Reposted from another thread here:
The new pulsing Lopresti PowerPulse is the same unit made by http://seatoneng.com/ or http://www.maxpulsemaxdim.com/comparisons.htm is a pretty cool compact form factor, I have to admit, I would use it for Incandescent or Halogen lamps. It is a GREAT product.
However, its built in warm up is NOT suitable for HID IF you are concerned about
ballast and bulb life. Its bulb warm up is not sufficient for HID because the
warm up time is much too short (~5 seconds) and most of the pulsing speeds are
too slow to be OK for HID bulbs.
XeVision was the first (4+ years ago) to offer Pulsing specifically designed for
the requirements of HID, after much discussion with the HID bulb manufacturers
about bulb operating requirements for long life (ARC plasma behavior and electrodes).
We make our own ballasts but these quality HID bulbs are ONLY made
by Philips or Osram (Sylvania).
The unit Lopresti is offering has only a 5 second warm up, OK for incandescent
or LED (not needed), but NOT good for HID.
HID requires the bulb arc plasma reach steady state or very close to it before
pulsing should start if one cares about HID system life. Anything less than 20
seconds of continuous warm up time is too short and will significantly affect
HID bulb life. Slow pulsing is also harmful, 60 ppm (1 Hz) per channel (120 ppm
both channels "wig-wag") is the approximate optimal speed considering both
bulb life and visual effectiveness for HID. Short warm up and / or slow pulsing
allows the plasma to cool off too much in pulsing operation, requiring very
much higher starting voltages to restrike the ARC, thus accelerating erosion of
the electrodes.
Once the HID bulb is warmed up, 20-30 seconds (sufficient) or more, if pulsing
is fast enough, the on pulse is long enough and the off period short enough the
plasma can stay hot enough to again sustain a low voltage arc (~85 VAC) as it
does in steady state without resorting to a high voltage restrike 25+ KV for
each pulse.
The Lopresti unit offers 44 ppm (22 ppm each channel) and 88 ppm (44 ppm each channel),
these are for both channels combined. Only the 120 ppm their fastest
rate (60 ppm each channel) is suitable for HID.
Note: XeVision has a Patent Pending regarding warm-up technology for HID (filed
over 4 years ago). The Patent office has granted our Patent about 1 month ago
and the final paperwork has been submitted for issuance from the US Patent office.
The original XePulse I and the about to be released XePulse II are covered
by this Patent. The XePulse II is about 20% of the size of the original unit
and the new unit includes additional patentable enhancements to insure maximum
HID system life while in pulsing operation.
Philips and Osram (the only quality D1S) bulb makers in the world. both claim a
Tc of either 2500 or 3000 hours. This bulb statistic means that only 63% of the
bulbs will still function (on/off) after that amount of run time in the lab.
Lopresti has used and still uses these 2 brands of D1S HID bulbs and yet still
claims a 5000 hour or 5 year warranty ???? This must be a hobbs meter based
warranty, not a true usage based warranty. Since most users will not use their
HID lights as a large % of total flight time this does not cause them to provide
many free replacement bulbs. And very few users will fly more than a couple
of hundred hours per year.
Without a proper arc chamber warm up Philips and Osram claim the bulb is only good
for about 20,000 starts. That is only 6 hours of continuous pulsing if it
is not in the plasma (steady state) instead of excited Xenon only as during the
initial starting. Depending on how someone operates their pulsing system, pulsing
while "cold" the warmup to steady state can be extended to over 5 minutes
which wears the electrodes at an accelerated rate. Once the arc gap gets large
enough and 105-110 VAC (max steady state bulb voltage) cannot sustain the arc
the bulbs life has ended. When a bulb is new it takes about 85 VAC and 0.4
amp (35 watt) (0.6 amp for 50 watts) to sustain the arc once warmed up. When the
bulb is cold it takes more power to keep the arc going. During this early phase
of bulb operation it can take 2X to 3X the power to the bulb to keep it "lit".
This extended overpowering to 70-90 watts is hard on the bulb this is the
bulb operation phase to be avoided for HID pulsing. Hot restriking after less
than a second of cool down (more than 30 seconds) it takes as much as 25,000
Volts to restart.
Every other company (6) which offers a pulsing system indicates 30 seconds to 1
minute steady on before pulsing should start (flip the switch) for HID.
The HID bulb manufacturers all agree that a close to steady state power to the
arc is mandatory for good bulb life and the higher the pulsing frequency the better
(that works well visibly). Hot restarting takes much more power if the bulb
is allowed to cool for more than 1/2 second. If pulsing only occurs while
the plasma state is well established (after 20-30 secs) then the power required
to re establish the arc is almost the same as to keep it "lit". Its all about
the impedance within the arc and under what conditions is it easiest on the
bulb and ballast to re establish the arc. Its all about adequately warming the
arc chamber up and keeping the off time between pulses short and the on time
of the pulses long.
I guess its their engineers (facts) "opinions" (Philips and Osram) vs Lopresti
sales team opinions. I think I'll stick with them, after all they are the bulb
experts.
The power being put into the bulb/ballast system can easily be monitored with an
amp probe on the cable to the bulb on an oscilloscope to see how the power varies
between operating the bulb these 2 different ways, "cold /cool" pulsing
or "hot" (warmed up) "steady state" pulsing.
One of Lopresti's people told me that their HID warm up was "instantaneous" Those
guys are miracle workers and can defy the laws of Physics.
--------
LED still has a long way to go to compete with HID as a landing light. This is
true in terms of total lumens and reach (distance).
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=271305#271305
