Question

State the problem that would occur if large induction motor such as bow thruster unit were started direct on line.

Outline 6 proactive design methods that may be employed to eliminate problem that occur during starting of large induction motor.

If large induction motor is started DOL it will take large starting current and it will produce a voltage dip at the supply bar

It will affect other consumers and further increase in voltage dip will cause generator protection to trip.

Lamp fluctuation.

Malfunctioning of electronics

Increased contact wear on contactor

Reduce voltage starting [star delta starter]

Zero pitch i.e. reduced load starting.

Dedicated gear ]i.e. special AE for bow thrusters]

Special motor [wound rotor motor, double cage motor]

Power management puts enough capacity on board to reduce the dip

Use a diesel engine to start a bow thruster

Use H.V. as these motor take less surge.