lutful
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join:2005-06-16
Ottawa, ON
 ·TekSavvy Solutions..
1 edit | isolation transformer
Sadly, I moved out of my cozy (and expensive) real office into my basement last week. 
I had lost equipment in the past even with decent surge protectors. I suspect the AC grounding is not good enough.
So I want to create an "isolated" AC system just for my computers and test gear.
I am looking for good quality 1000W+ isolation transformer with no connection whatsoever between the two grounds. The secondary-side ground wire will clamp to the main water pipe under the meter which happens to be located in a convenient corner of the basement.
During Google search I find a lot of hospital-grade isolation transformers. I could be mis-reading specs but they seem to leave secondary-side ground floating?
That won't work for me as I want to divert kilojoules to ground via water main.
I welcome your suggestions and comments. |
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Kord
join:2006-10-27 | »www.squared.com/
Not sure what Distribution panel you have, but you might look into circuit protection in the box.
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John Galt
Forward, March
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Happy Camp
1 edit | reply to lutful
How much power do you need/want...really?
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UHF
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| reply to Kord
said by Kord  : you might look into circuit protection in the box. I agree. A good quality and well grounded surge arrestor at the service entrance panel will help a lot. Point of use protectors are almost useless due to the highly inductive nature of the ground wire during a lightning strike. You need to have the protection close to the main earth grounding electrode. Usually that is at the main panel. Beware of any that don't list the joules rating. |
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John Galt
Forward, March
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| reply to lutful
I installed a ton of these in the labs for Lockheed-Martin, NASA and Loral Space Systems:
»www.solaheviduty.com/products/po···/cvs.htm
They are good enough for labs developing space flight hardware...but you might want to check if they are adequate for testing WISP gear.
They were attached to a "adequate grounding system"...250 lineal feet of deep-driven ground rods with an equipotential ground plane of about 20,000 square feet....plus, plus, plus.
I am concerned that the water pipe that you plan to use may not be a sufficient ground for your intended use. It is one thing to divert normal fault currents, quite another to have a real grounding system for testing.
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
1 edit | reply to lutful
said by lutful :I am looking for good quality 1000W+ isolation transformer with no connection whatsoever between the two grounds. The secondary-side ground wire will clamp to the main water pipe under the meter What you want is an ultraisolation transformer.
These have an electrostatic shield between the windings resulting in very low capacitance.
»www.surplussales.com/Transformer···s-2.html
Any surge on the primary, either common mode or differential is greatly attenuated by the very low capacitance. |
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public
join:2002-01-19
Santa Clara, CA
·DSL EXTREME
| reply to John Galt
said by John Galt :I installed a ton of these in the labs for Lockheed-Martin, NASA and Loral Space Systems: » www.solaheviduty.com/products/po···/cvs.htmThey are good enough for labs developing space flight hardware...but you might want to check if they are adequate for testing WISP gear. These are no good for isolation. These regulate AC voltage.
A really noisy rattling lump of iron. |
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John Galt
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| reply to public
said by public :What you want is an ultraisolation transformer. Damn...I guess I shouldn't have run off to made dinner and get a beer.
What was I thinking..!
THEN plug one of these (or similar):
»www.aplab.com/pe/ac-16.htm
into that system.
Power conditioning is a multilevel process. You have to start at the service entrance and work all the way to the load.
Install one of these at your service entrance:
»www.apcc.com/resource/include/te···features
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John Galt
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| reply to public
said by public :A really noisy rattling lump of iron. That part is true...
We initially mounted them on the wall like the engineers wanted. The hum was transferred to the floor above, which was impressive since it had massive pour-in-place concrete decks.
We ended up ripping the install out and bolting them to standoffs on the ground floor.
All the hum was gone...
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Keithb
join:2003-09-16
US
| We purchased a SmartUPS 3000 VA for our server room: »www.apcc.com/resource/include/te···b=models
Has worked fairly well, and has some built in functions. You might can kill a few birds with one stone. |
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skylabpc
join:2002-03-31
La Canada Flintridge, CA | reply to lutful
how about a true double conversion UPS, your load would be powered by the inverter and have no physical connection to the AC supply via transformer or anything else.... |
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lutful
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join:2005-06-16
Ottawa, ON
·TekSavvy Solutions..
