fig 3 is a similar View showing a further modification of our system.

In the apparatus according to our invention, an alternating current circuit l is connected to a direct current circuit 2 by means of a vapor electric converter 3 having a plurality of discharge paths therein.

For purposes of illustration, the electrical converter 3 is shown as a multi-anode single cathode device having the anodes 4 and cathode 5 received in a single container 6. A suitable control electrode such as a grid 8 is associated with each of the arc paths or". the converter 3.

A suitable source ll? of control potential is provided for the control electrodes 8. A negative terminal H of the control potential is connected to each of the electrodes 8 by means of a plurality of parallel connections it, each of the connections l3 having a voltage consuming device such as a resistor I4 therein for normally reducing the negative potential supplied to the electrodes 8 from the control source ii]. The positive terminal I5 is also provided with connections I6 including a distributor H for periodically and sequentially impressing positive control impulses on the electrodes 8 for releasing the arc paths and permitting the formation of a current carrying arc in the converter 3. Pref- 5 erably, the positive impulse paths I 3 are also provided with suitable resistors It for limiting the current flowing to the control electrodes 8. However, care must be taken that the positive impulse will be sufficiently powerful to overbalance the normal constant negative bias and permit the formation of the current carrying arc.

Connected in parallel with the voltage consuming devices I 4 of the negative bias leads I3 is a suitable switching mechanism for short cirouiting the voltage consuming devices I4. This short circuiting device comprises a vapor electric valve 20 which is normally constantly excited and has arc paths corresponding to each of the parallel connections to the electrodes 8.

Preferably, each of the arc paths of the auxiliary valve 20 is permanently connectedto the control electrodes 8 and a cathode 2-2 in the device 20 is adapted for connection to the negative terminal H of the control voltage source it). This auxiliary valve 23 is normally maintained inoperative by means of a high speed relay 25 responsive to abnormal operating conditions of the converter 3.

In the operation of our system, the occurrence of an abnormal current condition in the converter supplies potential to the high speed relay 25 which closes the connection between the auxiliary valve 20 and the negative terminal ll of the control voltage source It] thereby short circuiting the voltage consuming devices [4 in the biasing leads I3 and impresses a sufiiciently high negative potential on the control electrodes 8 so that the application of the normal positive potential impulses will not be effective to counterbalance the negative bias and permitthe formation of current carrying arcs in the several arc paths of the conveyor 3.

In the modification of our invention according to Fig. 2, the auxiliary valve 20 is maintained inoperative by means of suitable grids applied to each of the arc paths of the auxiliary valve 20. Normally, the grids 30 of the auxiliary valves are maintained at blocking potential but on the occurrence of a fault in the converter 3, a high speed contactor 3| releases the negative potential and applies positive potential to permit the short circuiting of the voltage consuming devices M in the biasing leads I3. In order to restore the device to operating condition, a suitable con-tactor 32 in series with the auxiliary valve 20 is opened to permit the grids 30 of the auxiliary valve 20 securing control of the auxiliary valve.

In the modification according to Fig. 3, the

control grids 38 of the auxiliary valve 20 are directly responsive to the current transformer which is, in turn, responsive to abnormal conditions in the vapor electric converter 3 being protected. While there is shown and described specific modifications of our invention, it will be apparent to those skilled in the art that changes and modifications can be made therein without departing from the true spirit of the invention or the scope of the appended claims.

We claim as our invention:

1. An electric conversion system comprising a multi-valve vapor-electric converter, a control electrode for each valve of the converter, a source of control potential for said electrodes, connections from one terminal of said source to each of said electrodes for constantly applying blocking potential thereto, voltage consuming devices in each of said connections, means forperiodically connecting an opposing potential of said source to said electrodes in predetermined sequence, said potential being of a value sufiicient to overcome the normal blocking potential, 2. vapor-electric device connected in parallel with said voltage consuming device, means for maintaining said device in operative condition and a relay responsive to the operating condition of said converter for controlling operation of said device. 10

2. An electric conversion system comprising a multi-valve vapor electric converter, a control electrode for each valve of the converter, 2. source of control potential for said electrodes, connections from one terminal of said source to each 15 of said electrodes for constantly applying blocking potential thereto, voltage consuming devices in each of said connections, means for periodically connecting an opposing potential of said source to said electrodes in predetermined se- 20 quence, said potential being of a value sufiicient to overcome the normal blocking potential, a vapor-electric device connected in parallel with said voltage consuming device, means for maintaining said device in operative condition, grid means in said device for blocking 'the discharge therein and means responsive to fault in said converter for releasing said grid means.

