Service manual
GENERATOR
INFORMATION
USE
OF
ELECTRIC
MOTORS
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 com-
monly
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 dri-
ven
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
(AMPERES)
STARTING
(AMPERES)
1/6
3.2
6.4
to
22.4*
1/4
4.6
9.2
to
32.2*
1/3
5.2
10.4
to
72.8
*
112
7.2
14.4
to
29.2*
3/4
10.2
20.4
to
40.8*
1
13
26
to
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
maJe
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.
Required
Operating
Speed
Run
the
generator first with
no
load applied, then at half the
generator's capacity,
and
finally loaded to its full capacity as
.
indicted
on the generator's data plate. The output voltage
should
be checked periodically
to
ensure proper operation
of
the
generating plant and the appliances it supplies.
If
an AC
voltmeter
or ampere meter is not installed
to
monitor voltage
and
load,
check it with a portable meter and amp probe.
NOTE:
When
the
vessel
in
which
the
generator is installed
conIIlins
A C equipment
of
120 volts
Qnly,
it
is
recommended
that
the
generator's
AC
terminal block be configured
to
pro-
vide
one
120 volt A C hot leg for
the
vessel's distribution
paneL
This
will
ensure
good
motor starting response
from
the
generator.
Generator
Frequency
Adjustment
Frequency is a direct result
of
engine/generator speed, as
indicated
by
the following:
o When the generator is run
at
1800 RPM, the
AC
voltage
output frequency is
60 Hertz.
o When the generator is run at 1500 RPM, the
AC
voltage
output frequency is
50
Hertz.
Therefore,
to
change the generator's frequency, the genera-
tor's drive engine's speed must be changed. A reconfiguration
of
the AC output connections at the generator is also neces-
sary.
Generator
Pf1aintenance
o 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.
Qogged ventilation openings may cause exces-
sive heating and reduced life
of
windings.
o For unusually severe conditions, thin rust-inhibiting petro-
leum-base coatings, should be sprayed or brushed over all
surfaces to reduce rusting and corrosion.
'TYpical
materials
suggested are Daubert Chemical
Co.
"Non-Rust AC-410"
and Ashland "Tectyle 506"
or
equivalent.
o In addition to periodic cleaning, the generator should be
inspected for (a) tightness
of
all connections, (b) evidence
of
overheated terminals and (c) loose
or
damaged wires.
o The drive discs on' single bearing generators should
be
checked periodically
if
possible for tightness
of
screws
and for any evidence
of
incipient cracking failure. Discs
should not be allowed to become rusty because rust may
accelerate cracking. The bolts which fasten the drive disc
to
the generator shaft must be hardened steel
SAE
grade
8,
identified by 6 radial marks, one
at
each
of
the 6 cor-
ners
of
the head.
o The rear armature bearing
is
lubricated and sealed; no
maintenance is required. However, if the bearing becomes
noisy or rough-sounding, have it replaced.
o Examine bearing at periodic intervals. No side movement
of
shaft should
be
detected when force is applied.
if
side
motion is detectable, bearings are wearing or wear on
shaft
of
bearing socket outside bearing has occurred .
Repair must be made quickly or major components will
rub
and cause major damage
to
generator.
I "'IIY'IWESTERBEKE
I
Eng;n~l!&
Generators
50