Wave generator

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A shaft generator ( English shaft-driven generator ) is an electrical generator mainly on ships that is driven directly or indirectly by the propeller shaft. For reasons of economy, it takes over the on-board supply of electrical energy if the speed of the main propulsion engine in sea operation is within a specified range.

Function and structure

Wave generator on a container ship
Propeller shaft in the shaft tunnel

Shaft generators are used in both DC and three-phase systems. DC wave generators are only used on very small ships such as sport boats and are comparable to alternators in motor vehicles. A built-in regulator keeps the voltage almost constant regardless of the speed and load.

Only three-phase generators ( synchronous generators ) are used on ocean-going vessels . The frequency in the vehicle electrical system should be almost constant, but the frequency of the voltage of the synchronous generator is due to the design an integral multiple of the speed. Depending on the other conditions of the machine system, there are the following types of system:

  1. Large ships are usually powered by a two-stroke engine and a fixed propeller. The shaft generator is built around the propeller shaft. The frequency depends on the propeller speed. With an electronic frequency converter , a voltage of the desired on-board power supply frequency is generated.
  2. Small and medium-sized ships for regional services are often equipped with a controllable pitch propeller . This means that the speed of the diesel engine can be kept constant and the propulsion of the ship can be adjusted independently of this with the propeller. This means that no electronic frequency converter is required.
  3. In small ships with special equipment, there are occasionally systems in which an automatic mechanical or hydraulic gearbox converts the variable propeller speed into a constant generator speed, or in which a special generator ( double-fed asynchronous machine ) ensures a constant frequency.

Variant 1 systems were built, but the generator was coupled to the propeller shaft via a gearbox and operated at a significantly higher speed than the propeller. With this type of construction, the generator and gearbox can be used for short, rapid speed changes, for example. B. are significantly burdened by swell. This is manageable, but the effort required makes this system variant uninteresting.

Web links

literature

  • Günter Franz: Rotating electrical machines: generators, motors, converters . 8th unchanged edition, Verlag Technik, Berlin 1990, ISBN 3-341-00143-3 .
  • K. Schwitalla, U. Scharnow: Lexicon of seafaring . various years, transpress VEB Verlag für Verkehrwesen Berlin, ISBN 3-344-00190-6 .