DE2234046A1 - CONTROL CIRCUIT FOR THE ENERGY SUPPLY FOR ELECTRIC DUST COLLECTORS - Google Patents

Description

DR. O. DMTMANN K. L. SCHIFF DR. A. ν. FIVE DIPL. ING. P. STRBHL

PATENTANVVAIjTI! 8 MUNICH OS POSTI ¹¹ ACH D5O16O

ENVIROTECH CORPORATION Our file: DA-K884 (501)

8 MUNICH 90 RiARIAHILFPLATZ 2 & 3

TELEPHONE: (Ο811) 45 83 54 " TELKGR .: EUROMARCPAT MUNICH

July 11, 1972 PS / k

Control circuit for the energy supply for electric dust extractors

(Priority: July 12, 1971 - USA No. 161,606) The invention relates to power control systems for electrical Dust extractors and relates in particular to control systems that enable the dust extractors to operate with maximum efficiency.

Conventional electrostatic dust extractors such as those used to remove suspended particles from Gaat> ti-ömen are used, work with relatively high DC voltages that are applied to their collecting electrodes. An increase in the energy level, in which the dust extractor works, to achieve maximum work performance leads first to sparking and then to arcing between the electrodes. The effectiveness of the dust extractor is at its maximum during sparking and drops when arcing occurs quickly.

In order to maintain the energy working level of the dust extractor, that optimal sparking but no arcing is achieved, it has been customary to sense the sparking and to integrate the signal representative of the spark formation twice in order to thereby generate a control signal which is used for this purpose will change the energy level of the deduster; such a system is shown in U.S. Patent 3,173,772. In practice it has been found that an integrated control signal of this type leads to higher and higher work levels Effectiveness; can lead.

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Although the use of control signals derived by double integration of spark pulses provides better dust collector performance has brought about, there is a need for a control system for dust collectors that is more flexible to responds immediately in the event of sparks or arcing and switches off the system immediately in the event of certain types of short circuits.

The present invention provides a system for controlling the energy level of a dust extractor using analog computer circuits, which are programmed to respond to sparks and short circuits in a way that that optimal deduster effectiveness is achieved and the deduster is nevertheless protected against harmful arcs and short circuits is. For this purpose, circuits are provided which generate reference pulses which instantaneous zero deflections of the the primary winding of the dust extractor high-voltage transformer · supply voltage, with the circuits providing an output signal to reduce the energy level of the dust extractor when the spark current pulses of the dust extractor match the reference pulses coincide. Highly sensitive spark detector circuits are also provided to monitor the energy level when Lower low intensity sparks. The energy is then quickly raised to a new level, slightly below the original level Level, and then slowly increased until sparking occurs again.

In order to ensure the interruption of the energy supply for the dust extractor in the event of harmful short circuits, the analog computing circuits are programmed so that the voltage and current of the dust extractor are monitored and compared and the energy supply to the dust extractor in the event of a short circuit to the contactor of the dust extractor is switched off. At the same time , the user of the dust extractor is made aware of the short circuit.

The invention is described in the detailed description below of a preferred exemplary embodiment in connection with the 'drawing

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nings. explained; in the drawings show:

1 shows a block diagram of a dust collector circuit operating according to the principle of the invention;

Fig. 2 is a schematic circuit diagram of the analog computer circuits (29) according to FIG. 1, which are programmed so that they are fed to a dust extractor Control energy depending on the formation of sparks and arcing and when short circuits occur turn off the power to the dust extractor and at the same time energize an alarm circuit; ·

Fig. 3 is a block diagram of the embodiment shown in Figure _2: analog computer circuits;.

4 shows a power supply for the analog computer circuits;

Fig. 5 is a schematic circuit diagram for the silicon

rectifier energy control (14) according to FIG. 1;

Fig. 6 is a block diagram showing the replacement of the

The circuit of Figure 1 shows thyristors used by a saturable choke;

Figures 7, 8 and 9 are timing diagrams for signals such as occur at various points in the circuits of FIG.

In the exemplary embodiment initially explained in particular with reference to FIG. 1 According to the invention, an energy source 10 supplies a voltage of 440 V at 60 Hertz, which the lines 11 and . supplied-is. Power is supplied via relay contacts MR1 and MR2 the primary winding of a high voltage transformer via an overload relay OLR and one to the upper terminal of this Primary winding connected line 16 and a silicon rectifier energy control 14 and an inductance or choke 15 are supplied. The secondary winding of the high voltage transformer 13 is connected via lines 17a and 17b to a rectifier bridge 18, the output of which is via a line 19 connected to a dust extractor 20 and by means of a line 21

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Grounded via a milliammeter 21a and a load resistor 22 is. A voltage signal representing the deduster current is picked up at the resistor 22 via a line 23.

Circuits for controlling the energy supplied to the dust extractor 20 are partially supplied via a step-down transformer 24, the primary winding of which is connected to the lines via lines 25a and 25b 11 or 12 is connected. The upper terminal of the secondary winding of the transformer 24 is via a line 26 with a Earth bus 27 and .via a line 28 with analog computer circuits 29 connected. The lower terminal of the secondary winding of the transformer 24 is via a line 30 with a. Series circuit connected, which has a relay break contact 1CR1, a normally closed stop pressure switch 31, a parallel connection of a normally open start pressure switch and a relay contact MR3 and a delay relay TDR which is connected to the ground bus 27. One Line 33 carries power from transformer 24 to the analog computer circuits 29

A line 35 connected to the transformer 24 via the line 30 is connected to a series circuit, the one Normally open contact 0LR1 of the overload relay, a normally closed pressure switch 36 and one with the earth bus connected first control relay 1CR comprises. Furthermore, there is a further series circuit between the line and the collecting line 27 switched on, the one normally open contact 1CR2 of the control relay and an alarm display 37. A line 38 connects the two series circuits and is on one side of the relay contact YR1 shown closed but normally open when the control circuits are energized. The relay contact YR1 is contained in d-n analog computer circuits 29, which is indicated by the dashed line surrounding the contact. The other side of the contact YR1 is connected to a line 39, which is connected to line 35 via a contact TDR1, which is normally closed shortly after the circuits are energized is.

