Electrical motors are used on almost all types of ships, e.g., as thrusters, but also as pump jets. As positioning systems they are indispensable on larger ships nowadays. They also play an important role on pipe and cable-laying ships, as well as on crane barges.
For special-purpose ships of this sort, the bow or stern thrusters can have an output of up to 5 MW.
The machines can be operated directly through the mains (DOL) in S1 or S2 mode or through a frequency converter. Variable-speed control is essential, however, when using them as positioning drives.