MAN B&W Auxiliary Propulsion System. Auxiliary propulsion mode
Clutching out the Alpha Clutcher is done remotely from the bridge. Auxiliary propulsion mode is established in less than two minutes. When clutching in, the Clutcher is remotely controlled from a panel in the engine room.
When operating in auxiliary propulsion mode, the shaft alternator is used as electric motor. This motor delivers power via the tunnel gear to the propeller shaft. When the Alpha Clutcher is clutched out, the main engine is disconnected from the propeller shaft and stopped. In this mode, however, the Alpha Clutcher will transmit the propeller thrust to the trust bearing of the main engine.
To obtain the best possible propulsion efficiency in auxiliary propulsion mode at limited electrical power, it is necessary to reduce the rate of speed of the propeller to match this limited power with the power absorption of the propeller. Therefore the tunnel gear incorporates a two-step gearing. One ‘step-up’ ratio for the tunnel ordinary propulsion mode with shaft alternator, and a larger ‘step-down’ ratio for the PTI auxiliary propulsion mode.