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Author Topic: ORC rectifier goes on fire Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-23-2005 09:28 PM                        Well, it's an ORC lamphouse so I am assuming the manufacturer of the big reactance rectifiers is ORC's as well. We are running 4.5k bulbs. During a routine show, with both lamps buring, all of a sudden I hear the crew on the bottom level of the control tower saying the "ballast" as they call it, is on fire -- the booth is on the top floor, lighting and sound on the two lower levels, rectifiers at the bottom, but we are in communication with clearcom. I still had light in both lamphouses, but the amp meter in projector 2 was reading half amperage. I climb down the tower and find the #2 unit does indeed have a small flame and sparks visible threw the grill top grill of the unit behind the power adjustment wheel. I instruct the house electrician to pull the power, which he does, killing they entire booth, communications, amphitheatre pole lights, plunging everything into darkness, except the for the fire in the rectifier. There is an audience of 4000, many sitting close enough to the tower and the fire to see it an to smell the smoke. I used a fire extinguisher to douce the flames which are now showing no signs of going out on their own, but burning more intensely. It did extinguish the flames. We played the rest of the show on one projector making five reel changes (PHANTOM OF THE OPERA with the Alloy Orchestra who played brilliantly across each reel change). Here's the question: could only some control components have failed on this unit that would make it easily repaired or with flames going on, do you think this is pretty much a done deal as far as tossing it on the junk pile? And if we need a new one, any recommendations for a switching power supply to replace it? Are those much smaller switching supplies as reliable as the monster transformer units that we are using? We were very lucky that no one in this audience called the fire department, which, quite frankly, I was sure was going to happen what with all the smoke and visible flames, plus the proliferation now of cell phones. If that had happened, the show would have been shut down completely, I am sure. As it turned out, it went very well after we got back on the screen. After the applause for Alloy, someone yelled out "Let's hear it for the projectionist," and I got enthusiastic applause. Very embarrassing. We've got to get a replacement before next week's enagement of THE SOUND OF MUSIC. Any manufacturer better than the rest?  |  IP: Logged Jason Burroughs Jedi Master Film Handler Posts: 654 From: Allen, TX Registered: Jun 99 posted 07-23-2005 10:46 PM                     The wheel you describe makes it sound like an IREM rectifier. Probably not too many salvageable parts in there, as many parts are plastic, or contain plastics which would have melted in the fire (also what was possibly producing the flames). The transfomer core itself may be salvageable if not too heavily damaged by fire or extinguisher.  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 07-24-2005 01:52 AM                       I'm with Jason. "Wheel" sounds like an IREM. Blue panels? Lessee.. flame. Low output current. Sounds like a diode shorted during operation. You were probably too far away to note if it was making a loud noise along with the fire? It probably would have burned itself open (electrically) in a few more seconds and you would've seen the light strobing on the screen.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-24-2005 09:01 AM                     I've got to say double check your breaker size when you install the new one. Mark  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-24-2005 10:29 AM                     Check the nameplate on the rectifier If it is an IREM another possibility that has happened in the past it is the connections on the contactor have come loose and burned If so the wires if not too badly burned can be shortend If it is an ORC it might be the old Miller welder conversions and they had aluminum wireing in them and are hard to repair  |  IP: Logged Tim Reed Better Projection Pays Posts: 5246 From: Northampton, PA Registered: Sep 1999 posted 07-24-2005 12:00 PM                       Of course! Forgot all about the contactor connections, Gord. That would've made a better fire. I was gonna mention the aluminum-to-copper splices in the old ORC rectifiers, but since he said, through the top grill of the unit, behind the power adjustment wheel that leads me to believe it's an IREM, since the ORC's adjustment was on the front panel.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-24-2005 12:12 PM                     I thought the same except we had some of them with a 6K oRC and the pannel was on the top so I thought I better cover all bases THe nameplat info is wtill what is needed  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 07-25-2005 02:26 AM                        I'll get the information when I get back to the site this week, but it probably is an IREM -- blue and gray with a sloped top with the adjusting wheel. BTW, I turned that wheel and whereas it usually has quite a bit of resistance to it, now it turns freely as if not connected to anything -- controls burned away perhaps? Right now the main issue is to get a rental from one of the cinema supply houses so we can run two machines on Friday for THE SOUND OF MUSIC. The producers can later decide whatever is cost effective to repair the unit or simply get a new one. Personally I would like to see them go with a new one of the lighter, more compact switching units types since these monsters need to be fork lifted into place each year. The lighter units would have a distinct advantage.  