The present invention concerns a brushless electric machine with a rotor having interior permanent magnets, characterised in that the rotor consists of a tubular core (1), said core (1) having N pairs of longitudinal slots (2, 3) having trapezoidal cross-section, a width La and a length L, where La/L is between 0.25 and 0.35, the two slots (2, 3) of a pair extending on either side of the median radial plane, at an angle of 7.5°±1.5°, the core having, in the region of convergence of each pair of slots, a longitudinal channel (10) opening on either side of the front ends of the core (1).