1 edit | reply to public
said by public :What you want is an ultraisolation transformer. These have an electrostatic shield between the windings resulting in very low capacitance. » www.surplussales.com/Transformer···s-2.htmlAny surge on the primary, either common mode or differential is greatly attenuated by the very low capacitance. Thanks for this suggestion and link. Several of these units fit my need and hopefully my budget with slow ground shipment. 
*** Just found this link from Google search:
»blackmagic.com/ses/bruceg/EMC/is···ans.html
An isolation transformer is designed to specifically address the problems associated with referencing its internal shields to ground. It is constructed with two isolated Faraday shields between the primary and secondary windings. When properly installed, the shield, which is closest to the primary winding, is connected to the common power supply ground and the shield closest to the secondary winding is connected to the shield of the circuit to be isolated.
The use of two shields in the construction of the isolation transformer diverts high frequency noise, which would normally be coupled across the transformer to the grounds of the circuit in which they occur. The two shields provide more effective isolation of the primary and secondary circuits by also isolating their grounds.
The isolation transformer adds a third capacitance between the two Farady shields, which may allow coupling of high frequency noise between the system grounds. However, increasing the separation between the two Faraday shields normally minimizes this third capacitance. |
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nunya
SEE ROCK CITY 475 MILES
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| reply to lutful
NEC now requires that all grounding conductors be run back to the source (panel). NEC requires the water pipe to be bonded to the utility grounded conductor. In most installations with metal water piping, the water pipe is the grounding electrode conductor for the house system, with a driven ground rod acting as a supplemental grounding electrode conductor. No part of the piping system may be used as a GEC after 5' from the water piping entrance.
For houses with metal piping inside, and plastic outside - the metal piping must still be bonded to the electrical ground.
Isolation transformers provide no protection against surges and sags.
Isolation transformers can help with harmonics on 3 phase systems though.
A better solution would probably be a panel surge arrestor / supressor, a decent UPS, and a properly sized and installed grounding system for the service.
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John Galt
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| said by nunya :NEC now requires that all grounding conductors be run back to the source (panel)... He could configure it as a separately-derived system. The fact that the system will be in the basement near the water piping entrance is helpful.
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skylabpc
join:2002-03-31
La Canada Flintridge, CA
| reply to nunya
best way to deal with harmonics in a 3ph system is to feed the load(s) via a 208v delta to 120/208Y K rated electrostatically shielded transformer, placed as close as practical to the load, with double neutrals and a non linear rated panelboard. The harmonic currents get circulated in the delta winding of the transformer and everything hums along without any problems. I have used this setup both on large (50,000+ watts) audio systems with amplifiers using switching power supplies, and large lighting dimmer installations (lighting dimmers are a nightmare with regards to harmonics and excess neutral currents)
yes i know this has nothing to do with wisp, but power is fun.... |
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lutful
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join:2005-06-16
Ottawa, ON
·TekSavvy Solutions..
| reply to nunya
said by nunya :Isolation transformers provide no protection against surges and sags. The "zerosurge" spec for Plitron medical isolation transformers ( »www.plitron.com/ ) looks much better than most panel surge protectors.
Although unaffordable for my basement setup, I am sure these units could be used for safely powering WISP cabinets.
said by nunya :NEC now requires that all grounding conductors be run back to the source (panel). That requirement applies only to the ground conductors on the "load" side of a single panel. There are exceptions to that general rule for cross-panel, subpanel and isolation scenarios.
The ground of isolated sockets are marked with a green triangle as shown in the photo above. Also medical isolation wiring follows IEC 60601-1 global standard in most countries. |
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nunya
SEE ROCK CITY 475 MILES
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O Fallon, MO
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| reply to lutful
Those are more than just isolation transformers.
I've put in hundreds of isolated ground receptacles and I'm quite familiar with the concept. Isolated ground receptacles simply depend on a dedicated equipment grounding conductor back to the panel.
I was generalizing a normal residential setup (single panel) on the ground, but the water pipe idea is still probably unacceptable. Although I see you are in Canada, so I do not know what the codes are there.
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