US2404614A - Electric control circuit - Google Patents

Description

Jul -23, 1946.

D. w. BoRsT 2,44%14 ELECTRIC CONTROL CIRCUIT Filed Sept. 1, 1942 Inventor: David W Borst y W if 24 His thorns Patented July 23, 1946 ELECTRIC CONTROL CIRCUIT David W. Borst, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application September 1, 1942, Serial No. 456,904

6 Claims.

My invention relates to electric control circuits and more particularly to control and protective circuits for electric valve translating apparatus.

Electric valve apparatus, such as electric discharge devices of the type employing an ionizable medium and including a control member for initiating arc discharges between the principal anode and cathode, have been applied rather generally to electric translating systems wherein the amount of power transmitted to a load circuit from an associated supply circuit is controlled. In accordance with the teachings of my invention described hereinafter, I provide a new and improved control and protective system for electric valve translating apparatus of this nature.

It is an object of my invention to provide a new and improved electric control circuit.

It is another object of my invention to pro vide a new and improved control or protective circuit for electric valve translating apparatus.

It is a further object of my invention to provide a new and improved control or protective circuit for electric valve apparatus of the type comprising an ionizable medium and which in-, cludes an immersion-ignitor control member associated with the cathode for initiating are discharges between the anOde and cathode.

It is a still further object of my invention to provide a new and improved misfire control and indicating system for electric valve translating apparatus.

Briefly stated, in the illustrated embodiment of my invention I provide a control or protective circuit for electric valve means or electric discharge devices of the type which employs an anode, a cathode and an immersion-ignitor control member associated with the cathode, which upon proper energization of the control member by the transmission of a current of predetermined value thereto, initiates an arc discharge between the anode and the cathode. Excitation means are provided for transmitting impulses of current to the control member. As a means for protecting the electric valve means and for controlling the operation of the system, I provide over-current protective means connected in circuit with the immersion-ignitor control member which interrupts th circuit thereto in the event excessive current is transmitted to the control member. I also employ, in connection therewith, means such as a relay designed to initiate a circuit controlling operation in the event the current transmitted between the excitation means and the control member decreases below a predetermined value. In this manner, a controlling operation is initiated or the protection of the electric valve means is accomplished in response to excitation over-current and under-current.

'For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims. The single figure of the accompanying drawing diagrammatically illustrates an embodiment of my invention as applied to a biphase electric valve rectifier.

Referring now more particularly to the single figure oi the drawing, my invention is there illustrated as applied to an electric valve translating system for energizing a load circuit, comprising a positive conductor l and a negative conductor 2, from an alternating current supply circuit 3 through translating apparatus comprising a transformer 4 and which may include a pair of electric valve means 5 and 6.

The electric valve means 5 and 6 are of the type employing an ionizable medium capable of supporting an arc discharge and each includes an anode l, a cathode of the self-reconstructing type, such as a mercury pool cathode 8 and an immersion-ignitor control member 9. The electric valve means 5 and 6 are also provided with relieving anodes H) which serve to reduce the duty imposed on the associated immersion-ignitor control members 9. The immersion-ignitor control members 9 are constructed of a material such as boron-carbide or silicon-carbide and have a electrical resistivity substantially large compared with that of the mercury of the associated pool. Arc discharges are initiated between associated anodes and cathodes by transmitting thereto impulses of current having a value equal to or greater than the critical minimum value of current which is necessary in order to establish cathode spots on the surface of the mercury pools.

I provide circuit controlling means for controlling the operation of the electric valve translating system. More particularly, I provide a circuit controlling means or circuit interrupting means H having principal contacts l2 and I3 and including a closing coil I4 and tripping means l5 which may include a pair of trip coils I6 and H, the former of which is controlled by apparatus described hereinafter and the latter of which may be energized from a shunt l8 in response to the current transmitted to th load circuit.

Excitation means [9 are provided for producing impulses of voltage for energizing the immersion-ignitor control members 9. The excitation means [9 may be energized from the alternating current circuit 3 and may be of the type arranged to transmit impulses of current alternately to the control members 9 of electric valve means and 6. The excitation means preferably comprises means exclusively electrical for producing the impulses of voltage or current which control the initiation of arc discharges within the electric valve means 5 and 6. In order to illustrate an application of my invention, I have chosen to show an excitation circuit which is disclosed and broadly claimed in a copending patent application Serial No. 413,232, filed October- 1, 1941, of Albert H. Mittag and which is assigned to the assignee of the present application. Although my invention is illustrated in connection with a particular type of excitation circuit, it will be appreciated that my invention may be applied with equal facility to other types of excitation circuits.

