Marine Electrics & Electronics

Acoustic Doppler Current Profiler

Acoustic Doppler Current ProfilerThe RDI Acoustic Doppler Current Profiler (ADCP) employs the Doppler principle to measure speed and direction of currents in the water column below a moving vessel.

 

The Theory of operation of Transformer

A big advantage of A.C. transmission is the ability to easily change voltage by means of a transformer. As there are no moving parts maintenance is very low and efficiency very high ( typically 98%).

   

Relays and Solenoids

The wire coil of the electromagnet, without its core of magnetic material is called the solenoid. If this solenoid is provided with a movable soft iron core and current flows through the turns of the coil , the magnetic field tends to pull the plunger in to the centre of the coil. Accordingly the coil with its moving centre is called the solenoid.
   

Types of Fluorescent Lights

Discharge lamps
Cold cathode type-only used for decorative lighting
Hot cathode

  • a, High pressure fluorescent
(i)Mercury vapour types) Used mainly for street lighting
(ii) Sodium type , ) but sometimes used for deck lighting
   

The Operation of Navigation Lighting System

When the double pole switch is closed the navigation light is illuminated. Current in the relay circuit causes the relay coil to energise so contact 'a' ,may be attracted to 'b'.

   

The Basic Construction of AC Switchboard

If voltages exceed 250 volts d.c. or 55 volts A.C. then the switchboard must be dead front (no exposed live parts at the front) of the metal clad type.
   

Limiting voltage dip and response time under impact loading

The effect of a large load suddenly switched on to a small power installation such as a ships plant will be an instantaneous dip in the generator voltage.