Topic 2 ME175 course questions

Question 1

Regarding a 3 phase motor, how would you change the direction of rotation?

Answer 1

Swap the outside phases.

Question 2

What functional tests could be performed to check the condition of a motor.

Answer 2

1. Earth continuity test - used to test if the earth is good.
2. Continuity test - used to test between phases when there is a load to check for an open circuit
3. Non contact test - used to check for a short circuit.
4. Insulation resistance test - To ensure no current can leak to the earth
5. Use a (Thermal imaging camera) TIC to find hotspots on a motor.

Question 3

How do we make HP air? List it’s uses onboard

Answer 3

HP air is made using a compressor (4 stages) As 276 bar is too high of a pressure to be used by most services onboard it is usually reduced down to a lower more usable pressure via a reducing station. Services used onboard include:

1. Charging breathing apparatus (EDBA, EBS)
2. Starting diesel engines
3. Flushing water out of the main ballast tanks.

Question 4

What is the importance of earth bonding straps?

Answer 4

Earth bonding allows a path of low resistance for electrical current (a lower resistance than the human body) to the hull of the ship and therefore provides a safe path to the ocean.