Abstract: A method and device for varying a d.c. voltage connected to an electrostatic dust separator so as to render more effective, in return for a low consumption of energy, the collection of dust on an electrode or electrodes incorporated in the dust separator. The d.c. voltage is set to a first level (basic level), said level having superimposed on it a number, in each case two or more, of voltage pulses forming a pulse group, with the consecutive pulse groups being separated from each other in a time sequence and supplied to electrodes incorporated in the dust separator.

Abstract: A control device for an electrostatic precipitator including a plurality of filter chambers connected in series to one another comprises a first component connected to a particle density sensor at the output of the last filter chamber for computing desired values of the particle densities at the outlets of the individual filter chambers in response to the difference between a desired particle density and a measured particle density of the outflowing gases at the output of the last filter chamber.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: An improved electrostatically operated dust collector is disclosed which includes a high voltage power supply circuit by way of which a direct current having high voltage fed from a commercial power supply network is applied thereto and a control circuit for controlling said high voltage power supply circuit. The improvement consists in that the dust collector further includes an intermittently operative electric power feed circuit in which feeding of DC electric power thereto is effected for a period of time T.sub.1, then feeding of electric power is intermitted for a period of time T.sub.2. The aforesaid steps are repeated. A preset circuit also forms part of the improvement in which circuit the aforesaid feeding time T.sub.1 and no-feeding time T.sub.2 are preset to a required value respectively. An intended energy saving is ensured by the improvement.

Abstract: A system and method for controlling energy input to a series of electrostatic dust separator devices having a common gas inlet and a common gas outlet. A detector unit is disposed in the gas outlet to detect the dust concentration or evaluate the actual dust loss in the exhausted gas. Energy control circuitry is coupled with each separator device to control the energy input to each separator device. The control circuitry is actuated by an actuating device to first change and then restore the energy input to each of the separator devices in a selected sequence to thereby change and restore the dust concentration in the exhausted gas. Computation circuitry is coupled with the detector unit to compute the change in dust concentration resulting from a certain change in energy input to each of the separator devices in the sequence.

Abstract: A charging apparatus constructed to provide a continuous ac voltage and periodic pulses between the corona electrodes and non-corona electrodes contained therein.

Abstract: A control device for an electrostatic dust separator (10,11) intended to control in relation to the recorded level of direct current (104) and direct current voltage (102) in the dust separator and with the help of the supply voltage (6a) passes through the zero point the switching in and/or out of the rectifiers (8, 8a) wired into the power supply lead (6a) to the dust separator, usually in the form of two thryistors. The recorded value for the current (104) and the recorded value for the voltage (102) together with the information in respect of the passage through zero of the supply voltage (100) are connected directly via conversion circuits (25, 26) to a data processing unit (112).

Abstract: A high voltage pulse generator is provided which so interacts with the parameters of an electrostatic precipitator that excellent pulse waveforms are obtained more efficiently by using less elaborate components than heretofore required. A major feature of the invention is the charging of the pulse forming network through the high-voltage d.c. source which energizes the precipitator for charge-particulate removal.

Abstract: An automatic voltage control system controls the voltage delivered to the primary winding (12) of a step-up transformer (10) and hence the power delivered to a dehydrator (40) so as to prevent the step-up transformer (10) from exceeding rated power when a current limit occurs. The automatic voltage control system controls the voltage applied to the primary winding (12) so as to maximize the voltage applied to the grid elements (38) of the dehydrator (40). Upon encountering a current limiting condition, the automatic voltage control system reduces to zero the voltage applied to the primary winding (12) and hence the power applied to grid elements (38) of the dehydrator (40) to dissipate the cause of the current limiting condition. The voltage is reapplied to primary winding 12 at a voltage level below where the current limit occurred. The voltage is then increased to maximize the voltage applied to the grid elements (38) of the dehydrator (40).

Abstract: A method is disclosed for controlling the DC voltage of an electrostatic precipitator having electrodes energized by a preset DC voltage in which the preset DC voltage has pulses superimposed thereon. According to the method, the pulses are periodically turned off. Thereafter, the corona discharge current caused by the DC voltage is measured and compared against a preset value. Thereafter, the DC voltage is adjusted in dependence upon the measured corona discharge current by it being increased or decreased depending upon whether the discharge current is lower or higher than the preset value.

Abstract: An electrostatic precipitator (10) of the type having a casing (12) defining a precipitation chamber (6) wherein a plurality of discharge electrode frames (32) are disposed alternately between a plurality of collecting electrode plates (20). Paired probe devices (50) are mounted on the collecting electrode plates for sensing the strength of the electrostatic field generated by at least one discharge electrode wire (36) at at least one location on each of the collecting electrode plates (20) disposed adjacent thereto. The electrostatic field strength sensed by the paired probe devices are compared with each other to provide an indication of the degree of imbalance, if any, existing between the sensed electrostatic fields experienced by the bounding electrode plates.

