I bought a 6000 watt home generator new and ran it twice. Haven't had
occasion to use it in the past 4 years. Started it up the other day and the
engine ran fine but the generator won't produce power. It was working fine
when I last used it.
I was told that it needed to be flashed. Can anyone tell me how to do that?
Thanks,
Chuck
This begs the question as to WHY a previously working genertor would need to
be flashed in the first place?
The rotation iron always magnitized in the same direction so what even could
cause it to lost its residual magnitism to the point where it can't
"bootstrap" up from near zero but NOT zero magnetism?
EMWTK
Here's how I have always done it...
Get to the brushes and disconnect them from the circuit board or
rectifier. Connect jumper leads to a 12V battery then connect them to
the brushes for a few seconds. Polarity doesn't matter. That's all there
is to it.
Q
Anth>> This begs the question as to WHY a previously working genertor would >> need to
While the generator is NOT running.
Temporarily (~10secs) connect up a charged 12V battery to one of the
110v outputs.
Disconnect battery and start generator..
What works for me is a special connector attached to the brushes,
with a 1 amp diode in series. If the alternator doesn't produce
power at startup I plug the starting battery (12 volt) in for a
few seconds.
Free men own guns - www(dot)geocities(dot)com/CapitolHill/5357/
Forgot one step.
After it's started, connect a resistive load, like a pair of 110v
incandescence light bulbs, to the unit as you bring the genny up to
speed & freq.
Before you flash it try prodding the throttle and see if some increased RPMs
will get it going.
I've done it with a 6 volt 5 Ah battery with success. I just connect one
side of the battery to the AC output and while the engine is running
momentarily connect the other side. Once the AC voltage starts to climb I
disconnect the battery. You might want to put a fuse in line with the
battery so you don't blow it up. Then run it for a while with a load (like
someone else said).
I've not done it sucessfully with the generator not running. It sounds
safer but had no effect on my particular genny.
Basically you need to magnetize the field winding with say a 12vdc source.
The owners manual typically will describe the procedure.
The last gen that I flashed was a industrial 50hz 3kw motorized generator. I
disconnected the field and fed 12vdc into the field windings. As long as the
field core is slightly magnetized it will be enough to get the stator to
produce enough voltage to get the exciter going.
Cheers
Get a 12 volt battery, use the one in your car or use a battery charger if you
have
one with sufficient current capability. Open up the connection box on the
generator
and find the leads coming from the stator. These connect to the outlets.
Disconnect
them from any other wiring and momentarily connect them to the 12 volts. Simply
brushing the wire from the battery against the generator wire will be enough.
Reconnect the stator wires and crank.
This pulse of current re-establishes the residual magnetism necessary to bring
the
generator up when started. This magnetism can go away over time.
If the above "static flash" doesn't work then do a "dynamic flash". Connect a
"Jesus
cord" (plug on one end, alligator clips on the other) to the outlet on the
generator.
Connect a 100 watt 120 volt bulb in series with the hot leg. Apply the 12 volts
between the bulb and the neutral of the line. The instant the DC current
flows, the
generator will start generating 120 volts AC. The bulb is to prevent much AC
current
from being applied to the battery. The bulb should light instantly and remain
lit as
long as the battery is connected.
If this doesn't work and if your generator has slip rings and brushes then the
next
step is to see if the brushes are stuck in their holders and/or the slip rings
are
glazed over, preventing the rotor field from being energized. At this point you
really do need the manual to assist with locating the brushes and accessing them.
John
--
John De Armond
See my website for my current email address
Hi Guys, I've read the article on flashing a generator and have tried all
recommendations to no avail. I have a small 3KW generator attached to a
Honda G200 petrol engine. I've had several problems with the engine but have
resolved these and it is running fine. My problem now is that I have no
output from the generator. I'm not sure how long the generator has been
stood without any use and suspect it is simply a matter of flashing it
again.
I've con checked the stator with a DVM and the windings seem to be intact as
are the windings in the rotor.
The unit is a dual 110V / 220V output and the stator has two separate
windings which via a switch and are either used in parallel for 110V or in
series for the 220V output. There is also a 10uf capacitor in the circuit
but I'm not sure where this connects?
The rotor would also appear to have two separate windings with what looks to
be a diode in series with each winding. Unfortunately I can't tell from the
markings on these to confirm if these are indeed diodes.. I also assume the
rotor is self exciting based on residual magnetism?
Would anyone have a circuit diagram of a typical generator set up as this or
provide me with a description as to the principles of how self exciting
rotors work.
Many thanks
Kindest Regards
Tom
It's a separate winding in the stator. The voltage is generally quite high -
250 or
more. It's strictly a parallel LC circuit.
John
--
John De Armond
See my website for my current email address
Thanks John, I suspect the capacitor at the moment. I've removed this and
checked it with a DVM I get a momentary short circuit reading and then it
returns to about 56 Ohms. I would have thought it should have returned to a
value much greater than this? I've ordered a replacement capacitor of the
same value and voltage to see if this makes any difference.
Many thanks
Tom
That cap sounds maybe OK, if you meant 56k instead of 56 ohms. Motor run caps
like
that commonly have an internal bleeder resistor. You should see the ohmmeter
kick
toward zero ohms and then drift back to the value of the bleeder. 56kohms is
about
right for a bleeder.
Can you run the generator? If you can, measure the voltage across the cap. If
the
cap is bad or leaky, the voltage will be below about 150 volts, usually way
below. If
the cap is good then the voltage is typically 250 volts or more. If you can
measure
frequency, the frequency will be the 3rd harmonic of whatever speed your
generator is
running at. If the cap is bad the frequency will be primarily the fundamental,
50 or
60 hz, depending on where you live.
