
40 Shipboard Electrical Power Systems
Allowing a 30% margin is common for growth and for uncertainties in loads during
a preliminary power system design of a new line of ship. In heritage design, a 10%
margin may be adequate.
Although each load has its own average contribution to the generator power rat-
ing, the wire ampere rating for each wired load must be based on its own peak kW
rating with 30% margin as follows:
Ampere ratingof each load wiring
Peak watts
1.3=
eeach load can draw
Load voltage Power factor×
(2.7)
The cargo-handling machinery during in-port unloading generally consumes high
power, making the P
inport-unload
the maximum load on ...