JPS58114754A - Electrical dust precipitator - Google Patents

Abstract

PURPOSE:To detect the generation of back corona quickly and to permit breaking of thyristors for a prescribed time, by providing a function generator to the control part of an electrical dust precipitator and controlling the conducting angles of the thyristors with the gate pulse signal thereof. CONSTITUTION:In an electrical dust precipitator, conducting angle signals are applied between the respective gates and cathodes of thyristors 1a, 1b from a function generator 4. The generator 4 is provided with a counter to be applied with the basic clocks synchronized with the frequency of an AC power source applied to the thyristors 1a, 1b, an ROM, a D/A converter, etc. AC electric power of high voltage is supplied to a bridge rectifier 60, and the rectified negative voltage of high voltage is supplied between dust collecting electrodes 62a, 62b. When back corona is generated in this stage, the signal thereof is transmitted to the monostable multivibrator of the generator 4, by which the ROM is disabled and the conducting angles of the thyristors 1a, 1b are broken for a prescribed time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic precipitator equipped with a function generator that periodically changes the conduction angle of a thyristor to obtain a desired change in high voltage. The present invention relates to an electrostatic precipitator that detects voltage and current, detects a reverse ionization phenomenon from differential values thereof, and controls a function generator based on these differential values.

In conventional electrostatic precipitators, the current or voltage value applied to the collecting pole is detected, and if these values exceed a reference value, it is assumed that an overcurrent or overvoltage has occurred and the thyristor is activated instantly. A known method is to cut off the trigger signal of the dust collector.Although this method was effective against arc discharge that occurs between the dust collection electrodes, it is difficult to detect the occurrence of back ionization phenomenon (back corona). This back corona phenomenon deteriorates dust collection efficiency, and its occurrence varies depending on the characteristics of the ash to be harvested, the shape of the dust collection electrode, etc.

Conventionally, a pulsed power source or an intermittent charging type power source has been used to eliminate this back corona phenomenon, but it has not been possible to sufficiently suppress the occurrence of the back corona phenomenon.

The present invention has been made in view of the above circumstances, and uses a function generator that generates a voltage in which back corona is less likely to occur, and also detects this back corona and controls the function generator. An object of the present invention is to provide an electrostatic precipitator capable of interrupting the 41!111L pressure applied to the 41!111L pressure for a predetermined period of time.

Furthermore, the present invention is based on the discovery that when a significant phenomenon of back corona occurs, the current value supplied to the current collecting electrode stably increases, but the voltage value actually decreases. 'Find the differential values of the current and voltage values,
It is an object of the present invention to provide a detection circuit that detects back corona from the comparison results of these differential values.

The invention will now be described in detail with reference to one drawing.

FIG. 1 shows an electrostatic precipitator according to the present invention, with reference numeral 1a.
, 1+ is a thyristor. These thyristors la,
For example, a single-phase alternating current of 200 μm is supplied to each of the 14 anodes and 1 cathode via a coil 2 and a primary winding of a high-voltage transformer 3.

Further, a conduction angle signal is applied from the function generator 4 to each gate φ quad of the thyristors la and 17. This function generator 4 includes thyristors 1a and 14 as shown in FIG.
The trigger circuit 5a of 2 (ig;) controls the conduction angle, respectively.
54, and a monostable multivibrator 6 that cuts off the conduction angle signals from these trigger circuits wr5a and 54 for a certain period of time.

(To the trigger circuit 5a of the synchronous transformer 7, a synchronous signal is applied to the clock terminal UK of the binary counter 0a via the diode 1''8a and the resistor 9a.The Zener diode lla receives the synchronous signal 5. This binary counter ioa is 1' T L or C-M
It is composed of an OS type IC and sends an 8-bit binary output to the address terminal A of the read memory (ROM) 12a.

This read memory 12m is composed of, for example, a 256.times.8-bit programmable ROM, and 8-bit data D of this ROM 12m is applied to a DA (digital/analog) conversion circuit 13a. This DA conversion episode lol! Reference numeral 13a is an open collector that optically combines 8-bit digital quantity and converts it into two capacitance values, to which each 8-bit data is applied and turns off and on the light emitting diodes 20a and 21ass*27a. Phototransistors 30a, 31a...37a are optically coupled to the mold back 714m and each light emitting diode 20m, 21a...27m.
And each wire is 30m phototransistor.