The generator may not build any voltage at all if the cap is bad. If it doesn't
then
hook a 12 volt car battery through a 120 volt, 100 watt lightbulb to the
generator's
output. That'll supply enough field to get it to come up and if it happens to
come
up to full voltage, the 100 watt bulb will protect the battery.
BTW, that's a standard motor run cap so you can pick up one at any appliance
parts
store, HVAC supplier or electric motor repair shop. If they see you coming,
it'll be
$30-40. If they give you the normal "wholesale" price, figure $5 to 10.
You can substitute a plastic cap, polypropylene or whatever, of the same voltage
and
capacity. Motor caps are no longer oil and paper. Inside the can IS a plastic
cap.
They just put 'em in the cans so as not to confuse the HVAC parts changers. The
can
is mostly hollow or oil filled.
John
--
John De Armond
See my website for my current email address
Hi Guys, I've done some testing this morning on the generator with a 240V
60W lamp in series with the stator windings to try and induce an EMF in the
windings.
I then took the following measurements:
Exciter windings with the Capacitor removed (Test points A - B) = 2.46V AC
Exciter windings with the Capacitor installed (Test points A - B) = 0.93V AC
Rotor Windings with the Capacitor removed = 153mV DC (Test points A1 - B1)
and 174mV DC (Test points A2 - B2)
Rotor windings with the Capacitor installed = 1.42mV DC (Test points A1 -
B1) (1.94V AC) and 1.42mV DC (Test points A2 - B2) (up to 10V AC changing).
I suspect one of the Rotor diodes may be faulty as I get the same changing
readings on the same winding if I rotate the rotor 180deg.
I've also rechecked the capacitor with the DVM and it is only reading 56
ohms after the initial charge kick.
The following is a link to the test set up and how I believe the windings
relate to each other.
formatting link
I'm not sure about the orientation of the diodes as these will have to be
disconnected before I can check them.
As soon as I have disconnected and checked the diodes I will update the
list.
I can't get your schematic to load any farther than the bottom of the rotor
diagram
so if there are any notes there I didn't see 'em. Tried Opera and Firefox.
That's odd behavior. Rotor diodes are a good suspect but I might also suspect at
this point a shorted turn in the stator. I'd do a couple of things. First,
increase
the current input. When I recommended a 100 watt light bulb, I was thinking
around 1
amp for our normal 120vac. If you had a 500 watt heater that you could put in
series, so much the better.
My other thought is, can you remove the stator from the rotor and test it
separately?
In the motor shop I'd now move to the Baker Surge Tester
formatting link
Unfortunately they've password protected their user manuals (!) so I can't send
you
there to see how this test works. In a nutshell, the instrument "rings" the
winding
with a high voltage pulse and analyzes its decay behavior. An OK winding will
ring
for 3 or 4 cycles while a compromised/shorted winding will either not ring at
all or
will damp down in one cycle.
If you have an O'scope then you can somewhat simulate this test by passing DC
through
the winding and snapping open the circuit with a cap-shunted switch (same as old
points-type car ignition) while monitoring the winding with the scope.
We have another gadget called a core loss tester. This involves passing a
couple of
loops of heavy cable through the stator and passing high current AC through it.
An
AC buzz-box welder will do. Then we scan each stator bar looking for
differences.
The instrument has a probe coil connected to a meter and headphones. The probe
is
held over the stator and gradually moved around. Any variation in intensity
registers. A shorted turn will essentially eliminate the magnetic field. That
area
of the stator will also get slightly warm from the circulating current.
I'm still not happy with that capacitor reading. 56 ohms is far too low for a
bleeder. I also don't think the meter would kick much initially with that little
resistance across it. Are you sure your meter is OK?
I normally don't suspect test instruments because they are so reliable but every
reading you reported below is highly abnormal. Do you have another meter you can
try? I've never seen a shorted rotor diode cause the excitation winding voltage
to
be that low.
At this point, if your meter is OK then I'd probably pull the rotor and stator
apart
and test each separately.
John
--
John De Armond
See my website for my current email address
Hi John, many thanks for your reply. The schematic is just a jpg image with
no additional notes. It should just show the stator windings (two coils in
series) the exciter windings with the capacitor in parallel and the two
rotor windings which I have now updated to include the capacitor in parallel
with these and the diodes. Let me know if you want me to send this to you
directly via e-mail.
I've rechecked the capacitor with another DVM and I get the same readings as
before, 56 Ohms. I don't suspect my original DVM as I've had this for a few
years and it has never let me down yet.
I've removed the diodes from the rotor and they appear to be ok. Forward
bias on both diodes gives me about 143 ohms and infinity on the reverse
bias. The diodes also have a small ceramic capacitor in parallel with them
which I didn't see until I removed them from the rotor.
The capacitors do not register anything when checked with the DVM and I
assume these are ok. I can't work out the size of these from the markings
(V350K10) but I'm guessing either nF or pF. The diodes are not like any
other diodes I have come across and look more like two diodes in series on
the same body. There are two sets of numbers on these, one on each body
casing I9445-6 & I9433-6. Can you identify these from the numbers?
The rotor winding would also appear to be ok as both of these show about 3
ohms with the diodes removed.
I think I'm back to replacing the main Capacitor when it arrives, it was
ordered on-line over the weekend and should be with me later in the week.
Thanks again
No idea what those numbers are. I tried my usual SWAG and stuck the numbers into
Google. No hits that made sense.
Yep, that's what I'd do next.
John
--
John De Armond
See my website for my current email address
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