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(12) Patent Application Publication (10) Pub. No.: US 2017/0178825 A1 GLOSSER Et Al

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(12) Patent Application Publication (10) Pub. No.: US 2017/0178825 A1 GLOSSER Et Al US 20170178825A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2017/0178825 A1 GLOSSER et al. (43) Pub. Date: Jun. 22, 2017 (54) UNIVERSAL CONTACT INPUT Publication Classification SUPPORTNG PROGRAMMABLE WETTING (51) Int. Cl. CURRENT HIH IMO (2006.01) GOIR 31/327 (2006.01) (71) Applicant: GE Intelligent Platforms, Inc., H02. I3/00 (2006.01) Charlottesville, VA (US) HIH I/60 (2006.01) (52) U.S. Cl. (72) Inventors: Richard Joseph GLOSSER, Salem, CPC .......... H0IH I/0015 (2013.01); H0IH I/605 VA (US); Venkatesh J. Hyderabad (IN) (2013.01); G0IR 31/327 (2013.01); H02J 13/00 (2013.01) (21) Appl. No.: 15/327,189 (57) ABSTRACT A system and method according to various embodiments can (22) PCT Fed: Jul. 22, 2014 include a universal contact input status detection circuit. A Voltage source wets a contact with a wetting Voltage. A (86) PCT No.: PCT/US2O14/0476OO current mirror circuit is connected across an input of the contact to provide a constant wetting current over a wide S 371 (c)(1), input Voltage range. The input voltage can be varied over a (2) Date: Jan. 18, 2017 range wide enough to include both AC voltages and DC Voltages. The current mirror circuit maintains the constant wetting current during varying wetting Voltage inputs across Related U.S. Application Data the input of the contact. A wetting Voltage sensor senses the (63) Continuation-in-part of application No. PCT/ wetting voltage provided to the contact so that the status of US2014/047223, filed on Jul. 18, 2014. the contact can be determined. -100 102 104 Wetting Wetting Voltage Voltage Sense 106 118 120 C t Opto- To FPGA & omparator lsolator Processor Surge Bridge Voltage Protection Rectifier Divider 8, AC/DC RC Filter 108 Programmable Constant Current Y-112 Source Patent Application Publication Jun. 22, 2017. Sheet 1 of 5 US 2017/0178825 A1 *8V/SOCH-,OL JOSS30OJE ??qeuuuueu6oud ?uÐJunOque?SuOO ?OunOS Patent Application Publication Jun. 22, 2017. Sheet 2 of 5 US 2017/0178825 A1 ºV/SOCH-,OL JOSS30OJ, 8|| ( <% ?O Patent Application Publication Jun. 22, 2017. Sheet 3 of 5 US 2017/0178825 A1 ?ue?SuOOg ?uÐJunC) ?OunOS Patent Application Publication Jun. 22, 2017. Sheet 4 of 5 US 2017/0178825 A1 ?ue?SUOO ?uÐJunO ?OunOS 0|| Patent Application Publication Jun. 22, 2017 Sheet 5 of 5 US 2017/0178825 A1 500 Passing a Wetting Voltage through the Contacts 502 Rectifying AC to DC, when an AC wetting 504 Voltage is used Maintaining the wetting current constant using 506 a Current mirror circuit Scaling down the Wetting voltage 508 Comparing the Wetting Voltage to a reference 510 Wetting Voltage FIG. 5 US 2017/0178825 A1 Jun. 22, 2017 UNIVERSAL CONTACT INPUT minimum current needed to flow through a contact to break SUPPORTNG PROGRAMMABLE WETTING through any film (contact oxidation) that may have been CURRENT deposited on the switch. Typically, this has been performed by different group of boards connected in order to Support a I. FIELD OF THE INVENTION wide range of contact input voltages. 0001. The present invention relates generally to control III. SUMMARY OF THE INVENTION ling a process. More particularly, the present invention 0008 Given the aforementioned deficiencies, a need relates to monitoring electrical contacts, especially relays, exists for a single circuit, capable of monitoring Switches, in and detecting the status of electrical contacts used in an general, and relay contacts, in particular, to determine the industrial or commercial process that are wetted with alter status of the contacts. There also remains a need for a single nating current (AC) voltage or direct current (DC) voltage. contact status detection circuit, which is capable of Support ing contact input voltage ranges, including both AC and DC II. BACKGROUND OF THE INVENTION Voltages. 0002. Over the years, a full range of relay products from 0009. A further need exists for a single circuit capable of highly specialized relays for communication equipment to maintaining constant wetting current across a wide input general-purpose relays have been designed to control nearly range. In addition, a need remains to provide a constant every function in commercial and industrial processes used current across a contact input (digital input) over a wide in everything from household appliances to industrial Voltage range as a means to abate contact oxidation (corro machinery. A power generation plant is one example of an sion/increased impedance) and improve reliability of the industrial process in which a large number of relays are used. signal chain. The relays in a power generation plant can be used to control 0010. A system according to various exemplary embodi a wide variety of equipment Such as motors, pumps, Sole ments can include a universal contact input status detection noids and lights. However, even the best relays may fail at circuit, comprising