Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Patent
1985-05-13
1987-11-03
Hix, L. T.
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
361235, 323903, 55105, 55139, B03C 366
Patent
active
047046724
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates on the one hand to a method and on the other hand to an arrangement permitting the simple variation of a voltage occurring between the electrodes of an electrostatic dust separator. This voltage is generated from a number of frequency-related current pulses which occur consecutively one after the other, in this way forming a pulse train.
DESCRIPTION OF THE PRIOR ART
Previously disclosed are electrostatic dust separators in which the voltage occurring between the electrodes of the dust separator is built up by supplying energy in the form of current pulses.
Also previously disclosed is the connection to the electrodes of the dust separator of a d.c. voltage on which is superimposed an a.c. voltage. The a.c. voltage in this case can have the form of pulses.
As an example of the prior art of the first mentioned kind reference may be made to the arrangement illustrated and described in English Patent Specification No. 728 061. Conditions have been created in this arrangement for the electrostatic separation of particles from a flow of gas passing over the electrodes by causing the voltage to vary within a range of frequencies of between 20 and 120 pulses per second, and by connecting between the pulses a positive potential of relatively small amplitude.
As an example of the prior art of the next mentioned kind reference may be made to the arrangement illustrated and described in Amer. U.S. Pat. No. 4,138,233. Presented here are various possibilities for the superimposition of pulses over a first level of d.c. voltage or for the connection of various a.c. voltages to said level of d.c. voltage, in this way attempting to render the dust separation more effective. What is shown here is that the d.c. voltage has superimposed on it square pulses, a complete sinusoidal oscillation, a half-wave rectified voltage or a periodically occurring complete sinusoidal oscillation. Reference is also made to the variation of the peak value, the pulse width and/or the periodicity.
Also previously disclosed is the superimposition on a d.c. voltage of individual pulses by utilizing an oscillating circuit, at the same time making use of control circuits to ensure that only one of the oscillating pulses will be supplied to the dust separator. The time between consecutive individual pulses is selected so as to be large, and returned energy from the dust separator is stored in a storage capacitor. As an example of the prior art in this respect reference may be made to an arrangement illustrated and described in U.S. Pat. No. 4,052,177.
Thus it may be established that a large number of proposals has already been disclosed relating to the variation of the voltage in a dust separator, and in respect of the energy supply via current pulses individual pulse lengths ranging from a few microseconds to tens of milliseconds have been proposed.
Also part of the prior art is the arrangement illustrated and described in English Patent Specification No. 684 226 in which the length of the period between two consecutive pulses is either `zero` or two pulses.
DESCRIPTION OF THE PRESENT INVENTION
Technical Problem
Against the background of what has previously been disclosed, it is clear that it must be a particularly challenging technical problem to create voltage conditions in the electrostatic dust separator and to select a variation in the supply of pulsed current such that a desired degree of cleaning will stand in a reasonable relationship to the cost of the control circuit and the other equipment which is to generate the necessary and appropriate variation in the voltage.
A particularly challenging technical problem is also encountered in conjunction with the creation of conditions such that a pre-determined degree of separation or degree of cleaning can be achieved, and such that the degree of cleaning can be regulated in a simple and efficient manner by the evaluation of easily accessible parameters.
A particularly challenging technical problem is also encountered in conjunction with the
REFERENCES:
patent: 4284417 (1981-08-01), Reese et al.
patent: 4486704 (1984-12-01), Gustafsson et al.
patent: 4490159 (1984-12-01), Matts
Flakt AB
Hix L. T,.
Rutledge D.
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