# US 10,502,778 B2 · Method and apparatus for electric arc detection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,778 B2 - Document ID: US10502778B2 - Status: Granted - Kind: B2 - Application number: 14/978,193 - Filed: 2015-12-22 - Published: 2016-04-28 - Granted: 2019-12-10 - Earliest claimed: 2013-06-26 - Assignees: SMA Solar Technology AG - Applicants: SMA Solar Technology AG - Inventors: Martin Putz - Web page: https://patentgrep.com/patent/US10502778B2 ## CPC - G01R 31/2832: {Specific tests of electronic circuits not provided for elsewhere (G01R31/2801, G01R31/316 take precedence)} - G01R 15/185: {with compensation or feedback windings or interacting coils, e.g. 0-flux sensors (using galvano-magnetic field sensors G01R15/20; conversion of DC into AC using transductors G01R19/20)} - G01R 19/0015: {separating AC and DC} - G01R 19/0046: {characterised by a specific application or detail not covered by any other subgroup of G01R19/00} - H02M 5/42: by static converters - G01R 31/12: Testing dielectric strength or breakdown voltage {; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing (G01R31/08, G01R31/327 and G01R31/72 take precedence; measuring in plasmas G01R19/0061; measuring dielectric constants G01R27/2617; ESD, EMC or EMP testing of circuits G01R31/002)} - H02H 1/0015: {Using arc detectors} - H02J 1/02: Arrangements for reducing harmonics or ripples - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY ## Abstract A method for detecting high-frequency AC currents in a DC circuit including a common mode choke with two partial windings includes tapping voltages dropping across the two partial windings due to the AC current, superposing the tapped voltages, and obtaining a superposed AC voltage wherein differential mode portions of the tapped voltages are summed constructively and common mode portions of the voltages are summed destructively; and measuring the superposed AC voltage. ## Claims ### Claim 1 A method for detecting high-frequency AC currents in a DC circuit comprising a common mode choke with two partial windings, comprising: tapping voltages dropping across the two partial windings due to the AC current; superposing the tapped voltages and obtaining a superposed AC voltage using a superposition circuit, wherein differential mode portions of the tapped voltages are summed constructively and common mode portions of the tapped voltages are summed destructively; and measuring the superposed AC voltage using a voltage sensing device. ### Claim 2 (depends on 1) The method according to claim 1, wherein the superposing of the tapped voltages using a superposition circuit comprises amplifying the tapped voltages by differential amplifiers and summing the output signals of the differential amplifiers. ### Claim 3 (depends on 1) The method according to claim 1, wherein the superposing of the tapped voltages comprises digitizing the tapped voltages by analog-digital converters and summing the thus digitized voltages. ### Claim 4 (depends on 1) The method according to claim 1, wherein the superposing of the tapped voltages using a superposition circuit comprises: applying the tapped voltage dropping across a first partial winding of the common mode choke to the inputs of a differential amplifier; and connecting a first end of the second partial winding of the common mode choke to a reference potential of an output of the differential amplifier, wherein a voltage dropping between the output of the differential amplifier and a second end of the second partial winding of the common mode choke is the superposed AC voltage. ### Claim 5 (depends on 1) The method according to claim 1, wherein the superposing of the tapped voltages using a superposition circuit comprises connecting a tapping path comprising a winding of a transformer in parallel to each partial winding of the common mode choke. ### Claim 6 (depends on 5) The method according to claim 5, wherein the superposing of AC voltage portions of the tapped voltages using a superposition circuit comprises connecting a capacitor or a voltage measurement device in series with the windings of the transformer in each of the tapping paths. ### Claim 7 (depends on 6) The method according to claim 6, wherein the superposing of the tapped voltages using a superposition circuit comprises providing the windings of the transformer within the tapping paths as a primary side winding and a secondary side winding of a common transformer, and arranging the capacitor in series with the primary side winding and the voltage measurement device in series with the secondary side winding of the transformer. ### Claim 8 (depends on 5) The method according to claim 5, wherein the superposing of the tapped voltages using a superposition circuit comprises providing the windings within the tapping paths as primary side windings of a common transformer which comprises a single secondary side winding. ### Claim 9 (depends on 5) The method according to claim 5, wherein the superposing of the tapped voltages using a superposition circuit comprises providing the windings within the tapping paths as primary side windings of individual transformers which each comprise a secondary side winding, wherein the secondary side windings of the individual transformers are connected in series. ### Claim 10 (depends on 1) The method according to claim 1, further comprising: comparing the measured superposed AC voltage with a threshold value; and indicating a presence of an electric arc if the measured superposed AC voltage exceeds the threshold value. ### Claim 11 An apparatus for detecting high-frequency AC currents in a DC circuit comprising a common mode choke with two partial windings, the apparatus comprising: tapping circuits configured to tap voltages dropping across the two partial windings; a superposition circuit configured to superpose the tapped voltages, wherein differential mode portions of the tapped voltages are summed constructively and common mode portions of the voltages are summed destructively, and a superposed AC voltage is obtained at an output thereof; and a measurement device coupled to the output of the superposition circuit and configured to measure the superposed AC voltage. ### Claim 12 (depends on 11) The apparatus according to claim 11, wherein the tapping circuits each comprise a differential amplifier and the superposition circuit comprises a summing circuit configured to sum output signals of the differential amplifiers. ### Claim 13 (depends on 11) The apparatus according to claim 11, wherein the tapping circuits each comprise a analog-digital converter and the superposition circuit comprises a summing circuit configured to sum output signals of the analog-digital converters. ### Claim 14 (depends on 11) The apparatus according to claim 11, wherein the tapping circuits are arranged such that a voltage dropping across a first partial winding of the common mode choke is applied to the inputs of a differential amplifier, and wherein a first end of a second partial winding of the common mode choke is connected to a reference potential of an output of the differential amplifier, and wherein the measurement devices are configured to measure the superposed AC voltage between the output of the differential amplifier and a second end of the second partial winding of the common mode choke. ### Claim 15 (depends on 11) The apparatus according to claim 11, wherein the tapping circuits for each of the partial windings comprise a tapping path arranged in parallel to the respective partial winding, and wherein the superposition circuit comprises a winding of a transformer arranged in each of the tapping paths. ### Claim 16 (depends on 15) The apparatus according to claim 15, wherein a capacitor or a voltage measurement device is arranged in series with the winding of the transformer in each of the tapping paths. ### Claim 17 (depends on 16) The apparatus according to claim 16, wherein the windings in the tapping paths are a primary side winding and a secondary side winding of a common transformer, wherein the capacitor is arranged in series with the primary side winding and the voltage measurement device is arranged in series with the secondary side winding of the common transformer. ### Claim 18 (depends on 15) The apparatus according to claim 15, wherein the windings in the tapping paths are primary side windings of a common transformer which comprises a single secondary side winding, wherein the measurement devices are configured to measure the superposed AC voltage dropping across the secondary side winding. ### Claim 19 (depends on 15) The apparatus according to claim 15, wherein the windings in the tapping paths are primary side windings of individual transformers which each comprise a secondary side winding, wherein the secondary side windings are connected in series and the measurement devices are configured to measure the superposed AC voltage dropping across the serial connection of the secondary side windings. ### Claim 20 (depends on 11) The apparatus according to claim 11, further comprising: a comparison circuit configured to compare the superposed AC voltage with at least one threshold value; and a signaling device configured to output a signal indicating an electric arc if the superposed AC voltage exceeds the at least one threshold.