Abstract: A method for detecting breakdowns in an electrostatic filter in which single measured values of equal phase of successive half waves of the filter voltage and crest values of successive half waves of the primary current are compared with one another and in which the differences of the measured values at which a breakdown signal is delivered are made dependent on the existing filter voltage or the primary current.

Abstract: A system for controlling the voltage of an electrofilter of the type which, after a voltage breakdown, substantially reduces the magnitude of the electrofilter voltage. After a predetermined deionization time, the filter voltage is raised to a new level which is lower than the filter voltage at which the initial voltage breakdown occurred, by a predetermined amount. The filter voltage is subsequently raised in accordance with a predetermined voltage-time function until a further voltage breakdown occurs. The electrofilter voltage is controlled by a microcomputer system in accordance with stored control parameter values. The stored control parameter values are advantageously recalled to control the electrofilter voltage in response to the operating state of a plant in which the electrofilter is employed.

Abstract: A power circuit for a precipitator utilizes a pair of silicon controlled rectifiers (SCR's) which are triggered by detecting the zero crossover of a power signal. The power transmitted through the SCR's is determined by the time period from the detection of the zero crossover to the generation of the trigger signal. Power signals are typically subject to noise which interferes with the detection of the zero crossover. Filters are provided for reducing the noise interference but function without altering the phase relation of the zero crossover of the filtered signal in respect to the unfiltered power signal. A pulse train of higher frequency than the power signal is generated to provide a plurality of triggering pulses for the SCR. Further, phase control signals are generated for each SCR to prevent the generation of trigger pulses when the SCR's are reverse biased.

Abstract: A method for operating an electrostatic precipitator with a DC voltage and superimposed pulses or superimposed AC voltage in which individual parameters such as amplitudes, pulse repetition frequency, pulse width, etc. are iteratively and continuously varied in such a manner that the sum of the pulse and the DC voltage power approaches a minimum. A computer which calculates, from the dust load and the absorbed electric energies of the filter, control commands for the DC and pulse voltage source is used for this purpose.

Abstract: In an electric dust collecting apparatus of the type that a dust collecting effect is achieved by applying a high D.C. voltage between dust collecting electrodes, wherein the high voltage is controlled via a typical power control device including thyristors, there is provided an additional control circuit for intermittently controlling the power control device to generate an intermittent high voltage output in such a manner that both the repetition rate and the pulse width of the D.C. high voltage output may be adjusted either manually or automatically so as to improve the dust collecting efficiency of the apparatus and to reduce the power consumption thereof.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: An active voltage divider providing output voltage overload protection operably effective in the event failure of the primary resistor should occur. Comprising the divider circuit is a differential amplifier operable as an integrator, a first pair of grounded diodes providing primary over-voltage protection for a first summing junction of the amplifier and a second pair of grounded diodes providing voltage backup protection for a second summing junction of the amplifier.

Abstract: A method and apparatus for providing a pulse-generating control to energize the electrodes of an electrostatic precipitator which includes means for producing a voltage between the electrodes of the precipitator after a voltage pulse has been applied to the precipitator electrodes which is higher than the voltage existing between the electrodes prior to the application of the voltage pulse and which voltage pulses are repeated until a preselected voltage is achieved between the electrodes.

Abstract: Voltage and current supplied to the primary winding of the transformer-rectifier (T-R) set of an electrostatic precipitator via silicon-controlled rectifiers and a reactor are automatically controlled by sensing spit and spark discharges within the precipitator and the phase shift which occurs between line voltage and line current (usually referred to herein as primary current) when precipitator voltage drops to a low value, as caused by a heavy spark or arc. Signals are developed therefrom which are used to control precipitator voltage through phase control of the SCR's. An arc is extinguished at the end of the current one-half cycle in which it starts. An inhibit circuit is provided for preventing detectable transients caused by SCR turn on from falsely triggering the automatic control system thereby permitting increased sensitivity in the spit sensing circuit.

Abstract: A system for automatically controlling the voltage of an electrostatic filter with respect to its breakdown voltage limit. The detection of secondary voltage breakdowns which occur within a post-breakdown time period after an initial voltage breakdown cause the filter voltage to be lowered to zero value. After a deionizing time period, the filter voltage is gradually raised during a predetermined rise time period until it reaches a new value. The duration of the deionizing time period and the rise time period may be advantageously computed in response to the history of voltage breakdowns, by a microcomputer system.

Abstract: The automatic recording of the current-voltage characteristic of an electrostatic filter in which the characteristic obtained upon stepwise variation of the control is displayed to the operating personnel and at the same time saturation phenomena and voltage maxima are picked up.

