Author Topic: Did someone attempt to run up conventional MV/HID faster?  (Read 3528 times)
merc
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Did someone attempt to run up conventional MV/HID faster? « on: September 17, 2018, 02:59:19 PM » Author: merc
I wonder if something like this is even possible? Did someone try to run up a 50W - 250W mercury vapour lamp to reach like ~50% output within 10 seconds and 90% in 30 seconds?
Using electronics to boost run up voltage/current this should be possible, shouldn't it? The quartz glass should withstand rapid temperature changes (it's even faster in halogen lamps) but the mercury vapours might not form and stabilise so quickly.
This quick run up would most probably shorten the lamp life but it would allow to spend stocked lamps in places where CFL run up speed is enough. Not sure about SON/HPS lamps and especially MH that appear to explode even without such a treatment. What do you think?
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dor123
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #1 on: September 18, 2018, 01:50:47 AM » Author: dor123
You can run MH lamps on electronic HID ballasts. These have a boosted run-up feature. My Osram HQI-TS 70W/WDL Excellence, runs-up within 2 mins thanks to the Philips electronic ballast inside my tracklight. Otherwise it would run-up within 3 mins.
With HPS lamps, I don't think electronic ballasts can accelerate their run-up. When I was in Eltam factory at 2013, we lighted a 90's Tungsram TC 100 HPS lamp on an Eltam EHID electronic ballast , and it didn't run-up faster than HPS lamps that operates on magnetic ballasts, reaching full output within 3:40 min.
Super HPS lamps, usually runs-up much faster than regular HPS lamps.
With MV lamps, there are no means to accelerate their run-up without shortening their life, since electronic ballasts for them, aren't available.
The boosted run-up of electronic HID ballasts, actually prolongs the lamp life, since the lamp reaching optimal performance in less time, so less emitter sputtering.
The reason for the shorter lamp life of xenon MH lamps for car headlights, isn't because of the accelerated lamp life, but because these lamps have very high xenon pressure and are operates on much higher loading than regular argon MH lamps for general lighting, and requires 30KV both for cold ignition and hot restrike.
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #2 on: September 18, 2018, 10:05:32 AM » Author: Medved
The burner assembly needs certain amount of heat to vaporize the mercury.
If you want to pump the heat in faster, it means higher currents.
And higher currents means higher cathode loads, so higher cathode temperature.
Because the cathodes warm up fully within 1..2s, the 8 seconds till the arctube warms up the electrodes will be severely overheating.
And I'm afraid it will be so much the electrodes will actually melt. Definitely the material evaporation will be way excessive, so the arctube will blacken rather quickly.
With normal lamp designs (so assuming standard ballast characteristics) the cathodes are designed already "on the border" for the evaporation to become excessive. Don't forget here we are not speaking about pure tungsten, but mainly about the electron emission material buffer (used to prevent black coating sputter), which uses to be very temperature sensitive.
So any larger current, even when only at runup, means the runup electrode temperature to become too high.
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merc
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #3 on: September 18, 2018, 03:18:55 PM » Author: merc
Thanks.
With HPS lamps, I don't think electronic ballasts can accelerate their run-up. When I was in Eltam factory at 2013, we lighted a 90's Tungsram TC 100 HPS lamp on an Eltam EHID electronic ballast , and it didn't run-up faster than HPS lamps that operates on magnetic ballasts, reaching full output within 3:40 min.
The electronic ballasts for HPS lamps are designed to prolong their live, reduce cycling, enable lower power levels in late night hours and possibly to eliminate the mains flicker. Maybe also their lower weight/size are reasons why they're used instead of magnetic ballasts. The fast run-up isn't so important for street lighting where most of HPS/SON lamps are used so electronic ballast don't have this feature.
With MV lamps, there are no means to accelerate their run-up without shortening their life, since electronic ballasts for them, aren't available.
IIRC, the main reason is they don't like HF and tend to resonate/vibrate in power.

The burner assembly needs certain amount of heat to vaporize the mercury.
If you want to pump the heat in faster, it means higher currents.
And higher currents means higher cathode loads, so higher cathode temperature.
Because the cathodes warm up fully within 1..2s, the 8 seconds till the arctube warms up the electrodes will be severely overheating.
And I'm afraid it will be so much the electrodes will actually melt. Definitely the material evaporation will be way excessive, so the arctube will blacken rather quickly.
With normal lamp designs (so assuming standard ballast characteristics) the cathodes are designed already "on the border" for the evaporation to become excessive. Don't forget here we are not speaking about pure tungsten, but mainly about the electron emission material buffer (used to prevent black coating sputter), which uses to be very temperature sensitive.
So any larger current, even when only at runup, means the runup electrode temperature to become too high.
But aren't MV electrodes glowing orange (some 2000K?) all the time the lamp is fully heated? While the auxiliary electrode is rather thin, the main electrodes are massive enough not to be heated up by the current. If the material isn't extremely electrically resistive, some 10A for a 125W lamp should be fine. So if the ballast detected the main arc stable, it could increase the current rapidly.
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #4 on: September 19, 2018, 04:29:17 AM » Author: dor123
@merc: You can reduce cycling with HPS lamps, also with magnetic gear, by using an anti cycle ignitors.
MV lamps are antique, so of the manufacturers, it isn't justified to make electronic ballasts for MV lamps. An electronic ballast for MV lamp would be simple, without a HV ignitor inside.
Electronic HID ballasts works at low frequency, square wave current, to prevent flickering and resonances.
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I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

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Medved
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #5 on: September 19, 2018, 09:52:18 AM » Author: Medved
But aren't MV electrodes glowing orange (some 2000K?) all the time the lamp is fully heated? While the auxiliary electrode is rather thin, the main electrodes are massive enough not to be heated up by the current. If the material isn't extremely electrically resistive, some 10A for a 125W lamp should be fine. So if the ballast detected the main arc stable, it could increase the current rapidly.

