Selection Of Motor Starter; Power Connections To Ac Motor; Power Connections To Dc Motor - Maxwell VWC 4000 Series Manual

2.5

SELECTION OF MOTOR STARTER

Several AC motor starter options for windlasses are
available, each with characteristic current demands
and start load limitations. Maxwell recommends that
selection of the best motor start system be entrusted
to experienced persons familiar with anchoring
procedures and the vessels generating capacity.
"Direct On Line" starter is the simplest way of starting
an AC motor and it will allow the windlass to start
under full rated load. However, this method requires
relatively high momentary starting current, which the
generators may have adverse effect to the rest of the
electrical system on board. See specifications for
current values at 400V in Section 1.3 and make sure
to recalculate it for the voltage used on board. Start
current may be limited to about half the above
amount by using a "Star-Delta" starter. However,
start torque is thereby limited to loads of about 25-
30% of the windlass rated capacity.
"Star-delta" and "soft starters" are not recommended
for starting windlass motors, as the motor torque is
severely limited during start up period. Since these
motors often have to start under load (when
retrieving the ground tackle), they might not be able
to move until they reach the full voltage and torque.
The benefit of starting at lower current would
therefore be lost. Also, the motor brake would
release immediately on start-up, which could cause
short movement of the chain in opposite direction.
The Variable Frequency Drives (VFD) offer accurate
control of current during start up period while
keeping high motor torque. They also offer various
other benefits like:

infinite speed control

running the windlass over its nominal speed

accurate current overload and thermal
overload control
Both "Direct On Line" starters and Variable
Frequency Drives are suitable and available from
Maxwell, customised to suit the anchor windlass and
stern capstan application.
2.6 POWER CONECTIONS TO AC MOTOR
Remove the motor terminal box cover and take care
not to misplace the sealing gasket and screws.
Select a suitably sized, waterproof cable gland for
the armoured supply cable. The selected gland fitting
must fit the terminal box, be capable of anchoring the
armoured cable, and allow an effective waterproof
entry seal to be made.
Make the line connections to motor terminals. Make
also an effective earth connection.
Separately and similarly, enter the 2 thermistor
cables to the motor terminal box, and connect to the
two auxiliary terminal connectors of the thermistor
circuit.
!
The selection of the type of motor starter
should be done by a qualified electrical
engineer, taking into consideration the power
generating capacity on board.
Maxwell offers both advice and different types of
custom made starters to complement our
windlasses.
!
The "up" and "down" start contactors must be
mechanically or electrically interlocked to
safeguard the motor, in the event that an
accidental attempt is made to start the motor in
both directions simultaneously.
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