The external vibrator is a three-phase asynchronous motor. So-called eccentric weights (discs) are fixed eccentrically at the ends of the rotor shaft. At rotating, centrifugal forces are generated. These forces can be adjusted by moving the discs at standstill. The discs are divided so that the centrifugal force can be easily regulated.

Each weight at rotation creates a centrifugal force vector whose direction is determined by the centre of motion (centre of rotor) and the centre of gravity. Since the total centrifugal force is determined by the resulting centrifugal force vectors, counterbalancing (twisting) of the discs is a way to increase or decrease the total centrifugal force (see fig. 2 and 4).

External vibrators can create centrifugal forces up to 100 kN and more. To obtain great durability despite the rough operating conditions, external vibrators are equipped with vibration-proof, high temperature proof stator windings, special bearings with increased load capacity, and vibration-proof power cables.