There's a thread or two on here that talk about using 208V line reactors......

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bbaumer

bbaumer

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Indiana
to reduce fault current.

Where have those of you that said you've used them found them? All I can find are line reactors to be used in combo with VFD's. Those type do not significantly reduce fault current.

I've got a few situations where we've discovered a lot of our old gear is under rated. I can replace a ton of gear in a few buildings - high $$ and lots of down time, replace the transformers (low impedance single phase cans wired for 3 phase) with new pad mounts - logistically very difficult as these are in below grade vaults plus a host of other issues or add isolation transformers between the existing cans and the MDP's (possible, but with the new DOE regs Jan 1st, not looking viable) or add these impossible to find current limiting 208V line reactors.

Also have the same deal on one service that is 240V ungrounded delta. Transformer sizes required are between 150 and 500KVA if I go that route.

Thoughts anyone?
 
Pics of the cans to help clarify part of the situation. Click to enlarge. They are only 1.6% impedance which give me nearly 50KAIC on the 208 and 240V secondaries. Several of the load side distribution breakers are rated much lower, like 18K, 14K and 10K. This amount of fault current at the service makes us under rated at several points in the distribution system according to the PTW SKM model.

I know I said xfmr sizes from 150 to 500 and one of the pics shows three 25kva cans. Those are for a small 240V ungrounded delta service. I'm going to remove them and feed that board from the 208V service next to it via a 208 to 240V step up dry type transformer.
 

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I've never installed them, but I've run into them a number of times where they've been used downstream to reduce fault current. Look up dry-type air core reactors and that'll at least put you in the right direction instead of VFD reactors. There are a mess of them specifically sold for current limiting.
 
big john said:
I've never installed them, but I've run into them a number of times where they've been used downstream to reduce fault current. Look up dry-type air core reactors and that'll at least put you in the right direction instead of VFD reactors. There are a mess of them specifically sold for current limiting.
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:thumbsup:
Since the purpose of the VFD reactor is to provide a high impedance to high frequency components of the voltage waveform but at normal current levels only, they will be iron core.
But to maintain inductance at very high currents requires an air core. That is the critical design feature and will potentially make them much larger.
Some folks just take a very long section of wire (such as try cable) and coil it up in the corner of the room. You have to route each wire separately though. No multiconductor cable unless you are just looking for the resistance effect (which does help.)
 
big john said:
I've never installed them, but I've run into them a number of times where they've been used downstream to reduce fault current. Look up dry-type air core reactors and that'll at least put you in the right direction instead of VFD reactors. There are a mess of them specifically sold for current limiting.
Click to expand...

Can you provide a link or source? The ones I've found and called the manufacturer about they say their units don't significantly reduce fault current. Thanks.
 
ron said:
We've used these http://www.hammondpowersolutions.com/product/reactors/ and http://www.acutran.com/Inductors-Reactors/index.html

The impedance rating and thus the amount of millihenrys are important

I've used iron core, due to the air core type having EMI issues when installed in a regular commercial building.
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Current limiting iron core reactors could be pretty hard to find because core saturation can defeat the current limiting unless the core is very large. And that in turn risks excessive VD for normal current.
 
GoldDigger said:
Current limiting iron core reactors could be pretty hard to find because core saturation can defeat the current limiting unless the core is very large. And that in turn risks excessive VD for normal current.
Click to expand...

Cant these reactors also create morbid transients? Im thinking a car ignition coil or HID ballast. The HID ballast is also an iron core reactor, and when the ignitor opens the current at a particular time in the waveforum the bulb gets a 4,000 volt kick.
 
mbrooke said:
Cant these reactors also create morbid transients? Im thinking a car ignition coil or HID ballast. The HID ballast is also an iron core reactor, and when the ignitor opens the current at a particular time in the waveforum the bulb gets a 4,000 volt kick.
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Inductive kickback, yes, but that's more of an issue on DC systems. On AC, the zero cross of the incoming sine wave kills it quickly. It still happens, but only when the circuit is switched off, and AC contacts have to contend with that in their design and ratings.
 
Jraef said:
Inductive kickback, yes, but that's more of an issue on DC systems. On AC, the zero cross of the incoming sine wave kills it quickly. It still happens, but only when the circuit is switched off, and AC contacts have to contend with that in their design and ratings.
Click to expand...

Which could happen during switching?
 
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