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Between the line 39 and the ground ~ collecting line 27 is a further series circuit, which also has a relay contact TDR2, which is normally opened shortly after the circuits have been energized a contact 1CR3 of the first control relay and a second control relay 2CR. With a contact 2CR1 of the second control relay are lines 40 and 41 and connected to a contact 2CR2 of the ■ second control relay lines 41 and 42, these Lines 40, 41 and 42 lead to an alarm system of the user, as indicated in the drawing.

^{Lines 42 1} and 43 are connected to the analog computer circuits 29 and carry information about instantaneous zero deflections of the primary voltage of the transformer 13, such as those caused by the formation of sparks or arcs in the dust extractor 20.

To the energy control 14 by the output signals of the analog computer circuits To control, two line pairs 44a, 44b and 45a, 45b lead from the analog computer circuits 29 to the power control 14. Another line 46 carries energy from the line 33 to the energy controller 14, which is grounded via the line 46a is.

To manual or automatic operation of the control circuits to select the dust extractor, a selector switch 125 is actuated, the circuits in the analog computer circuits 29 controls. If manual control is chosen, the user can control the circuits set by changing a potentiometer 50 in a suitable manner. The potentiometer is via lines 51, 52 and 53 connected to the analog computer circuits.

During operation, the start pressure switch 32 is actuated in order to act on the main relay T-IR and the delay relay TDR '. Contacts MR1, MR2 and MR3 of the main relay. close immediately and connect the AC main power source 10 to the silicon rectifier power controller 14 and the high-voltage transformer 13. After a delay of, for example, .1 3 seconds, the contact TDR1 closes (Um delay relay, and

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the contact TDR2 of the delay relay opens. The relay contact MR3 serves as a holding contact for the main relay and the delay relay .

During the delay of 13 seconds, the power control has been switched on by the analog computer circuits 29, so that the High voltage converter 13 energy is supplied. As a result, the energy supplied to the deduster increases to a certain level Value, either via the manual control of the potentiometer 50 when the selector switch 125 is in the position for located manually, 'or via the automatic operation of circuits, which are explained in detail below. It should also be noted that the relay contact YR1 during the 13 seconds long interval.

Assume that a spark or an arc occurs in the dust extractor 20 on, the analog computer circuits 29 receive signals from the resistor 22, which the deduster current in the line 23 and other signals on lines 42 and 43. Assuming normal sparking occurs, the analog computer circuits speak respond to these spark signals by generating control signals on the basis of which the energy control temporarily reduce the energy supplied to "transformer 13," as explained in detail below.

If a short circuit occurs in the dust extractor 20, the signals on the lines 23 and 42, 43 meet certain conditions which programmed into the analog computer circuitry as explained below are, and the relay contact YR1 closes and thereby acts on the alarm display 37 and the first control relay 1CR. The normally closed contact 1CR1 opens and throws off the main relay KR and the delay relay TDR. The contact 1CR2 of the first Control relay also closes and keeps the first control relay energized until pressure switch 36 is actuated. By closing of contact 1CR3 of the first control relay, the second control relay is energized, no that contact 2CR1 opens this relay - and contact 2CR2 closes so that the user can see a display

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maintains that there is a short circuit condition in the deduster.

The further operation of the energy control for the decongestion r About will after reading the description of the analog computer circuits 29 can be better understood in conjunction with the drawings.

For a description of the analog computer circuits 29, reference is made to FIG. Referring to the a schematic diagram of these circuits 29 shows, furthermore to FIG. 3, which shows a block diagram of the circuits 29 for an easier understanding of the computer arrangement " shows, as well as on Fig. 4, in "which the power supply for the Analog computer circuits is shown.

According to FIG. 4, an energy supply 200 is fed via lines 28 and 33. The power supply delivers a direct voltage of +15 volts on line 201, a DC voltage of -15 volts on line 202, with both voltages' on the Earth line 203 are related. The different ones marked with + and - Voltage points in the schematic circuit diagram according to FIG. 2 are connected to lines 201 and 202, respectively Therefore, when the lines 28 and 33 shown in FIGS. 1 and 4 are acted on, they are energized.

The lines 42 and 43, the potential of the power line have lead to a step-down transformer 60. It should be noted that the dedusting voltage Vp between the lines 42 and 43 equal to the voltage on the primary winding of the high voltage transformer 13 is. From the transformer 60 lines 61 and 62 lead to a capacitor 63, the harmful high-frequency voltage components suppressed. The input of a full-wave rectifier bridge is also connected to lines 61 and 62 64 connected.

