Circuit arrangement for automatic control of the voltage of an electrical filter

<td>sweden's</td><td>GIVE</td><td>PUBLISHING LETTER No. 354 976 int ci B 03 c 3/68</td>

<td>e3S3 PATENT-</td><td>AND</td><td>Patent Application. No 2861/70 Revenue 4 III Validity Day 4 III 1970 Ans. generally available on 9 IX 1970</td>

<td colspan="2">Registration Office</td><td>Ans. laid out and laid out the publication was published on 2 17 1973 Priority requested from 8 III 1969</td>

(Federal Republic of Germany DT, 19 11 923)

SIEMENS AG, BERLIN AND MUNCHEN, FEDERAL REPUBLIC OF GERMANY DT

Inventor: L Vukasovic, Miinchen

Agent: N Larfeldt

Device for automatic control of the filter voltage in an electro filter

The invention relates to a device for automatic control of the filter voltage in an electrical filter, with a setting element for changing the filter voltage, with a control set which leaves on the output side an adjusting amount acting on the setting part, which depends on a control voltage applied to the input of the control set, which includes a control capacitor located via a charging current circuit, of which the voltage of the capacitor control voltage depends, and with a controllable discharge current circuit which is parallel to the control capacitor which lies in control dependent on the filter voltage and / or the filter current.

Through such plants, the filter voltage is lowered at each overflow or at the attainment of a limit current, a certain amount and from there constantly rises until a new overflow occurs and the limit current is again reached. The filter voltage is thus dependent on the voltage of a control capacitor which, via a relatively high ohmic resistance, is connected to a direct voltage source with usually very high voltage to provide a slow and as linear increase in the voltage as possible. However, it is undesirable that the time between the system switch-on and the attainment of the filter's optimum operating state (first estimate) is undesirably large.

The object of the invention is to shorten this time span.

The invention is characterized in a device of the type mentioned in the introduction, that parallel to the charging circuit lies a coupling link containing auxiliary power which is so adapted that the control capacitor at the closed coupling link charges faster than via the charging current circuit, that a limit switch is applied. which emits a signal only when the filter current is greater than the predetermined limit value, and that the switching state of the switching link is so dependent on the switching position of a control switch and the signal to the limit sensor, atfc the switching link is only closed in time between the device switching on by the switch and the time at which the limit switch gives a signal for the first time after switching on.

In a preferred embodiment of the invention, there is a thyristor parallel to the control circuit of the coupling link and parallel to it. this is a circuit which contains the switching distance closed at the switch-off system of the actuator, and that the control distance of the thyristor is so connected to the limit sensor that the thyristor is lit by the first signal of the limit value sensor after switching on the system.

Of particular importance is the invention in connection with a control capacitor located in the charging circuit, known in the known manner as a constant current controller coupled transistor.

²5 The invention is explained in more detail with the aid of the drawing. Pig. Fig. 1 shows the principle coupling diagram for an embodiment of the invention and Fig. 2 shows details of the control unit indicated in Fig. 1 with St.

In Fig. 1, the power circuit is only symbolic. It consists of an electro-filter designated P, which is connected via a rectifier G to a secondary winding of a high voltage transformer T. The primary winding of this high-voltage transformer is connected via a smoothing throttle serving to improve the form factor, an adjusting detail operating with antiparallel-coupled thyristors and a current transformer U to the terminal U of a single- or multiphase AC network.

The control pulses for the thyristors of the setting detail are provided by a control set I, to which is applied the AC voltage of the synchronization and, on the side, via a terminal A, a phase position of the control pulses relative to the output voltage of the control voltage In view of the magnitude of the control voltage, genius a delay signal supplied via a terminal L is blocked without delay. The extinguishing signal is always output by the control unit St when a breakthrough or a short circuit occurs in the filter. A special case possible at the start of the operation is explained later.

The control voltage U_Tläm is left from the control unit St and is dependent on a signal supplied proportional to the filter current by a transformer W, supplied from the transformer W and by an impact and a breakthrough respectively. one^- arc in filter F indicating signal. The latter is obtained by means of a photoelectric semiconductor contained in the control unit St, which is subjected to the light radiation of a light bulb 1, which lamp is connected in parallel with resistors r28 and 'r29 to the electric filter F and therefore lights up only when the filter is working, the light bulb lights up. when an overlay appears in the filter.

The structure of the control unit St is explained by means of Fig. 2.