Abstract: A method for controlling the voltage of an electrostatic filter at the breakdown limit in which, when a breakdown occurs, the voltage is reduced by an amount which is determined by the breakdown voltage and the prior history of the breakdown and the waiting time to the next increase of the filter voltage is made dependent on the ratio of the voltages at successive breakdowns by comparing voltage amplitudes which immediately precede the breakdowns.

Abstract: A shorting and test mechanism for an electrostatic air cleaner uses an electrically conductive spring element attached to an access door to the air cleaner whereby an opening movement of the door effects a motion of the spring to contact the high voltage electrode support assembly to discharge any residual electrical charge on the high voltage assembly to ground. Conversely, the closing of the access door forces the spring away from the high voltage electrode assembly to permit a normal operation of the air cleaner. The spring is further connected to an electrically insulating test button located in an opening in the access door to induce by an operator a selective motion of the spring toward the high voltage electrode assembly whereby to test for the existence of the high voltage on the electrode assembly by providing an electrical arc path to ground through the spring when the test button is depressed.

Abstract: An automatic electronic reset current cut-off protection circuit for electrostatic precipitator air cleaner power supplies of the type utilizing a ferroresonant transformer having a primary winding, a secondary winding for producing relatively high voltage and a tertiary winding for producing a relatively low voltage. The circuit operates to inhibit power supply operation in the event of an overload in the ionizer or collector cell by sensing a voltage derived from the high voltage and comparing the sense voltage with a fixed reference. When the sense voltage falls below a predetermined value, current through the transformer primary is inhibited for a predetermined time. Current flow is automatically reinstated and the circuit will cyclically cause the power supply to shut down until the fault has cleared. The reference voltage is derived from the tertiary winding voltage resulting in increased sensitivity of the circuit to short duration overload conditions.

Abstract: A control system for automatically maintaining a maximum output voltage across the electrodes of a precipitator under varying load conditions without requiring manual readjustment of sensitivity controls. A spark threshold detector provides a threshold crossing signal when a spark occurs across the electrodes of the precipitator. Control circuitry including a ramp generator is responsive to the threshold crossing signal for providing a ramp signal which is effective to vary the voltage applied to the precipitator as a function of the desired spark rate. A sensitivity adjust circuit produces a compensating signal proportional to the magnitude of the ripple on the voltage applied to the precipitator. The DC level of the spark threshold detector is adjusted in accordance with the compensation signal so that the detector is insensitive to variations in the ripple whereby the predetermined spark rate is automatically maintained.

Abstract: A method and apparatus for optimizing the operating efficiency of an electrostatic precipitator based on controlling the average input power of the precipitator electrodes in response to control signals derived by sensing changes in specific instantaneous peak voltages associated with the average electrode voltages. The method is particularly well suited for electrostatic precipitators processing high resistivity fly ash and exhibiting an inflection region in its KVmin electrode voltage characteristic. The apparatus is organized to serve as a stand alone control system, or as an adjunct to existing electrostatic precipitator control systems.

Abstract: A thyristor power controller for rapidly varying the current delivered to a load and including: a clock circuit for developing a clock pulse for each zero crossing of an AC source, an analog phase circuit responsive to an adjustment current and operative to produce a firing signal for each clock pulse, a first thyristor acting on a positive half cycle of an AC source, a second thyristor acting on a negative half cycle of an AC source, a first thyristor control circuit enabling and disabling the first thyristor, a second thyristor control circuit enabling and disabling the second thyristor, and a thyristor selector operative to route the firing signal to the first or second control circuit.

Abstract: There is provided a precipitator system including a voltage controller which produces from an alternating power source a variable output. This variable output drives a high voltage converter which applies a high voltage to a precipitator. This variable output is controlled by a control signal from a command subsystem. Preferably, the command subsystem is operative to repress the drive to the high voltage converter in response to its loading exceeding a predetermined limit during a corresponding limit interval. After this limit interval, the command subsystem is operative to rapidly restore productive drive to the high voltage converter, preferably by the next half cycle of the power source that has a polarity opposite to that existing at the beginning of the limit interval. In this fashion stablized operation is quickly achieved. Also included, preferably, is a conductive element that is coupled to the high voltage converter.

Abstract: An improved precipitator voltage control system including an automatic voltage control (AVC) circuit, a firing circuit, an alarm circuit, a power-saving circuit, a remote set-point control circuit and a power supply, all of which are mounted on a single, readily interchangeable circuit board. The automatic voltage control circuit includes a highly responsive spark detection subcircuit which causes the transformer/rectifier voltage to be reduced to zero at the end of the half-cycle in which a spark occurs and then causes the voltage to remain at zero for a short period of time after which voltage is reapplied in a dual ramp manner causing it to rapidly reach a level below the precipitator arcing potential and then increase at a slower rate to the threshold of sparking. The firing circuit drives silicon-controlled rectifiers (SCRs) through optical couplers which provide several thousand volts of circuit isolation.