With the output of the rectifier bridge 64 is a detector for Detection of instantaneous "zero voltages connected to a line supplies a negative output pulse of one millisecond duration,

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whenever the voltage at the primary winding of the transformer 13 and thus at the rectifier bridge Gk experiences a zero deflection. With regard to the dedusting voltage wave, it should be noted that it will generate reference or marker output pulses at the beginning, in the middle and at the end of a cycle of the voltage Vp. Reference pulses v / ground are also generated when sparks occur in the deduster and cause _{zero deflections of the voltage V p.}

Resistors 65 and 66 serve as voltage dividers, with the largest part of that voltage being dropped across resistor 65 exists at the output of the bridge when the bridge voltage is high enough so that current flows through a Zener diode 67. A resistance 68 forms a discharge path for a voltage reversing capacitor 69 as well as an input impedance for that on a function amplifier 70 lying tension. Resistor 71 acts as an amplifier feedback resistor when the amplifier output signal has negative polarity. However, due to the action of a diode 71a, the feedback resistance is effectively zero and thereby produces zero gain when the amplifier output seeks positive to ground.

At the output of the amplifier 70, a negative pulse of one millisecond length occurs on the line 65 'whenever a zero deflection occurs _{in the primary voltage V p of the dust extractor.} This is accomplished by charging the capacitor 69 when the primary voltage 'Vp is above zero. If this voltage drops to zero during the normal zero crossing at the points zero, at half or the full period or as a result of sparking or arcing within the dust extractor 20, the negatively charged electrode of the capacitor 60 via the parallel connection of the resistors 65 and 66 effectively grounded. The resulting input voltage is therefore positive and the amplifier output emits a negative pulse on line 65 *. A voltage divider formed by resistors 72 and 73, in conjunction with an amplifier input resistor 7k, forms a fixed negative

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Reference voltage that eliminates the possibility of the amplifier 70 false output signals generated.

An inverter 75 serves to transmit the negative polarity pulses of 1 millisecond duration on line 65 ^! to convert into positive pulses of 1 millisecond duration on an output line 76. Each pulse places a gate 77 in an open or on state for one millisecond. In this state of the gate, all the signals passed through are inverted in their polarity.

The deduster current flows through line 21, through the milliammeter 21a and the load resistor 22, these elements being shown in a dashed box for the sake of explanation of analog computer circuits to facilitate. The line 23 leads from the resistor 22 to a clamping and filter circuit The output signal of the clamping circuit is transmitted via a line 81 fed to gate 77 and appears on a gate output line 82, when the gate is in the on state, i.e. when it is triggered by the positive pulse with a duration of one millisecond from the inverter 75 is open.

To illustrate the operation of the clamp and filter circuit 80, Reference is made to Figure 7 which illustrates the signals at two points in the circuit. Curve A shows a signal which indicates the deduster flow in line 23 at the input of the Kiemmund filter circuit 80, while curve B shows the output signal of clamp and filter circuit 80 on line 81. You can see that this is the upper part of curve A. acts and that the leading and trailing edges of the pulse shown in curve B from the points at 0 and at half Period are a long way away. This prevents the occurrence false signals at the output of the gate by ensuring that the signal representing the dust extractor current does not appear during normal operation of the circuit without sparking overlaps with the reference pulses from the inverter.

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The output of the gate 77 is connected via the line 82 to a fast override circuit 83, which by the Lines 45a and 45b with one in the silicon rectifier power controller 14 arranged winding 84 of a silicon rectifier trigger unit connected is. The override

circuit is used to give the trigger unit an instantaneous apply strong control current when the gate output pulse occurs on line 82. Thus, a transistor switch can be used to generate a large current in winding 84 initiate. The result is the gate output signal at the input of the. Overdrive circuit off'-a strong spark, the After oscillations, the transistor switch turns on a current in the winding 84 which causes the silicon rectifiers be switched out of phase by the trigger unit for half a period. Is the sparking proportionate weak, the effect of the override circuit depending on the gate output signal of the winding 84 supplied current that the silicon rectifier are only partially switched in phase opposition.

The override circuit 83 is to compensate for the time delay required, which is inherent in the magnetic amplifiers used to trigger the silicon rectifiers. The application a large current to the magnetic booster winding 84 overcomes such a delay. Becomes a trigger circuit that responds instantly to control currents, as is the case, for example, with a transistorized silicon rectifier trigger unit is the case, the fast override circuit 83 can be omitted.

The gate output pulses on line 82 are also fed via lines 86 and 87 to a currently responding network, formed by circles that double integration of the gate output pulses. As in the U.S. Pa- " tentschrift 3 173 772 explained, the double integration of a spark signal results in a signal that contains the energy of the spark pulses, represents their rate of rise and their size. These

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Property allows the derivation of a control signal that allows the operation of dust extractors at high energy levels with greater Effectiveness made possible.

The currently responding network leads to a gate output signal negative polarity from a double integration and forwards a signal to the input of a control amplifier 88. the The effect of the control amplifier output signal is an instantaneous deflection into positive polarity and a ■ Return on an edge lasting 100 milliseconds to a. negative polarity, which then, if the influences of further still ' input signals to be described are neglected, is equal to the level before the occurrence of the negative gate signal.

If you look at the currently appealing network in detail, a resistor 89 thus forms a load resistor which represents part of the discharge path for a coupling capacitor 90. A resistor 91 limits the pulse current and, together with a diode 92, completes the discharge path for the capacitor 90. The Resistor 91 and a capacitor 93 effect the first integration of the gate output pulse, while a diode 94 and a Capacitor 95 perform the second integration. Diodes 96 and 97 are control diodes, and a resistor 98 forms the output resistor of the double integration stage.

