CA2069881C - Electrical control system for electrostatic precipitator - Google Patents

Abstract

Form factor measurement and fault detection equipment to determine proper sizing of electrical components and efficien-cy of an electrostatic precipitator (22) by calculating a system form factor from either primary voltage or current. A power source (10) connects serially to an inverse parallel SCR 1 and SCR 2, to a current limiting reactor (16), and to a T/R set comprising a transformer (18) and rectifier (20) which supply power to precipitator (22). A current transformer (26) senses input current be-tween the reactor (16) and T/R set (18, 20) to signal an input scaling and signal conditioner (28) connected to a current meter (34), a voltage meter (39) and a computer (40) having a display monitor (42). The computer (40) is also connected to an SCR con-trol circuit (24) of SCR 1 and SCR 2. The appropriate electrical characteristic is converted to both its RMS value and average va-lue and then sent to the computer (40). The computer (40) divides the RMS value by the average value and sends the resulting form factor value to the display (42). If system form factor value is not sufficiently close to the purely resistive circuit value of 1.11, then equipment resizing is needed to increase system efficiency. Additionally, secondary electrical characteristics are used to calculate fractional conduction. If the fractional conduction is not sufficiently close to a desired level, equipment adjustments are made to increase system efficiency.

Description

20~g~81 ~ WO 91/0X053 PCr/US9010371~

ELECTRICAL CONTROL SYSTEM FOR ELECTROSTATIC PRECIPITATOR
F~,a~ rolln~ ~anr~ Summary of th~ Invention This invention relates generally to electrostatic precipitators for air pollution s control and, more specifically, concerns the electrical control of electrostatic ~)1 t~ d~Ol ~.
('ontimlollc emphasis on environmental quality has resulted in ia. l"d~ ly strenuous regulatory controls on industrial emissions. One technique which has proven highly effective in controlling air pollution has been the removal of undesirable 0 particulate matter from a gas stream by cl~ o~ld~ic ~ An electrostatic iLdLUI is an air pollution control device designed to electrically charge and collect particulates generated from industrial processes such as those occurring in cement plants, pulp and paper mills and utilities. Particulate laden gas flo~s through the precipitator where the particulate is negatively charged. These neg3tivel~ charged particles are attracted to, and collected by, positively charged metal plates. The cleaned process gas may then be further processed or safely discharged lo the atmos-phere.
To maximize the particulate collection, a p,~ ,ilalur should be operated at the highest practical energy level to increase both the particle charge and collection 20 .`arahjliti~C of the system. Co.~,ul,tlllly~ there is a level above which "sparking" (i.e., a temporary short which ereates a conductive gas path) occurs in the system. Left uncontrolled, this sparking can damage the ple~ iLdlo~ and control system. The key tOI"~ theefficiencyofanclc.llo~lalicpl~ iLdlu~ istooperateatthehighest energy level possible.
2s Ideally, the ClC.LIu~Ldlic precipitator should constantly operate at its point of greatest efficiency. Unfortunately, the conditions, such as tUII~ ,IaiUI~, CUlllbU:~I;U
rate, and the chemical ~UIIIIJU~iL;~III of the particulate being collected, under which an CI~LIu~LdLiC ~ àlul operates are constantly changing. This complicates the c~ ati-)nofparameterscriticaltoa~ Jildlol~soperation~ Thisisparticularlytrue 30 of the current limiting reactor (CLR) which controls and limits the current entering the precipitator and matches the Ul~ iLdLOI load to the line to allow for maximum power transfer to the ~ ;LalOI.
The current limiting reactor (CLR) has two main functions. The first is to shape the voltage and current wave forms that appear in the precipitator for maximum 3s collection efficiency. The second function of the CLR is to control and limit current.
Power control in a p~ J;LdLul is achieved by silicon controlled rectifiers (SCRs). Two SCRs are connected in an inverse parallel dlldllg~.lll.,.lL in series _ . . . _ _ . . .

