Well,the OP mentioned "inverters" and MY post questioned why an inverter
was used when the generator already makes a sine wave output.
Then someone else mentioned Honda,and I researched that to answer my own
generating a sine wave from a DC supply requires switching large
currents.the switchuing generates harmonics.
Now,the sine wave output may be very clean and right on freq,but the
inverter's switching circuitry may radiate those harmonics,that could be
picked up by other instruments.
It takes very careful design to minimize radiated noise.
I have a similar problem with my 1850 but the output voltage drops at
about 1100 watts load. The diodes appear ok, but I have no way to test
the varistors in parallel with them.
The problem started with a snapped governor lever which would have
caused very high engine speed. That would have created a very high
output voltage which I suspect could have damaged the diodes and/or
varistors causing them to fail as the load increases. I hope to replace
both and see what happens. Any thoughts?
I've put together a small page showing the repairs.
Well, I never understood why, but, in automobile terms, I thought
alternators had higher output at low speeds than generators did, but
lower output at high speeds. Or that the voltage woudln't increase
that much. A) Does your Powermate use an alternator? B) Am I right
about what I thought. C) Would that make you wrong?
Did the load increase? Or did the load stay the same and output
voltage increase? But I guess the second would make the voltage
across both the dioades and the varistors increase, which is what you
had in mind. Still, would that be enough to make them fail? I guess
if they were not much better than the expected output one or both
The generator operates at a constant speed of 3600RPM in order to
produce a 60Hz output.
Under no load the output is about 120VAC. It remains relatively
constant up to about 1100 watts load. After that as the load increases
it drops considerably, down to about 90VAC with a 1300 watt load. It
should be capable of 1500 watts output continuously at 120VAC.
The governor in the engine failed and would have caused it to rev very
high at full throttle. During this time the output voltage would have
gone very high, and possibly caused damage to the diodes and/or the
varistors. These components are on the rotor, and somehow connect with
the field coils. I'm still trying to understand better how a brushless
output generator somewhat self regulates its output voltage.
I've repaired the governor problem, and the engine works well now.
However the next step is to ensure all components on the generator side
are good in order to produce the proper power output.
The frequency of the AC power is determined by the number
of poles the genset has in relation to the speed. A two
pole generator runs at 3600rpm whereas a four pole generator
runs at 1800rpm. The output voltage is determined by the field
voltage supplied by the voltage regulator. The field voltage
may only be 12 volts DC to get the generator to output 120VAC.
A small change in field voltage produces a large change in output.
Thanks for all the response folks! Just to clear up some stuff, it is
a two pole rotor so I believe I need 3600 RPM. Second, (unless I am
really up in the night) there is NO inverter in this baby, it
It sounds like (particularly from people who have owned them) that
there may be NOTHING wrong with it which is kinda' sad. Well, I am
going to go out and tinker with it some more...
Latest and Greatest.
Okay, I un-soldered the diodes and checked them one more time, good
to go. Put the whole thing back together, and fired it up.
Same problems, If I want 60Hz I get about 90 volts. If I want 120
Volts I get about 70Hz. (In my house for comparison the Kill A Watt
shows 59.9Hz and 122.0 Volts) Just to see what would work, I tried
hooking up my table saw, it took a second but it did spin up and I am
sure that baby pulls some amps! I then tried my battery charger, no
luck it would not even turn on (which is kind of the reason I want
this gen anyway). And on the 12 Volt socket I get 24 Volts!!! I'm
not out any money here, just time. But, after I burned my thumb on
the exhaust trying to tweek the rpm's I decided enough is enough. If
I had a shotgun I would end this units pain and suffering...
Thanks to everyone who posted
I actually bought a new engine for mine (the first one didn't last very
long) and it just never seemed to have enough output. I even tried
connecting it to a 4 HP Honda engine. I broke the cooling fan on the rotor
when I connected it to a 10 HP engine, just to see if the low output was due
to not enough engine power. I found another use for that Honda engine and
I'm looking for another use for the replacement engine (compressor
perhaps?). I replaced all the diodes, checked the resistors, checked the
coils, and I just can't find anything wrong with it. Come to think of it,
you may have a bad capacitor. That might cause the low frequency. Make
sure you get one with the exact same value. It should at least get a
battery charger to come on (assuming it's a high-frequency smart charger
type). Your DC voltage seems a bit high but I wouldn't be surprised to see
17 or 18 volts. For emergency battery charging only.
BTW Coleman gets about $250 for a new rotor. The cooling fan on my cheap
Chinese generator starting falling apart (at 3000 hours) and they only want
$25 for a new rotor. The whole generator usually sells for about $250 (or
less on sale). My Coleman engine only lasted about 300 hours.
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