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 07-25-2005 08:47 PM                        Switchers tend to be unreliable....not just the Strong ones. The IREM, if that is correct, has a "nut & bolt" arrangement just beneath the cover under the wheel. This is easily replaced if that is bad. This is responsible for moving the core up/down in the "variable saturable core " transformer. It may be heavy, but reliable it is also. Repair would seem likely. From a geography standpoint, Bid Sky in New Jersey would seem a likely place to start...they keep the parts. Louis  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-25-2005 09:25 PM                     quote: Louis Bornwasser Switchers tend to be unreliable I don't quite buy that Louis, Strong has done a pretty darn good job on their switchers. We have a bunch of Strong switchers running out here and have less trouble with them than with Christies blowing diodes!! The trick is to be sure to surge protect the booth feeds or each individual booth panel... hopefully you are doing that anyway though. I worked on a 3kw switcher that shut down thermally a few weeks ago in Idaho.... but the booth was amost 110 degrees and both heat sinks in it were found clogged with a large amount of dust bunnies.... that on top of the high booth temp tripped the clixons. A good clean out and this Strong switcher that was dated inside at 12/27/90 is running just fine today. BTW: The theatre personel switched out this rectifier with a spare one in less than 30 min.... was set up with quick disconnects. Thats alot safer repair than having cinema personel atempt to change bad diodes around three phase power!! Mark  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 07-25-2005 10:09 PM                     I have greater faith in the IREM than in a switcher any day  |  IP: Logged Dick Vaughan Phenomenal Film Handler Posts: 1032 From: Bradford, West Yorkshire, UK Registered: Jul 2000 posted 07-26-2005 07:09 AM                        quote: Gordon McLeod I have greater faith in the IREM than in a switcher any day Hear hear! Now if we could only persuade IMAX to use IREM's at least for 7kw lamps instead of Miller welding supplies!  |  IP: Logged Brad Allen Jedi Master Film Handler Posts: 688 From: Evansville, IN, USA Registered: May 2000 posted 07-26-2005 01:37 PM                     Mark, what surge protectors do you use on booth panels? Brand, model?  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 07-26-2005 06:59 PM                  So Louis, Gordon, and Dick... WTF are yous smokin'? I'd take a switcher (Especially the new Strong series) over an IREM N3 ANY DAY! The IREMS' HUM, BUZZ, VIBRATE and have terrible DC ripple that ya HAVE to have the auxially DC choke to keep the lamp from flickering and failing! That's just their good points. I have had more of those fail than ANY other rectifier including swithchers. As far as surge/lightning protection on the mains... Ummmmm, A good cinema/electrical engineer would spec that in the "Facility Requirements" specification for the electrical contractor to install. Square D and Siemens make some great ones.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 07-26-2005 07:30 PM                     Most of the theatres that we spec'd them into have Square-D. There is one problem with them though and that is that they don't have any protection between the three legs and ground, just the three legs and neutral. It has not been any problem though but I'd perefer the extra protection if the contractor is going to bother placing them into the systems. There is another surge protector that we will be spec'ing in on upcomming jobs that protects between both ground and neutral and the three legs, its a bit more expensive but the added protection is certainly worth the small increase in price. I will try to look up the data sheets tommrrow and get back here. I completely agree with Phil on the Irem issue. I won't sell em but I will sell a Christie as the DC has about half or less the amount of ripple, inrush is about the same on both as long as the relay card in the Irem is functioning. I an one of the very few techs that happens to own an ORC inrush/rupple meter kit and you'd all be amazed at the high ripple that comes out of an Irem.... about 10 to 12% usually. Check Osrams specs on theor lamps and you find they only allow about 5 to 6% ripple. the ripple fomr a switcher is at shuch a high frequency that its basically invisible to the lamp. The lowest ripple spec out there is from any Kneisley unit, the single phase units are the lowest at 3 to 4% max. BTW: Gord, you can't JUST add extra capacitance to an Irem to lower the ripple, doing so drastically increases the inrush current and then you have to compensate for that somehow too. For some reason the inrush seems to increase to the square of the old spec if the capacitance is merely doubled. So one could jump from say 300 aps to more than triple that inrush just by adding a second bank of the same type cap. Perhaps Phil can explain this........ Mark  |  IP: Logged

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