WO 91/0X053 2 ~ 6 9 8 8 1 P~US90/0371 between the power source and the pl ~ dLUI high voltage ~ rù~ . . The power source is an slt~rn~tin~ current (AC) sinusoidal wave form whose value is zero at the beginning and end of every half cycle, and is a positive value during one half cycle and a negative value during the next half cycle. For a power source with a 60 Hz. frequency, S thiswouldoccurevery8.33millicPconl1~ (10millicernn-1cfora50Hz.powersource).
Only one SCR conducts at a time on alternate half cycles. The automatic voltage control provides gating such that the dlJIJI Upl i~lLC SCR may be switched on at the same point during the half cycle to provide power control. The SCR remains switched on or in rnn~ ctinn until the current passing through the SCR falls below a specified value o for the device. The cycle is then repeated for the next half cycle and the opposite SCR.
The SCRs cannot be switched off by the automatic voltage control. If the precipitator spark level is reached with no control of current to the precipitator, equipment damage can occur. The CLR provides a means of controlling and limiting the current rlow to the ~Ic~ dlOI until the conducting SCR switches off at the end of the half cycle.
5 Because of its critical role in ~ e elc.~lu~Ld~ic precipitator perfor-mance, it is vital that the CLR be properly sized. In the prior art, the CLR is si~ed at 30%-50% of the impedance of the Lld.-aru--ll.l/l..lirl~.l (T/R) set. This calculation results in a rough estimate of the ~ uliaL~ CLR size for a given arplic:~tinn The actual electrical efficiency is subjectively measured by viewing the shape and duration 20 of the wave form of the secondary current with an oscilloscope and estimating the fractional r~n~lllrtinn The CLR is then adjusted by trial and error in an attempt to obtain the desired fractional rnn~lllrtinn and, thereby, collection efficiency. Fraction-al rnnrlllrti~n and other methods used to size CLRs in the prior art have been crude and inaccurate, allowing for operational inrfficjellcy and equipment damage including 2s blown fuses, equipment failure and inefficient ~.lrUlllldlll,e from other ~,UIIII~UII~
of the system.
The ulu-lu~liull output of many industries may be limited by the amount of pollution discharged. The ~u.~ sets limits on the amount of pollution a facilitymay generate and discharge. In the event this limit is exceeded, a facility is suhject to 30 fines and temporary or permanent shut-down. Therefore, in terms of profitability, it is imperative that the electrostatic ~ dlUI operate at its highest efficiency, and in the event of a m~lfilnrtinn ",;";"..,;"~ down time is a high priority.
The prior art requires time consuming c~lrn~ onc to determine initial opera-tion settings for ~JIC~Ip;~dLUI controls. In the event of a m~lfilnrtinn or fault, deter-3s mining the exact problem and repairing or replacing the faulty ~ P.~l is timeconsumingandoftenrequiresdi~d~ ,ll)lillgofmuchofth~lc. ;~ dlo~ oritscontrols.

WO91/080s3 2~9~8 ~ PCI/~lS90/03714 .

These limitations of the prior art all lead to operation inefficiency, equipment damage, in~qll~tf~ p~.ru~ dll~c and increased pollution emissions.
Summ~l~ of the Jnvention A long felt need in the air pollution control industry remains for illlUl uv~lllcnts S intheelectricalcontrolofclc~llu~lalic~lc~;~)ildlul~toalleviatethemanyoperational and p~-rulllldll~c difficulties which have been encountered in the past. The primary goal of this invention is to fulfill this need.
Given the critical role the CLR plays in ~ e electrostatic precipitator . rul lllallcc, this invention provides an on-line means that accurately and dynamically o measures fractional conduction for sizing the CLR, replacing the "trial and error" used in the prior art. Another accurate method of analysis is to measure the root mean square (RMS) value and the average value of the primary current, then divide RMSby average to obtain the form factor. The theoretical form factor in a purely resistive circuit is 1.11. It is well known in the art that at a low form factor of d~Ulu~dll.dlely 1.2, maximum power transfer and collection efficiency is achieved. Accordingly, an object of this invention is to calculate the form factor to provide a ve}ifiable basis on which to measure electrical efficiency of the CLR and other electrical components.
Since a form factor can be calculated using primary voltage as well as primary current values, it is also an object of this invention to give the user the option of using either 20 value.
The electrical efficiency of the ul~ Jih~ùl is also dependent upon the secon-dary current waveforms. It is well known in the art that the length of time the secondary current waveforrn pulse is present during the half cycle is determined by the correct matching and proper design of the u, 1~.ipi~dlUI (,UIII~)UII~ . For example;
2s the T/R set, CLR and the size of the ~ ildlOI field must be matched for the precipitaIor to have maximum attainable collection efficiency for the application.
Prior art requires point by point l~ul ~,.ll~lll of secondary current wdvcrul lllS using an oscilloscope or similar device. Fractional ~nn~ ctirn is then calculated from the waveforms shown on the ~srill~ccopp 30 The duration of the pulse relative to the maximum duration possible (8.33 millic~corl~c for 60 Hz. applications and 10 mi1lisrconrlc for 50 Hz. applications) is known as the fractional ronflllr ion A fractional con~ tion of I would be considere~
ideal. That is, the secondary current pulse would be present for the entire half cycle of 833 millisPrQn(lc Fractional ~u, l"~ ~io,.~ of .86 normally yield full rated average 3s currents on a u, ~ dlOl load. Fractional fon-il-ctionc less than .86 result in less than full rated average currents on the precipitator which decreases the collection efficien-ey. Th~refore, it is a further object of this invention to ~ontinl~ucly measure the ~ ~ =

secondary current waveform and report the fractlonal conduction so that ad~ustments can be made, elther manually or automatically, in system c A~ts to 1nt~1n maxlmum collection efflciency. This ablllty to automatically measure and report secondary current fractlonal conductlon ls not available under the prior art.
It is also an ob~ect of this invention to give the user the optlon of uslng elther the form factor or the secondary waveform fractlonal conductlon as a means to slze the CLR.
Another ob~ect of thls lnvent lon ls to provlde these values ln such a way as to facllltate manual or automatlc ad~ustments to the CLR.
A further ob~ect ls to reduce start -up t lme by allowlng PIOYL -hle operatlng lnstructlons that can be calculated and down loaded lnto the automatlc voltage control.
Thls wlll relleve the operator of lnltlally havlng to calculate values and set the automatlc voltage control, CLR, and other electrlcal ,~ nt:~; whlch wlll save tlme and reduce operator error.
Another ob~ect of the lnventlon 18 to provlde a calculator from whlch the lmpedance of the CLR ls calculated.
Another lmportant ob~ect 18 to mlnlmlze repalr and troubleshootlng tlme and expense by provldlng an automatlc voltage control wlth the ablllty to dlagnose fault condltlons and ~uggest po~slble correctlve measures.
Another ob~ect of thls lnventlon ls to reduce repalr tlme and costs by locating oi'ten damaged n~-lts in an ... . . _ .. .. _ .. _ _ .. . ... ... _ .. .

