Studio Electrical Discussion from Utility to Outlet deleted
- Thread starter Boswell
- Start date
Help Support GroupDIY Audio Forum:
Sorry to have missed a day.
Thoughts to ignore:
> it should be producing EXACTLY half of its input on its output, but it's not.
So try it backward. Maybe it's mis-marked. If you are scared of foolin' with 240V, try a 12VAC filament transformer. Same idea: 12V in, 12V out, or something is wrong. If it is 12V in, 13V out, reverse it and it should be 12V in 11V out. (If not, you either have a measurement glitch or you have a new Law Of Nature.)
> How did you calculate 250 va for the autoformer?
The VA of the buck/boost winding is the percent change of voltage (at least for small changes). You want a 10% change on a 2,000VA load, you need a 200VA buck winding. I rounded-up, though now I find you have a 2,500VA iso-tranny so I was right.
> We typically have 125 v lines here in Texas.
Argh. That's too high. Especially when my office suffers with 112V and my monster Ampeg gitar amp makes 18 Watts actual measured power.
> do I have to worry with 127 volts feeding the audio studio?
99% of gear won't notice. A few things will run better: table-saw, A/C, computers.
How much 1% stuff do you have?
Old-old Fender guitar amps were wound in days of 110V wall juice. There's a lot of tolerance in there, but 125V is really pushing the tolerance. However the first part to fry is the power caps, and after 45 years they are long-gone.
General room incandescent lamps in 115V rating will die in a few weeks at 127V. Even 120V rating won't have full life. (Sure will be bright while it lasts.) 130V lamps are available, maybe locally in 125V land.
Obviously most in-gear lamps are either on regulated juice or seriously de-rated for long life (or both), or are LEDs which don't have to be, and typically aren't, worked anywhere near burn-out power level. It's just the dang $1 lightbulbs in the ceiling fixtures and desk-lamps that will die a lot. And you probably shouldn't run those on your limited "clean" power feed. Let them eat crap. Same crap as the rest of the house, same life-span.
> about 30 seconds before I say, "damn, that's hot".
Big power iron runs hot. Simple economics; also scale effects of surface/volume ratio. The economics of iron and modern insulation seem to suggest normal full-load operating temperatures that would fry an egg, literally. Spending 10% more for high-high-temp varnish saves 10% of costly iron and copper. Sharpen your pencil, your best deal is HOT.
High temp at no-load may be normal, but is made worse by high line voltage.
Thoughts to ignore:
> it should be producing EXACTLY half of its input on its output, but it's not.
So try it backward. Maybe it's mis-marked. If you are scared of foolin' with 240V, try a 12VAC filament transformer. Same idea: 12V in, 12V out, or something is wrong. If it is 12V in, 13V out, reverse it and it should be 12V in 11V out. (If not, you either have a measurement glitch or you have a new Law Of Nature.)
> How did you calculate 250 va for the autoformer?
The VA of the buck/boost winding is the percent change of voltage (at least for small changes). You want a 10% change on a 2,000VA load, you need a 200VA buck winding. I rounded-up, though now I find you have a 2,500VA iso-tranny so I was right.
> We typically have 125 v lines here in Texas.
Argh. That's too high. Especially when my office suffers with 112V and my monster Ampeg gitar amp makes 18 Watts actual measured power.
> do I have to worry with 127 volts feeding the audio studio?
99% of gear won't notice. A few things will run better: table-saw, A/C, computers.
How much 1% stuff do you have?
Old-old Fender guitar amps were wound in days of 110V wall juice. There's a lot of tolerance in there, but 125V is really pushing the tolerance. However the first part to fry is the power caps, and after 45 years they are long-gone.
General room incandescent lamps in 115V rating will die in a few weeks at 127V. Even 120V rating won't have full life. (Sure will be bright while it lasts.) 130V lamps are available, maybe locally in 125V land.
Obviously most in-gear lamps are either on regulated juice or seriously de-rated for long life (or both), or are LEDs which don't have to be, and typically aren't, worked anywhere near burn-out power level. It's just the dang $1 lightbulbs in the ceiling fixtures and desk-lamps that will die a lot. And you probably shouldn't run those on your limited "clean" power feed. Let them eat crap. Same crap as the rest of the house, same life-span.
