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 closetand its own 20A circuit; it worked great there.Now I live in an apartment, and any time it powers up, any lights on thesame circuit will dim and flicker - even fluorescent ones, which I don'tget, but whatever. Worse, even in its "sleep mode", it powers up every fewminutes to do something - rotate the rollers to prevent flattening, or heatthe something to do the something, etc.At first I assumed it was the typical "old apartments are not designed formodern appliances" problem. But I've moved twice since then, and my latestapartment was built last year to the new (2002) code. Everything's 20A.A little searching reveals that this problem is called "inrush" and ispretty common; appliances can draw more than their rated value as they kickin. 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 toget my paperwork done by more than just the computer monitor's LCDbacklight. 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 wouldstore power and dole it out when needed, preventing the printer fromdrawing more than its share? My first thought was a UPS, but from what Iread, they're actually lousy at dealing with inrush, let alone protectingthe 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 instorage, and (c) the last thing I built was an Edison-to-phone-plugconverter, which I swear was absolutely necessary (I was digitizing thepower waveform) but should probably disqualify me from ever buildinganything again.Jay-- Jay Levitt |Boston, MA | My character doesn't like it when theyFaster: jay at jay dot fm |...

Jay,I have the same problem with a laser printer. I eventually put it on a separate circuit so it wouldn't interfere with other stuff.The UPS still may be a good solution, but keep in mind that there are (at least) two types of UPSi.The cheaper ones feed the output from the input until an undervoltage is detected. Then, their outputs switch over to the internal supply. This type won't help your problem.There is another type and I think it's referred to as an "online" UPS. It always feeds its outputs from the internal supply and uses the input voltage only to charge its batteries. This may provide the buffering you need, but you'd have to try it to see if the results are acceptable.Bob

Can I buffer the effects of inrush?

Dec 05, 2007 21 Replies

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Phil Allison 18 years ago

** 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

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Eeyore 18 years ago

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

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

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