PURPOSE: $>To improve generating efficiency of driving force, by controlling the output current to be in a predetermined value from the magnet power source in an acceleration control system.

CONSTITUTION: An electromagnetic pump is composed of a dipolar magnet 1, positive and negative electrodes 2 arranged face to face with conductive driven fluid (e.g. sea water) between them, a sensor 3 to detect the flow velocity of sea water and a speed detector 4, and a current control output generator 5 to issue control commands of output current to a magnet power source 6. This acceleration control system detects the flow velocity V0 with the sensor 3 when it is produced to the sea water. An output signal is produced to the magnet power source 6 from the above-mentioned detector 4 and from the current control output generator 5 that received this signal, the command to control the output current. As a result, it is controlled so that magnetic field B will always be proportional to 1/V0.