It first contains a rectifier g, preferably in two-way coupling, to which a voltage proportional to the filter current is applied via the input terminal B. To this rectifier g is connected via a resistor r27 an RC link c6, r26, whose resistance r26 is changeable.

With the changeable part of this resistance, via a zener diode nl4, a voltage divider r24, r25 is connected in parallel. Parallel to the resistance r24 lies the series connection of the control distances of a transistor p10 and a thyristor pp. The transistor PLO cooling conductor is connected to resistors r6 and r8 to the positive terminal P²5 voltage source.

This direct current source has an outlet located between terminal P and a negative terminal N. M and leaving the place between P and M and M and N a voltage of 24 volts. Between the terminal M and the terminal N. lies in series connection a first control capacitor c4, a resistor r20, θη diode nlO, a transistor p8 emitter-collector distance and a diode nl3 clamp N.

Parallel to r20, nlO, ρδ and nl3, a p7 emitter collector distance of a transistor lies in series with a resistance rl8. The base of this transistor is connected to one of the resistors rl6 and rl7 formed and between the terminal M and the emitter of the transistor p8 emit voltage divider. The transistor p7 holds the liquid charge current flowing through it substantially constant at an easily adjustable value through rl7 and / or r18.

The first control capacitor c4 is connected in parallel via a dead resistor. r-15 is a second control capacitor c5, from which the voltage U., .. for the control set I, whose capacitance is, however, a^J Just have a fraction, of the same with it. first control capacitor c4. For discharging the control capacitors in response to the filter current, to the first control capacitor c4, via a resistor r11, the transistor p4 of the transistor p4 is connected in parallel, which transistor base via the resistor r £ is connected to the transistor p10 collectively or through the resistor rS.

For discharging the control capacitors at a break in the filter, a transistor p5, whose emitter-collector distance is connected in parallel via a changeable resistor rl3 to the first control capacitor c4 and via a resistor r4 and a diode n9 to the second control capacitor c5, serves. The time constant from the control capacitor c5 and the resistance rl4 is chosen so small that the control capacitor c5 at the transducer p5 is almost completely discharged due to a filter overlay, on the other hand, however, the unplugging time constant is also determined - by the resistance rl5 and the condenser that the voltage at the second control capacitor c5, after failure of an overshoot and the blocking of the transistor p5, rises extremely rapidly to the voltage of the first control capacitor c4.

On the other hand, the discharge of the first control capacitor c4 at a breakdown and throughput of the transistor p5 goes much slower, as determined by the size of the resistor rl3, so that the voltage at the control capacitor c4 after a breakage is only a negligible percentage at rl3 adjustable.

For receiving a filter cover, the light bulb part 1, already shown in FIG. 1, which is arranged via a foot element f, serves to expose the light-sensitive area of ​​the photo element to the light radiation of the light bulb 1. The fato element f is connected in parallel via a diode nl to the base-enitter array of a transistor p1 that it can pass through transistor p1 upon the irradiation of the photo element at the occurring voltage.

The transistor p1 together with a transistor p2, the resistors r2, r3, u4 and a capacitor c1 form a monostable tilting step. Where the light bulb 1 is lit - thus during normal filter operation - the transistor p1 is passed through and the transistor p2 is blocked. At a break in the filter, the light bulb I lights up and the transistor p1 enters the locking state, which results in the transistor n2's throughput. In this case, it previously discharges via r4, r2 and p1 the capacitor cl charged via p2, n3&gt; n2 and r2 and thus maintains. - irrespective of the operating state of the filter - the blockage of the transistor p1 and thus the throughput of the transistor p2 for a time determined by the time constant of this discharge circuit.

The base of the transistor p5 is connected via a resistor r9 and a capacitor c3 to the collector of the transistor p2 and via a resistor r9 to the terminal M. In addition, a resistor r10 is parallel to r9 and c3. For blocked transistor p2 (normal operation), capacitor c3 is charged to a voltage of the specified polarity. At a throughput of transistor p2, this capacitor can discharge through p2, a diode n3, the emitter base distance of transistor p5 and resistor r9, so that transistor p5 is always routed simultaneously with transistor p2. The discharge circuit of capacitor c3 is preferably so adapted that the throughput of transistor p5 is not terminated before the end of the reversing time of the monostable rocking stage.

