Marine heave compensating device and winch drive

摘要

A winch for use in a heave compensation system has a winch drum (42) driven by an AC asynchronous motor (50) via a gearbox (52). The motor (50) is controlled by a variable speed control (58) as a function of heave speed. The motor (50) and its drive train, and the winch (42), are chosen to have low inertia. The winch pays out and reels in to compensate for heave substantially instantaneously, without the need for prediction of wave patterns.