To illustrate the operation of the instantaneously responding network, reference is made to Figure 8, curve C of which is a timing diagram of the gate output pulse on line 87 at the input of the double integrating network. Curve D specifies the signal which occurs at the output of control amplifier 88 as a function of the respective input signal which is generated by the double integration stage from the pulse according to curve C. You can see the current negative deflection and the subsequent gradual rising edge. This effect provides a momentary and immediate reduction in the deduster output level by reducing the current that is applied to a control device arranged in the silicon rectifier power controller 14.

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winding 99 is fed to the trigger unit. The power is then passed to the deduster on a rapid basis as shown in FIG Plank fed back; this function is described in detail below.

When operating a dust extractor, optimum effectiveness can be achieved by applying a voltage to the dust extractor electrodes which is just below the value at which sparking occurs, i.e. below the threshold voltage. It is therefore It is desirable to set the operating voltage of the dust extractor to a level slightly below that after the sparking Voltage at which the spark or arcing was initiated. In the system according to the invention such Threshold voltage or such a setting point automatically through the operation of a monostable long-term multivibrator Reach 110.

The gate output pulses on line 86 become the input of the multivibrator 110 supplied, which when applied to an output line 111 a pulse of negative polarity of 170 milliseconds in duration (see Fig. 8). This negative output pulse of the multivibrator 110 is transmitted via a line 112, a resistor 113 and a diode 114 a storage capacitor 115 supplied. The one occurring on capacitor 115 The voltage is limited upwards by a Zener diode 116 which, in conjunction with a resistor 117, has a certain discharge impedance for '· forms the capacitor 115. The voltage across the capacitor 115 appears across a resistor 118 and a potentiometer 119. The voltage at the potentiometer tap 120 is a Line 121 is fed to a control signal mixer 122a.

To initiate the operation of the analog computer circuits, a capacitor 122 charged through a diode 123, which generates a rising voltage; this voltage is via a line 124, the switch 125 - if this is in the automatic position - a conductor 126, a potentiometer 127 - which controls the

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Permitted setting of the maximum level for the setting value and a line 128 of the mixer 122a fed. A zener diode 129 limits the amount of voltage that can appear across potentiometer 127 to prevent mixer 122a signals that are too high are supplied.

If the threshold value or set point is to be set manually, switch 125 is brought into the manual position. This causes line 126 to pass through line 52 is connected to the potentiometer 50 shown in FIG. The line 51 connects the potentiometer 50 via a resistor 130 with a DC voltage of -15 volts. The set point can then be set manually by actuating the potentiometer 50 can be set.

If the switch 125 is moved to the manual position, the capacitor 115 is grounded via a resistor 131, and the Capacitor 122 for the beginning of the rising edge is over a resistor 132 grounded.

The deduster flow signal is fed to the control signal mixer via a line 140 122a, which is used to algebraically add the three input signals and a resulting output signal on a line 141 which is connected to the input of the control amplifier 88. The deduster power signal serves as a feedback signal and, in conjunction with the signal from capacitor 115, causes a decrease of the output signal on line 141, which would otherwise be determined by the signal from capacitor 122 or from potentiometer 50 would be determined. In other words, that of the control amplifier 88 generated control current (milliamps) is reduced by signals with switch-off polarity from capacitor 115 and line 140, which counteract the signals generated by capacitor 122 or manual potentiometer 50.

If only slight sparking occurs in the dust extractor 20, so-

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it may be that the zero deflections of the voltage Vp are not sufficient, to generate pulses to open gate 77. However, it is important to recognize such slight sparking and lower the voltage on the deduster electrodes by reducing the energy supplied to the deduster. To the Carrying out this function, a highly sensitive spark detector includes a differentiating stage 145, the deduster flow receives representative signals from line 23 via line 146. Are the current signals flowing through the dust extractor stable, as shown in curve R of Fig. 8 during the time period, the differentiator 145 generates on a line 147 no output pulse. A spark in the dust extractor, which as a result its property causes a rapidly increasing current pulse, but generates an output pulse at the differentiating stage 145, which activates a monostable multivibrator 148. The resulting negative output pulse of 16 milliseconds Duration on an output line 149 is fed to the input of the control amplifier 88 via a diode 150 and a resistor 151, thereby reducing the negative current supplied to control winding 99 for one period. This will make the Silicon rectifiers switched in phase opposition and reduce the energy supplied to the dust extractor.

The negative output pulse on line 149 is also over a line 152 to the long-term monostable multivibrator 110 fed. The resulting negative pulse of 170 milliseconds Duration is applied via line 112 to storage capacitor 115 which, as described above, is the threshold or setting level of the deduster 20 lowers.

If a short-circuit condition occurs between the high-voltage elements within the dust extractor and earth, a short-circuit alarm system causes the energy to be switched off at the dust extractor 20. Such a short-circuit condition is determined by _{monitoring and monitoring the magnitude of the primary voltage V p of} the high-voltage transformer and the magnitude of the deduster current

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be evaluated. A pre-programmed into these analog circuits short circuit condition means that the primary voltage Vp is low, for example 2 to 40 volts is effective, and that the Entstauberstrom greater than or equal to 5% of the maximum Entstauberstroms if the monostable multivibrator is not been operated 110th The operation of the circuit will be readily understood in connection with the detailed description below.