3. A control system for a .multi-valve vapor electric converter comprising a control electrode 30 for each of the valves, a source of blocking potential for said electrodes, parallel connections from said source to each of said electrodes, volt-- age consuming means in each of said parallel connections for preventing cross application or 35 potentials applied to said electrodes, a source of potential capable of over-balancing the blocking potential applied to said electrodes and means for periodically applying said potential to said electrodes for releasing the same and means for 40 rendering said applications ineffective comprising auxiliary electric valves connected in shunt with said voltage consuming means between said electrodes and said source of blocking potential, and means responsive to fault in said converter for controlling said auxiliary valves.

4. A protective system for a multi-path vaporelectric converter comprising control grids in each path of the converter, a source of blocking potential for said grids, a resistor in series with each of said grids for reducing the potential applied to said grids from said source and means operable by the closing of a single contactor for simultaneously short circuiting all of said resistors.

5. A protector system for a multi-path vapor electric converter comprising control grids in each path of the converter, a source of blocking potential for said grids,l a resistor in series with each of said grids .for reducing the potential applied to said grids from said source, :a. multi-path electric valve connected in parallel with said resistors and a single pair of contacts responsive to fault in said converter for activating said valve. v 6. A protective system for a multi-valve vaporelectric converter comprising a control electrode for each valve of the converter, a source of control potential for saidelectrodes, connections from said source for supplying blocking potential to said electrodes, voltage consuming devices in said connections for reducing the blocking potential normally supplied to the electrodes, means for successively applying potential to said electrodes of a value suificient to release the valves of the converter, an electric discharge device connected 7.5

in parallel with said voltage consuming devices, switching means in series with said discharge device and means responsive to fault in said converter for operating said switching means.

7. A protective system for a multi-valve vaporelectric converter comprising a control electrode for each valve of the converter, a source of control potential for said electrodes, connections from said source for supplying blocking potential to said electrodes, voltage consuming devices in said connections for reducing the blocking potential normally supplied to the electrodes, means for successively applying potential to said electrodes of a value sufficient to release the valves of the converter, electric discharge devices respectively connected in parallel with each of said voltage consuming devices, and switching means responsive to fault in said converter for rendering said discharge device efiective to short circuit said voltage consuming devices.

8. A protective system for a vapor electric converter comprising a control grid for each valve of the converter, a source of control potential for said grids, said source having positive and negative terminals, connections from each of said terminals to each of said grids, voltage consuming devices in the negative connection to each grid, means in the positive connections for periodically supplying positive potential to said grids and means responsive to fault in said converter for rendering said voltage consuming devices inoperative.

9. A protective system for a grid controlled vapor electric converter comprising a source of control potential, control electrodes in said converter, means including voltage reducing devices for supplying potential from said source to said electrodes, an auxiliary grid controlled discharge device connected in shunt with said voltage re- 10 ducing devices, means for applying blocking potential to the grids of said discharge device during normal operation of the converter and means responsive to fault in said converter for releasing the grids. 15

10. A protective system for a grid controlled vapor electricconverter comprising a source of control potential for said grids, means including voltage reducing devices for supplying potential from said source to said grids, a grid controlled 20 auxiliary discharge device connected in shuntwith said voltage reducing devices, a source of blocking potential connected to the grids of said auxiliary device and means responsive to abnormal current condition in said converter for ap- 25 plying a potential for releasing the grids of the v auxiliary device.

FRANZ SOCHER. CLEMENS HOFMANN.

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