easily accessible locatlon. All over-voltage protectlon is posltloned ln a plug-ln board. In the event that the automatlc voltage control ls damaged by over voltage, or modlflcatlons are needed for another appllcatlon, thls board can be removed and repalred wlthout dlsassembllng the entlre automatlc voltage control.
A further ob~ect of thls inventlon 18 to provlde a portable, stand-alone form factor and fractlonal conductlon meter for u~e separate from an automatlc voltage control.
Thl8 meter wlll calculate form factor or fractlonal conductlon for any electrostatlc preclpltator or slmllar equlpment and ~l~,tely lnform the operator how efflclently the equlpment ls performlng.
Another object of thls lnventlon 18 to provlde a novel method for calculatlng form factor and fractlonal conduct lon .
The present lnventlon may be summarized as an apparatus for detectlng and curing the performance of an electrlcal clrcuit operatlng at an efflclency level departed from a deslred level of efflclency, said spparatus comprising, senslng means for senslng the electrlcal characterlstlc waveforms of sald control system; comparlng means connected to sald senslng means for comparlng sald sensed electrlcal characterlstlc waveforms wlth theoretlcal characteristlcs to provide an indlcatlon of system operatlng efflclency~ and a current llmltlng reactor, whereln ad~ustments are made to sald current llmltlng reactor when sald system operatlng efflclency departs from sald deslred level, thereby controlllng power to - 4a -, ~ _ _ _ _ _ _, , _ , , , _ ~ 206988 1 sald circult and alterlng the waveform that 18 sensed to substantlally a desired waveform to 1ntA1n system operatlon at sald deslred level o~ e~f lclency.
Descrlptlon o~ the Drawlnqs - 4b -r.~ ~
, . . .

WO 91~08053 Pcr/USso/0371 5 2o698~ 1 In the a..u~ drawings whieh form a part of the specifieation and are to be read in conj~l~rtion therewith, and in whieh like referenee numerals are used to indicate like parts in the various views:
Fig. 1 is a bloek diagram of an electrieal sizing circuit eonstrueted in aeeordanee s with a preferred t;--.l,o;li--.~ of the invention for an automatie voltage eontrol eircuitry;
Fig. 2 is a bloek diagram illustrating in greater detail the input scaling and signal rr~n~liti(7nin~ eircuitry 5~ y shown in Fig. 1;
Fig. 3 is a block diagram illustrating in greater detail thG ulll~u~ a of the o computer control srh~m:~tirolly shown in Fig. 1; and Fig. 4 is a block diagram of the form factor and fractional r- n~ctil~n meter ofthis invention illustrated as a stand-alone test illa~l ulll.,~
This invention specifically contemplates determining the form faetor and fraetional ron~ tion of an clc.~l usLdlic precipitator to aecurately measure whether S the electrical eomponents are sized properly. A deviee to measure the form faetor and fractional ron~ rtion is described both as part of an automatic voltage control system and as a stand-alone meter. The invention calculatGs form factor and fractional ;ù ~ utilizing electrical ~ .. d.~cl ;a~ics such as voltage and current.
Utilizing the form factor to properly size electrical c~ as part of an 20 electrostatic precipitator's automatic voltage control is shown generally in Fig. 1 of the drawings. A power source 10, typically a 480-volt, single phase, AC power source, has two output terminals 12 and 14. Output terminal 12 connects serially to an inverse parallel SCR 1 and SCR 2, to a current limiting reactor 16, and to one side of the primary of a step-up Ll dllarUI 111.1 18. Output terminal 14 connects to the otber side of 2s the primary of L.dlljrull.l~l 18. The secondary of lldllar(JIllll,l 18 is connected across a full-wave rectifier 20 which supplies power to ~ dLul æ. Tl dllar~,l lll.. 18 and full-wave rectifier 20, in UIIII~illd~iOIl, is commonly referred to as the T/R set.
The positive output of rectifier 20 passes through a current meter 34 and resistor 32. The resistor 32 connects with an input scaling and signal rnnriiti~n~r 28 30 The negative output of rectifier 20 connects both to ~ Ui~dlUI 22 as well as through a resistor 36 and a resistor 38 to ground. The voltage aeross resistor 38 is sensed by a voltage meter 39 and voltage meter 39 connects with input scaling and signal con-ditioner 28.
A current ~Icl.laru~ .l 26 senses the input current and sends a signal to input 35 scaling and signal .ulldi~io"cr 28. The primary of a potential ~Id~arul~ l 30 is connected across the power input before Ll ~Illa~Ol 1ll~.l 18 and the secondary of trans-former 30 is connected to the input scaling and signal r~n~iitir)n~r 28.