A transformer 155 fed via lines 42 and 43 is used to transform the high voltage and the To separate the alarm circuit from the energy circuit. Parallel to the: secondary winding of the transformer-155 is a rectifier bridge 156, and a capacitor 157 is used to dissipate high frequencies to protect the rectifier bridge. For current limitation a resistor 158 acts and a capacitor 159 acts as a filter. Resistors 160 and 161 serve as a bias resistor and as a voltage divider. The maximum voltage that may occur at the resistor 161 is generated by a Zener diode 162 limited to 10 volts. Resistor 163. provides an input resistance to amplifier 164. One of a resistor 165, which is at +15 volts, as well as a potentiometer 166 formed voltage divider forms together with the input resistance a misery & tension queHe. A feedback capacitor 167 conveys a characteristic curve with infinite gain and with a smooth transition between the one for the amplifier 164 State of saturation and the other. A load resistor is formed by a resistor 168.

A current monitoring circuit is similar to the voltage monitoring circuit just described. There is an input resistance 170, which is connected to the resistor 22 via a line 171 and the line 140, is subjected to a voltage signal, which represents the size of the deduster flow. A resistor 172 connected to -15 volts, a potentiometer 173 and. ' a resistor 174 act as a displacement voltage

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source. A feedback capacitor 175 mediates for the amplifier 176 shows a characteristic with infinite amplification and a smooth transition between one state of saturation and the other. Resistor 177 acts as a load resistor for amplifier I76.

A part of the negative pulse of 170 milliseconds duration on the output line 111 of the monostable long-term cult vibrator 110 is transmitted via resistors 178, 179 and a diode 180 to a differentiating network which is formed by a capacitor and a resistor 182. By supplying this signal to amplifier 176, a deduster flow is simulated which is greater than 5 % of the maximum deduster flow. This "simulation" occurs when, as a result of a deduster short circuit, a multivibrator pulse of 170 milliseconds is generated at very low values of the deduster current. A resistor 183 serves as the input resistance of amplifier 176 in order to simulate deduster currents of over 5%.

The voltage monitoring circuit and the current monitoring? circuit together perform a voltage and current comparison function. The output signals of amplifiers I76 and 164 Diodes 184 and 185 are fed so that the relay YR is shed if both input signals of these diodes are negative Have polarity. If the signal is switched between amplifiers 164 and 176, a diode 186 acts as a free-running one Diode for ^ as relay YR. -

The relay YR is normally energized when the dust extractor is in operation, so that the relay contact YR1 (see FIG. 1) is open is. When the relay YR is switched off, the contact YR1 closes, so that current flows between the lines 38 and 39, which - how clearly shows from Fig. 1 - causes the first control relay 1CR and the main relay MR respond and the relay contacts MR1 and MR2 can be opened so that the energy from the deduster 20. is taken away.

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For a more detailed explanation of the silicon rectifier power control 14, FIG. 5 shows a typical network used in the deduster power control system disclosed herein leaves. In the line 12 is a pair of oppositely directed thyristors 200 'and 201' connected in parallel, the commonly referred to as controllable silicon rectifiers. These thyristors can be, for example, the type 260 ED of the company V / estinghouse act in order to meet the requirements, namely peak voltages of over 1200 volts in forward and reverse, mean currents on the order of 175 amps and holding currents on the order of 30 milliamps to endure. Between the lines 12 and 16 is a holding current resistor 202 ', which a current through the silicon rectifier conducts, which is slightly larger than its holding current.

The in line 12 between the silicon rectifiers 200 ' and 201 'provided choke 15 and the primary winding of the transformer 13 result in the usual way a minimum circuit impedance in the event of sparks or short circuits in the dust extractor. The choke also provides a smoothing effect in the Primary winding of the high-voltage transformer supplied voltage and current curve and: additionally enforces a safe Limitation of the rate of change of current.

In parallel with the thyristors 20Q - * - αηύ 201 * there is a rectifier protective circuit 203 ^f . This protective circuit includes a thyrator 204 which determines an absolute maximum voltage that may occur at the silicon rectifiers. The Thyrektor 204, an unpolarized device, zisht current from the energy source 10 via the choke 15, if the voltage on the silicon rectifier energy control becomes too high.

In the protective circuit, a resistor 205 is further provided to charge a capacitor 206 through diodes 209 and 210 and a resistor 207 to charge a capacitor 208 through diode 211 and 212th Discharge paths for capacitors 206 "and

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200 are formed by resistors 213 and 214, respectively. Resistors 215 and 216 provide an even voltage distribution diodes 209 and 210, while resistors 217 and 218 produce the same voltage distribution across diodes 211 and 212. High voltage leakage capacitors 219 »220, 221 and 222 protect the diodes 209, 2,10, 211 and 212 against high-frequency voltages. It should be noted that the values of the circuit elements in the rectifier protection circuit are selected so that the used A high resonance frequency and the lowest possible quality can be achieved in the areas of the inductances in order to ensure that no vibrations occur. The quality is between 5 and 10 and the resonance frequency between 4.5 and 2 KHz.

A silicon rectifier trigger unit 225 provides gate pulses with correct phase via a line 226 to the rectifier 200 'and via a line 227 to the rectifier 201'. The trigger unit used in the dust extractor power system according to the invention can be of conventional design and can be a magnetic amplifier with associated circuitry to provide rapidly increasing pulses which are in phase such that Rectifier conduction angle from 0 to 180 ° for control currents of, for example, 0 to 5 milliamperes on the lines 44a, 44b leading to the control winding 99 (FIG. 5). _ Lines 46 and 46a supply "the trigger unit 225 with energy. Lines 45a and 45b from the override circuit." 83 feed the winding 84 of the magnetic amplifier in the trigger unit with a strong control current to switch off the rectifiers quickly.

