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Author Topic: When to strike the Xenon in the morning Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 08-24-2004 10:10 PM                        quote: Andrew Jefferson the automation backs the amps down from 140 down to about 50 amps in-between shows. Wow. I was always under the impression that xenons needed to burn within a narrow margin of their specified rating. Wouldn't going way down to only 50A be detrimental to the life of a bulb rated at 140A? And just out of curiosity how do you rig the automation to control the rectifier output amperes? I've got this picture in my mind of one of my 180A monster reactance rectifiers with the big crank wheel on top....I see the automation switching on a humungous 10hp reversible motor that's been bolded to the top of the rectifier, the crank wheel has been removed and the motor shaft has been welded to the crank shaft; switched in one direction the motor turns the rectifier shaft up, the other direction turn it in the opposite direction....am I close?  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 08-24-2004 10:19 PM                        Frank... not knowing the specifics of Andrew's power supply, I can only guess. However, in the times when I've lost a leg on my 3 phase, my current has dropped way down.... I think it's higher than 50 amps, but I don't remember. I haven't had a respectable power outage since I outfitted my place with an emergency generator! I suppose you could put in a contactor that would lift the third leg off the primary. That would knock the wind out of the output current pretty effectively on a high reactance supply. The caps on the output would probably deal with it reasonably well... at least for idle purposes. Any flicker wouldn't be seen by the audience. Just speculating, of course. Who knows? Maybe they put a big resistor bank in series with the primary! Oh... funny on the motorized wheel crank! That would be worth a video!  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 08-24-2004 10:26 PM                        If I was going to do what you speculate, Jack, I'd wire the two pots in parallel and connect/disconnect one of them with the relay. This would be better than flipping between two different pots since who knows what the rectifier will do in the brief period of time it takes for the relay to move. Probably not much (you might get a spike or sag), but you might as well avoid it since it's just as easy, and cheaper, to do.  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 08-24-2004 10:32 PM                        That's what I was looking for, Daryl. Thanks. Plus, if you had a failure in the circuit, you could just adjust the other pot. That addresses my concern regarding any relay failure... simple. I don't have any concerns about whether the supply can handle this. Any reason that it would cause the bulb particular grief? How about the older supplies that had this feature built in. Was there any issue as far as the bulb was concerned. If not, I'm probably going to try it... if nothing else, just to see how it goes. During breaks, the notion of dropping my 7kW bulbs down to the point they aren't trying to cut through the front of the lamphouse is pretty appealing. I'd be interested to know if any effect on the bulb offsets wear and tear... high temperature on the douser... and electric savings. For that matter... anyone know why an "idle circuit" didn't become more mainstream? Obviously, the idea isn't a new one.  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 08-24-2004 11:09 PM                        If you select a relay that requires power to the coil to make the circuit go into standby mode, and thus usually fails leaving the circuit in full power mode, you won't have to worry (too much anyway) about making any adjustments to the pots in the event of a relay failure. Assuming an increased resistance on the pot increases the rectifier output you'd want a relay that is normally open, otherwise you'd want a relay that is normally closed. Of course this may be a trade off of relay life for a nicer failure mode depending on your operating schedule since the relay will be powered, in this setup, the whole time you're in standby mode. Still, given the shorter life, I'd still do it this way since a failure is less likely to cause problems on your one night off a month. Come to think of it, depending on how the rectifier output follows the pot and the size of the second pot you add, you might not even be able to achieve full output if the second pot is connected. So, I'd say, the above failure mode is the definite way to go. Also, depending on the automation, you might not even need another relay. If you've got an "electrical" automation you might already have a spare relay. If you've got a "mechanical" automation there might already be a spare switch or relay. I have no idea about the benefits or downsides when it comes to the lamp itself. In the little experience I have with lamps running in standby I don't remember having to order a special lamp, but I'm sure somebody else will know which lamps are happy with a standby current and which aren't, of any ups/downs and what standby current you should run at.  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 08-25-2004 01:39 AM                        All good points. Unfortunately, little valid statistics to go by. So... I'm going to give it a try. It may take a while, but I'll set up a low-current idle scenario & track whether it has any effect on lamp performance and hours. It may not be "official". However, I'm as cheap as the next guy when it comes to expenses out of my wallet. If this seems a bad idea, I'll sure let everyone know! ... hope I don't blow up a bulb... or a reflector... or a power supply... or burn down my booth... or a screen... or burn a pizza... or...........  |  IP: Logged Daryl C. W. O'Shea Film God Posts: 3977 From: Midland Ontario Canada (where Panavision & IMAX lenses come from) Registered: Jun 2002 posted 08-25-2004 02:05 AM                        Little? More like none! (from me anyway) Someone else might chime in tomorrow. I know a few people are on the road right now, so it might be a bit before you get any responses. FWIW, I think Imax and other such venues run their lamps on standby (reducing ignitions) more for arc stability reasons than economical reasons. You wouldn't serve bacon on that pizza, would you?  |  IP: Logged Richard Fowler Film God Posts: 2392 From: Ft. Lauderdale, FL, USA Registered: Jun 2001 posted 08-25-2004 02:35 AM                     Some power supplies and lamphouses in Asia have a "simmer" option in addition to adjustments to an electromagnet in the lamphouse to control the arc plasma. LP Associates in the USA will also do this on special order.  |  IP: Logged Dick Vaughan Phenomenal Film Handler Posts: 1032 From: Bradford, West Yorkshire, UK Registered: Jul 2000 posted 08-25-2004 02:45 AM                        The IMAX GT systems put the 15kw lamps in to standby between shows and also on the unused eye during 2D shows. Smaller eg 7kW SR systems leave lamps full on but we do have dowsers built from boilerplate!  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 08-25-2004 12:22 PM                        I was just fancying that big motor trying to control the wheel on a reactance rectifier, but in all probability a switching supply would be more likely; don't most of them have trip pots for amperage output control? Additional resistance could easily be switched into and out of the circuit by the automation. I don't imagine the trim pots are carrying anything but a low control voltage in the regulation circuitry. This would probably be a very logical place to control the output amperage. But of course I am just guessing. (You like that big motor welded to the rectifier crank wheel, eh, Jack?!). But my question still remains....isn't burning a 140A rated xenon at 50A very, VERY bad for the bulb? Didn't I see a warning on the xenon box once saying never to burn the bulb above or BELOW the rated amperage range? Or did I dream that? (which certainly is very possible).  |  IP: Logged Bill Langfield Master Film Handler Posts: 280 From: Prospect, NSW, Australia Registered: Apr 2001 posted 08-25-2004 01:47 PM                        Frank, Using IREMS?, of course they have no way going into stand-buy, unless you build your motorised crank for the tap. (Let me know how that goes, sounds like fun project - I visulise a cordless hi-torque drill with a decent power supply replacing the battery. Remove the hand crank, mount the drill in there, set the speed control on low, hook up the On/off and For/rev to some free automation relays, AND your off!!) That idea of losing a phase (I think Jack suggested) to erm 'fake' stand-by is a freaky, interesting one. Andrew works for the same company as me and by his description they use exactly the same gear, and methods. (His cinema is 3 hours drive from me and Ive never been there, must ask if I can visit one day. The full=140amps and stand-by=50amps, MIGHT be outside what Im used to. Its more like 100-120 full, 60-70 standby. But that is not a static figure, depends on the cinema size. Most multiplexes here, say for example a 10, normally have 2x500 and 8x250 seaters. However I don't really know how his place is set up. Like you, I too must re-read the min operating Amps of each bulb, to ensure we are not running TOO low when in standby. But generally I've felt comfortable with around 65amps.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 08-25-2004 02:08 PM                        quote: Frank Angel But my question still remains....isn't burning a 140A rated xenon at 50A very, VERY bad for the bulb? Lamp manufacturers usually publish a recommended current range in the technical data for each lamp. For example: http://www.osram.com/pdf/service_corner/technicalinfo/xbo_4000WHSe.pdf quote: Current control range A 80 - 150 So for this 4000 watt lamp, Osram recommends between 80 and 150 amperes. Below that range, the arc becomes more unstable, so the plasma may wander, or the lamp may go out and then try to restart at too low a current. I recall that if the lamp runs too cool, it may blacken sooner too.  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 08-25-2004 05:29 PM                        That may be true, John... but it seems to me that the manufacturers' current range listings are done for long-term use... not intermittent periods. This question will probably not be answered unless we get one of the lamp guys here to weigh in on whether short-term operation at low amperage is any big deal (hint, hint!). Frank: It may seem funny, but what you suggest could probably be done. I once worked in a theatre that had auditorium lights powered by multi-stack Variac transformers. They had gear reduction drives on the top, where you might have expected a control wheel. Limit switches controlled the stop points... probably much like a masking or curtain motor. It was a very reliable and trouble-free system for its time. To use Bill's comment... what you're thinking of would be "freaky"... but probably doable. Dunno about the high-torque drill motor, though!  |  IP: Logged Andrew Jefferson Film Handler Posts: 23 From: Brisbane, QLD, Australia Registered: Jul 2004 posted 08-25-2004 07:17 PM                     Sorry for my absence and leaving you guys in the dark about my lamphouse setup. I use the "USHIO/XEBEX KCX-160U2/4" rectifier; it has two pots on the side, one for full current, and one for stand-by current. It has a connection behind the front panel for a "Remote", with this you can turn the lamphouse power on/off, place the lamphouse in full/stand-by, and strike the lamp, there is also feedback from the lamphouse showing whether the lamp is actually on. I have only the full/standby, and lamp feedback connected to the automation. In the morning I strike with the lamp on full power (using toggle switches on the lamphouse piggybacked into the remote on the rectifier), after a min or two of warm up I’ll switch the toggle switches to “Auto” on the lamphouse. Then when Showtime hits the automation puts the lamphouse in full mode starts the motor, and opens the zipper. If the lamp chooses to fail, the automation alarm will sound via the “Lamphouse Feedback” connection on the rectifier remote socket.  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 08-25-2004 09:16 PM                        I would say if the plasma really starts to get unstable and wander as you lower current, you've gone too low. Likewise, if you find the lamp sometimes goes out and has to reignite, you've probably gone too far.  |  IP: Logged

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