# US 2014/0153145 A1 · Method and system for open neutral protection circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0153145 A1 - Document ID: US20140153145A1 - Status: Published application - Kind: A1 - Application number: 13/693,169 - Filed: 2012-12-04 - Published: 2014-06-05 - Earliest claimed: 2012-12-04 - Assignees: Ericson Manufacturing Company - Inventors: Ronald W. Hughes - Web page: https://patentgrep.com/patent/US20140153145A1 ## CPC - H02H 11/00: Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result - 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) ## Abstract An open neutral protection method and apparatus including a blocking diode arrangement to prevent connection of power in circuits when the power source has an open neutral. In particular, when more than one branch circuits are connected to a power supply with more than one hot power lines, blocking diodes prevent back feed currents from activating relays connecting the power source to the branch circuits when the power source has an open neutral. ## Claims ### Claim 1 An open neutral protection circuit, comprising: a first control switch for selectively connecting a power source to a first circuit, wherein the first control switch comprises a first element for opening and closing the first control switch, wherein when a first current flows through the first element, the first control switch connects the power source to the first circuit; and a first blocking diode to prevent a second current from flowing through the first element, wherein the first element is connected to the first blocking diode. ### Claim 2 (depends on 1) The open neutral protection circuit of claim 1, wherein the first control switch is a first relay and the first element is a first coil, and wherein the first coil is connected in series with the first blocking diode. ### Claim 3 (depends on 1) The open neutral protection circuit of claim 1, wherein the first element is arranged to conduct the first current from a first hot line of the power supply to a neutral line of the power supply, and wherein the second current has a path from the neutral line to the first hot line through the first element. ### Claim 4 (depends on 1) The open neutral protection circuit of claim 1, further comprising: a first free-wheel diode arranged in parallel with the first element to dissipate energy stored in the first element when source power is removed. ### Claim 5 (depends on 1) The open neutral protection circuit of claim 1, wherein the first circuit comprises a first ground fault circuit interrupter (GFCI). ### Claim 6 (depends on 1) The open neutral protection circuit of claim 1, further comprising: a second control switch for selectively connecting the power source to a second circuit, wherein the second control switch comprises a second element for opening and closing the second control switch, wherein when a third current flows through the second element, the second control switch connects the power source to the second circuit; and a second blocking diode to prevent a fourth current from flowing through the second element, wherein the second element is connected to the second blocking diode. ### Claim 7 (depends on 6) The open neutral protection circuit of claim 6, wherein the first control switch is a first relay, the second control switch is a second relay, the first element is a first coil, the second element is a second coil, and wherein the first coil is connected in series with the first blocking diode and the second coil is connected in series with the second blocking diode. ### Claim 8 (depends on 6) The open neutral protection circuit of claim 6, wherein the first element is arranged to conduct the first current from a first hot line of the power supply to a neutral line of the power supply, and wherein the second current has a first path from the neutral line to the first hot line through the first element, and wherein the second element is arranged to conduct the third current from a second hot line of the power supply to the neutral line of the power supply, and wherein the fourth current has a second path from the neutral line to the second hot line through the second element. ### Claim 9 (depends on 6) The open neutral protection circuit of claim 6, further comprising: a first free-wheel diode arranged in parallel with the first element to dissipate energy stored in the first element when source power is removed; and a second free-wheel diode arranged in parallel with the second element to dissipate energy stored in the second element when source power is removed. ### Claim 10 (depends on 6) The open neutral protection circuit of claim 6, wherein the first circuit comprises a first ground fault circuit interrupter (GFCI) and the second circuit comprises a second GFCI. ### Claim 11 A method of providing open neutral circuit protection, comprising: selectively connecting a power source to a first circuit with a first control switch comprising a first element, wherein when a first current flows through the first element, the first control switch connects the power source to the first circuit; and preventing a second current from flowing through the first element with a first blocking diode, wherein the first element is connected to the first blocking diode. ### Claim 12 (depends on 11) The method of claim 11, wherein the first control switch is a first relay and the first element is a first coil, and wherein the first coil is connected in series with the first blocking diode. ### Claim 13 (depends on 11) The method of claim 11, wherein the first element is arranged to conduct the first current from a first hot line of the power supply to a neutral line of the power supply, and wherein the second current has a path from the neutral line to the first hot line through the first element. ### Claim 14 (depends on 11) The method of claim 11, further comprising: dissipating energy stored in the first element when source power is removed with a first free-wheel diode arranged in parallel with the first element. ### Claim 15 (depends on 11) The method of claim 11, wherein the first circuit comprises a first ground fault circuit interrupter (GFCI). ### Claim 16 (depends on 11) The method of claim 11, further comprising: selectively connecting the power source to a second circuit with a second control switch comprising a second element, wherein when a third current flows through the second element, the second control switch connects the power source to the second circuit; and preventing a fourth current from flowing through the second element with a second blocking diode, wherein the second element is connected to the second blocking diode. ### Claim 17 (depends on 16) The method of claim 16, wherein the first control switch is a first relay, the second control switch is a second relay, the first element is a first coil, the second element is a second coil, and wherein the first coil is connected in series with the first blocking diode and the second coil is connected in series with the second blocking diode. ### Claim 18 (depends on 16) The method of claim 16, wherein the first element is arranged to conduct the first current from a first hot line of the power supply to a neutral line of the power supply, and wherein the second current has a first path from the neutral line to the first hot line through the first element, and wherein the second element is arranged to conduct the third current from a second hot line of the power supply to the neutral line of the power supply, and wherein the fourth current has a second path from the neutral line to the second hot line through the second element. ### Claim 19 (depends on 16) The method of claim 16, further comprising: dissipating energy stored in the first element when source power is removed with a first free-wheel diode arranged in parallel with the first element; and dissipating energy stored in the second element when source power is removed with a second free-wheel diode arranged in parallel with the second element. ### Claim 20 (depends on 16) The method of claim 16, wherein the first circuit comprises a first ground fault circuit interrupter (GFCI) and the second circuit comprises a second GFCI. ### Claim 21 A method of providing open neutral circuit protection, comprising: connecting a first blocking diode in series with a first element of a first control switch to prevent a first back feed current from flowing through the first element, wherein the first control switch selectively connects a power source to a first downstream circuit when current flows through the first element. ### Claim 22 An open neutral protection circuit, comprising: means for selectively connecting a power source to a first circuit when a first current flows through a switching means, the switching means connecting the power source to the first circuit based on the first current; and means for preventing a second current from flowing through the switching means when a neutral line of the power supply is open.