Question 16 CEL02 - Chief Engineer - Limited (Alt)

The Correct Answer is B **Explanation for Option B (Correct Answer):** The Azipod is a specific type of marine propulsion system trademarked by ABB. The name is a portmanteau of "azimuthing electric podded drive." 1. **Electric Drive System:** Azipods are fundamentally electric. The main engines (usually diesel generators or gas turbines) produce electricity, which powers the propulsion motor. 2. **Propulsion Motor Installed in a Submerged Housing (Pod):** The electric motor that drives the propeller is housed within a sealed, watertight structure (the pod) located outside the ship's hull, under the water. 3. **Capable of Swiveling (Azimuthing):** The defining characteristic of the Azipod system is its ability to rotate 360 degrees around the vertical axis. This rotation allows the propeller thrust to be directed in any direction, providing exceptional maneuverability without the need for rudders. **Explanation for Incorrect Options:** **A) It is an electric drive system using water jets.** * **Incorrect:** Azipod systems use conventional fixed-pitch propellers driven by the internal electric motor. Water jets are a different form of propulsion (often used on high-speed vessels) that suck in water and forcibly expel it. **C) It is an electric drive system that incorporates a DC motor.** * **Incorrect:** While older or smaller marine electric drives might use DC motors, modern Azipod units overwhelmingly use **AC (Alternating Current) synchronous or asynchronous (induction) motors**. AC motors are preferred for high power output and reliability in large-scale marine propulsion. **D) It is an electric drive system in which the motor drives a controllable-pitch propeller (CPP).** * **Incorrect:** The vast majority of Azipod systems utilize **Fixed-Pitch Propellers (FPPs)**. Since the unit can swivel (azimuth) 360 degrees and the speed of the electric motor can be precisely controlled via variable frequency drives (VFDs), changing the pitch of the propeller blades (as done with a CPP) is unnecessary for speed control, reversing, or maneuvering.