> about 30 seconds before I say, "damn, that's hot".
Big power iron runs hot. Simple economics; also scale effects of surface/volume ratio. The economics of iron and modern insulation seem to suggest normal full-load operating temperatures that would fry an egg, literally. Spending 10% more for high-high-temp varnish saves 10% of costly iron and copper. Sharpen your pencil, your best deal is HOT.
High temp at no-load may be normal, but is made worse by high line voltage.
[quote author="PRR"]Sorry to have missed a day.
[/quote]
One day without you is an eternity
. Thanks for being so dedicated, PRR.
I'll take your advice into consideration and consider building that autoformer. Argggg...
BK
[/quote]
One day without you is an eternity
. Thanks for being so dedicated, PRR.I'll take your advice into consideration and consider building that autoformer. Argggg...
BK
Well, the saga of the autoformer is back.
One of my UPS's refuses to to on line with 125 volts feeding it, and the other one is in line-compensation mode, saying the line voltage is high and probably adding an autoformer tap itself!
So I bought a 250 va "220 to 24" volt transformer at Skycraft as PRR recommended. I discover the primary has both a "240" and a "230" tap. I'd like to try using the primary in "autoformer" mode, tapping into the Topaz on the 230 tap while feeding the line in on the 240 tap. If that brings the secondary of the Topaz closer to 120 volts I'll be more comfortable than the more radical PRR solution. I fear the original PRR solution (using the 24 volt winding as a bucking winding) would take the voltage down too far.
Trying my best to make sure I don't overload anything, it seems to me I calculate the load on the autoformer by the voltage difference times the current.... nominal "10 volts x 10 amps (maximum) = 100 va so that's safe, right? 10 volts comes from the nominal 240 - 230 tap difference.
BK
One of my UPS's refuses to to on line with 125 volts feeding it, and the other one is in line-compensation mode, saying the line voltage is high and probably adding an autoformer tap itself!
So I bought a 250 va "220 to 24" volt transformer at Skycraft as PRR recommended. I discover the primary has both a "240" and a "230" tap. I'd like to try using the primary in "autoformer" mode, tapping into the Topaz on the 230 tap while feeding the line in on the 240 tap. If that brings the secondary of the Topaz closer to 120 volts I'll be more comfortable than the more radical PRR solution. I fear the original PRR solution (using the 24 volt winding as a bucking winding) would take the voltage down too far.
Trying my best to make sure I don't overload anything, it seems to me I calculate the load on the autoformer by the voltage difference times the current.... nominal "10 volts x 10 amps (maximum) = 100 va so that's safe, right? 10 volts comes from the nominal 240 - 230 tap difference.
BK
[quote author="mediatechnology"]Bob, are you sure that the Topaz doesn't have additional tap(s) on the primary? Can you e-mail me a pic of the terminals? If so mediadialupATmindspringDOTcom (spam-bot prevention in the addy)
I need to think about your auto-former question a little more but it does seem that you could use the 230V tap to feed the Topaz.
What is the primary current of the Topaz with load?
Wayne[/quote]
Hi, Wayne. Happy Sunday! I'm glad you followed my convoluted query. Folks, I need to know if a little 250 va transformer can be used as an autoformer to drop the 240 volt line a little. The load of the Topaz will be no more than 10 amps at "240 volts" as I have it fused at 10 amps and I'm "rating" the secondary at 120 volts 20 amps.
Here's an ASCII schematic of the source into the primary:
I'm POSITIVE the Topaz does not have any more taps. It's a very sealed unit with four identical-looking screw terminals on barrier strips each side. One side is labelled H1 through H4 and the other side X1 through X4 in the classic 220/110 configuration mode. You put pre-supplied jumpers on the barrier strip depending on your configuration and you're limited to permutations of 220 and 110. And two additional wires terminated in Stacons that are the two Electrostatic shields. Those are all the wires you can see and you couldn't take it apart if you wanted to.
BK
I need to think about your auto-former question a little more but it does seem that you could use the 230V tap to feed the Topaz.
What is the primary current of the Topaz with load?
Wayne[/quote]
Hi, Wayne. Happy Sunday! I'm glad you followed my convoluted query. Folks, I need to know if a little 250 va transformer can be used as an autoformer to drop the 240 volt line a little. The load of the Topaz will be no more than 10 amps at "240 volts" as I have it fused at 10 amps and I'm "rating" the secondary at 120 volts 20 amps.
