Patent Publication Number: US-2022228269-A1

Title: Cathodic protection system and minaturized constant current rectifier

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This continuation application claims the benefit of non-provisional U.S. patent application Ser. No. 16/297,982 filed Mar. 11, 2019, which is hereby incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The subject matter herein relates generally to cathodic protection systems and more particularly to cathodic protection systems for steel-in-concrete structures utilizing a constant current rectifier with a voltage limiter. 
     In order to protect steel-in-concrete structures, primarily including, but not necessarily limited to, individualized balconies on condominium or apartment-style units, from cracking, various cathodic protection systems have been utilized. In all such systems, an anode or a string of anodes is either laid on the concrete or embedded in it. The anodes are connected in a circuit containing a rectifier and the steel reinforcing bars. The current from the rectifier is sent through the circuit wiring to the anode at which point it passes through the concrete itself to the reinforcing bars and from there through a negative return cable to the rectifier. 
     One type of cathodic protection system is sometimes referred to as an overlay system. That system comprises disposing a plurality of flexibly interconnected anodes on the concrete deck or base to be protected and cementing them in place. That system basically consists of applying a conductive paint completely over the surface of the concrete layer containing the reinforcing bars. Thereafter, preferably, a series of small diameter platinum wires are attached to the concrete paint layer utilizing, e.g., strips of self-adhesive fiberglass mesh tape. The mesh is then covered with a layer of conductive paint. The anode system is completed and covers the entire concrete surface excluding a small radius around metal; typically, 2 inches in diameter and one inch from the edges. A cosmetic acrylic paint can then be put over the conductive paint. The anodes are connected to a rectifier controller through a header cable. 
     A need to provide constant, individualized current to each balcony has proven to be necessary for a combination of reasons. The traditional method using the typical cathodic protection rectifier uses a designed amount of protective current supplied to all the combined unit areas. In a residential condominium-style structure consisting of many exclusive use units, the cathodic protection rectifier method may: oversupply protective current to some exclusive balcony units, undersupply protective current to other exclusive balcony units, or supply no protective current to a number of exclusive balcony units. 
     There is no way to decipher whether all the unit balconies are receiving the design current or any protective current at all. An oversupply of current results in the burning of the anode, causing separation of the anode from the concrete—resulting in little ongoing protection. An undersupply of current or no supply of current allows for the corrosion to continue. Given these issues, there exists a need for customizable current protection without destructive testing. The disclosed invention achieves this goal by having an adjustable rectifier installed into each condominium receptacle area, where the direct current supplied to a unit varies according to the specific need of each such unique unit. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, a cathodic protection system utilizing a miniaturized constant current rectifier is provided. In the preferred embodiment, the system includes a power supply, electronic board converter, header cable, anode wire, and conductive transmitter, typically a conductive coating. 
     The miniaturized constant current rectifier preferably includes a power supply, an electronic circuit board to convert residential AC 120 V to Direct Current, and an electronic circuit board to adjust the output of Direct Current and to limit the voltage. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of the reinforcing steel mat in a concrete balcony slab. 
         FIG. 2  is an elevation view of the reinforcing steel mat in a concrete balcony slab. 
         FIG. 3  shows the AC power, rectifier, header cable, and anode wire placement. 
         FIG. 4  shows placement of an adhesive fiber mat over an anode wire to hold it in place for painting of a concrete slab, anode wire, and tape. 
         FIG. 5  shows the system portrayed without electrical wiring. 
         FIG. 6  is a flowchart of the entire cathodic system according to an embodiment. 
         FIG. 7  is a flowchart of the miniaturized constant current rectifier according to an embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following detailed description illustrates the claimed invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the claimed invention, including what is presently believed to be the best mode of carrying out the claimed invention. Additionally, it is to be understood that the claimed invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The claimed invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description 
     As shown in  FIGS. 1-6 , the cathodic protection system  100  of the invention is designed specifically to provide customizable constant current to individualized balcony condominium-style or similar type units  10 . The system utilizes a state of the art miniaturized constant current rectifier (See  FIG. 7 ) to ensure complete coverage. 
