Laser printer draws current in a spike, what for?

In alt.engineering.electrical ehsjr@bellatlantic.net wrote:
| phil-news-nospam@ipal.net wrote:
|
|>In alt.engineering.electrical Andrew Gabriel <andrew@cucumber.demon.co.uk> wrote:
|>
|>| In article <MMyWVDBvauMBFw+u@jmwa.demon.co.uk>,
|>| John Woodgate <jmw@jmwa.demon.contraspam.yuk> writes:
|>|> According to US sources, problems such as you report never occur, and
|>|> they don't need to implement the IEC versions of those ENs as US
|>|> standards. So you are actually just imagining the flicker. (;-)
|>|
|>| The irony is this is quite common in the US, but I've never seen
|>| it happening in a 240V country ;-)
|>
|>We do have 240 volts. The problem is that we also have the NFPA that
|>publishes the NEC which in 210.6(A)(2) restricts the voltage for cord
|>and plug equipment to a maximum of 120 volts relative to ground, thus
|>disallowing the use of the 240 volt connection for the typical laser
|>printer.
|>
| I don't get your point. Our (US) 240 volt circuits are
| 120 volts relative to ground. I've got a 240 volt
| cord and plug connected air conditioner. NFPA
| does not prohibit 240 volt appliances, so I'm
| missing your point.

I intended to also include the 1440 watt limit from the code. Loads
over 1440 watts can be supplied with 240 volts, no problem.


| In any event, you don't need a 240 volt circuit
| to solve the problem of dimming lights when the
| laser printer fuser heats. Put the printer on a
| separate circuit. Essentially, that is what putting
| it on a 240 volt circuit would do anyway, so
| the fact that it draws less current on 240 wouldn't
| matter.

It would help some. The voltage drop in the wiring up to the point where
the circuits diverge, and the transformer impedance, will be there to some
degree, but the lower current of a 240 volt connection will reduce it. OTOH,
having it on the other phase of 120 apart from the lights will avoid it.

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[Julie]

~Dude17~ wrote:

X-No-Archive: Yes

I've got a laser printer that draws current in spikes and it
makes the lights flicker as well as causing a UPS on the same circuit
to switch over to battery due to excessive dV/dT. Unfortunately, I
don't have a way of putting the printer on its own circuit unless I
want to use a long extension cord.

Your printer is already on its 'own' circuit -- if it wasn't, the lights would
get brighter, rather than dimmer/flicker.

 

[Julie]

Julie wrote:

~Dude17~ wrote:

X-No-Archive: Yes

I've got a laser printer that draws current in spikes and it
makes the lights flicker as well as causing a UPS on the same circuit
to switch over to battery due to excessive dV/dT. Unfortunately, I
don't have a way of putting the printer on its own circuit unless I
want to use a long extension cord.

Your printer is already on its 'own' circuit -- if it wasn't, the lights would
get brighter, rather than dimmer/flicker.

Scratch that -- outlets on a circuit aren't in series.

 

[Tzortzakakis Dimitrios]

AGAIN!No need for UPSs in the 21st century.We had an udersized one in the
computer lab, in our college, with the result when everuthing is on it
"tripped" (also a small blackout).It's so silly as to power your
refrigerator from a generator set.

--
Dimitris Tzortzakakis,Iraklion Crete,Greece
major in electrical engineering
freelance electrician
dimtzort AT otenet DOT gr
? "~Dude17~" <dude17@sacbeemail.com> ?????? ??? ??????
news:b959931f.0408290758.2592a92d@posting.google.com...

X-No-Archive: Yes

I've got a laser printer that draws current in spikes and it
makes the lights flicker as well as causing a UPS on the same circuit
to switch over to battery due to excessive dV/dT. Unfortunately, I
don't have a way of putting the printer on its own circuit unless I
want to use a long extension cord.

When it's in sleep state, it draws about 0.22A. When I print
something, it draws about 8A RMS to heat up. After it's done
printing, it stays in "ready to print" state for about ten minutes
before going to sleep and this is where problem starts.

Had the printer for a while, but I finally bothered to check it out on
scope.

I captured the event on my storage oscilloscope and this is what I
found:

At the start of cycle it draws 26A RMS for about 32mS or two cycles
and tapers down to 8.5A RMS after 550mS. Between the start and 550mS,
there's two spikes of about 8mS where current is only drawn from half
of the cycle. After 550mS, the current draw drops to 0.22A RMS, then
starts this whole cycle again after 15 seconds.

If you're a visual type of person, here's the actual capture:
http://dude17site.tripod.com/printer.html

Is there a reason it needs to draw current in this pattern instead of
spreading it out over a longer period of time?

 

[Andrew Gabriel]

In article <chlmbc$7g3$1@usenet.otenet.gr>,
"Tzortzakakis Dimitrios" <dimtzortihatespam@nospamotenet.gr> writes:

AGAIN!No need for UPSs in the 21st century.We had an udersized one in the
computer lab, in our college, with the result when everuthing is on it
"tripped" (also a small blackout).It's so silly as to power your
refrigerator from a generator set.

This depends where you live. The quality and nature of problems
varies enormously from one locality to another. Where I am in the
UK, we experience momentary drop-outs enough to reboot PC's about
once every 2 years, and power outages of an hour or more perhaps
once every 10 years. This means rather few people will bother with
a UPS or generator, but there are circumstances where this level
of failure is unacceptable, so you will find them used sometimes.
I used to work in a small rural village, where momentary drop-outs
happened every couple of weeks, and we did use UPS's in that case.
Eventually we complained to the supplier. They investigated and
found a cable fault in the 11kV feeder to the village, after
which the problem went away. Normally, they are very rare in the UK.
(There are reasons to suspect this high quality/reliability
electricity supply the UK has become used to over last ~50 years
is likely to come to an end over the next 10 years though.)

I have installed computer equipment in several non-UK European
cities, and it is my experience (10 years ago now) that many of their
supplies were generally nowhere near as reliable as ours in the UK.
Power outages of mintues to an hour were quite common, and then
everything is on UPS's backed by generators. Momentary drop-outs
were insignificant though.

Don't have as much experience of this in the US, but momentary
drop-outs seemed to be a significant issue in several locations,
enough to reboot systems sometimes, so UPS's are commonly used.
Extended outages seem to be few and far between (except when
the rolling power cuts were running in California).

There are places in the world where electricity is only provided
for a certain number of hours per day, or even on an unpredictable
basis. (And of course many places where there's none at all.)

--
Andrew Gabriel