A magnetic trip with a fixed magnetic circuit polarised by a permanent magnet. The magnetic circuit includes two preferably identical parallel wafers each defining a main branch and a deflection tab with the presence of a coil on each branch. At their ends opposite to the mobile pallet, the wafers have in cross-section an L shape. The insulation structure carrying the coils is formed of two half-shells tightly holding the wafers. The trip can be used in circuit breakers.