a Voltage source that wets a contact with Some point. a wetting Voltage. A wetting Voltage sensor senses the 0003. In the example scenario above, a control system wetting Voltage provided to the contact. A current mirror needs to monitor the relays within the power plant to circuit is connected across an input of the contact to provide determine their status in order to ensure that certain func a constant wetting current over a wide input voltage range. tions associated with the process are being performed. In The input Voltage can be varied over a range wide enough particular, contact input status detection circuits are used to to include both AC voltages and DC voltages. The current detect the status of relay contacts when in use in the field. mirror circuit maintains the constant wetting current during The contact input status detection circuit monitors provide varying wetting Voltage inputs across the input of the an indication of potentially degraded electrical relay perfor contact. A divider Scales down the wetting Voltage. A comparator that compares the wetting Voltage to a reference mance due to contamination. wetting Voltage to provide a digital output Voltage. A pro 0004. In industrial environments, contamination rou cessor determines the status of the contact in accordance tinely interferes with the operation of the relay's contact. with the digital output voltage. The detection circuit is Contaminants, which can include oxidation films or foreign integrated on a single circuit board configuration. particles, tend to produce contact resistance readings that are 0011. A method of detecting a status of a contact accord either high or unstable. Contamination commonly happens ing to various exemplary embodiments can include wetting with low current applications, usage in high temperature and a contact with a wetting Voltage; sensing the wetting Voltage humidity environments, and during extended periods of provided to the contact; providing a constant wetting current Storage. across an input of the contact over a wide input voltage 0005 For example, in small currents and low voltage range; maintaining the constant wetting current during vary applications, oxidation of relay contact is simply a buildup ing wetting Voltage inputs utilizing a current mirror con of corrosion on relay contact surfaces over a period of time. nected across an input of the contact, Scaling down the The contacts develop oxidation, which is a thin layer of wetting Voltage; comparing the wetting Voltage to a refer oxide on the contact Surface. It causes problems by increas ence wetting Voltage to provide a digital output voltage; and ing the resistance across the contacts which, depending on determining the status of the contact in accordance with the the amplitude of the Voltage being Switched, can cause loss digital output voltage. The detection of the status of the of signal or overheating of the contacts. contact is implemented on a single circuit board. 0006. Oxidation on relay contacts is especially a problem 0012. Further features and advantages of the invention, as with Small currents and low Voltages, because they cannot well as the structure and operation of various embodiments punch through the oxide layer once it accumulates and of the invention, are described in detail below with reference becomes too thick. However, higher Voltages may punch to the accompanying drawings. It is noted that the invention through the oxidation layer during relay Switching. Thus, the is not limited to the specific embodiments described herein. issue with Switch contacts is Voltage. Current through the Such embodiments are presented herein for illustrative pur contact is strictly a function of the Voltage and the imped poses only. Additional embodiments will be apparent to ance of the circuit the contact completes. By varying the persons skilled in the relevant art(s) based on the teachings current, the Voltage varies. Once the Voltage is great enough, contained herein. the punch through Voltage is achieved. 0007. One conventional approach to resolve this issue for IV. BRIEF DESCRIPTION OF THE DRAWINGS Small currents and low current applications is by passing the 0013 FIG. 1 shows a schematic diagram of an exemplary required wetting current through the relay contacts so that it circuit used to detect the status of an electric contact in punches through the oxide layer. The wetting current is the accordance with the present teachings; US 2017/0178825 A1 Jun. 22, 2017 0014 FIG. 2 is a schematic circuit diagram of an exem Supporting universal contact input voltage range, including plary contact status detection circuit in accordance with the both AC and DC voltages, and maintaining a constant present teachings; wetting current across a wide input range. 0015 FIG. 3 is another exemplary embodiment of a 0025 Various embodiments provide a system and schematic circuit diagram of a contact status detection method that provides a constant wetting current across a circuit in accordance with the present teachings; wide input range.
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