Thez are not heated bz the passing current through the electrode wire, but by the ion (cathode) and electron (anode) bombardment. Normally there is about 10..15V voltage drop between the electrode surface and the bottom side of the arc, similar voltage at the anode side. This voltage drop accelerates the ions, which when hitting the cathode deliver their kinetic energy to the cathode material in the form of heat. So that means the cathode is heated by the power dissipated across that 10..15V drop. This ion bombardment does not cause that much sputter, because the individual ion energy is not that high. But there are a lot of such ions, so together they do deliver the heating power to the cathode material.
This is the main mechanism, which keeps the electrodes at emission temperature during lamp operation. There is a stabilizing mechanism: When the electrode is too cold, the cathode drop increases, so the ion velocity increases, so they deliver more heat to the cathode, recovering its temperature. But the normal operating temperature is already on the border of its capability (cathode fall of 10V), higher temperature won't cause any lower drop anymore. The point is, the lamp is designed so to suffer minimum wear, so minimum sputtering (so minimum voltage), but as well minimum evaporation (no too excessive temperature). Because the sputtering uses to be faster mechanism, the designs uses to work on the "hotter" side of the optimum. It means the lamps can tolerate lower current (with dimming,...), but not much any higher current (faster runup).

So when you boost the current, the electrodes will get too much heating power (the situation may get worse as you may actually saturate the cathode emission, so then the voltage drop, so the ion speed rises with rising currrent), they evaporate too fast or even melt down (and that is an immediate death).

By the way these limitations are base for the difference between general lighting 35/39W MHs vs automotive MHs. The general lighting ones have their cathodes designed for maximum nominal operation life, but the automotive needs to deliver minimum light output 2s after ignition, so the cathodes are beefier. The general lighting type cathodes are designed for 1A runup current, the automotive for 3A. The consequence is, the automotive run too cold during normal operation, contributing (beside other effects as well) to their shorter life (~1000hour automotive, 10+khours the general lighting).
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #6 on: September 21, 2018, 12:41:29 AM » Author: BlueHalide
I once installed some 250w metal halide indoor uplighters that used an electronic ballast which ran up the lamp extremely fast for the wattage, between 20 and 30 seconds to full brightness! Curious, I plugged one into a watt meter and for the first 10 seconds the fixture draw was over 6A, then gradually stepped down to the normal 2.4A over the next 10 seconds.
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #7 on: September 21, 2018, 01:23:08 AM » Author: Medved
You may speed up the runup a bit without harming the lamps that much by a ballasts that really exercises the maximum the lamp components allow (the current during runup, then responds to the bulb temperature by monitoring the arc voltage changes). But the improvement could be no more than half time to full brightness (it means the bulb is not yet fully warmed up, but that is compensated by an elevated power; so e.g. the color could still be off) and about 30% to full runup (so all parameters correspond to fully warmed up lamp).
Faster runups require higher currents and that means beefier cathodes. Some makers may produce their lamps designed this way and sell systems utilizing that for the fast runup (or other functionalities; Venture was quite "free thinking" in bending the standard specs to get some extra functionality in a few areas), but then you can not use standard spec lamps there, because those will most likely wear out prematurely.
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merc
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #8 on: September 22, 2018, 03:12:52 PM » Author: merc
Electronic HID ballasts works at low frequency, square wave current, to prevent flickering and resonances.
Yep. But the "square" wave also means harmonics (high frequencies) and I'm not sure if MV lamp would like that. It could be OK if it's fine for HPS/MH lamps. Don't know and don't have an electronic ballast to perform a test.

@Medved: Thanks for explaining on the electrode heating and self stabilisation process.
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Re: Did someone attempt to run up conventional MV/HID faster? « Reply #9 on: September 23, 2018, 09:44:58 AM » Author: Medved
Yep. But the "square" wave also means harmonics (high frequencies) and I'm not sure if MV lamp would like that. It could be OK if it's fine for HPS/MH lamps. Don't know and don't have an electronic ballast to perform a test.

What matters is the frequency spectrum of the magnetic forces the arc imposes onto itself (and other current carrying parts in the vincinity), so proportional to square of the current (F= something * I^2). Because it is this force, what is responsible for exciting the resonances.
Because the power of two disregards the sign, the square wave becomes a steady, constant force, so no HF (or very low, so negligible; from the limited slope times), even no LF, nothing to vibrate the arc (and so potentially excite some resonances) at all. Hence why it is the best driving method for AC HID's.
And there is no reason, why it shouldn't apply to MV...
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