Specifications
5.0KW
Be
GENERATOR
SINGLE
PHASE
Testing
Component
Resistance
Values
Rotating
Field/Auxiliary
Windings
and
Diodes
Two sets of windings are found in the rotor assembly. An AC
voltage
is
produced
in
two groups
of
windings as the rotor
turns at rated rpm. The AC voltage passes through each
of
the two diodes mounted
on
the isolated fixture
just
before the
rotor carrier bearing. The AC sine wave
is
changed to a
DC
and this DC voltage is passed through the two groups of.
. rotating field windings producing a DC field around these
windings. This field affects the AC winding
of
the two main
stator groups inducing
an
AC voltage in these windings that
is available at the AC terminal block connections.
1.
Rotating Field! Auxiliary Windings
5.0 KW
BCG
3.8
Ohm
To
check the resistance values, rotate the engine's crank-
shaft to position the diode(s) on the generator's shaft at
12
o'clock.
To
make a quick check
of
these windings,
presume the diode is
OK
and place one
of
the ohmme-
ter's leads
on
the connection at the top
of
the diode and
the other lead at the connection at the base
of
the diode.
Compare readings with the value above.
If
a distinct dif-
ference is noted in the ohm value, carefully unsolder the
lead on the top
of
the diode and remove the diode from
its isolated heat sink using a thin walled, deep well
7116
in
(11
mm) socket.
NOTE:
The aluminum heat sink that the diode threads into
can be bent carefully outboard to
make
easier access to
the diode.
With the diode removed, both leads for the first group
of
rotating field!auxiliary windings will be isolated with no
interference from a possibly faulty diode.
Check the resistance value
of
the rotating windings by
placing the ohmmeter's leads across the two exposed
leads.
Also, verify that no continuity exists between these wind-
ings and the rotor shaft by leaving one ohmmeter lead
attached to the winding lead and the other ohmmeter lead
touching the shaft: no continuity should exist.
If
continu-
ity is found, a short exists
..
Repeat this same check on the second group
of
windings.
Rotate the engine's crankshaft
180
0
to
position the sec-
ond diode and connections at 12 o'clock. .
No continuity should be found between these two groups
of
windings.
2. Diodes 8 - 9.5 ohms (approximate) using a
260 Simpson
Analog Meter
To
check the diode, unsolder the connection from the top
of
the diode. Place one ohmmeter lead on the connection
at the top
of
the diode and the other ohmmeter lead
to
the
diode's base. Then reverse the position
of
the ohmmeter
leads.
LOW
RESISTANCE
H.\(-*B~f
DIODE
INFINITE
RESISTANCE
A low resistance should be found with the leads
in
one
direction, and infinite resistance (blocking) in the other
direction. Different meters will read different resistance
values through the diode.
NOTE:
Different meter models
may
show different ohm
values, but should read the same
jor
both diodes.
Diode Rating: 1600 amps 26 Amps
The diode's rating is far in excess
of
the circuit's require-
ments. Most likely a diode failure will result from an
overspeed
or
load surge.
Main
Stator
Windings
Single
Capacitor
0.6 Ohms
Dual
Capacitor
0.4 Ohms
BC
Model
0.3 Ohms
Residual voltage measured between #1-#3 and #4-#6 will be
2-3 volts AC between each pair
of
leads at the terminal
block. This would be an indication that the stator windings
are okay. Check exciter windings and artificially excite the
generator.
r-
b
------------1-;
I I
I I
I
I
: 2
!b~
I 5
: 6
'--
---
----------
NOTE:
The numbered leads on the
terminal block are
not
in any
numerical order. They are
shown below.
~----..,
1 4 3
000
5 2 6
000
TERMINAL
BLOCK
Group
#1
- Measure resistance value between terminal with
lead #1 and terminal with lead #3. (Check that there
is
no
continuity
of
Group #1 windings to the case ground.)
Group
#2 - Measure resistance value between terminal with
lead
#4
and terminal with lead #6. (Check that there
is
no
continuity
of
Group #2 windings to the case ground.)
Check for a possible short between the two groups
of
stator
windings by placing one lead
of
the ohmmeter on the termi-
nal with the stator lead #3 and the other ohmmeter lead on
the terminal with stator lead #6. There should be
no
continu-
ity between the two groups
of
stator windings.
Engines & Generators
53