Switch unit, method for assembling a switch unit, and circuit breaker for a medium voltage circuit

A medium voltage circuit breaker, the circuit breaker comprising:

• a switch unit, comprising:
• a first switch contact;
• a second switch contact, which is movable between a first position, wherein the first switch contact contacts the second switch contact, and a second position, wherein the second switch contact is separated from the first switch contact;
• a positioning element to position an arc chute on the switch unit, wherein the arc chute comprises a plurality of substantially parallel metal plates, the positioning element being arranged to guide an arc, which is created between the first switch contact and the second switch contact, into the arc chute in an arc displacement direction in order to be extinguished;
• at least one gas emitting element comprising a gas emitting layer having a layer surface facing the first switch contact and the second switch contact, wherein the gas emitting element is arranged at a distance to the first switch contact and the second switch contact, and wherein upon an interruption operation of the circuit breaker at its nominal current, the arc between the first switch contact and the second switch contact will vaporize a portion of the gas emitting layer;
• a first horn electrically connected to the first switch contact for guiding a first foot of the arc to a first stack of parallel metal plates of the arc chute;
• and
• a second horn electrically connected to the second switch contact for guiding a second foot of the arc to a second stack of parallel metal plates of the arc chute, wherein the layer surface of the at least one gas emitting element is parallel to at least a portion of the first horn and the second horn in a moveable direction of the second switch contact;
• and
• wherein more than 70% of a surface of a metal plate of the first stack of parallel metal plates and the second stack of parallel metal plates faces a surface of an adjacent metal plate;
• an arc space disposed between the first stack and the second stack of parallel metal plates;
• wherein the arc chute is symmetric to an axis traversing the arc space which is parallel to a stacking direction of the first stack of parallel metal plates and the second stack of parallel metal plates, and wherein the stacking direction of the first stack of parallel metal plates and the second stack of parallel metal plates is substantially parallel to the arc displacement direction, which is substantially orthogonal to a moving direction of the second switch contact.