Adapter for an automation field device

An adapter for introduction into a two-conductor line between a field device of automation technology and a non-Ex capable supply isolator to make the field device Ex capable, the adapter, comprising:

• an adapter housing having first and second connecting elements for connecting a first two-conductor line via which the adapter is connectable with the supply isolator and having third and fourth connecting elements for connecting a second two-conductor line via which the adapter is connectable with the field device;
• and
• an adapter electronics arranged in the adapter housing,
• wherein the adapter electronics connects the first connecting element with the third connecting element using a first electrical connecting line and the second connecting element with the fourth connecting element using a second electrical connecting line such that the first connecting line conducts a loop current coming from the supply isolator from the first connecting element to the field device connectable to the third connecting element and the second connecting line conducts the loop current coming from the field device via the fourth connecting element back to the second connecting element at the supply isolator,
• wherein the adapter electronics further includes an overvoltage protection system designed to limit a voltage applied across the third and fourth connecting elements to a first maximum value in the event of failure,
• wherein the adapter electronics further includes an overcurrent protection system adapted to prevent a rise of the loop current above a maximum electrical current value in the event of failure such that a power issuable to the field device is limited, and
• wherein the adapter electronics further includes a circuit adapted in the non-failure case to control a voltage applied to the overvoltage protection system from a minimum input voltage, which lies across the first and second connecting elements, to a second maximum value lower than the first maximum value.

An automation system, comprising:

• a non-Ex-i capable supply isolator;
• an automation field device that is embodied in such a manner that it fulfills the requirements of ignition protection type intrinsic safety Ex-i;
• and
• an adapter, including:
• an adapter housing having first and second connecting elements for connecting a first two-conductor line via which the adapter is connectable with the supply isolator and having third and fourth connecting elements for connecting a second two-conductor line via which the adapter is connectable with the field device;
• and
• an adapter electronics arranged in the adapter housing,
• wherein the adapter electronics connects the first connecting element with the third connecting element using a first electrical connecting line and the second connecting element with the fourth connecting element using a second electrical connecting line such that the first connecting line conducts a loop current coming from the supply isolator from the first connecting element to the field device connectable to the third connecting element and the second connecting line conducts the loop current coming from the field device via the fourth connecting element back to the second connecting element at the supply isolator,
• wherein the adapter electronics further includes an overvoltage protection system designed to limit a voltage applied across the third and fourth connecting elements to a first maximum value in the event of failure,
• wherein the adapter electronics further includes an overcurrent protection system adapted to prevent a rise of the loop current above a maximum electrical current value in the event of failure such that a power issuable to the field device is limited, and
• wherein the adapter electronics further includes a circuit adapted in the non-failure case to control a voltage applied to the overvoltage protection system from a minimum input voltage, which lies across the first and second connecting elements, to a second maximum value lower than the first maximum value;
• wherein the adapter is connected with the non-Ex-i capable supply isolator at the first and second connecting elements by a first two-conductor line and with the field device at the third and fourth connecting elements by a second two-conductor line.