Parallel to the control distance of the pnp transistor p5 is the control distance of an npn transistor p6, which emitter-collector distance of the transistor is connected via a resistor rl2 between terminals P and M. The output terminal L is connected to the collector of this transistor.

The voltage divider formed by resistors r4, r10 and rl9 is so adapted that the control current of the transistor ρβ at blocked transistor p2 suffices to pass through transistor p6, p5 is then blocked. Furthermore, the base of the transistor p6 is connected via a diode n8 and the resistor r3 to the terminal P. The resistors r8 and r6 are so adapted that at these connection points of connection at the drawn position of a switch, or at a controlled transistor p10 rated current) ruled such a potential that diode n8 is blocked, n8 is conductive, when s is switched and p10 is blocked.

For determining a metallic short circuit in the electro filter, a relay P. equipped with a working contact, which is connected via an emitter-collector circuit of a transistor P3, employs a diode n5 and the switch s between terminals P and N. The base of the transistor p3 is connected via resistors r5 and r7 as well as via a diode n7 to the transistor p2 collector, p3 thus obtains a through current at blocked transistor 35 p2 (normal operation). Between the resistors r-5 and r7 and the emitter of transistor p3 lies a capacitor c2 of relatively large capacitance, the size of which together with resistor r5 determines the time elapsed between a short circuit in the filter (throughput of transistor p2) and relay R switch-off.

The transistor p8 collector is connected via a diode nll and a resistor r21 to the transistor p2 collector and via a further diode nl2 and a resistor r22 to the emitter of transistor p3. In addition, the emitter of the transistor p3 lies via a resistance r23 to the base of the transistor p8. The resistor r21 is approximately as adapted as r4, so that at blocked transistor p2 but at through transistor p8, at the collector from p2, approximately the potential of the terminal M lies. This prevents recharging of capacitor c3 at through transistor p8 (during the voltage start at the filter after switching on). Therefore, the periodic extinguishing of the light bulb (throughput of p2) caused by the wave of the filter voltage during the start-up process cannot cause any voltage drop during this period. p8 then receives via a r8 and ηδ • a control current, unless s is switched on (operation) and p10 is blocked.

The resistors of the relay R and of the resistor r22 are so adjusted that the emitter of the transistor p3 during this operation state is so negative that the diode n5 remains blocked and the transistor p3 remains controlled.

The switch s serve to ensure a defined initial state during commissioning of the plant. In the plotted circuit position, the transistor pS base via r23 and diode n5 is connected to terminal N, so that this transistor blocks, however, the transistor p4 connected in parallel to the first control capacitor c4, while its base via resistor r6 and diode n6 are also connected. with the clip M. When no voltage is present in the electro filter, the transistors n2 and p5 are also controlled, p6 is thus ~ blocked and at the terminal L is the extinguishing signal. The control capacitors are discharged.

In addition, the switch in the drawing position extinguishes the thyristor p9 after switching off the system.

For commissioning of the system, the switch is placed in the second switching position, in which the cathodes of diodes n5 and n6 are connected to terminal M. ' As a result, the connection points of the resistors r6 and r8 become so positive that the transistor p4 locks and p6 enters the conductive state. Thus, the extinguishing signal at the terminal L fails so that the control set I (Fig. 1) outputs control pulses to the setting detail an S, the phase position of these control pulses being dependent on the voltage

Ujm at the second control capacitor c5 ·

In addition, transistor p8 receives a through current through transistor p3 and resistor r23. Therefore, the control capacitors c4 and c5 are charged via r20, nlO, 08 and nl3 to a voltage of the polarity indicated in the figure, the charging time constant has a very low value, since the filter voltage dependent on the voltage of the control capacitor c5 must achieve the breakthrough value so quickly. possible after installation of the plant.

As soon as the transistor p8 leads to the switching of the switch, a current also flows through the resistors r4 and r21 and the diodes nll and nl3, which, as a result of the aforementioned matching of the resistors, results in the potential of the transistor p2 collector. regardless of the filter operating state and the switching position of the monostable rocker, approximately the potential of the clamp M corresponds. However, transistor p3 nevertheless receives a control current via n7, r7, r5, 10 emitter base distance, r22, nl2, emitter collector distance from p8 and nl3, since the emitter potential of p3 at the aforementioned alignment of relay R and resistor r22 is more negative than the potential of the terminal M, the relay R therefore remains activated.

