Electrically heatable honeycomb body and method for operating it

1. An electrically heatable honeycomb unit, comprising:

a honeycomb body being a catalytic converter and having cavities formed therein through which a fluid can flow;

a power feed line having a sleeve attached to an outside of said honeycomb body;

at least one power distribution structure, said power distribution structure being connected to a power source via said power feed line, said power distribution structure delimiting said honeycomb body; and

at least one closed-loop control element made of a material with a positive temperature coefficient (PTC) and can be placed at least in thermal contact with the fluid flowing through said honeycomb body, said at least one closed-loop control element disposed only in at least one of said power feed line or said power distribution structure, said at least one closed-loop control element being formed at least partially in said sleeve, said closed-loop control element configured to trip and thus decrease a flow of current upon the fluid raising said closed-loop control element above a closed-loop control temperature.

2. The honeycomb unit according to claim 1 , wherein said closed-loop control element projects at least partially into an interior of said honeycomb body.

3. The honeycomb unit according to claim 1 , wherein the fluid can flow at least partially around said closed-loop control element.

4. The honeycomb unit according to claim 1 , wherein said closed-loop control element is formed from at least one material selected from the group consisting of a titanate ceramic and a barium titanate ceramic.

5. A method for operating an electrically heatable honeycomb body through which a fluid can flow and contains at least one power distribution structure connected to a power source via a power feed line to supply the electrically heatable honeycomb body with power, which comprises the step of:

providing a power supply via at least one self-regulating closed-loop control element being at least in thermal contact with the fluid, the self-regulating closed-loop control element conducting current to the electrically heatable honeycomb body for ohmically heating the electrically heatable honeycomb body being a catalytic converter; and

tripping the self-regulating closed-loop control element to decrease the current flow upon the fluid raising the self-regulating closed-loop control element above a closed-loop control temperature.

6. The method according to claim 5 , which further comprises setting the closed-loop control temperature of the closed-loop control element to correspond to a temperature of the fluid being higher than or equal to an activation temperature of at least one of the following components:

a catalytically active coating on at least parts of the honeycomb body; and

at least one catalytically active coating of a structure for conditioning exhaust gas, the structure being formed downstream of the honeycomb body.

7. The method according to claim 5 , wherein the fluid at least partially flows around the closed-loop control element.

8. An electrically heatable honeycomb unit, comprising:

a honeycomb body being a catalytic converter having cavities formed therein through which a fluid can flow;

a power feed line;

at least one power distribution structure, said power distribution structure being connected to a power source via said power feed line; and

at least one closed-loop control element made of a material with a positive temperature coefficient (PTC) and can be placed at least in thermal contact with the fluid flowing through said honeycomb body, said at least one closed-loop control element configured to control a flow of current into said honeycomb body for heating said honeycomb body via ohmic heat, said closed-loop control element configured to trip and thus decrease the flow of current upon the fluid raising said closed-loop control element above a closed-loop control temperature.