To a. Gain control for the rectifier circuits, the output voltage is fed directly to a step-down transformer 230 which turns ampere-turns for gain feedback supplies to the trigger unit. With the secondary winding of transformer 230 is a rectifier bridge 233 connected via a current limiting resistor 232. The transformer 230 is on one side via a line 14a ah

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the power line 16 and with its other side over the Line 146 connected to power line-12. A parallel Current divider resistor 233 connected to the output of bridge 231 lies par * UeI to a potentiometer 234. By setting the Potentiometer, the gain is changed by changing the amount of feedback to the trigger unit via a line 235 and a resistor 236 is regulated. At the booster winding, a minimum resistance is determined by the value of the resistance 236 set.

Because the silicon rectifiers 200 'and 201 · are made conductive, the rectifier unit 225 responds to the sum of the control current (control ampere-turns), the bias current generated by an internal bias voltage source (bias-ampere-turns) and the amplification current (amplification ampere-turns). at. The control ampere-turns ground from a 0 to 5 milliamp DC current. derived, which is given by the control amplifier 88 (Fig.2) on the lines -44a and 44b. As stated, the control current is changed in order to set the operating level of the deduster. . ■ ₍ ■

It should be noted that the gain ampere-turns is a direct function of the output voltage of the silicon rectifier power controller is. By adjusting the potentiometer 234 to set the size of the ampere turns to be withdrawn a variety of gain curves can be achieved.

In the present circuit came a conventional silicon rectifier trigger unit used, for example, from the company Magnetic Specialties as a trigger unit Part No. 1395 is available. Another trigger unit that can be used , is available from Firing Circuits Inc. of Norwalk, Connecticut U.S..A. as model no. 233F372 available. The latter has Trigger unit an external bias connection, the. from a suitable direct current source can be fed.

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About the analog computer circuits and the entire dust extractor energy control system To be more clearly understood, reference will be made to the description of the operation of the system in FIGS. 2 and 3 as well as in FIG Reference is made to the timing diagrams of Figures 8 and 9. To initiate operation of the dust extractor 20, the start switch is turned printed, whereby - as explained above in connection with Fig. 1, the main relay MR applied and energy to the analog computer circuits 29 so / ie the silicon rectifier power control 14 is placed. As shown in FIG In the automatic position, the energy supplied to the dust extractor increases in accordance with the voltage that builds up on the capacitor 122 automatically to. This rising voltage is fed to the control signal mixer 122a, where it is combined with the feedback signal of the The deduster current on line 140 (i.e., the voltage across resistor 22) is algebraically summed. The resulting signal at the output of the mixer stage is fed to the control amplifier 88 via line 141, which causes a control current to flow through the control winding 99 in the silicon rectifier trigger circuit flows. Depending on the energy level at which the dust extractor works most effectively and on the one to be described Manner is achieved, a control current of, for example, up to 5 milliamps switches the silicon rectifier 200 ' and 201 'over a certain angular amount on phase, the angular amount of the from the AC voltage source 10 in the deduster 20 corresponds to the amount of energy to be fed ;.

If manual operation is desired, switch 125 is placed in its manual position and potentiometer 50 is turned off gradually adjusted to increase the voltage applied to mixer 122a. The remaining circles work in the same way As described in connection with automatic control.

During the continuous operation of the dust extractor energy control system, as shown during period 1 of the combined waveform R in FIG. 8, the detector has instantaneous detection

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Zero voltages, the gate 77, the highly sensitive spark detector, the monostable multivibrator 110 and the short-circuit alarm stage have an influence on the energy control.

The energy supplied to the dust extractor 20 increases and increases the voltage on the deduster electrodes, a point is reached at which a spark occurs within the deduster. Referring to the curves in Fig. 9 for a better understanding of the operation of the system when a spark occurs determine that dust extractor current pulses E, which are represented by the voltage across resistor 22, occur regularly, until. a spark F occurs in the deduster. The control function of the system then causes the dust collector current to decrease to a value indicated by the G pulse.

The primary voltage Vp at the transformer 13 is shown in curve H. Attention should be paid to the regular zero crossings which, according to the rectification by the bridge 64, generate zero deflections of the oscillating voltage. With each zero deflection, the detector generates a reference pulse with a duration of one millisecond and a negative polar- ~ to detect instantaneous zero voltages. tat, which is converted into positive polarity by the inverter 75 and results in the positive pulse K. Likewise, a spark iri = .d.e_m deduster results in a. Zero deflection J of the primary voltage V _p , and the detector reacts by generating a further pulse L. While the pulses K and L are fed to the gate 77 and put it into the on-state, pulses M for steady state, which are derived by the clamp and filter circuit 80 from the voltage at the dust collector current resistor 22, the gate input line 81 is supplied. Normally the pulses K and M are fed to the gate 77 out of phase, so that as a result no gate output signal is generated. When a spark occurs, however, as explained above, a pulse L is generated, and a signal indicating the flow of the dust collector current, N, coincides with the pulse L and causes at least part of the pulse to be generated.

209ÖÖ5 / I 103 "''

pulses N through the gate 77 is turned on. As a result, a gate output pulse occurs. 0, the size and shape of which depend on the properties of the deduster current flowing as a result of the spark or arc. For example, a strong current spark often leads to interference and continued oscillation, which results in several zero deflections and a larger gate output signal. The fast override circuit 83 responds to the gate output pulse 0 by sending a strong cut-off current into the winding of the trigger unit, which reverses the phase of the silicon rectifiers and immediately reduces the current flow through the dust extractor, as shown by the composite curve R in FIG. 8 is shown.