Here's an ASCII schematic of the source into the primary:
Code:
LINE----------Com------------->to Topaz
)
)
)
230-------------->to Topaz, 10 amp load (max)
)
LINE----------240I'm POSITIVE the Topaz does not have any more taps. It's a very sealed unit with four identical-looking screw terminals on barrier strips each side. One side is labelled H1 through H4 and the other side X1 through X4 in the classic 220/110 configuration mode. You put pre-supplied jumpers on the barrier strip depending on your configuration and you're limited to permutations of 220 and 110. And two additional wires terminated in Stacons that are the two Electrostatic shields. Those are all the wires you can see and you couldn't take it apart if you wanted to.
BK
You've got to be a bit careful here. Transformers don't just have one rating, there's a whole family of curves in the A/V plane, of which the "VA rating" is just the headline.
Taking the original rating of 220V 250VA, the primary winding will have been designed for a working current of around 1.5A, allowing for typical load power factors. So hoping to put 10A through a tenth of the winding may cause overheating in that section, if not burn-out.
[quote author="mediatechnology"]Bob;
I read PRRs comments again (the voice of reason) and he makes a point I completely missed: Is it possible that the Topaz is reversed? Me duh!
[/quote]
Well, I could never find an exact Topaz schematic, but I looked on the net for a similar Sola and they all seem to be standardized as H is standard abbreviation for primary and X is secondary, to the best of my recollection. I've already sealed it up so I'd have to open it up to be sure.
But let's think about this. I hope no one gets confused with this. This Topaz is configured as a 2:1 right now, but I can use its secondary as a reference what my wall sockets are reading right now and pretend that's its ratio. I know that when my wall sockets are at 123 volts the Topaz is putting out 125, so it's not that far off spec.
So, pretending it's a 1:1 transformer, if I reverse it, it would put out 121 volts. Not too shabby. The math is divide 123 by 125 and multiply by 123.
Hmmmm... that's attractive. 121 volts....
But I feel uncomfortable using it as it wasn't intended. H is designated as primary for some reason, eh? If it weren't a special kind of noise reduction design I'd feel more comfortable reversing it. But if you say go, I'll reverse it for the sake of science. It will take me a couple of hours as I have a big 12/3 black rubber cable going into the 220 volt primary side with a strain-relief cable clamp on it, and a fuse. And I have a 110 volt duplex outlet on the secondary side, all mounted on the screw-on plates so it won't be that bad.
I think the UPS's OV threshold must be 124 or 125... It has no problem with the 123 volt wall tap but it doesn't like the 125 from the Topaz. It stays on battery and won't go on line. And the other, more modern UPS is in "OV" mode, tapping the 125 line down.
I remember also seeing some military grey Topaz before of exactly this model. I think this was a standard design from the 80's or 90's. I think these four terminal per-side models were quite common; I've never seen a multitap one (but I've only examined 3 or 4 in my entire life).
BK
I read PRRs comments again (the voice of reason) and he makes a point I completely missed: Is it possible that the Topaz is reversed? Me duh!
[/quote]
Well, I could never find an exact Topaz schematic, but I looked on the net for a similar Sola and they all seem to be standardized as H is standard abbreviation for primary and X is secondary, to the best of my recollection. I've already sealed it up so I'd have to open it up to be sure.
But let's think about this. I hope no one gets confused with this. This Topaz is configured as a 2:1 right now, but I can use its secondary as a reference what my wall sockets are reading right now and pretend that's its ratio. I know that when my wall sockets are at 123 volts the Topaz is putting out 125, so it's not that far off spec.
So, pretending it's a 1:1 transformer, if I reverse it, it would put out 121 volts. Not too shabby. The math is divide 123 by 125 and multiply by 123.
Hmmmm... that's attractive. 121 volts....
But I feel uncomfortable using it as it wasn't intended. H is designated as primary for some reason, eh? If it weren't a special kind of noise reduction design I'd feel more comfortable reversing it. But if you say go, I'll reverse it for the sake of science. It will take me a couple of hours as I have a big 12/3 black rubber cable going into the 220 volt primary side with a strain-relief cable clamp on it, and a fuse. And I have a 110 volt duplex outlet on the secondary side, all mounted on the screw-on plates so it won't be that bad.
