Synchronous machine

A synchronous machine including two relatively movable parts, each having a respective ferromagnetic core and separated by an air-gap, wherein one of said parts is provided with a symmetrical, three-phase Y-connected armature winding intended to have one of a sinusoidal line voltage and a sine-wave supply current, and another of said parts is provided with a field magnet system, wherein the armature winding and the field magnet system are constructed so that an air-gap magnetic flux linked with the armature winding has a density whose mean value, as determined over an active length of the air gap in a direction perpendicular to a direction of relative movement of the two relatively movable parts, presents a variation along the air gap in said direction of relative movement in accordance with a uniform periodic function:

• f(.alpha.,.beta.),
• whose positive and negative half-periods are mirror images of each other and whose periods coincide with an extension of two pole pitches of the field magnet system in said direction of relative movement, and which have a form such that within one-half of a positive half period of a function:
• f(.alpha.,.beta.)=1 for 0.ltoreq..alpha..ltoreq..pi./2,
• and ##EQU3## and where .alpha. is the extension along the air gap in said direction of relative movement and varies from 0 to .pi./2 over said one-half of said half-period of the function, and .beta. is a constant not greater than about 0.22.pi..