Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
2000-08-21
2002-10-22
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C205S726000
Reexamination Certificate
active
06469918
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to solid state cathodic systems for reducing or preventing corrosion of metallic devices, structure or apparatus by applying a rectified DC potential across the metallic apparatus having a minimal AC component. The present invention also relates to methods for making and method for using the systems.
More particularly, this invention relates to solid state cathodic systems for reducing corrosion of metallic devices, structures, or apparatus where the cathodic systems transform, rectify and convert an AC input from an AC power source into a substantially square-wave output having a substantially constant DC component and a minimal AC component, i.e., the output appears substantially as a square-wave output when viewed at or near a frequency of the output and appears substantially as a DC output when viewed at a relatively long time. The present invention also relates to methods for making and method for using the systems.
2. Description of the Related Art
Prior art cathodic protection devices are known in the art such as those manufactured by JA Electronic of Stafford, Tex. These devices operate by applying an electric field across a metallic apparatus such as a pipe or a segment of pipe. The electric field and current associated therewith substantially reverse the electrochemical reactive of the metals to oxidative processes and corrosive processes which relate to the electrochemical behavior of metals in their metallic state. By applying an electric field and its associated current across the metallic apparatus, corrosion and rusting of the metal in the apparatus is reduced and even eliminated, greatly increasing the service life of the apparatus. These devices operate primarily by rectifying an AC source and applying the rectified field and current across the apparatus or a portion thereof. However, these prior art devices are not solid state devices, require high power overhead, are fairly large and difficult to control and monitor remotely and generally apply a simple rectified current to the apparatus.
Thus, there is a need in the art for compact cathodic protection apparatus using a standard AC input with reduced power overhead, improved remote control and monitoring capabilities and an output current wave form which produces a substantially pure DC output with a minimal residual AC component.
SUMMARY OF THE INVENTION
The present invention provides a solid-state square-wave cathodic apparatus including a rectifier unit for converting an AC input into a rectified output having an AC inlet and a converter unit for converting the rectified output into a square-wave rectified output. The apparatus also includes an outlet having an anodic terminal and a cathodic terminal. The rectified, square-wave output has a minimal AC component and appears as a substantially DC output when viewed at a relatively long time frame, affording better corrosion protection to a portion or all of a metallic apparatus, device or structure. The apparatus can also include remote control hardware and communication hardware and software so that the apparatus output can be monitored and remotely controlled to optimize the corrosion protection of the metallic structure.
The present invention provides a cathodic corrosion inhibiting apparatus including an inlet for receiving an AC current or connected to an AC power source. The apparatus also includes a transformer unit for changing a voltage and current of the AC input to form a transformed AC output. The apparatus further includes a solid state rectifier unit for converting the transformed AC output into a rectified output and a converter for converting the rectified output into a substantially rectified, square-wave output. The apparatus also includes outlets having an anodic terminal and a cathodic terminal. The rectified, square-wave output has a minimal AC component and appears as a substantially DC output when viewed at a relatively long time frame, affording better corrosion protection to a portion or all of a metallic apparatus, device or structure. The apparatus can also include remote control hardware and communication hardware and software so that the apparatus output can be monitored and remotely controlled to optimize the corrosion protection of the metallic structure.
The present invention also provides a cathodically protected metallic apparatus including an AC power source connected to the AC input of the cathodic corrosion inhibiting apparatus of the present invention, a cathodic corrosion inhibiting apparatus of the present invention, and a metallic apparatus connected to the power and ground terminals of the cathodic corrosion inhibiting apparatus of this invention, where the cathodic, apparatus produces a square-wave output which appears as a substantially DC output when viewed on a relatively long time frame and the output provides better corrosion resistance to the metallic apparatus.
The present invention also provides a cathodically protected pipeline including a pipeline and a plurality of cathodic units of the present invention located at given intervals along the pipeline to reduce corrosion at all point along the length of the pipeline.
The present invention further provides a method for inhibiting corrosion of metallic apparatus including applying a substantially DC current across the apparatus or a portion of the apparatus where the substantially DC current comprises a substantially square-wave output signal having sufficient voltage, current and power to maintain the structure at a voltage of at least about −850 mV DC.
The present invention still further provides a method for making the a solid-state square-wave cathodic apparatus of this invention.
REFERENCES:
patent: 4080272 (1978-03-01), Ferry et al.
The University of Oklahoma. College of Continuing Education. Norman, Oklahoma. 39thAnnual Corrosion Control Course. Proceedings. 1992. pp. 1-412.
Chevron USA, Inc. Bakersfield Division Pipeling, Cathodic Protection Training Manual. Donald S. Hansen. Justification for Cathodic Protection; pp. 13-34.
Omcon, Inc.
Patel Rajnikant B.
Strozier Robert W.
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