I think the UPS's OV threshold must be 124 or 125... It has no problem with the 123 volt wall tap but it doesn't like the 125 from the Topaz. It stays on battery and won't go on line. And the other, more modern UPS is in "OV" mode, tapping the 125 line down.
I remember also seeing some military grey Topaz before of exactly this model. I think this was a standard design from the 80's or 90's. I think these four terminal per-side models were quite common; I've never seen a multitap one (but I've only examined 3 or 4 in my entire life).
BK
BTW, current line voltage here is 122.1 so I hope it was just topping off at 123 the other day I measured it.
And if you say I can reverse it, I better check its ratio to ITSELF. I now see that two outlets in the house differ by a volt. One outlet is exactly 120, another is 121 right now, amazing. So before leaping to conclusions I better pull the cover off the 220 side of the Topaz VERY CAREFULLY and measure its ratio.
And if you say I can reverse it, I better check its ratio to ITSELF. I now see that two outlets in the house differ by a volt. One outlet is exactly 120, another is 121 right now, amazing. So before leaping to conclusions I better pull the cover off the 220 side of the Topaz VERY CAREFULLY and measure its ratio.
[quote author="mediatechnology"]OK, I guess I'm confused. Is there a problem with it producing high line if your outlets that are being fed from it are 123?[/quote]
No, the outlets being fed from it, on a given day, are 125 volts. I was saying that on a given day, other outlets in the house were producing 123 while the Topaz was producing 125, so it seems to be producing about 2 volts more than other outlets in the house. But see my other post right now about not being able to trust any outlet as a reference. If you say so, I'm going to measure the EXACT primary to secondary ratio of the Topaz.
No, the outlets being fed from it, on a given day, are 125 volts. I was saying that on a given day, other outlets in the house were producing 123 while the Topaz was producing 125, so it seems to be producing about 2 volts more than other outlets in the house. But see my other post right now about not being able to trust any outlet as a reference. If you say so, I'm going to measure the EXACT primary to secondary ratio of the Topaz.
[quote author="mediatechnology"]It might not be a bad idea. Is the primary problem then that the UPSs aren't liking it?
I don't think the actual gear is going to care.
EDIT: I'm not suprised that the one UPS is tapping it down but the other seems problematic in itself.
Sorry I'm re-imaging a crashed computer. Maxtor 60 and 80G drives are very unreliable.[/quote]
Thanks, Wayne. The primary problem is that the UPS's are not liking it, so I want to retap the power. The older UPS does not have a bunk/boost winding so it just says, "I won't work" when the line voltage is high. The newer UPS knows what to do.
You think the H and X windings on the Topaz are interchangeable?
--------------------------------
I know you're a computer expert, but let me share how I'm dealing with boot drives and cloning.
Get two of the interchangeable removeable drive bays from Compusa. That's a good brand because they use a Centronix-like connector and it seems to be pretty reliable. Other caddy/drawer systems I've tried are too cheap and make the IDE/ATA unreliable.
Set all your jumpers on the drives to CABLE SELECT. Now, you will never have to rejumper again or open up the computer again when you want to clone. The master/slave function now simply follows which drawer you stick your caddy into.
Plug one drive in a caddy into one bay and that becomes the "master" and another in the other bay and that becomes the slave. Your BIOS is set to boot from the master.
Using "Acronis True Image" software (do NOT use Norton Ghost or the Semantic replacement, they suck royally, in fact, they don't work) clone from the master to the slave and then remove the clone caddy from the drawer and put it on a shelf. Periodically reclone the boot drive to stay up to date...
When (if) your boot drive goes south, just plug the clone into the master drawer and reboot. All your major data should be on a separate RAID server so really all you're doing is getting your apps and registry cloned and maybe some specialized data.
Lather, rinse, repeat.
Done. No more wires to move, messy floors to mop.
If it's one of the newer motherboards with SATA boot drives, things are simpler, no jumpers to deal with but still Acronis is the best.
BK
I don't think the actual gear is going to care.
EDIT: I'm not suprised that the one UPS is tapping it down but the other seems problematic in itself.