'd69'~8~
WO 91/08053 ` rcr/us9o/o37 The output of input scaling and signal ( ~ ;nl~f, 28 is connected to a com-puter 40 which is connected to an SCR control circuit 24. Computer 40 is also connected to a display 42 and bi-directionally connected to an input/output port 44.
Display 42 may typically comprise an LM4457BG4C40LNY LCD display module such S as ~ r~ ltdbyDensitron.
Input scaling and signal ~ nn~iitinnPr 28 is shown in detail in Fig. 2. Primary current is received from current 1, ~ul~rul lll~i 26 and flows to two separate circuits, an averaging circuit 46 and an RMS circuit 48. The averaging circuit 46 has two opera-tional amplifiers 50 and 51 and two diodes 52 and 53. The up~ iulldl amplifiers 50 10 and 51 may typically comprise TL032CP chips as m:lmlf:~rtllred by Texas II~LI Ul~ lL~
of Dallas, Texas; and diodes 52 and 53 may typically comprise IN4148 diodes as also " .~ . ", r . I " l ~,d by Texas Il~ ulll~,llL~ of Dallas, Texas. The output of averaging circuit 46 connects with computer 40. The RMS circuit 48 has an operational amplifier 54, typically the above mentioned TL032CP chip, and an RMS converter 56, typically an 15 AD536AJD chip as m:~nllf:~rtllred by Analog Devices of Norwood, Ivl~ IIIC~P~
The output of RMS circuit 48 connects with computer 40.
Primary voltage is received from Ll,~ rullll.l 30 and flows to an RMS circuit 58. RMS circuit 58 is identical to RMS circuit 48 except that RMS circuit 58 receives primary voltage. The output of RMS circuit 58 connects with computer 40. The values 20 of a resistor 60 and a resistor 62 control whether the averaging circuit 46 receives primary voltage or primary current.
Secondary voltage is received from voltage meter 39 and passes through two operational amplifiers 64 and 65 (both typically TL032CP chips as m~nllf~rtllred by Texas Ill~LlUlll~l~Ls of Dallas, Texas) and enters computer 40. Secondary current 25 present in lu,c.i},iL~Iol 22 is received from current meter 34 and passes through external resistor 32. Resistor 32 converts the secondary current to a voltage which is directly lu, UpUI liull~l to secondary current. This voltage passes through resistor 37 and voltage .;olll,UrlrlUI 41 on its route to computer 40. Voltage UIll~ Lul 41 is a LM311N device as made by National SPmiron~ t()r Corporation of Santa Clara, 30 California.
Computer 40 is detailed in Fig. 3. A mllltirlPYPr 66 of computer 40 receives data from input scaling and signal ~u...l;liull~ . 28. Multiplexer 66 may typically comprise an ADG508AKN chip such as .,.~",lr~ l--l~,d by Analog Devices of Nor-wood, rl ' Mllltirlpvpr 66 is connected directly to a logic means 72 and 35 connected in series with a buffer 68, an A/D converter 70 and logic means 72. The buffer 68 may typically be a Texas III~LI Ulll~llLs TL032CP operational amplifier chip and the A/D converter 70 may typically comprise an AD573JN chip such as manufac-wo 91/08053 -2~ ~ 9 8 8 1 Pcr/usso/o37l4 ,.

tured by Analog Devices of Norwood, ~ "~ Logic means 72 is connected to SCR control circuit 24 and display42, and is bi- directionally connected to input/out-put port 44 and bi-directionally connected to a memory means 74.
Fig. 4 is a block diagram of a form factor and fractional ~on~ rtion meter as 5 would be used as a stand-alone device. External sensor 76, which senses both primary and secondary electrical cll~la-t~ Li~, is cormected to the input scaling and signal con-lition~r 28 which connects with computer 40, and computer 40 connects to display 42. A power source 78 will power input scaling and signal c.~, ..l ;~ io, .- 28, computer 40 and display 42. Power source 78 may consist of circuitry allowing the meter to plug o into an external power source, or a battery or similar power supply. Sensor 76 may typically be a clamp as found on many models of current meters. It should be understood that sensor 76 may comprise a plurality of sensors. Sensor 76 is shown in block form for illustrative purposes.
In operation, the primary ~ ., .l ~vl l ;., ~ , l of this invention is to work in coopera-15 tion with an ele.~lu~dlic ~ d~Ul automatic voltage control device. A repre-sentative example of an cle.,~l us~,lic ,U~ UtOl automatic voltage control is shown in my earlier patent U.S. Patent No. 4,605,424, issued August 12, 1986 and entitled "Method and Apparatus for Controlling Power to an Electronic Pl~ lol", which is ill~ul~ulaL~d by reference herein. It should be recognized that, while these two 20 inventions may share hardware, the problems addressed by each are distinct. The '424 patentcontrolsvoltageorpowertotheyl~ ila~ulwhilethisinventionaddressesthe inrffirirn~yofil,l~,uu~,,lysizedcu,llpo~ of anelectrostaticlvl~ dlol~
Upon start up, input/output port 44 is utilized to . ",.,.,.""~ illrul llldliUll to logic means 72 within computer 40. Cull~lllull;.alion may be ~rr/~mrliche(l through a 25 built-in keyboard, portable lap-top computer, remote computer connected to the input/output port 44 directly or by modem, or by a similar means. Equipment size and power levels are - ~ which allows initial c~ tion~ by logic means 72 to determine the proper setting of CLR 16 and other settings for other C~Ui,lJI~ ll. CLR
16 and other equipment may be set ~ ", ~ lly, or the alJ~l U,Ol iale values may be 30 sent to display 42 and the equipment set manually according to the previouslycalculated settings. The l",l,c 1- ~ of CLR 16 is calculated using calculator screens ~Jl u~ a~lllllcd into computer 40. The irnre~l~nr~ is expressed as a per~c-,ldgc of the T/R set.
In addition to equipment size and power levels, the desired spark rate, SCR
35 firing angle, fault conditions and all other information required by the automatic voltage control to supply power to the ,U~ ild~UI is communicated through input/output port 44 to logic means 72. This relieves the operator from having to WO91/080S3 ~9~81 Pcr/usgo/037l~ ~

