Posted by Ulysses on June 19, 2009, 11:14 am
> I know that this has been asked (and answered) many times before, but
> as it did not effect me at the time, I did not fully absorb it.
> Here is the description that was passed on to me:
> My Craftsman 5600 watt generator (model 580.675610) uses a 10.0 HP
> Briggs and Stratton engine and it runs great. While the unit starts on
> the second pull after sitting for several months, it does not produce
> an AC. The last time I discovered this issue (October 2008), I
> contacted Sears and the technician who came out to service the
> generator did something called 'flashing the field coil' with a small
> battery. Apparently the residual magnetism in the alternator weakens
> through lack of use and this simple procedure of flashing the coil is
> enough to excite the field and it resumes producing AC.
> Even though I didn't need to run the generator over the past winter, I
> thought it was important to drain the old fuel out of the tank and
> yesterday when I started the generator (for the first time since
> October 2008, it would not produce AC. I called Sears and a technician
> called me back to confirm the service call, but he told me I would
> have to run this unit more often to ensure the residual magnetism in
> the alternator didn't weaken in order to ensure it produces AC each
> time it starts.
> I find it odd that I would have to start this particular generator
> more often in order to ensure a constant flow of AC - each time it is
> started. Is this a design fault with the unit or could there be
> something wrong with this particular generator?
> So, thanks in advance for assistance. Mainly the question is "Is this
> an indication of a fault in the unit, or just the design and is there
> a way to prevent this from happening if the generator sits for several
> months?
I would not be very happy with such a generator but I wouldn't necessary
call it a flaw--some seem to hold the residual magnetism better than others.
A couple of things you could try: when you first start it have a voltmeter
attached to the AC output and try prodding the governor to increase the
engine speed momentarily. Some generator heads will start producing if you
do this. Also, when you do run it on occasion are you running it with a
load? Try connecting a 3000 watt or so load and run it for a few minutes.
Might help, might not. Put some Sta-Bil (gasoline stabilizer) in the gas
and run it more often. Personally I would not leave gas in the tank (or
carburator) longer than about six months, even with the stabilizer.
I have flashed field coils with the generator running. Someone said to do
it only with the engine not running. What I do is have a volmeter attached
and as soon as the meter starts moving disconnect the "flash" battery. If
you are not quick enough then bad things could happen.
Posted by Ralph Mowery on June 19, 2009, 12:29 pm
> I have flashed field coils with the generator running. Someone said to do
> it only with the engine not running. What I do is have a volmeter
> attached
> and as soon as the meter starts moving disconnect the "flash" battery. If
> you are not quick enough then bad things could happen.
My owners manual says to have the generator running when flashing the field
coil.
You are not flashing the 120/240 windings so it should not really be that
dangerous.
Posted by lost on June 19, 2009, 5:18 pm
As a matter of fact, the last brushless alternator I worked on had a shorted
cap on the exciter. After repair, it generated ok. The alternator case was
noticeably magnetic. So, in answer to your question, I have flashed the
stator in several generators that required such action. I did not try
magnetizing the alternator case like I suggested. I was trying to separate
the op from having to flash the stator. My own genny has brushes and every
time it's started the pole pieces are made magnetic. It will never require
the field coils to be flashed. Some people are worried about working on
things electrical; me, I'm too silly to care. James
>I know that this has been asked (and answered) many times before, but
> as it did not effect me at the time, I did not fully absorb it.
> Here is the description that was passed on to me:
> My Craftsman 5600 watt generator (model 580.675610) uses a 10.0 HP
> Briggs and Stratton engine and it runs great. While the unit starts on
> the second pull after sitting for several months, it does not produce
> an AC. The last time I discovered this issue (October 2008), I
> contacted Sears and the technician who came out to service the
> generator did something called 'flashing the field coil' with a small
> battery. Apparently the residual magnetism in the alternator weakens
> through lack of use and this simple procedure of flashing the coil is
> enough to excite the field and it resumes producing AC.
> Even though I didn't need to run the generator over the past winter, I
> thought it was important to drain the old fuel out of the tank and
> yesterday when I started the generator (for the first time since
> October 2008, it would not produce AC. I called Sears and a technician
> called me back to confirm the service call, but he told me I would
> have to run this unit more often to ensure the residual magnetism in
> the alternator didn't weaken in order to ensure it produces AC each
> time it starts.
> I find it odd that I would have to start this particular generator
> more often in order to ensure a constant flow of AC - each time it is
> started. Is this a design fault with the unit or could there be
> something wrong with this particular generator?
> So, thanks in advance for assistance. Mainly the question is "Is this
> an indication of a fault in the unit, or just the design and is there
> a way to prevent this from happening if the generator sits for several
> months?
