Abstract: A low-voltage multipole circuit breaker with high electrodynamic strength comprises a case made of insulating material, subdivided into a front compartment housing an operating mechanism commanding opening and closing of the circuit breaker and a rear compartment separated from the front compartment by an intermediate wall. The rear compartment is itself subdivided into individual compartments by separating partitions, each individual compartment housing one of the poles of the circuit breaker. The operating mechanism is linked to a pole shaft common to all the poles. The pole shaft is located in the rear compartment and supported by bearings passing through the separating partitions.

Abstract: The tripping adjustment range of a magnetic trip device with a plunger core is increased by providing, in the movable plunger core, a groove whose edges define polar surfaces bounding air-gaps with the edges of the yoke in such a way as to generate in the minimum adjustment position a force which is added to the attractive force of the movable core by the stationary core, and inversely a force in the maximum adjustment position which is subtracted from the attractive force of movable plunger core. The trip device excitation coil is offset with respect to the yoke to increase the adjustment range, and a return device with adjustable stop and decreasing return force as the movable core approaches the stationary core, contributes to increasing this tripping threshold adjustment range.