manually set the equipment and helps to eliminate operator error. I~rulllldLiull and calculated values required for future reference are sent from logic means 72 to memory 74.
The desired power level is sent from logic means 72, within computer 40, to 5 SCR control circuit 24 where the power level is converted into an SCR firing angle.
Power is applied to p.e.,;~ d~u~ æ in terms of SCR firing angle degrees. The sinusoidal electrical cycle consists of 360 degrees, and consists of a positive half cycle and a negative half cycle with respect to polarity. Each SCR can be fired anywhere from 0 degrees to 180 degrees in the electricai cycle, 0 degrees being full power and 0 180 degrees being 0 power. When an SCR is fired at 45 degrees, for example, it will conduct from 45 degrees to 180 degrees. Therefore, a difference in firing angles can be represented as a distance along the abscissa of the sine wave. Due to polarity reversal, the SCR stops eonAllctin~ when the current passing through the SCR falls below a specified value for the device.
The normal operating state of SCR 1 and SCR 2 is 180 degrees which allows 0 power from power source 10 to pass through to ~ d~UI 22. After SCR firing circuit 24 translates the power level into the ~ Jlu~Jli,lt~ angle, this angle is sent to SCR I and SCR 2 which begins allowing the ~ JIUUI i~le power to pass from power source 10 down line to step-up II llafOIlll. I 18 and fuli-wave rectifier 20, and even-20 tually to 1~l t ~ d~UI æ.
SCRlandSCR2inherentlyproducesharprisesinp~ 1l.,;l lca~c~,1ivefiring angles dictate each SCR to energize. Thus, a primary object of CLR 16 is to filter and shape the signal leaving SCR 1 and SCR 2. Ideally, the shape of the secondary current filtered wave will be a broad, rectified sinusoidal waveform since 2s the average value produces work. Such a waveform yields the best UlC~ d~UI
collection efficiency. Ideally, the peak and average values of the signal entering pl "~ a~o~ 22 will be very close.
In addition, maximum power transfer is attained when load imreA~n~e matches line i,.,l,eA ,.,. - CLR 16 is set so that its inductance matches total circuit 30 impedance including the ~ dlUI load. This is attained by measuring the form factor and sizing the equipment within the circuit to attain a form factor d~)~l Od.llillg 1.11.
Full-wave rectifier 20 converts the AC signal which passes through SCR 1 and SCR 2 into a pulsating DC signal. The positive output of full-wave rectifier 20 passes 35 through current meter 34 and resistor 32 to ground. The negative output of full-wave rectifier 20 connects directly to ,ult~;l)ildlOI æ as well as through voltage dividing resistors 36 and 38 to ground. Voltage meter 39 is in series with metering resistor 36.

2~69~f~
WO 91/OiO53 PCI /US90/0371 Current meter 34 and voltage meter 39 are utilized to sense operating conditions when sparking occurs in plc~;~Jildlvl 22 and to sense fault ~ o n-iitil-nc The data obtained from voltage meter 39 and current meter 34 are sent to input scaling and signal ~n(litioner 28 and eventually to computer 40.
5 Current Lldll~rvllll~l 26 measures the primary current and IIL~ rvlll-~l 30 provides the primaty voltage with respect to ll ~l~rul 1~ 18. These values are sent to inputscalingandsignal ~o...llliv~ 28wheretheyareconvertedtoastatewhichallows the form factor to be calculated.
The circuitry that is principal to this invention can be found in hg. 2. Primary0 current and voltage along with secondary current and voltage each enter input scaling andsignal.ol-.l;liv,.~ 1 28. Primarycurrentfromcurrent~ld.l~rol.ll~,. 26isintroduced and flows to averaging circuit 46 and RMS circuit 48.
The first half of averaging circuit 46 is a precision rectifier consisting of anoperational amplifier 50 and two diodes 52 and 53. This precision rectifier provides 5 a DC output that is not offset by the voltage drop of the diodes. A second operational amplifier 51 provides an averaging circuit such that the input of the total circuit 46 is AC and the output of the total circuit 46 is DC, ~l VIJVI Liol~dl to the average value of the AC wave. The output of averaging circuit 46 is routed to computer 40.
The primary current also enters an RMS circuit 48. Operational amplifier 54 20 provides an input buffer and signal L ~ while RMS converter S6 changes the AC input to its RMS value and this value is routed to computer 40. Computer 40 now has primary current in two forms: average and RMS.
T.~.~ro..l.~r 30 provides primaty voltage to input scaling and signal con-ditioner 28. The primary voltage enters RMS circuit 58 which changes the AC input 2s to its RMS value, in the same manner as RMS circuit 48, and this value is routed to computer 40.
Two resistors 60 and 62 are provided. When resistor 60 is short and resistor 62 isopen,theinputscalingandsignalL~..~.l;l;r)l-f . 28isconfiguredtoreadthetrueRMS
value and average value of the primaty current for measuring form factor. By opening 30 resistor 60 and shorting resistor 62, the true RMS value and average value of the primary voltage can be used to calculate form factor. At all times the true RMS of both primaty voltage and primary current are provided. Resistors 60 and 62 allow the option of calculating either the average of the primary current or the average of the primary voltage so that the form factot can be calculated using either current or 3s voltage.
Secondary current and voltage signals from circuitry associated with current meter 34 and voltage meter 39 both enter input scaling and signal ~onrlitionf~r 28 3 ~6~8~ Pcr/usso/o37l1 ~

