DIYbanter - View Single Post

On Sat, 25 Mar 2006 14:57:52 GMT, (Speechless)
wrote:

On Sat, 25 Mar 2006 03:07:30 GMT, Carl Byrns
wrote:

Yeah, these days you have to under rate the cheapos by a factor of 3
to 3.5 for induction motor starting; otherwise, the term,
"instantaneous field collapse" takes on a meaning they don't teach in
electrical engineering school -- you ain't seen nothing until you've
seen a cheapo decelerate from 3600 rpm to zero in three revolutions.
Just make sure you are not standing inline with the engine when the
crankshaft exits the crankcase or you might be shopping for a set of
dentures. The cheapos are built for resistive loads only.

In the interests of reducing shipping costs for the mass market,
they've reduced rotating mass on the cheapos to the point where it is
nonexistant and advertise it as making the gen set more "portable."
The surge current capacity on a cheapo is near zero.

From my post about my old Kohler Electric Plant:
"It's a monster- Kohler K181 single cylinder cast iron engine and a
Kohler generator section. The generator section has three windings-
AC, starting, and a (IIRC) 200 amp 12/24 volt DC winding for
jump-starting cars or trucks. The big DC circuit can, according to
legend, be modified for use as a welder. The one in mine is tied off.
The thing weighs about 300 pounds and the AC output is only 2200 wats,
making less-than-portable. However, it has so much rotating mass it
will pick up sudden loads smoothly (like the time I had it powering a
fridge, halogen lamp. and a kerosene salamander and plugged in another
fridge I thought was off. It wasn't and the entire genset jumped off
the ground a couple of inches. The fridge started just fine.)
The starter winding is neat- press the button and the engine quietly
starts to spin up- no gear noise."

Just a note- all of the burned out portable gennys I've seen at the
flea market or in a repair shop seem to have OK engines and roasted
generator sections. The windings look like something from a washing
machine motor. Oh, yeah- they're usually Colemans.

-Carl