The device comprises a solid-state switch and a pair of mechanical contacts electrically connected in series. The solid-state switch is housed in a compartment towards the rear of the moulded case of the device, in thermal contact with an external metal plate. The solid-state switch housing is separated by an insulating partition from the remaining part of the moulded case, which contains the contacts, their operating mechanism, the arc chute and the trip unit. The power terminals and control terminals of the solid-state switch are located on the small side faces of the case on either side of the movement plane of the movable contact, which extends parallel to these small side faces. |