Secondary voltage passes through U~ dliOil~l amplifiers 64 and 65 which providesisolation and scaling before it is routed to computer 40. The secondary current signal from resistor 32 is routed through resistor 37 to voltage ~u~ Lul 41. Voltage ~UIII~)~IdLUl 41 compares the voltage proportional to the secondary current in s ,u~ ,ila~o- æ with a reference voltage. Ideally, the reference voltage would be zero volts. Preferably, since voltage CUIII~ UI 41 is not an ideal device, and therefore, has some input offset voltage, the reference voltage is set slightly above zero volts.
The output of voltage ~u...~. 41 will become positive when the secondary current present in l~-c~;yi~lul æ is greater than zero. The output of voltage com-o parator 41 will become zero volts when the secondary current present in ~ u,æ iS zero. Therefore, the output of voltage ~;ull~ lUl 41 is a pulse width that is~IlUlJUl~iO~ to the length of time that the secondary current pulse is present in pl~ d~Ol 22. This pulse width is routed to computer 40.
Computer 40 is pre-,ulu~lallllllcd with the maximum duration of pulse width possible for various line & ~.1U~ ;C5, or, alternatively, computer 40 could calculate the maximum pulse width possible for a desired frequency. For example, 833 mil-liseconds for 60 Hz. and 10 millic~cr,n~lc for 50 Hz. Computer 40 measures the duration of the pulse width received from voltage ~ ol 41 and divides the measured pulse width by the maximum duration of pulse v~idth possible for selected 20 line frequency to obtain fractional ~ ;u" It should be llntl~rstood that although division is preferred, the actual and theoretical values may be compared in another manner to obtain fractional ~ i.., . data.
Fractional rr,n~ rtjr,n data is stored in memory 74 of computer 40 so that is can be ~"b~ lly retrieved. The data can be displayed locally on display 42. In 25 addition,itcanbell~-l-~---i~l~dtoaremotecomputerorotherdisplayorcontroldevice.
If the fractional conduction is not ~urrici~lllly close to a preferred level, corrective equipment I-'Ij- ~l 1.,...1~ are made toyield a more efficient output. Fractional conduc-tions of .86 normally yield full rated average currents on a 1~ C.;~ Iul load.
Ml-ltirl~Ye- 66 accepts each of the output signals of input scaling and signal 30 r~n~litir,n~-r 28. Upon a signal from logic means 72, I..,lllil,l.... 66 allows one of the inputsignalsfrominputscalingandsignali.,..,l;l;~. .28topass. Thissignalpasses through buffer 68, is converted to a digital signal at the AID converter 70 and enters logic means 72. When logic means 72 receives both an RMS value and an average value for either primary current or primary voltage, the RMS value is divided by the 35 average value to obtain the form factor. It should be understood that the RMS and average values could be compared in another manner to obtain form factor data. The form factor value is then transmitted to display 42. Display 42 can be a liquid crystal WO 91/080S3 2 ~6 9~ 8 ~ PCr/USsO/03714 display or similar digital display, a CRT displaying the value graphically, a printed numerical or graphical ~ s~l-~Liu-l or similar display. It is also lln~lPrctood that the form factor value can be transmitted to input/output port 44 and obtained remotely.
An operator evaluates whether this form factor value is sufficiently close to the 5 l.lI ideal value. If not, e.lu~ sizing is manually adjusted. It is also understood thatthiscanbeaclosedloopsystemwheretheCLR 16is~ltr,m~tir~11yadjustedupon the d~l~,l ll.i-lalion of a poor form factor.
To mirlimize repair and trouble shooting time in the event of ""~ r~ .,y system ~,lro.---a..~e, plu~;laulllll~,d help screens are employed. The programs diag-o nose fault conditions and display heip screens on display 42. The help screens suggestpossible corrective measures to the operator so that alJ~lU~JIiale corrective adjust-ments may be made to increase system operating efficiency to a desired level.
Ail four inputs to mllltirlPY~r 66 are retrieved and analyzed by logic means 72 rapidly and ~u.,l;,..,u~ y. When logic means 72 tlPtPrminPc that current meter 34 iel-~d a sudden increase in current, a spark condition in p,~ o, 22 is analyzed. Upon d~,~ll--i-lil.~ a spark in ~ a~ùl æ, logic means 72 transmits i--rulll~àliul- to SCR control circuit 24 to not energize again until the spark is extin-guished. Since SCRs cannot shut offuntil the current passing through the SCR falls below a specified value for the device, up to an 8.33 millicPcr,n~i delay, CLR 16 limits 20 the current to yl ~ ul æ until the SCRs actually stop . .,n~ The time delay before rc Cll~ ;;L;II~ and the procedure for d~- l--i--ill~ the alJ~I UIJl ia~ firing angle with which to start energizing the SCRs is part of the automatic voltage control logic sequence and is detailed in the '424 patent.