Sorry I'm re-imaging a crashed computer. Maxtor 60 and 80G drives are very unreliable.[/quote]
Thanks, Wayne. The primary problem is that the UPS's are not liking it, so I want to retap the power. The older UPS does not have a bunk/boost winding so it just says, "I won't work" when the line voltage is high. The newer UPS knows what to do.
You think the H and X windings on the Topaz are interchangeable?
--------------------------------
I know you're a computer expert, but let me share how I'm dealing with boot drives and cloning.
Get two of the interchangeable removeable drive bays from Compusa. That's a good brand because they use a Centronix-like connector and it seems to be pretty reliable. Other caddy/drawer systems I've tried are too cheap and make the IDE/ATA unreliable.
Set all your jumpers on the drives to CABLE SELECT. Now, you will never have to rejumper again or open up the computer again when you want to clone. The master/slave function now simply follows which drawer you stick your caddy into.
Plug one drive in a caddy into one bay and that becomes the "master" and another in the other bay and that becomes the slave. Your BIOS is set to boot from the master.
Using "Acronis True Image" software (do NOT use Norton Ghost or the Semantic replacement, they suck royally, in fact, they don't work) clone from the master to the slave and then remove the clone caddy from the drawer and put it on a shelf. Periodically reclone the boot drive to stay up to date...
When (if) your boot drive goes south, just plug the clone into the master drawer and reboot. All your major data should be on a separate RAID server so really all you're doing is getting your apps and registry cloned and maybe some specialized data.
Lather, rinse, repeat.
Done. No more wires to move, messy floors to mop.
If it's one of the newer motherboards with SATA boot drives, things are simpler, no jumpers to deal with but still Acronis is the best.
BK
[quote author="mediatechnology"]Bob;
As to the transformer I do think they are interchangable H and X.
snip
[/quote]
Hi, Wayne.
Looks like we're on the same wavelength with both ghosting and with transformers! I just took the cover off the 220 side of the Topaz. I measured 246.0 volts on the primary loaded. That shows what a high voltage Progress Energy is producing. And each half of the dual, series-connected primary windings measures 123.0 volts. At that moment, the secondary is reading 126.1 volts loaded, quite a voltage gain for a supposedly precision "2 to 1" transformer.
If my ratio math proves right, reversing H and X should yield right around 120 volts! That would be very nice. Manufacturing "intolerances", eh. I'll rewire it tomorrow and report back.
Wouldn't it be ironic if it turns out the voltage gain is not due to winding ratios, but due to the lower impedance of the parallel-connected secondaries versus the series-connected primary? Stand by for that.
BK
As to the transformer I do think they are interchangable H and X.
snip
[/quote]
Hi, Wayne.
Looks like we're on the same wavelength with both ghosting and with transformers! I just took the cover off the 220 side of the Topaz. I measured 246.0 volts on the primary loaded. That shows what a high voltage Progress Energy is producing. And each half of the dual, series-connected primary windings measures 123.0 volts. At that moment, the secondary is reading 126.1 volts loaded, quite a voltage gain for a supposedly precision "2 to 1" transformer.
If my ratio math proves right, reversing H and X should yield right around 120 volts! That would be very nice. Manufacturing "intolerances", eh. I'll rewire it tomorrow and report back.
Wouldn't it be ironic if it turns out the voltage gain is not due to winding ratios, but due to the lower impedance of the parallel-connected secondaries versus the series-connected primary? Stand by for that.
BK
> if a little 250 va transformer can be used as an autoformer to drop the 240 volt line a little.
Boswell's point is good. Your proposal will pull 10A through 10V of a 230V 1.1A winding. The copper is undersized. It may not smoke and flame, since the total heat in the box is not large, OTOH you could have local toasting and you might not even know until it broke-down.
My plan called for a 24V 10A winding, which will carry 10A even standing on (or hanging below) a 250V pedestal.
I actually expect you to turn-up a 24VCT winding, which you could use for a 12V buck (about -6V on the wall-plug side). I guess CT windings are rarer.
But counting on thumbs: 127 now, with a 90% buck, is 116V. That IS a standard line voltage which anything you own should eat for breakfast lunch dinner and latenite snack. Any US gear which isn't happy midway between 115 and 117 is sick.