Posted by Bruce in alaska on June 19, 2009, 6:10 pm
> I know that this has been asked (and answered) many times before, but
> as it did not effect me at the time, I did not fully absorb it.
>
> Here is the description that was passed on to me:
>
>
> My Craftsman 5600 watt generator (model 580.675610) uses a 10.0 HP
> Briggs and Stratton engine and it runs great. While the unit starts on
> the second pull after sitting for several months, it does not produce
> an AC.
snipped for Brevity...
> So, thanks in advance for assistance. Mainly the question is "Is this
> an indication of a fault in the unit, or just the design and is there
> a way to prevent this from happening if the generator sits for several
> months?
Ok, so you have a Sears (Generac) Genset where the engine runs just
spiffy, but no Juice comes out the Plugins.... and you PAID the Sears
Guy to come out and "Flash the Field" last time this happened.... and
now it has happened AGAIN... but you didn't pay attention to what the
guy did last time, and it must be a Design Error, cause it SHOULD "Just
Work".....
Welcome, to the world of Technology that you use, but don't understand..
Your Genset has TWO Windings. A fixed Stator (or Output) Winding, and a
rotating Field (or Exciter) Winding. There is a electrical connection
between the two windings, and usually some sort of Ac/Dc Rectifier -
Voltage Regulator System that controls the Excitation so you get 120 Vac
60 Hz Output out of the Stator Winding while putting just little juice
into the Field Winding. When the Genset has set unused for long periods
of time, (long is relative to the design of the genend) the Iron Core of
the rotating Field and it's Winding loose the slight Magnetism that
builds up when the genset is used. Your Genset REQUIRES this slight
Magnet response, to get things generating, and if it isn't there, you
get NO juice out of the fixed Stator Winding. To induce this slight
Magnetic Field, back into the Iron Core you need top "Flash the Field
Winding"..... To do this, you disconnect the Field Winding, from the
Ac/Dc Rectifier - Voltage Regulator System, and connect a 12 Vdc battery
across the Field Winding. this may be done with, or without the engine
turning, but most folks do it WITH the engine running. It should only
take a FEW Seconds to induce the Required Magnetic Field, into the Field
Winding and Field Core, and if you use a Voltmeter to monitor the output
you will see that the genend will be making juice while this is being
done. Once the Field Core Magnetic Response is recharged, it should hold
for a few months to a few years depending on the design of the Core.
Certainly for a few months anyway. Once Flashed, you stop the engine,
and reconnect the wires back to where they came from and reassemble
things back to the original State. Start up the engine, and Shazzamm,
You Gots Power....
If not, then you need to walk yourself over to www.SmokStak.com,
Register, (it is free) and tell our Resident SmartGuys, all about your
"Tail of Woe"... and they can get you educated and running again, right
quick... Everything you EVER "didn't" want to know about Generators in
general, and Generac Generators in particular, can be had over there,
and our Resident Smartguys, have hundreds of ManYears of experience with
Generators from 100 Watts, to many MegaWatts.....
--
Bruce in alaska
add <path> after <fast> to reply
Posted by Curbie on June 19, 2009, 8:35 pm
They also have enormously experienced and helpful folks with steam, it
seems from Bruce's comments, just an all round good bunch.
Curbie
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> as it did not effect me at the time, I did not fully absorb it.
> Here is the description that was passed on to me:
> My Craftsman 5600 watt generator (model 580.675610) uses a 10.0 HP
> Briggs and Stratton engine and it runs great. While the unit starts on
> the second pull after sitting for several months, it does not produce
> an AC. The last time I discovered this issue (October 2008), I
> contacted Sears and the technician who came out to service the
> generator did something called 'flashing the field coil' with a small
> battery. Apparently the residual magnetism in the alternator weakens
> through lack of use and this simple procedure of flashing the coil is
> enough to excite the field and it resumes producing AC.
> Even though I didn't need to run the generator over the past winter, I
> thought it was important to drain the old fuel out of the tank and
> yesterday when I started the generator (for the first time since
> October 2008, it would not produce AC. I called Sears and a technician
> called me back to confirm the service call, but he told me I would
> have to run this unit more often to ensure the residual magnetism in
> the alternator didn't weaken in order to ensure it produces AC each
> time it starts.
> I find it odd that I would have to start this particular generator
> more often in order to ensure a constant flow of AC - each time it is
> started. Is this a design fault with the unit or could there be
> something wrong with this particular generator?
> So, thanks in advance for assistance. Mainly the question is "Is this
> an indication of a fault in the unit, or just the design and is there
> a way to prevent this from happening if the generator sits for several
> months?