The '424 patent also details how fault conditions are recognized and power shut 25 down attained. But, in the '424 patent, determining what type of fault, the cause, specific location of the fault and potential solutions is left to the operator. The present invention incorporates diagnostic ~ i c which greatly reduce down time~ There-fore, computer 40 is fitted with non-volative memory 74, a device capable of retaining i~rul lllaLiu-l when the power is removed. When the analog inputs to input scaling and 30signal ....I;~jr.~ . 28 provide logic means 72 with a known fault condition, the i--rul IllaLiull necessary to troubleshoot the ~ t~l 22, or its control circuits, and Suggesl corrective action can be retrieved from memory 74 and ~l al~ll.;LItd to display 42. For instance, if the primary and secondary current is found to be very high and the primary and secondary voltage found to be very low, this indicates a short condition.
35 The memory device containing its pre-~,lu~;.all.l..~d illrul~llaLiull informs the com-puter 40 of a short condition. Computer 40 then analyzes the condition, retrieves the wo 91/0X053 ~ 20 6 ~ 8 ~ ~ Pcr/usso/o37l~ ~
~u,u~, wu~dil~æforashortandthecorrectivemeasurespre-,ulu~l~ulull.,dintomemory 74, and routes them to display 42.
A major problem with the prior art has been that automatic voltage controls areconnectedtoa~ lul thatoperatesonanumberofvoltages. Thelinevoltage 5 is normally from 380-575 volts, 50-60 Hz. The secondary voltage is roughly 50,000 volts. The automatic voltage control runs on five (5) volts. The electrical supply is 120 volts. These diverse voltages create difficulties when isolating and protecting the circuitry from varying voltages.
For instance, a shorted primary to secondary ll~u~rul.ll~,. 18 can deliver 0 damaging voltages. Therefore, a means must be available of protecting the automatic voltage control that can be easily and quickly repaired. This invention provides the automatic voltage control with a plug-in input circuit board where all the scaling and over-voltage protection is contained. When the automatic voltage control is wired into the system, it does not have to be removed to be repaired. This results in 5 significant time and cost reductions.
The above mentioned form factorand fractional c on~illrtion lll~laul-,lll.,lll can be a part of the automatic voltage control that controls the SCRs or can be developed as a separate testing device to measure the efficiency and proper sizing of CIC.LI ùal~--iC
,UI~,.;t~i~lUI ulll~JO~ lla. Fig. 4 shows a form factor and fractional conduction meter 20 as a stand-alone device. This device consists of sensor 76 which can typically be a clampfoundonmanypresentcurrentLI~ ru~lll.,.~. Sensor76willsensetheprimary current of an CIU.ll u~lrliC ~ ;u;t;~Lul or similar device and provide this as an input toinputscalingandsignal~ iitionrr28. Inputscalingandsignal~.".i;l;.",~ . 28will convert this current Ill~ ul~,.llellL to the average current and true RMS values. The 25 true RMS value and average current value will be sent to computer 40 where the form factor ~ ' ' will be performed.
Additionally, sensor 76 detects the secondary current in the ~ Lul . Input scaling and signal non~iitio~ r 28 receives the secondary current signal and converts it to a pulse wave signal with a pulse width l ~ al,llLil~g the duration of time secondary 30 current is present in the pl~,.;piLa~ol. This converted signal is sent to computer 40 where the fractional ~Qn illrtion ~lrlll~ti~nc are performed. Once the form factor and fractional ~on illctinn are determined, these values will be transmitted to display 42 for the operator to read and analyze the efficiency of the equipment being measured.
Power source 78 will be available to drive each of these ~Ollll~ull~llLa. As a stand-alone 3s portable device, this form factor and fractional con~illcti~n meter will be valuable to quickly and safely determine the present operating efficiency of electrostatic ,UI~ ,;L~lu.~ and similar equipment.

