Bc Generator; Ac Terminal Connections - Westerbeke 6.5 MCG Service Manual

BC GENERATOR SINGLE PHASE
DESCRIPTION
. The BC generator is a brushless, self-excited generator. which
requires only the driving force of the engine to produce an
AC output. The stator houses two sets of windings; the main
stator windings and the exciter windings. When the generator
is started, residual magnetism in the four rotating poles
induces a voltage in the stator which then generates an even
larger voltage in the exciter windings. This mutual build up
of voltage in the four rotating poles and in the exciter wind-
ings quickly reaches the saturation point of the capacitor(s)
and a regulated energy field is then maintained in the stator.
At the same time,this regulated field produces a steady volt-
age in the stator windings which
can
then be drawn off the
generator's AC terminals to operate AC equipment. The
generator is a single-phase, reconnectable
~20
volt AC
two-wire or 115 volt AC two-wire or 230 volt AC two-wire,
at 50 hertz.
The generator's data plate gives the voltage, current and
frequency rating of the generator. An AC wiring decal is
affixed to the inside of the louvered cover at the generator
end. A diagram of the various AC voltage connections is
proviged on the decal. An Integral Controller (IC) is mounted
inside the generator and supplies a continuous
DC.charg~
to
the generators starting battery when the generator
IS
runrung.
Bearings: The bearings are sealed type and permanently
greased requiring no maintenance during their working life
(approx. 30,000 hours).
AC TERMINAL CONNECTIONS
t 4 '2 5
CIRCUIT.
BREAKER
L1
1
6
CIRCUIT
BREAKER
N l1
-
ISOLATED
POST
(NEUTRAl}.
4
ISOLATED
POST
120V/60Hz
N
3
230V/50Hz
NOTE: Correctly poi)ition the case ground wire (white/green)
onto the neutral/ground terminal.
67
MOTOR DATA
'The power required to start an electric motor is considerably
more than is required to keep it running after it is started.
Some motors require much more current to start them than
others. Split-phase (AC) motors require more current to start,
under similar circumstances, than other types. They
are
commonly used on easy-starting loads, such as washing
machines, or where loads are applied after the motor is
started, such as small power tools. Because they require
5
to
7 times as much current to start as to run, their use should be
avoided, whenever possible, if the electric motor is to be
driven by a small generator. Capacitor and repulsion-
induction motors require from 2 to 4 times
as
much current
to start as to run. The current required to start any motor
. varies with the load connected to it. An electric motor
connected to an air compressor, for example, will require
more current than a motor to which no load is connected.
In general, the current required to start 115-Volt motors connected
to medium starting loads will be approximately as follows:
MOTOR SIZE AMPS FOR AMPS FOR
(HP) RUNNING
(~TARTIN~l
(AMPERES) AMPERES
1/6
3.2 6.4 to 22.4*
1/4 4.6 9.2to 32.2*
1/3
5.2 1 o.4 to 72.8 *
1/2 7.2 14.4 to 29.2*
314
10.2 20.4 to 40.8*
1 13 26to 52
*NOTE: In the above table the maximum
Amps for Starting
is
more for some small motors than for larger ones. The reason
for this is
that
the hardest starting types (split-phase) are not
made in larger sizes.
Because the heavy surge of current needed for starting
motors is required for only an instant, the generator will not
be damaged if it can bring the motor up to speed in a few
seconds. If difficulty is experienced in starting motors,
tum
off all other electrical loads and, if possible, reduce the load
on the electric motor.
Generator Maintenance
Maintaining reasonable cleanliness is important. Connections
of terminal boards and rectifiers may become corroded, and
insulation surfaces may start conducting if salts, dust, engine
exhaust, carbon, etc. are allowed to build up. Clogged venti-
lation openings may cause excessive heating and reduced life
of windings.
In addition to periodic cleaning, the generator should be
inspected for tightness of all connections, evidence of
overheated terminals and loose or damaged wires.