Film-Tech Forum ARCHIVE: ORC single phase xenon PSU problem

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Posted by Luciano Brigite (Member # 1104) on 10-01-2003, 07:22 PM:

Hello,
I have an ORC xenon power supply that went down on me this weekend, it's one of their single phase psu ,I found the schematic on the manuals section, page 74 of 82 of the orconII console . It's pretty much what I have here except for a few details:
This power supply was somewhat modified ( de-assmebled and re-assembled inside a wood [Eek!]

box, the terminal strip for current control is gone and in it's place a rotary switch was placed, also the booster circuit is modified, compared to the schematic I mentioned, the reistor pos. r1 (100ohm,50W) has a light bulb in it's place but seems to work allright and allows you to see the insides of this thing when the xenon bulb is on..
Now comes the deal.. the schematic says that there are 3 kinds of transformes and 2 current coils ( the L1 in the schematic)
-1 for 115V, -3for 208/230 - 50A and -5 for 208/230 65A . for xformers and -1 115v -3 208V for L1 .
this one has -3C marked on the xformer , the coding on the coil couldn't be seen. I'm assuming it's -3.
This psu is being run at 220V ,switch at mid position ,wich would be the tap 3 on the coil ( don't know if the wiring on the coil was messed up or not since it has spate terminals on the winding for the wires) the xformer has only 2 connections for primary, 2 for the boost circuit and the secondary and the numbering doesn't match at all the ones in the schematic.
The problem with it is that setting the tap at any of the fist 5 positions will keep the bulb current at about 40A, give or take a few and wen advanced to the last tap on the coil it'll go over 100A [Eek!]

and everything inside it will hum very loud and go hot in a few minutes. I checked everything i'd think that could be giving trouble but find nothing, I'm suspecting that the L1 is shorted somewhere inside it between the taps 5 and 6 or the coil and transformer aren't for 220V.
From the schematic I believe its a psu for a 1.600W xenon at max. and it was being used to power a 2.000W bulb on a [bs]

theatre

Doesn anyone has any idea about the ratings for this -3C (full code is 1144416-3C)transformer and what could be causing this current jump?
Can the L1 coil be replaced by a electronic power control? ( I'm aware that a triac based control can generate noise in the lines but with a proper filter at the input it shouldn'b be a problem..)
One last note. while testing it ( using a 2.000W bulb) before the diodes went poof on me, the bulb strikes on the first try ( if cold) and will keep lit for 10~15 minutes then starts flickering and goes off, from there, re-strike becomes a nightmare .replacing the diodes didn't refresh anything.
I suggested a new ( and proper) PSU but they want to keep this "firebox" as I called right at the first look ... [thumbsdown]

Posted by Dave Macaulay (Member # 813) on 10-02-2003, 07:13 AM:

First, a triac control isn't a good plan. The transformer won't like it and the triacs won't like it because of the waveform distortion and the huge high frequency component in the chopped power waveform. Notice that there aren't any commercial rectifiers that work this way, and that comercial dimmers are marked "incandescent/non-reactive load only". Only a sine wave source is really acceptable, like a variable autotransformer... but high current models cost the mint.
As far as your unit goes... what you describe is so scary that I recommend declaring it unrepairable just to get rid of it (a wood case?!), although it might be fixable. If the main transformer is bad then it isn't worth fixing. You can check it by isolating the coil wires and measuring resistance, both from each wire to the others and to ground. Each coil segment should have pretty low (but not zero) DC resistance and any leakage to ground means it's trash.

Posted by Jack Ondracek (Member # 1466) on 10-02-2003, 08:31 AM:

I'm with Dave on this.
You don't want to be known as the last person to service that "firebox" if it burns the theatre down.

Posted by Mark Gulbrandsen (Member # 72) on 10-02-2003, 08:37 AM:

Dave,
The ORC 1000 was basically a triac driven transformer(actually 2 scrs's back to back. The iron end of things can be designed for that mode of operation if desired. A transformer not designed for that type of drive signal will saturate quickly.
Mark @ CLACO

Posted by Gordon McLeod (Member # 33) on 10-02-2003, 09:20 AM:

Sanrex built SCR driven rectifiers as did strong
Odds are there is a short in one of the windings and that is hy it is behaving as it is
I would just put it in the dumpster and be done with it
The rewinding of the transformer is more than it is worth

Posted by Luciano Brigite (Member # 1104) on 10-02-2003, 02:51 PM:

The main transformer seems to be good and I didn't notice any leakage between the windings and the core, same apply to the coil in series with the transformer.I measured resistance from the windings and all of them came out as zero ( measured with an analog meter, will take readings again with a digital meter as soon as I find the darn thing) for now all I need to make sure is that the transformer and series coil are for 220V operation and the max bulb wattage it was designed for. (if wasn't the 3C making at the end of the transformer coding i'd know it for sure after looking at the shematic, for now I'm just guessing it's 220V input and runs a bulb up to 1600W)
I'm thinking that the problem is with the coil since it's what controls the current/voltage in it. since the entire thing was de-assembled (not by me) could be possible that this coil was hit or dropped and the gap between the E/I lamination went off and is making the coil to not operate as it should be?

Sure thing is.. if it has a way to be fixed, the PSU won't go back to the theatre inside the wood box..already found a decent box to stuff the things in, even if it'll make me spend thw whole day fitting everything inside .

(BTW.. that's not the first time I see xenon psu's that are encased in a wood box ... a metal framing with wood panels on all sides. this one is all wood, except for a crappy metal base that looks more like one of those metal shelves we can see in storage areas of offices or shops [Roll Eyes]

)

Posted by Gordon McLeod (Member # 33) on 10-02-2003, 09:02 PM:

The coil being in the AC part of the circuit limits the output current more efficiently than a resistor would
EPRAD made a interesting rectifier (constaVolt acutally made it) that had 3 inductors in serries with the input to the 3 phase transformer and the taps on them and 3 output chokes set the current output
It was highly efficient as at 100amp output it was internally fused at 10 amps per phase

Posted by Luciano Brigite (Member # 1104) on 10-03-2003, 05:18 PM:

I decided to have the L1 coil re-wound and see what happens,after all it's this coil that (should) control the current in the transformer's primary and everything else in the output of the rectifier.
If it doesn't solve ,then I'll give them the [fu]

and let them without Xenon projection untill they decide to get a new unit [evil]