     Referring to an embodiment illustrated in  FIGS. 3-5 , the rebar  4  is placed at approximately ¾″ below the surface of the concrete  6  in the reinforcing steel mat  20 . Anode wire  8  is placed in a 1/16″ groove  12  cut into the concrete  6  for aesthetic reasons or directly on top of the concrete surface. An adhesive fiber mat  14  is placed over the anode wire  8  holding the wire in place so that conductive paint  16  can be added. 
     The power supply  18  includes a header cable  22  which supplies Direct Current. 
     As known to those who work in this field, a standard sized cathodic protection system is typically designed to protect up to forty balconies. Its cabinet, an integral piece of the total rectifying unit, usually measures 1.5 ft. deep×2 ft. wide×3 ft. high, or a total of 9 cubic ft. of space. Moreover, given their standardized features, the cathodic protection unit cannot effectively be made smaller no matter the number of balconies to be protected. Referring to  FIG. 7 , in an embodiment depicted therein, the miniaturized constant current rectifier (MCCR)  30  operates from Component Block A  32 , AC wall power (85 VAC to 265VAC at 50Hz or 60Hz, European or American power). The Component Block B is an AC to DC converter  34  with sufficient power capability to deliver the appropriate power (voltage and current) to the Component Block C Constant Current Control Circuit  36 . Such a miniaturized unit, designed to effectively protect an individual unit, only occupies @ 0.15 cubic ft., i.e., around 60× smaller that a standard cathodic protection rectifier which can fit into a half cell concrete block (8″×8″×8″). 
     Component Block B  34  typically uses (but is not limited to) common AC to DC conversion topologies such as switch-mode power supply (SMPS), AC Offline Switcher, Buck Converter, Fly Back, Fly Forward, continuous conduction, discontinuous conduction, step down transform and full or half bridge rectifier, AC to DC wall wart type. Component Block B is typically transformer isolated with a low voltage DC output for safety. Component Block B typically outputs insulated low voltage DC electrical power (such as 3.3V, 5V, 9V, 12V, 15V, 24V) for consumer safety, but it is not limited to low voltage DC electrical power. 
     Component Block C Constant Current Control Circuit  36  is responsible for accepting the input power (typically low voltage DC electrical power) and providing constant protective current to Component Block D Cathodic Protective Assembly. In cases where Component Block B is providing power other than low voltage DC, Component Block C has the capability to convert such power back into electrical current such as via an adjustable current potentiometer. From an electrical circuit perspective, Component Block D Cathodic Protective assembly  40  behaves as a variable electrical impedance/resistance based on the chemical reactions between the rebar, concrete and the coating. As the electrical impedance/resistance changes over time in Component Block D, the Constant Current Control Circuit will maintain the same current flowing. The voltage will adjust accordingly as the impedance/resistance of Block D changes. The voltage adjustment is used as a limiter to fail-safe to current flow. The adjustable voltage limiter is set at a value approximately no greater than, preferably 20-30% higher than the operating voltage. The operating voltage can be determined by the required voltage to maintain the desired current. 
     The exact implementation of the Constant Current Control Circuit can be varied (e.g., DC to DC converter, Buck, Boost, Boost-Buck, CUK, Linear current regulation, Current Mirror, etc.) so long as the device supplies a constant (stable) current at a desired level even though the impedance of the cathodic protective assembly changes. Examples of material changes may include, among other factors, changes in ambient temperature, salt intrusion, rain, dry season, wet season, wind direction, concrete chemistry change, etc. The Constant Current Control Circuit has the capability to manually adjust the current to account for various cathodic protective assemblies that are to be protected (e.g., in a concrete pad with rebar, the current requirements may be approximately in the range of 0.5 mA to 2 mA per square feet). As a protective feature, the constant current control circuit has an adjustable maximum voltage output. As the concrete cures, the impedance/resistance changes, usually decreasing with time; the rebar potential changes and usually less current flow is required for protection. Once the maximum (limiting) voltage is reached, the constant current control circuit automatically switches from constant current regulation to constant voltage regulation as an overprotection device. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.