This is topic Switching power supplies in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Russ Kress (Member # 461) on 09-24-2000, 10:19 PM:
I have noticed that the lamps in our 4000 watt applications are begining to flicker and have striking problems far before reaching their warranty limits.The power supplies are Strong switchers and will accept either single or three phase power. We wired them in single phase and used the third phase on the breaker to power the exhaust fan on the roof in order to idiot proof the exaust fans.
We're going to pull an additional wire and connect all three phases on Tuesday. Will this solve the problem?
Question #2: Can I share one of the phases with the exhaust fan to maintain the the certainty of the fan running when the lamp house is powered up?
The power supplys already provide plenty of current in the single phase configuration, but I was told that running them this way could increase the potential of AC ripple hitting the lamps.
Even if I had an occasional "loss of cooling" melt down, it would still be cheaper in the long run as opposed to getting about a third of the rated time out of the bulbs.
Russ
Posted by Aaron Sisemore (Member # 145) on 09-25-2000, 02:09 AM:
With a switching supply, the 60 Hz AC gets electronically converted to a high frequency AC before being rectified and filtered. Therefore it shouldn't matter whether you are operating it with single or three-phase current.As for ripple, unlike standard power supplies working at 50/60 Hz there should be practically zero ripple voltage as the high frequency AC, after rectification, is much easier to filter than 50/60 Hz...
Aaron
Posted by Russ Kress (Member # 461) on 09-27-2000, 01:39 AM:
Well, I asked because I was told that three phase was better for the supply.As far as the mis-ignition goes, the lamp ignites, produces very little light, and draws about a third of the recommended current.
If you look at the arc through the filter, it is dancing all over the quartz envelope instead of between the cathode and anode.
Re-striking always fixes the problem, but the audience sees this too.
We are striking the lamp at "start plus seven seconds" and not using the change-over dowsers because they have a nasty habit of closing and staying closed when the power blinks.
We have eleven screens, but five seperate projection booths.
The 2k lamps strike instantly. The problem is isolated to the 4k lamps.
Russ
Posted by John Pytlak (Member # 331) on 09-27-2000, 03:48 PM:
Russ: sounds like you have some failure of a component in the power supply. Don't know if 3-phase would help. But if you decide to use 3-phase, I would NOT recommend connecting anything else to the 3-phase breaker, especially a heavy (and unbalanced) load like an exhaust fan. Consider using a relay to control the fan on its own circuit, actuated by turning on the lamp power supply.------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Posted by Gordon McLeod (Member # 33) on 09-27-2000, 07:47 PM:
what make of lamp?
Posted by Sean McKinnon (Member # 612) on 09-27-2000, 10:48 PM:
CALL YOUR TECHNICAL SERVICE PEOPLE NOW!!!
This happened in one of my old theatres 2k units the lamp would show the exact same symptoms. we could also smell burning that seemed unrelated we called our service company and they could not find the burning (neither could the electricians) The tech told us it must be excess oil burning off. One day A customer came out and said the picture turned off so I went upstairs and the rectifier was smoking. Bo**on Light And Sound Incorrectly wired the unit when they installed over a year from the incident and the Hot lead was loose and burned up the internal componenets this could be VERY serious.
Posted by George Roher (Member # 91) on 09-27-2000, 11:29 PM:
Those Strong switchers seem to have a lot of problems. We had one explode a couple months ago at one of the theatres I work in. I wasn't on duty at the time but I'm told it was fairly exciting. Actually, two weeks ago I had to cancel a show in another theatre because a switcher went dead on me. Most of the theatres around here that use switchers have had problems with them.
Posted by Russ Kress (Member # 461) on 09-28-2000, 12:35 AM:
Gordon,Lamphouse is Strong Super 80
Lamp is Osram
Posted by Dave Cutler (Member # 515) on 09-28-2000, 12:47 PM:
I have also had a lot of problems with Strong switchers. At the AMC I used to work at we would blow one every couple of months. It only occured with the 4-7kW switchers in the 4 big houses. It got so bad we always had 2 extra switchers sitting around so we could change them out quickly. They said it was some problem with the power coming into the building, but I never had a chance to check it out myself.