In the event of a short circuit, for example a fault in the main power supply lines, which causes the deduster flow opposite lags the deduster voltage by 90, the reference pulses K and the deduster current M (FIG. 9) coincide so that Gate output signals are generated.

The spark signal F (FIG. 9) is also fed to the highly sensitive spark detector and from the differentiating stage 145 differentiated, which supplies the monostable multivibrator 148 with a switch-on pulse. The resulting negative momentum from 16 milliseconds duration (Fig. 9) is via the Leitimg 149 dem Control amplifier 88 is supplied, which reduces the current flow through the control winding 99. So the occurrence of a spark leads to a reduction in the energy supplied to the dust extractor 20, even if the spark is so weak that there is no perceptible zero deflection of the primary voltage Vp and no output from the gate 77 causes.

The gate output pulse C (Fig. 8) is also transmitted over the lines 06 and 87 the currently appealing one formed by the DoppeLintegrator- Network fed. The parameters of the spark pulse determine the output signal D of the double integrator shown in FIG. 8, which is fed to the control amplifier, This causes a quick one

2 0 988 5/1193

Reduction of the current flowing through the control winding 99, as a result of which the deduster current shown in curve R is reduced will. Was the spark not very strong and not as strong as, for example an arc which - as explained below switches off the system - a rapid but not momentary ' The energy flowing through the winding 99 supplies the energy to the dust extractor again. As part of the response of the double integrating network, the energy is passed to the deduster on the edge of, best shown in FIG 100 milliseconds quickly supplied again.

If one examines the pulse diagrams more closely, one finds that that the deduster current during a period 2 following a spark pulse F, which is period 1 (continuous mode of operation) terminated, is rapidly reduced to 0. During the period 3 the double integrating circuit mediates a re-supply of the power according to a rapidly rising edge. Of the the maximum voltage level reached at the end of this edge is equal to the operating level before the spark less of an additional reduction, the. on one stored in the capacitor 115 due to the operation of the monostable multivibrator 110 Charge is based. As discussed above, the 170 millisecond negative pulse is applied to capacitor 115 via line 112.

During period 4 shown in FIG. 8, the deduster increases current gradually as a result of the discharge of the capacitor 115. This results in an output signal from the control signal mixer 122a, which causes control amplifier 88 to pass the current through control winding 99 along a slowly rising edge elevated. This slow increase in the energy level of the dust extractor continues until a new spark level is reached and the whole process then repeats itself. -

As explained above, in certain cases the spark in the deduster is so weak that the zero deflections in the primary voltage V _p

209685/11

" ²⁴ " * 2234D46

insufficient to generate pulses from the detector to detect instantaneous voltages which open gate 77 and therefore output impulses to the currently responding Metzwerk and the override circuit 83 would send. In such cases, the highly sensitive spark detector acts so that a negative Pulse of 16 milliseconds is fed directly to the control amplifier, which reduces the current level in the control winding 99 and thereby reduces the energy supplied to the dust extractor. In addition, the negative pulse of 16 milliseconds switches Engage the monostable multivibrator 110, which charges the capacitor 115 for the purpose noted above.

If a short circuit occurs in the dust extractor, it is useful. to completely remove the energy from the system by energizing the main relay MR and opening the main relay contacts MR1 and MR2 (FIG. 1). In order to carry out this function, the size of the voltage on the primary winding of the high-voltage transformer 13 and the deduster current are monitored and evaluated by the short-circuit alarm level. During a short circuit condition; So the primary voltage is very low, for example between 2. and 40 volts effective, and the dust extractor current is greater than or equal to 5% of the maximum dust extractor current, if the monostable multivibrator 110 has not been actuated.

The detection of a short circuit is conveyed by the analog computer circuits in that values of voltage and current combinations are determined which can in no way represent a short circuit, and in that this fourth is programmed into the short circuit alarm stage and all other combinations of the primary voltage V _p and of the deduster flow can be defined as an indication of a short circuit condition. A table of the logic function of the circuits is given below.

20988R / 1 193

Deduster stream

Multivibrator pulse of 170 milliseconds

alarm

<1OO ■ <5% <1OO > 5% <1OO > 5% O 00 '' <5% - > 1OO < 5% > 1OO > 5% > 100 > 5% ^ 100

No ■ ■ No. Yes Yes no Yes Yes no no no Yes no no no Yes no

From the above description it can be seen that the short-circuit alarm level works according to the table. So are the inputs of diodes 184, 185 of. amplifiers 176 and -164 both negative, the relay YR drops out and the contact YR1 closes. As explained above, this leads to an excitation of the main relay MR, whose contacts MR1 and MR2 open.

In connection with the operation of the short circuit alarm system, it should be remembered that the negative pulse of 170 milliseconds from the monostable multivibrator 110 simulates a dust collector current greater than 5% of the maximum current in the event of a short circuit at a very low one Value of the dust extractor occurs. Such a low value v / would not be sufficient to actuate the amplifier 176 via the line 140, 171 and the resistor 170. However, the highly sensitive spark detector is able to detect such short circuits even with small deduster currents and to operate the monostable long-term multivibrator 110. It should be noted that a fault in the main power lines even with a very low deduster current, which is below 3% of the high ts tropu; causes the.