O9l/0805~ 2~3881s ~ PCr/[!S90/03714 ' ` 13 From the foregoing it will be seen that this invention is one well adapted to attain all end and objects hc.~,;.l.lbuve set forth together with the other advd~ s which are obvious and which are inherent to the structure.
It will be understood that certain features and ~ "~ if)n~ are of utility 5 and may be employed without reference to other features and ~ub~blllbil~d~ . This is contemplated by and is within the scope of the claims.
Since many possible ~mhodim~ntc may be made of the invention without departing from the scope thereof, it is to be ~ od that all matter herein set forth or shown in the L , .~;llg drawings is to be interpreted as illustrative and not in o a limiting sense.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS,

1. An apparatus for detecting and curing the performance of an electrical circuit operating at an efficiency level departed from a desired level of efficiency, said apparatus comprising:
sensing means for sensing the electrical characteristic waveforms of said control system;
comparing means connected to said sensing means for comparing said sensed electrical characteristic waveforms with theoretical characteristics to provide an indication of system operating efficiency; and a current limiting reactor, wherein adjustments are made to said current limiting reactor when said system operating efficiency departs from said desired level, thereby controlling power to said circuit and altering the wavefoam that is sensed to substantially a desired waveform to maintain system operation at said desired level of efficiency.

2. The apparatus as in claim 1 in cooperation with an electrostatic precipitator control system including means for calculating the form factor of said system, wherein said sensing means senses electrical characteristic waveforms selected from the group consisting of voltage and current, said apparatus further comprising:
a conditioning circuit, connected to said sensing means, for conditioning the electrical characteristic that has been sensed into values utilized in calculating said form factor, said conditioning circuit including means for changing the electrical characteristic that has been sensed into its average value and means for changing the electrical characteristic that has been sensed into its RNS value;
said comparing means comprising a computer with logic means for calculating said form factor value, said computer connected to said conditioning circuit and said adjusting means, whereby said logic means include means of retrieving said RNS value and means of retrieving said average value and comparing said RNS value with said average value to obtain said form factor value, whereby said adjustments made to said current limiting reactor if system operating efficiency departs from a desired level are based on said form factor value; and a source of electrical power connected to said conditioning circuit and said computer.

3. The apparatus as in claim 2, said control system including a transformer, said transformer having a pri-mary side and a secondary side with primary and secondary electrical characteristics associated therewith, whereby said sensing means sense the primary electrical charac-teristic waveforms selected from the group consisting of voltage and current for utilization in the calculation of said form factor value.

4. The apparatus as in claim 1 in cooperation with an electrostatic precipitator control system including means for calculating the fractional conduction of said system, wherein said sensing means senses the electrical current waveform in said precipitator, said apparatus further comprising:
a conditioning circuit, connected to said sensing means, for conditioning said electrical current waveform into a value indicative of the duration of time said electrical current is present in said precipitator;
a computer connected to said conditioning circuit for calculating said fractional conduction, said computer including logic means, said logic means including means for retrieving said value indicative of the duration of time said electrical current is present in said precipi-tator and comparing said value to a theoretical value at a preselected frequency to obtain said fractional conduc-tion value, whereby adjustments are made to said current limiting reactor to increase system operating efficiency if said fractional conduction value departs from a de-sired level; and a source of electrical power connected to said conditioning circuit and said computer.

5. The apparatus as in claim 4, said control system including a transformer, said transformer having a pri-mary side and a secondary side with primary and secondary electrical characteristics associated therewith, whereby said sensing means senses the secondary electrical cur-rent waveform for utilization in the calculation of said fractional conduction value.

6. The apparatus as in claim 1 in cooperation with at electrostatic precipitator control system, said control system having a transformer, said transformer having a primary side and a secondary side with primary and sec-ondary electrical characteristics associated therewith, said apparatus including means for calculating the form factor and fractional conduction of said control system, said apparatus further comprising:
said sensing means for sensing the primary waveform electrical characteristic waveforms of said control system;
detecting means for detecting the secondary electri-cal characteristic waveforms of said control system;
a conditioning circuit, connected to said sensing means and said detecting means, for conditioning said sensed primary electrical characteristics into values utilized in calculating said form factor value and condi-tioning said detected secondary electrical characteris-tics into values utilized in calculating said fractional conduction value, said conditioning circuit including means for changing said sensed primary electrical charac-teristics to their average value, means for changing said sensed primary electrical characteristics into their RMS
value, and means for changing said detected secondary electrical characteristics to a value indicative of the duration of time a secondary current is present in said precipitator;
a computer connected to said conditioning circuit for calculating said form factor and said fractional conduction, said computer including logic means, said logic means including means of retrieving said average value from said conditioning circuit and means of re-trieving said RMS value from said conditioning circuit, and means of comparing said RMS value with said average value to obtain the form factor value, and said logic means further including means for retrieving said value indicative of the duration of time said secondary current is present in said precipitator and comparing said time value to a theoretical time value at a preselected fre-quency to obtain said fractional conduction value, where-in said form factor value and said fractional conduction value indicate system operating efficiency; and a source of electrical power connected to said conditioning circuit and said computer.

7. The apparatus as in claim 6, wherein said sensing of primary electrical characteristics further includes sens-ing the primary electrical characteristic waveforms selected form the group consisting of voltage and cur-rent; and said detecting of secondary electrical characteris-tics further includes detecting the secondary electrical characteristics selected from the group consisting of voltage and current, whereby said form factor value and said fractional conduction value provide a plurality of measurements each individually indicating said system operating efficiency.

8.. The apparatus as in claim 1 in cooperation with an electrostatic precipitator control system, to recognize circuit fault conditions and to de-energize said electro-static precipitator upon the detection of a fault condi-tion, said apparatus further comprising:
display means connected to said computer;
memory means connected to said computer;
means for storing pre-determined fault conditions in said memory;
means for storing potential causes and corrective measures to said fault conditions in said memory; and said logic means further including means of deter-mining said fault conditions, and de-energizing said electrostatic precipitator upon determination of a fault condition; said logic means further including means to analyze said fault conditions, means to retrieve the corrective measures pre-programmed into said memory for the appropriate fault, and means to route said corrective measures to said display.

9. The apparatus as in claim 8 including an input/output port connected to said computer, and wherein said logic means includes means to transmit said form factor value and other operating conditions to said input/output port, and means to receive from said input/output port initial operating conditions, fault conditions, initial electrical equipment sizing and other information necessary for the start-up and operation of said electrostatic precipitator.