The capacitors 40a, 41a, . . . , 47m are connected to the collectors of the capacitors 31ae, . The emitters of these phototransistors 3Qa, 31a@-.37a are commonly connected and connected to the cathode of the thyristor la. Further, the other ends of the capacitors 40a, 41a, . . . , 47m are also commonly connected to form a common terminal C. A diac (silicon control element) 50 is connected between this common terminal C and the gate of the thyristor 1a! A resistor 51a is inserted between the common terminal C and the thyristor Ia at the 7-node connection.

The trigger circuit 54 has the same circuit composition as the trigger circuit 5a except that it controls the conduction angle of the thyristor 14.

In this way, the function generator 4 is a thyristor la.

By controlling the conduction angle of each of the voltage transformers 14, a desired AC voltage of 50 Hz can be supplied to the primary side of the voltage transformer 3. Furthermore, it is possible to send out conduction angles (envelopes of a and a) having a 256 order arrangement to this combination resistor Hm.

The secondary winding of this high-voltage transformer 3 is supplied with an alternating current voltage that increases the envelope edge of the yuzui function by +4''.

This high voltage AC power is supplied to the bridge rectifier 60,
! 111t high negative voltage is connected to the grounding shunt resistor 61
The dust is supplied between the dust collecting electrodes 62a and 624 through the dust collecting electrodes 62a and 624. Between the dust collecting electrodes 62a and 624, voltage dividing resistors 63 and 64 are inserted to detect the voltage.

The following phenomenon occurs between the dust collecting electrodes 62a and 624. In other words, the collecting electrodes 62M and 6 are considered normal, but if X is larger than Y, unevenness occurs.

This current change @X, that is, the current differential value is
The current value supplied to a, 624 is temporarily stored at predetermined time intervals, and this temporarily stored value is obtained by subtracting it from the current current value.

Further, the voltage change amount Y, that is, the voltage differential value is
The voltage value applied to a, 624 is temporarily stored at predetermined time intervals, and this temporarily stored value is obtained by subtracting it from the current voltage value.

That is, the current differentiation circuit 65 includes an AD converter 66 that converts the current flowing through the shunt resistor 61 into an 8-bit digital sum IA, and a register 67 that stores this digital 1tlA using the synchronization signal CK from the function generator 4. A subtracter 68 is provided for subtracting the memory 111B of the register 67 from the digital quantity IA.

Further, the voltage differentiating circuit 69 includes an ADf converter 70 that converts the voltage of the voltage dividing resistor 64 into an 8-bit digital quantity YAK, a register 71 that stores this digital quantity VA in synchronization with the synchronization signal CK, and a register 71 that stores the digital quantity VA in synchronization with the synchronization signal CK. The subtracter 72 subtracts the stored value VB from the digital amount vA.

Outputs X and Y obtained from these current and voltage differentiating circuits 65 and 69 are applied to a comparator 73, respectively.

This comparator 73 sends a packed corona detection signal Z to the trigger terminal 1 of the function generator 4, the monostable multivibrator 6, when X is smaller than Y. As a result, the monostable multivibrator 6 operates in the ROM 12a, 12 for a predetermined period of time.
4 is disabled, and the conduction angles of thyristors 1m and 14 are cut off for a predetermined period of time.

This predetermined time is adjusted by the capacitor 74 and the resistor 75, and is the time required for the bank corona to disappear, for example, from 0.1 seconds to 1 second.
0 seconds is set.

Figure 3 shows the electrostatic precipitator shown in Figures 1 and 2 constructed using, for example, an 8-bit microcomputer, and the parts corresponding to the parts shown in Figures 1 and 2 are shown in Figure 3. The same symbols are attached.

In this figure, when the CP (J80) is powered on,
The initial routine stored in FtOM81 is executed.

This initial routine stores the OU in the counter 83 in the RAM 82 that stores the offset amount from the start address of the areas (function areas) 12a and 124 that store functions in the ROM 81.
170-do. Next, in the function areas 12a and 124, the contents of the function areas 121 and 124 indexed by the contents (offset address) of the counter 83 are transferred to the latch-type output capacitors 14a and 14 via the accumulator in the CPU 80.
4, respectively. Thereafter, the contents of the counter 83 are incremented by one. In addition, the digital amount of current from the AD converter 66 is transferred to the IB in the RAM 82 via the 7 cumulator.
Stored in Q area 84. The digital amount of voltage is transmitted from the AD converter 70 to the VB area 85 through the Akiemulator.
Stored in

Further, this CPU 80 recognizes each synchronization signal from the power supply as an interrupt signal, and based on these, the function area 12
A routine is executed to send the contents of I24 to the output ports 14a and 14A via the achievator, respectively. In this case, the counter 83 is counted up by one of the synchronization signals from the power supply.

