Circuit breaker with parallel connected pole compartments

A circuit breaker comprising:

• an insulating case;
• at least one pair of contiguous pole compartments, the contiguous compartments of said pair of pole compartments being separated from one another by a partition wall and juxtaposed inside said insulating case;
• an arc extinguishing chamber located in each of the contiguous compartments of said pair of pole compartments;
• a first pair of separable contact parts located in one of the contiguous compartments of said pair of pole compartments;
• a second pair of separable contact parts located in the other of the contiguous compartments of said pair of pole compartments;
• an operating mechanism linked to the first and second pairs of separable contact parts to cause the first and second pairs of contact parts to separate simultaneously;
• means for electrically connecting in parallel each contact part of the first pair of separable contact parts with a corresponding contact part of the second pair of separable contact parts, and forming a single pole of ultimate breaking capacity lcu for a voltage vcu and power factor kcu;
• a lower arcing horn located in each contiguous compartment of said pair of pole compartments;
• the arc extinguishing chamber of each of the contiguous compartments of said pair of pole compartments including an inlet opening outwardly from a side of the compartment where the contact parts are located, the inlet being confined in one direction by said lower arcing horn, said lower arcing horn being located to receive a foot of an electrical arc at its entry into the chamber;
• and
• at least one communicating aperture located in the partition wall, said aperture having dimensions and a location such that, when a current of an intensity equal to 50% of the ultimate breaking capacity lcu of the pole for a voltage vcu and power factor kcu flows through the pole, the ratio of the arcing energy in one of the contiguous compartments of said pair of pole compartments to the other of the contiguous compartments of said pair of pole compartments is greater than ⅙, the arcing energy being measured for each compartment by the integral
• W=∫to14v(t).i(t)dt
• where:
• W is the integral measuring the arcing energy,
• v(t) is the instantaneous value of the voltage at the terminals of the contact parts,
• i(t) is the instantaneous value of the current intensity flowing through the contact parts,
• t0 is the time when separation of the contact parts begins,
• t4 is the time when the current intensity flowing through the contact parts ceases;
• and
• wherein the aperture is located and has dimensions such that the lower arcing horns in the contiguous compartments of said pair of pole compartments are located facing one another on each side of the aperture.