Referring more particularly to the excitation means I9, I employ for producing an alternating voltage of peaked wave form which comprises a capacitance 2E1 which is discharged once every half cycle of voltage of supply circuit 3 through a circuit including a nonlinear inductive reactance 2| and an inductance 22 having an intermediate or neutral connection 23 connected to the oathodes 8 of electric valve means 5 and 6. The excitation circuit l9 may be energized from the supply circuit 3 through a phase shifting circuit 24 of the type also disclosed and claimed in the above-identified patent application Serial No. 413,232. This circuit may include a transformer 25 and phase shifting means including a saturable inductive reactance 26, a capacitance 21 and an inductance 28. A linear inductive reactance 29 is connected between the phase shifting circuit 24 and excitation means I9.

As a means for protecting the immersion-ignitor control members 9 in the event an excessive current or over-current is transmitted to the control members, I connect in series relation therewith over-current responsive means such as fuses 30 and 3| which open the circuits to the control members in the event the control members fail to perform their intended function as, for example, under those conditions when the material. of the control members becomes sufficiently wetted to prevent the establishment of sufliciently high gradients at the surface of the mercury pools. I also connect in series relation with the control members 9 of electric valve means 5 and 6 unidirectional conducting devices 32 and 33 which assure the transmission of only unidirectional impulses of current to control members 9.

The relieving anodes ll] of electric valve means 5 and 6 are connected to the excitation means l9 through circuits including conductors 34 and 35 which are exclusive of that portion of the system including the fuses 3i and 3!.

I provide means which are selectively responsive to the magnitude of the excitation current transmitted to the'control members 9 of the electric valve means 5 and 5. More particularly, 1 provide means which, so long as the excitation currents supplied to the control members remain above the predetermined minimum critical value, maintains the normal operation of the system. If the excitation current transmitted to control members 9 decreases to a value less than the minimum critical value, the means operates to initiate a circuit controlling operation such as the opening of the circuit interrupter l I.

As a means for accomplishing the above deinterrupter I l scribed operations, I provide apparatus such as electromagnetic relays 36 and 37 having actuating coils 38 and which are arranged to maintain their contacts 39 open so long as the excitation current remains above a predetermined value.

Under normal operation of the electric valve means 5 and E, the average value of the excitation current remains at a relatively small value due to the fact that the currents transmitted through the control members 9 and associated cathodes 8 encounter a relatively high resistance. In order to maintain the relays 36 and 3i in an energized condition, even though the currents to which these relays are responsive are of a peaked nature and of relatively short duration, I connect in circuit between the excitation means l9 and the control members Q impedance elements, such as resistances it and M. The resistances 4i] and ii provide a circulating path for the flow of current through the actuating coils so that even though the impulses of current are peaked and of relatively short duration, a substantially continuous energization of the actuating coils 3B is effected.

Relays 36 and bi control the energization of control circuit 12 which may be energized from a suitable source of current, such as a battery 43, and which is connected to trip coil l5 of circuit Either relay 36 or 31, by closure of its contacts 39, may complete the circuit 42 and trip the circuit interrupter ii. If desired, circuit indicating means, such as lamps 44 and 35, may be connected to the control circuit 42, and in the particular arrangement illustrated are, under normal conditions energized, and deenergized when the contacts of the associated relay are closed. When such an arrangement is utilized, it will be appreciated that the current consumed by lamps M and 45 must be appreciably less than the current required to trip the circuit interrupter I l.

The operation of the embodiment of my inven tion illustrated in the single figure of the drawing will be explained by considering the system when it is operating as a bi-phase rectifier to transmit unidirectional current to the load circuit. Electric valve means 5 and 5 are rendered conducting alternately. The magnitude of the voltage supplied to the load circuit is determined by the time during the respective half cycles of applied anodecathode voltage at which the electric valve means are rendered conducting. The load voltage is increased as the times of initiation are advanced towards the beginning of the positive half cycles, and is decreased as the times of initiation are retarded. The time of the transmission of the impulses of peaked current to the control members 9 is controllable or adjustable by means of the saturable inductive reactance 26 which controls the phase of the alternating voltage applied to excitation means l9.

The protective system which I provide not only serves to protect the immersion-ignitor control members 9 from excessive current conditions, but also serves to control the translating system in the event the desired excitation current is not transmitted to the control members 9. For example, if the excitation current transmitted to the control members 9 increases to an excessively large value due to the failure of the ignitor, such as breakage or under those conditions where the ignitors become wetted, the excessive current causes the fuse 3!) or 3! to melt, thereby opening the circuit to the control members. If the arc has not been established at this time between the relieving anode J and thecathode 8,-either relay 36 or 31 will become deenergized causing that relay to close its contacts 39 and effect energization of the trip coil I 6 which trips interrupter I! and disconnects the load circuit from the translating apparatus.