> One of my UPS's ... is in line-compensation mode, saying the line voltage is high and probably adding an autoformer tap itself!
It is probably not that smart. It is probably running its inverter at 5% power. Which is doing things the hard way, but avoids the difficulty of hot-tapping a winding. But it means that parts which may have been designed for a 10-100 hour life (you are not supposed to live on overvoltage) are working full-time. Not at full power, but affordable UPSes are incredibly under-engineered (actually super-carefully engineered as close to the bone as the market will stand).
> primary windings measures 123.0 volts. At that moment, the secondary is reading 126.1 volts
Uh-huh. Transformers have loss. A tranny that size may run 2.5% loss at full load. It is often done to step-up by the amount of loss, so at full load the output is "right", equal to input. And your in/out voltages are 2.5% apart.
Here everything is against you. Your line voltage IS too high. Your UPSes are too fussy. Your iso-tranny is correcting a problem that you sure do not have. Your line is too high, and you may never touch the 2,500VA full-load. I suspect your load is hundreds, not thousands of watts.
I'd run it in 2.5% step-down. The side effect is that your two internal shields should be switched: the one closer to what you use as primary goes back to the fusebox, the one closer to your working secondary goes to your in-room technical ground. It may make no difference if "wrong", but that's how it should be connected. Primary electrostatic crap drained back to source, leakage from that (and any crap from load) drained to load ground.
Boswell's point is good. Your proposal will pull 10A through 10V of a 230V 1.1A winding. The copper is undersized. It may not smoke and flame, since the total heat in the box is not large, OTOH you could have local toasting and you might not even know until it broke-down.
My plan called for a 24V 10A winding, which will carry 10A even standing on (or hanging below) a 250V pedestal.
I actually expect you to turn-up a 24VCT winding, which you could use for a 12V buck (about -6V on the wall-plug side). I guess CT windings are rarer.
But counting on thumbs: 127 now, with a 90% buck, is 116V. That IS a standard line voltage which anything you own should eat for breakfast lunch dinner and latenite snack. Any US gear which isn't happy midway between 115 and 117 is sick.
> One of my UPS's ... is in line-compensation mode, saying the line voltage is high and probably adding an autoformer tap itself!
It is probably not that smart. It is probably running its inverter at 5% power. Which is doing things the hard way, but avoids the difficulty of hot-tapping a winding. But it means that parts which may have been designed for a 10-100 hour life (you are not supposed to live on overvoltage) are working full-time. Not at full power, but affordable UPSes are incredibly under-engineered (actually super-carefully engineered as close to the bone as the market will stand).
> primary windings measures 123.0 volts. At that moment, the secondary is reading 126.1 volts
Uh-huh. Transformers have loss. A tranny that size may run 2.5% loss at full load. It is often done to step-up by the amount of loss, so at full load the output is "right", equal to input. And your in/out voltages are 2.5% apart.
Here everything is against you. Your line voltage IS too high. Your UPSes are too fussy. Your iso-tranny is correcting a problem that you sure do not have. Your line is too high, and you may never touch the 2,500VA full-load. I suspect your load is hundreds, not thousands of watts.
I'd run it in 2.5% step-down. The side effect is that your two internal shields should be switched: the one closer to what you use as primary goes back to the fusebox, the one closer to your working secondary goes to your in-room technical ground. It may make no difference if "wrong", but that's how it should be connected. Primary electrostatic crap drained back to source, leakage from that (and any crap from load) drained to load ground.
[quote author="PRR"]> if a little 250 va transformer can be used as an autoformer to drop the 240 volt line a little.
Boswell's point is good. Your proposal will pull 10A through 10V of a 230V 1.1A winding. The copper is undersized.
[/quote]
Thanks for the warning, PRR! I had neglected to consider the size of the copper of the primary of the unit. Anyway, today I'm going to experiment with reversing the Topaz and will report back.
That's easy as pie. Each shield comes out of the internal harness to the correct side of the transformer. The "H" shield comes out on a wire with a stacon on the side of the H winding and it would be impossible to get it to the other side unless I extended it and ran it outside the housing!
