Electricity: power supply or regulation systems – External or operator controlled – Using a transformer or inductor as the final control device
Patent
1994-11-22
1998-01-06
Hecker, Stuart N.
Electricity: power supply or regulation systems
External or operator controlled
Using a transformer or inductor as the final control device
363 90, 323903, G05B 2462, H02M 542
Patent
active
057059233
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates generally to the control of electrostatic precipitators and, more specifically, concerns the electrical adjustment of an electrically variable current limiting reactor (VICLR) utilized in an electrostatic precipitator control system.
Controlling air pollution is an important environmental goal and is the subject of increasingly strenuous regulation. Electrostatic precipitation, which involves the removal of undesirable particulate matter from a gas stream; is one highly effective air pollution control technique. An electrostatic precipitator is an air pollution control device designed to electrically charge and collect particulates generated from industrial processes. These particulates flow through the precipitator where they are charged. Oppositely charged plates then attract and collect these negatively charged particles. The cleaned gas may then be further treated or discharged to the atmosphere.
Maintaining precipitator collection at its greatest efficiency is an important, yet often difficult task. Conditions under which electrostatic precipitators operate can fluxuate dramatically having a detrimental effect on the operating efficiency of the precipitator. Less than maximum precipitator efficiency results in increased pollution to the atmosphere--perhaps to the point of exceeding regulatory limitations. Accordingly, controlling and maintaining precipitator collection efficiency is an important objective.
BACKGROUND OF THE INVENTION
The background for the present invention is significantly described in U.S. Pat. No. 5,068,811 (the '811 patent), issued Nov. 26, 1991 and entitled "Electrical Control System for an Electrostatic Precipitator" which is incorporated by reference herein. The '811 patent teaches that the waveforms that make up the voltages and currents in the precipitator control system are highly important to precipitator collection efficiency.
More particularly, the '811 patent teaches that two measurements which are highly effective for evaluating waveform shapes, and their effect on the precipitator collection and electrical efficiency, are primary form factor and secondary fractional conduction. Maintaining form factor and fractional conduction at desired levels produces maximum system operating efficiency. This is accomplished through proper sizing of electrical components embodied in the control system. Particularly significant is the appropriate sizing of a current limiting reactor (CLR) utilized by the system.
Generally described, electrical circuitry within the control system as disclosed in the '811 patent monitors system electrical characteristics such as voltages and currents on both the primary and secondary side of a transformer rectifier (TR) set. An input scaling and signal conditioner contains circuitry for manipulating these characteristics into data useful for calculating form factor and fractional conduction. This data is sent from the signal conditioner to a computer with logic and memory capabilities for calculating the form factor and fractional conduction values.
For purposes of the present invention, the input scaling and signal conditioning circuitry and the computer, including the computer's peripheral devices such as display, input/output port, and keyboard, are collectively referred to as the "automatic voltage control" or AVC. The computer within the AVC is also connected to a SCR firing circuit which is in turn connected to inverse parallel SCRs which are connected serially with a power source. In the most general of terms, these SCRs, when triggered, allow power flow to the overall electrostatic precipitator control system. The SCRs are connected to the CLR which is in turn connected to a transformer rectifier (TR) set which powers the precipitator.
During operation, if the form factor or fractional conduction departs unacceptably from a desired value indicating undesirable and inefficient waveform shapes, the inductive sizing of the CLR is adjusted to yield desired waveforms which in turn result in desired fo
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patent: 3374609 (1968-03-01), Kide
patent: 4405965 (1983-09-01), Weldon et al.
patent: 4558271 (1985-12-01), Poole
patent: 5068811 (1991-11-01), Johnston et al.
patent: 5515262 (1996-05-01), Johnston et al.
Johnston David F.
Lawrence Timothy Gerald
Mahler Michael McCall
BHA Group, Inc.
Hecker Stuart N.
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