:. ■). ν ■: ■:

2 0 9 0 8 fi / T Hi J

Deduster current lags behind the deduster voltage by 90 °. As can be seen from the curves in FIG. 9, such a lag of the deduster current compared to the primary voltage by 90 °, regardless of how small the current is, causes the reference pulses K and the current pulses M to coincide, which leads to a gate output signal; this signal actuates the multivibrator 110, which simulates a dust collector current above 5% of the maximum current.

According to the description above, the invention works A silicon rectifier power control system to regulate the power supplied to the dust extractor 20; instead of this the analog computer circuits and the other circuits can also use an energy control with a saturable choke be used. According to FIG. 6, in which the same elements as' in FIG. 1 have been given the same reference numerals. in the power line 12 between the power source 10 and the high-voltage transformer 13 a saturable choke 300 switched on. A control winding 301 in the reactor 300 is powered off a DC-to-AC power amplifier 302. The control lines 44a and 44b from the control amplifier 88 in the analog computer circuits '29 carry a direct current of 0 to 5 milliamps to the power amplifier. Alternating current is fed to the power amplifier via lines 303 and 304, which are connected to lines 28 and 33, respectively.

In operation, the analog computer circuitry operates as described in connection with the silicon equator controller was except for the fact that the rapid overdrive scarf fcung 83 can be omitted. The short circuit alarm stage works just as well with a saturable control circuit Throttle.

2 0 9 8 8 5 / Π 91

Claims (12)

223A046 IT Claims . 1 .j system for controlling the alternating current power which is fed to a high-voltage transformer for feeding an electrical dust extractor via a rectifier device, characterized by a device (60, 64, 70, 75) for generating reference pulses corresponding to instantaneous zero crossings of the transformer (13) supplied voltage, a device (22, 80) for generating the signals representing the dust extractor current, a gate device (77) to which the reference pulses and the dust extractor current signals are supplied, and the output signals which represent the dust extractor current signals are generated when as a result of a Spark or arcing in the dust extractor, the reference pulses coincide with the dust extractor current signals, as well as a device (14) which responds to the gate output signals and reduces the power supplied to the dust extractor. 2. System according to claim 1, characterized in that that the device (14) for reducing the power includes a device (91, 93, 94, 95) for double integration of the gate output signals includes. 3 / system according to claim 1, characterized by a device (88, 115, 122a) for increasing the $ 03885/1103 Cleanly supplied power following a power reduction. 4. System according to claim 3, characterized in that the device (88, 115, 122a) for increasing the power during a preliminary period immediately following the sparking causing the degradation increased the power supplied to the dust extractor rapidly and more slowly after this period. 5. System according to claim 4, characterized by a highly sensitive spark detector (145, 148) on the is responsive to the sparking dust collector current signals and generates output signals, the device .. (14) responds to these output signals to reduce power and reduces the power supplied to the deduster. 6. System according to claim 1, characterized by a saturable inductance (300) connected upstream of the high-voltage transformer (13), to which the device (302) is connected to reduce the power supplied to the dust extractor. 7. System according to claim 1, characterized by Thyristors (200 ', 201 ·) for supplying power to the' Transformer (13) ^ wherein the device (14) for 5/1193 reduction a trigger unit (225) for modulation of the thyristors "at certain phase angles and thus to control the power supplied to the dust extractor as well as a Device for supplying a control current to the trigger unit for moving the phase angle forward or backward for the Thyristor control and thus to increase or decrease the power supplied to the dust extractor, with the. Gate output responsive device (14) the control current changes and the die.Triggeinheit auf responds to the changed control current, relocates the phase angle of the thyristor control and thus the deduster input power reduced., ν. ■ 8. System according to claim 7, characterized by a further device for. -Change of the trigger unit (225) trains sensing ¹ th control current to the forward shift of the phase angle for the Thyristoraussteuerung and thus to increase the dust collector following the Leißtungßherabsetzung-supplied power. ,, .-> _: - - _; .- ■ ...-- <. 9. System according to claim 1, _v ge k en η ζ e .ic h η et .by a voltage monitoring stage (155, 161, -164) which generates an output signal when the high-voltage transformer (13). A current monitoring stage (170, - 176); which generates an output signal when the current rises above a certain value, as well as an output signal .sfjignalo the S and current monitoring level responsive device (YR, KR), the power supplied to the transformer in the event of a short circuit that causes the transformer voltage falls below the certain Uert and the deduster flow over the certain value increases, interrupts. 10. System according to claim 9, 'characterized by an alarm circuit (2CR, 40, 41, 42) which is activated by said device (YR, MR), \ rQnn a short circuit occursjder causes the transformer voltage to drop below the specific value and the deduster flow rises above the inspected value. 11. System according to claim 9 »characterized by a device (110) which has a deduster flow above of the specific value is simulated if a short circuit occurs in the dust extractor at a relatively low energy level, -which on the. Output signals of the voltage and current monitoring levels responding device (YR, MR) also responds to the output signal of the simulator and an alarm circuit (TOR, 40, 41, 42) when one occurs Short-circuit activated, which causes the transformer voltage The amount of dedusting flow drops below the specified value and / or the simulated deduster flow over the increases at a certain value. 2098dS / 12. System according to claim 11, characterized in that that the simulating device (.110) a device for generating of pulses in short circuit conditions in the dust extractor that cause the dust extractor current to reduce the voltage across the Cooking voltage transformer (13) lags by 90 °, as well as a circuit that responds to these pulses and the Entstauberstroni generates simulating output signals. 209685/1193 L e r s e i t e