Furthermore, cpugo executes a routine to detect back corona every time these synchronous 4M signals are sent out.

This routine starts by loading the digital value of the current from the AD conversion@SS into the accumulator and pushing it onto the stack. The contents of the IB area 83 are subtracted from the contents of this accumulator, and the subtraction result is stored in the X area 86 via the accumulator. Next, the data (in this case, the digital value of the current) pushed onto the stack is Ii
It is stored in the j area 83. Similarly, At) Conversion gain 70
The digital value of the voltage from is loaded into the accumulator and bushed into the stack. The contents of the VBIJI area are subtracted from the contents of this accumulator, and the result of the subtraction is stored in the Y area 87. Next, the digital value of the voltage pushed onto the stack is popped up and VB@
It is stored in area 84.

Next, the contents of the X area 86 and Y area 87 are compared, and
If it is less than or equal to, then an interrupt signal is accepted (1124). Alternatively, if X is greater than Y, cpuso sends 00 to output port 148.14. This interrupts the conduction angle of thyristor la114. Thereafter, cpusO ignores the interrupt signal for a predetermined period of time. After a predetermined period of time elapses, the wave returns to normal state.

As explained above, according to the present invention, the negative voltage supplied to the dust collecting electrode can be changed from aoKV to 2 in one period of 5.12 seconds, for example.
It can be varied arbitrarily between 0KV. This fluctuation can significantly improve the dust collection efficiency compared to the case where a negative voltage corresponding to the average is applied. Further, when a back corona occurs, it can be detected quickly and accurately, and there is also an advantage that there is no need to cut off the thyristor and waste power.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electrostatic precipitator of the present invention, FIG. 2 is a diagram showing a function generator, and FIG. 3 is a diagram showing an electrostatic precipitator of the present invention using a micro combinator system. 1m, 14... Thyristor, 2... Coil 3...
High voltage transformer, 4...function generator 5a, 54...
・Trigger circuit, 6...monostable multivibrator, 7
...Synchronous transformer, 8a...Diode, 9B
m...resistance, 10a1, binary counter, 111@, fist Zener diode, l2@11 @-read memory,
13a...DA (digital/analog) conversion circuit, 1
4a...buffer, gQa, 21a...27a...
・Light emitting diode, 30a, 31a...37a...
Phototransistor, 40m, 41a...47a...
・Capacitor, 591@a・Diac (series control element), 51a...Resistor, 60...Prige rectifier,
61... Shunt resistance, 62m, 624... Dust collection electrode,
63.64--Voltage dividing resistor, 65...-Current differentiator circuit,
66...ADg converter, 67...Register, 68-...
・Subtractor, 69・@-Voltage differentiator, 70・-Fist AD converter, 71---Register, 72Φ・・Subtractor, 73-
--Comparator, 74...Capacitor, 75...-Resistor,
80...CPU. 81...ROM, 82...RAM, 83...Counter, 84..., VB area 86...X area, 871
1., Y area.

Claims (3)

[Claims] (1) Using a thyristor, a high-voltage transformer, and a silicon rectifier [In an electrostatic precipitator that applies a high voltage between collecting electrodes, a function generator is provided in the control section of the thyristor,
An electrostatic precipitator characterized in that a conduction angle of a thyristor is controlled by a gate pulse signal of this function generator. (2) The function generator includes a counter to which a basic clock synchronized with the frequency of the commercial AC power supply applied to the thyristor is applied, a ROM to which the output of this counter is applied to each address terminal, and a ROM of this ROM. The electrostatic precipitator according to claim 1, further comprising an L/A converter that converts a digital output into an analog output, and the analog output is applied to the thyristor. (3) In an electrostatic precipitator that uses a thyristor, a high-voltage transformer, and a silicon rectifier to apply a high voltage between dust collection electrodes, a function generator that controls the conduction angle of the thyristor and a high voltage applied between the dust collection electrode The voltage differential circuit includes a voltage differential circuit that detects a differential value of a voltage, and a current differential circuit that detects a differential value of a current supplied between the precipitate electrodes, and the An electrostatic precipitator characterized by controlling a function generator.