Yamaha EF4500iSE Theory & Diagnostics Manual page 48

Yamaha Generator Theory & Diagnostics Guide
THEORY FOR AVR TYPE GENERATORS WITH
BRUSHES
This type of generator unit is used in Yamaha's
EDL6500S diesel generator. It is still a self-exciting
BRUSH TYPE AVR GENERATOR
type generator, but uses a brush and slip ring set up
to complete the loop that turns the rotor into a large
magnet.
Generation of electricity begins when a small per-
manent magnet inside the rotor begins to spin inside
the sub-coil. That AC voltage is then sent to the AVR
circuit board, where it is full wave rectified into DC
voltage.
The DC voltage is then sent from the AVR board to
the main field coil in the rotor, through the brushes
and magnetizes the rotor. This causes the main coil
in the stator to suddenly increase voltage to the
rated output.
TROUBLESHOOTING PROCEDURES FOR AVR
TYPE WITH BRUSHES
The troubleshooting procedure is very similar to the
other types. The big difference with this type is that
it is not necessary to remove the rotor from the gen-
erator assembly to test it. This is because there are
no diodes soldered inside and the windings can be
tested through the slip rings
Once again we'll quickly go through the steps that
we've already covered and detail the new ones a
little more closely.
First verify the problem. If the voltage is a little low,
make sure that the engine RPM is correct. On this
model, the RPM should be set at 3,250.
This is be done by using the special photoelectric
tachometer that is designed for diesel engines.
Follow the directions with the tachometer for proper
usage and this models Service Manual for proper
adjustment procedures.
If there is still little or no voltage from the receptacle,
then check for 120 volts AC between the red and
white wires and 120 volts AC between the brown
and blue wires on the generator unit.
If the voltage is good, check the wiring and the con-
trol box. If not, proceed to testing the generator.
Disconnect all of the wires from the generator unit,
in preparation for the tests.
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