Can I buffer the effects of inrush?

[Phil Allison]

"Sjouke Burry"

Phil Allison wrote:
"Jay Levitt"
Now I live in an apartment, and any time it powers up, any lights on the
same circuit will dim and flicker - even fluorescent ones, which I don't
get, but whatever.


** The light output from a CFL ( compact fluoro) is FAR less affected
by a drop in the AC supply voltage than incandescent or normal
uoros - so try using them.


There is a very nice industrial unit,(timer+relay), which
is intended to limit inrush current,

** The OP simply does ** NOT ** have an " inrush current " problem.

His laser colour printer draws very high AC current for many seconds while
it heats part of it's mechanism from time to time.

Even a small, B&W model will draw 1kVA doing this.

The solution is to either stabilise the AC supply to the lamps in use, or,
simpler still, use the damn lights installed in the ceiling - as they
are normally on a separate circuit.



........ Phil

 

[Eeyore]

Phil Allison wrote:

"Sjouke Burry"
Phil Allison wrote:
"Jay Levitt"
Now I live in an apartment, and any time it powers up, any lights on the
same circuit will dim and flicker - even fluorescent ones, which I don't
get, but whatever.


** The light output from a CFL ( compact fluoro) is FAR less affected
by a drop in the AC supply voltage than incandescent or normal
uoros - so try using them.


There is a very nice industrial unit,(timer+relay), which
is intended to limit inrush current,

** The OP simply does ** NOT ** have an " inrush current " problem.

His laser colour printer draws very high AC current for many seconds while
it heats part of it's mechanism from time to time.

Exactly. It's a 'warm-up' problem.

Even a small, B&W model will draw 1kVA doing this.

The solution is to either stabilise the AC supply to the lamps in use, or,
simpler still, use the damn lights installed in the ceiling - as they
are normally on a separate circuit.

I'm forever astonished at this kind of problem that Americans get. Of course
running kit off 120V instead of 230 makes it all the worse, but even so, I
*never* see lights dim when significant loads are switching in and out over here
in the UK.

Graham

 

[default]

On Wed, 5 Dec 2007 14:32:15 -0500, Jay Levitt <jay+news@jay.fm> wrote:

I have a relatively-ginormous Xerox 7750DN color laser printer, rated 12A.
I bought it when I was living in a large house, where it had its own closet
and its own 20A circuit; it worked great there.

Now I live in an apartment, and any time it powers up, any lights on the
same circuit will dim and flicker - even fluorescent ones, which I don't
get, but whatever. Worse, even in its "sleep mode", it powers up every few
minutes to do something - rotate the rollers to prevent flattening, or heat
the something to do the something, etc.

At first I assumed it was the typical "old apartments are not designed for
modern appliances" problem. But I've moved twice since then, and my latest
apartment was built last year to the new (2002) code. Everything's 20A.

A little searching reveals that this problem is called "inrush" and is
pretty common; appliances can draw more than their rated value as they kick
in. The usual answer is to run a dedicated circuit.

Since I'm renting, I'd prefer not to do that. Yet it would be very nice to
get my paperwork done by more than just the computer monitor's LCD
backlight. I've got to do *something* now that the sun goes down at 4:30.
(Yes, wait till spring, I know.)

Is there some battery-like device I could plug the printer into that would
store power and dole it out when needed, preventing the printer from
drawing more than its share? My first thought was a UPS, but from what I
read, they're actually lousy at dealing with inrush, let alone protecting
the upstream supply from it.

Ideally, I'd like to find an off-the-shelf device, rather than build one,
since (a) I'm lousy with electronics, (b) all my soldering gear is in
storage, and (c) the last thing I built was an Edison-to-phone-plug
converter, which I swear was absolutely necessary (I was digitizing the
power waveform) but should probably disqualify me from ever building
anything again.

Jay
The question should be can you do it economically?

UPS in that power range are going to be very expensive and the printer
may not like the harmonic distortion they add. The type of UPS you
need would have to maintain constant voltage - not make an abrupt
switch from mains power to battery power - sometimes called "full time
ups" - all the power is always derived from the battery as the
battery is also being charged. Or a ferro resonant ups - the FR
transformer holds up the AC for a cycle or two while the ups switches
on line.

Can you run a heavy extension cord to an outlet that doesn't
interfere?

Be nice to know exactly what, inside the printer, causes the problem.
There may be something you could do that would alleviate it at that
point. If the inrush is something like an induction motor coming on
line - you can't really do much about it, but if the inrush is a
capacitor charging or heater with a low impedance cold or a quartz
lamp there are things you might be able to do.

May be a better idea to put a regulator/UPS on the load that causes
the irritation rather than the printer.

motor generator and large flywheel?

Get a smaller printer and only power up the big one when you need it?
Bound to cost less.
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