However, all standard grounding diagrams of isolation transformers show all the shields being tied together and to the utility ground. I don't know if I can upload an image her, I'll try uploading a schematic, but basically I have the shield on the primary connected to a ground chassis screw of the transformer on the primary side along with the utility ground. And on the secondary side I have the shield connected to a ground chassis screw on that side, and this also joins the neutral of the 110 V duplex outlet at that point.
Boswell's point is good. Your proposal will pull 10A through 10V of a 230V 1.1A winding. The copper is undersized.
[/quote]
Thanks for the warning, PRR! I had neglected to consider the size of the copper of the primary of the unit. Anyway, today I'm going to experiment with reversing the Topaz and will report back.
That's easy as pie. Each shield comes out of the internal harness to the correct side of the transformer. The "H" shield comes out on a wire with a stacon on the side of the H winding and it would be impossible to get it to the other side unless I extended it and ran it outside the housing!
However, all standard grounding diagrams of isolation transformers show all the shields being tied together and to the utility ground. I don't know if I can upload an image her, I'll try uploading a schematic, but basically I have the shield on the primary connected to a ground chassis screw of the transformer on the primary side along with the utility ground. And on the secondary side I have the shield connected to a ground chassis screw on that side, and this also joins the neutral of the 110 V duplex outlet at that point.
I hope I haven't made a mistake. All shields, chassis, U ground and utility ground are commoned. That's the way that I've seen all isolation transformer schematics and there is safety to consider. I cannot legallly create an isolated ground or neutral for the secondary to the best of my knowlege. Basically I've connected the utility ground to the chassis and the primary shield at a chassis ground point on the primary side. And the neutral, u ground, chassis and secondary shield are joined at a chassis screw point on the secondary side. This conforms with other schematics I've seen of how to wire an iso tranny.
You can view a pdf of the schematic I drew.
http://ftp.digido.com:8000
your name is topaz your password is topaz
Click on the pdf and if you can view pdfs you'll see it in a new window.
You can view a pdf of the schematic I drew.
http://ftp.digido.com:8000
your name is topaz your password is topaz
Click on the pdf and if you can view pdfs you'll see it in a new window.
SUCCESS
Thanks, everyone.
First I tested the Topaz in reverse on the bench and proved it is a RATIO thing, not an impedance thing. Then I rewired it, and after reversing primary and secondary, under load it's delivering 117.8 right now. We should be fine, and neither UPS is complaining anymore. I had resisted that solution only because I was concerned that isolation transformers may be designed specially wound, or their shields perhaps, to best work in one particular direction.
As for the grounding, if Studio B weren't on the second floor, I'd install a second ground rod, and isolate the studio ground from the incoming ground. If I had a separate ground rod, would it be proper to float the primary shield from the chassis, connect it to the utility ground, and then connect the secondary neutral, transformer chassis, u-ground, and shield to the studio ground?
Comments?
Thanks again,
Bob
Thanks, everyone.
First I tested the Topaz in reverse on the bench and proved it is a RATIO thing, not an impedance thing. Then I rewired it, and after reversing primary and secondary, under load it's delivering 117.8 right now. We should be fine, and neither UPS is complaining anymore. I had resisted that solution only because I was concerned that isolation transformers may be designed specially wound, or their shields perhaps, to best work in one particular direction.
As for the grounding, if Studio B weren't on the second floor, I'd install a second ground rod, and isolate the studio ground from the incoming ground. If I had a separate ground rod, would it be proper to float the primary shield from the chassis, connect it to the utility ground, and then connect the secondary neutral, transformer chassis, u-ground, and shield to the studio ground?
Comments?
Thanks again,
Bob
SSLtech
Well-known member
Shouldn't have to ask permission... I've been lurking of late and learning TONS! -Thanks to ALL the contributors!
I was just at Skycraft, looking at B-I-G capacitors (SSL E-series computer 5V reservior caps) and so I took a little trip round to the Copper-and-Iron aisle and had a peep at what Bob was talking about.. -Bob, if that works for you and you recommend it, are you planning on taking the second Topaz, or would you mind if I scored it?
Keith
I was just at Skycraft, looking at B-I-G capacitors (SSL E-series computer 5V reservior caps) and so I took a little trip round to the Copper-and-Iron aisle and had a peep at what Bob was talking about.. -Bob, if that works for you and you recommend it, are you planning on taking the second Topaz, or would you mind if I scored it?
Keith
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