Eric - I'm guessing you're associating "soft start" with motors and the
long times inherent with heavy weight & limited horse power. I
checked the inductance of a 10 amp 120 volt transformer & it showed .5
henry. The time for 240 volts & 46 amps comes to .095 seconds. (t =
inductance * current / voltage).
Keep in mind that I am guessing on this, but if you can find an addon
"soft start" device with adjustable timing, it might be effective.
I'd like to hear the result, too.

Hul


wrote:
On Thu, 30 Oct 2014 22:49:20 +0000 (UTC), Hul Tytus
wrote:

Eric - a "soft start" on/off switch might be a possible cure. In concept
it turns on the current when the cycle is nearly over and then turns of as
the current passes zero. On the next cycle the current is turned a little
earlier. After ?? cycles full power is turned on for all cycles.
Mouser Electronics shows a 40 amp triac, which is the "switch" in a
soft start device, for roughly $2. Probably need a micro controller to
control the triac - $.50, along with a pc board & some caps & a transistor
or 2. Then a "heat sink" and, probably, a healthy fan.
All told, the cost isn't much so someone has probably built such a
gadget for sale as an "add on". If you can't find one, look for someone to
build it and offer to do some testing for him.

Hul

Greetings Hul,
Soft start may not be the ideal. When welding, if a soft start is
used, it takes longer to do the weld. This not only translates to
lower throughput it also frustrates the worker who wants to get as
many parts out the door as possible. I know that for me, as a
machinist, even when I worked for someone else, I hated stuff that
slowed me down. At the end of the day my pay would be the same but I,
like most folks, jest wanna git the job done. Thanks for your
suggestion though, it may be that even though not ideal in all
situations it will be the best solution. I will consider this when I
try to help my friend out. I had to use soft start on one of my CNC
machines in the past when the power available was just a little too
low. Fortunately for me I was able to adjust the spindle drive for a
softer start.
Cheers,
Eric
wrote:
A friend of mine here on Whidbey Island has a welding business. It's
pretty new, only a few years now. Anyway, he called me yesterday with
an electrical problem. Puget Sound Energy (PSE) has had complaints
from neighbors about voltage spikes or drops, my friend wasn't clear
on this, but they showed him a graph which I have yet to see. The
solution PSE is proposing is a new xmfr at the pole. PSE told my
friend the problem is because of the hard starting welder. The welder
is an older xmfr type machine with lots of copper. At full load it is
rated at 11 kw, which is about 46 amps. But I don't know what the
current spkies to when he first steps on the pedal. The machine is now
wired for single phase but can be wired for three phase. What he wants
to know is if he ran the welder from a Rotary Phase Converter would
the current spikes and voltage drops be less. I don't know. I also
don't know if there is a way besides my friend paying thousands for
PSE to install a new xmfr on the pole for this situation to be
ameliorated. He can't afford at this time for a new welder with a
softer start setting. Besides, the hard fast start means his employee
can make more welds. Any help would be greatly appreciated.
Thanks,
Eric