During the quick charge of the control capacitors via the conductive transistor p8, the transistor p6 receives a through current through the resistor r8 and the diode n8, so that no extinguishing signal is at the terminal L, the control set I (Fig. 1) thereby gives control pulses to the setting part S, whereby these control pulses are voltage Uj, at the second control capacitor c5.

²⁰ With the increase of the voltage at c5 and the corresponding increase of the filter voltage, the filter current and thus the voltage taken at the resistance r26 also increases. At a certain value of the voltage at r26 (at the rated value of the filter current), the zener diode nl4 becomes current permeable and the transistor p10 and thyristor p9 through 25 are controlled. Via the conductive thyristor p9, the current of the relay R flows (via p3 and the resistor r23), in addition, the transistor p8 passes in the blocking state, since its control distance is short-circuited by p9 · Thus, the exponential fast charge of the control capacitors via p8 and further the blocking of the output signal of the output signal goat via r21 and nil ended. The thyristor p9 remains guided in the drawn switching position until a feedback of the switch s takes place, ie. until shutdown of system without regard to transistor p10 control state. Therefore, during operation the control capacitors can only be charged via the transistor p7 and the resistor rl8 with constant current.

Because of the diode nl3 in the control circuit of the transistor p7, the charging of the control capacitors is practically independent of the ambient temperature, which is of considerable importance at very large time constants. Otherwise, the control circuit of the transistor p7 is relatively low-ohm, so that it is possible without further ado_et the changeable resistance rl7 far away from the other plant in an operating pulp.

during operation, the filter current exceeds the rated value, transistor p10 is temporarily transmitted and with that transistor p4, so that the control capacitors c4 and cg are discharged somewhat, which results in a decrease in the filter voltage, the filter current goes back below the rated value and the transistors go back i, the lock state. Thereafter, the voltage rises slowly again linearly at the control capacitors and in the filter. In this way, the filter current is limited for as long as no voltage-dependent depth reduction to the rated value such that no overshoot occurs in the filter.

In the case of a breakthrough in the filter, regardless of the filter * the current size of the transistor pg is discharged through the capacitor c3 discharge and thereby the first control capacitor c4 is discharged via rl3 a determined, relatively small degree and the second control capacitor 15 cg is almost completely discharged via rl4. In addition, during a throughput of pg forced transistor p6, in the interrupt state, the output of control pulses to the setting detail is interrupted by the occurrence of an extinguishing signal at the terminal I ». At. at the end of the monostable tilting phase, the reversal time of transistor pg blocks transistor pg again and the second control capacitor cg recharges at a relatively high speed to the voltage of the first control capacitor c4, correspondingly rapidly also increases the voltage of the filter, as transistor n6 becomes conductor at the transistor longer beforehand. The speed of the control capacitor cg charging 25 is thereby adapted to the system, so that the filter voltage rises as fast as possible without oscillations to the value determined by the first control capacitor c4.

During the exponential charging of the control capacitors (throughput of p8), the transistor pg need not obtain any control current through the resistor r9. This is achieved in that the transistor pd receives a throughput via r8 and n.8, so that the voltage at the base-emitter distance of the transistor p6 lies as a barrier bias to the control distance of the transistor pg. However, the control current for p6 via r8 and n8 lapses when the filter current reaches the rated current at the end of the start time 35 and, accordingly, the transistor p10 is controlled. RLU.

Are⁷ however, upon first switching on transistor p10 after commissioning of the system, an overshoot is provided in the filter or arc and thus, transistor p2 is then passed, transistor p6 is neither via resistors r4 and r10 nor via resistor r8 and diode n8 a control current, so that this transistor blocks and at the terminal L an extinguishing signal for blocking control pulses for the setting detail S. At the same time, the transistor p5 receives through the resistor rl9 a through-flow current so that the discharge of the second control capacitor c5 is also ensured, a through-through of this transistor p5 through the capacitor c3 via the transistor p2 would not, however, be possible at the end of the exponential charging of the control capacitor c3. could not yet be charged because of the throughput of transistor p8. Thus, during the time following the exponential charging of the control capacitors, the output of an off signal and the discharge of both control capacitors takes place through the transistor p5 without regard to the filter at the current at each break in the filter. at the end of the exponential recharge, a voltage drop through p5 is allowed and the output of an extinguishing signal is allowed only when an overshoot or arc is present in the filter and the filter current has reached or exceeded the rated value.

The invention is also useful in systems for controlling an electron or ion beam for material processing.