The system which I provide also serves toindicate an electric valve which misfires, or to initiate a circuit controlling operation in the event an electricvalve misfires. 'For example, in one type of circuit employing this type of electric valve, I have found that the normal ignitor average current is 0.09 ampere, If the associated relieving anode fails to conduct current, th average current increases to approximately 2.5 amperes and this value of current is sufiicient to melt the associated fuse 30 or 3|. Therefore, if the ignitor becomes wetted, thus failing to establish the cathode spot, the associated fuse Will melt, or if the relieving anode becomes defective through breakage or if its lead becomes disconnected the same operation will take place. In like manner, the system which I provide will indicate or control in response to a disconnected or broken relieving anode.

While relays 36 and 31 are arranged and designed to close their contacts 39 when the average current derived from the excitation means I9 decreases to a value below a preset minimum value, it will be appreciated that the system which I provide operates to afiord over-current protection as well as under-current protection. For example, in the event the current transmitted to either of the immersion-ignitor control members 9 exceeds a safe value established by the ratings of fuses 30 and 3|, and in the event the holding anode circuits are not completed, relay 36 or 31 will be deenergized, thereby initiating the indicating or controlling operation. Relays 36 and 31 may be designed to drop out, that is close contacts 39, in response to a single failure to conduct or misfire of the associated electric valve means or 6. Of course, these relays may be arranged so that the contacts 39 are not closed unless the failure to conduct continues for a predetermined number of half cycles, or cycles, of voltage of the alternating current supply circuit 3.

While I have shown and described my invention as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changes and modifications ma be made without departing from m invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode and an immersion-ignitor control member, circuit controlling means for said translating apparatus, excitation mean for energizing said immersion-ignitor control member, means connected in series relation with said control member and responsive to current therein above a predetermined value for decreasin the current traversing the excitation circuit to below a predetermined minimum value, and means connected t said excitation circuit and responsive to current below said minimum value for controlling the operation of said circuit controlling means.

2. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathod and an immersion-'ignitorcontrol member of the type requiring the transmission of a predetermined min imum current thereto inorder to initiate an arc discharge between said anode and said cathode, circuit controlling means for controlling the power transmitted between the first mentioned circuits, excitation means for energizing said inrmersion-ignitor control member, means respon. sive to current above a predetermined maximum value and connected inseries relation with said control member for opening the circuit thereto, and means connected between said excitation means and said control member and responsive to current thereto below a predetermined minimum value for controllin the operation of said circuit controlling means.

3. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode, a relieving anode and an immersion-ignitor control member of the type requiring the transmission thereto of a predetermined minimum current in order to initiate arc discharges between said anode and said cathode, excitation means for transmitting impulses of current to said control member, means for connecting said relieving anode to said excitation means, means responsive to current above a predetermined maximum value and connected in series relation between said excitation means and said control member and in a branch circuit exclusive of the connection to said relieving anode for reducing below a predetermined minimum value the current from said excitation means to said control member and said relieving anode, and minimum current means connected in series relation with said control member and said relieving anode and operative in response to current to both said control member and said relieving anode below said minimum value.

4. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode and an immersion-igniter control member of the type requiring the transmission of a predetermined minimum current to said control member in order to initiate an arc discharge between said anode and said cathode, circuit controlling means for connecting said translating apparatus in power transmitting relationship between the first mentioned circuits, excitation means for transmitting impulses of current to said control member, current responsive means connected in series relation between said control member and said excitation means and arranged to open the circuit to said control member in the event the excitation current exceeds a predetermined value, and means connected between said excitation means and said control member and responsive to current less than said minimum value for controlling said circuit controlling means.

5. In combination, a supply circuit, a load circuit, electric translating apparatu connected between said circuits and comprising electric valve means including an anode, a cathode and an immersion-ignitor control member of the type requiring the transmission thereto of a predetermined minimum value of current in order to initiate an arc discharge between said anode and said cathode, circuit controlling means for connesting; said translating apparatus in power transmitting relationship between the first mentioned circuits, excitation means for transmitting impulses of current to said control member, a fuse connected in series relation with said control member, a control circuit connected to said circuit controlling means, and relay means connected between said excitation means and said fuse and arranged to control the energization of said control circuit when the excitation current transmitted to said control member decreases to a value below said minimum value.

6. In combination, a supply circuit, a load circuit, electric translating apparatus connected between said circuits and comprising electric valve means including an anode, a cathode and an immersion-ignitor control member of the type requiring the transmission of a predetermined minimum current thereto in order to initiate an are discharge between said anode and said cathode, circuit controlling means for connecting said translating apparatus in power transmitting relationship between the first mentioned circuits, excitation means for energizing said control member and comprising impulse generating means for transmitting impulses of current to said control member, protective means comprising means for opening the circuit to said control member in the event the current transmitted thereto exceeds a predetermined value, a control circuit for controlling said circuit controlling means, and relay means connected between said excitation circuit and the protective means and arranged to control the energization of said control circuit in the event the excitation current transmitted to said control member decreases to a value below said minimum value.

DAVID W. BORST.

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