Posted by Mark Gulbrandsen (Member # 72) on 09-28-2000, 05:51 PM:
I'd be willing to bet that the failure rate is actually very low if you take into consideration that there are thousands and thousands of Strong switchers out there. They have bene around along time. I've heard problems of failures and DC lead connectors burnning off the sides of the units but I still have as of yet to have this happen. In the last three years I can only remember one switcher going bad. It had been in service for about 6 years. Strong provided another unit on repair exchange for around 300.00. You couldn't have your tech change all the diodes in an Irem for that amount of $$. If one looked at the failure rate of other rectifiers....Irem, ORC, LP you would probably see parallel lines in the failure department. We have several switchers for our Super Troupers that get knocked around in our rental department and we have yet to experience any trouble with them.
Mark
Posted by Gordon McLeod (Member # 33) on 09-28-2000, 07:59 PM:
Do the klamps try to ignite repeatedly or just sit there dead
Check the noload voltage of the rectifier
also check the autostrike board's relay and zenier diode
Posted by John T. Mellor (Member # 468) on 09-29-2000, 10:13 PM:
We recently had all of the switchers at several locations replaced by strong due to a failure to ignight. They are using DC to ignight on the newer models . we also have had premature darkening of the envelope I havent had a chance to check but I think that they need to check for too much ripple in the DC. you may want to call strog Directly to see if they have any solutions. I ptrefer Knisley rectifiers over most of the others we had two at our drive in and ran 4k lamps at 150 amps and never had a problem the rectifiers are 20 plus years old and never had a new diode we used Osram bulbs and Knisley sreies I lamphouses with glass reflectors hope it helps
John
Posted by Pat Moore (Member # 380) on 09-30-2000, 06:52 AM:
OK, I'll throw a post on this one and see what happens. You guys all know where I'm coming from anyway.If there's been an issue with Switchers, it's reliability. Putting that aside for a moment, when they work they work very elegantly, and they really do work the greatest majority of the time. The advantages are, of course, light weight, very high power efficiency and ideal power characteristics for a xenon lamp.
There is virtually NO AC ripple on the output of the Switcher -- <.5%. Darkening of lamps is a contamination issue and won't be affected by ripple, unless it's really, really high, to a point where you couldn't watch a projected image on screen. Excessive ripple will cause the anode to develop bubbles and high spots, and the cathode tip will round off or crack very quickly. One problem you won't have with switchers is ripple.
The Switcher has very low inrush characteristics during the ignition cycle. Inrush is around 150% or less of the nominal current, compared with 250-300% or more from many magnetic (brute force) supplies. That's one feature, along with the low AC ripple, that promotes longer lamp life.
The output of the system is "tailored" to produce an "ideal" power characteristic during ignition to make it more reliable. One challenge in this is the different lamps -- an ORC 2kw acts differently from an Osram. Heck, there are variances in the same lamp designs from the same manufacturers. Lamps age differently and the arc gap varies with age. They have slightly different fill pressures, different mix of thorium and tungsten in the electrodes, etc. As some of these designs and specifications have changed and varied over time, we've tried to cover those changes with modifications in the Switcher.
ALL lamp manufacturers have tested Switchers at various stages -- we've sent them just about everywhere for analysis and have worked closely with Osram and others in many instances.
I know I've encountered many more instances where a Switcher will light a lamp better than a standard supply could. In some testing I've done (tests unrelated to this topic), I've struck and run 2kw lamps at 15A -- the switcher will ignite them and maintain a steady arc even at that low a current setting. This is a special circumstance and not necessarily good for the lamp, but the Switcher will do it more often than not.
Okay -- back to the coffee...
Posted by Russ Kress (Member # 461) on 09-30-2000, 06:56 PM:
Hey Pat!You are correct about lamp life. Our 2k average lamp life jumped off the scale when we converted to switchers. The things paid for themselves.
Single or three phase for 4000 watts?
Russ
Posted by Pat Moore (Member # 380) on 09-30-2000, 07:48 PM:
Russ;
It's my understanding that the 4kw version can run on single-phase input and still power a 4kw lamp. Needs a pretty hefty single-phase breaker, though, because the current draw would have to be something over 25A.
Posted by Russ Kress (Member # 461) on 09-30-2000, 09:52 PM:
They are on 30 amp, double pole breakers. They're not tripping.It just seems like the igniter occasionally stops before it's completed the ignition?
As stated before, the lamps run fine. Every now-n-then they require motivation to start.
Either pressing the ignite button or turning of the lamp house power and then turning it back on fixes it every time.
This is new to me.
Russ