Voltage regulator to buck sub-240 volt down to 120 volt?

KeithWHare
KeithWHare Solar Expert Posts: 140 ✭✭✭
in Off Grid Solar & Battery Systems #1
I'm in the Dominican Republic installing a battery backup system (Magnum MS4024, e-panel, etc.) at a clinic in Batey Seven.

We are going to replace the 12-2 with ground currently being used as entrance cable with #4 or so, but reports are that the voltage is low anyhow. One suggestion for a local person is to run entrance for nominal 240 volt, then add a voltage regulator to buck it down to a consistent 120 volts.

Anything anyone can tell me about this level of voltage regulator technology?

Keith
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Comments

  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?

    I would want to know exactly what the voltage is, and is it more or less constant at that voltage, if not constant, what is the range of changes. Also what have been the loads on that 12/2 entrance cable? Could be, if the loads are sometimes large, just changing the 12/2 to #4 could well cure the problem.
    What problems have you been running into, that is prompting you to consider changing from 12/2 to #4 ?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?

    There are large and smaller AC Stabilizers/Regulators that used switched auto transformers.

    And, I have seen (in decades past) UPS Systems that also contain switching auto transformers too (running on a switched transformer is more efficient than running on UPS). It was an APC brand system--But looking at their website--Turns out they were purchased by Schneider and the website is now pretty much unusable to find actual equipment and specifications. :p

    There are also ferroresonant transformers too--But they tend to be big and heavy (expensive). But they are pretty rugged/bullet proof. You might find some used ones for scrape value.

    If you have highly variable AC voltages from the grid, changing to heavy gauge wiring probably will not help a lot. If the problem is voltage drop from the 12/2 wire and voltage sag during heavy loads--And the power from the grid is "stable"--Then rewiring can help.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?
    BB. wrote: »
    There are also ferroresonant transformers too--But they tend to be big and heavy (expensive). But they are pretty rugged/bullet proof. You might find some used ones for scrape value.

    -Bill

    Just a caution from personal experience: A ferro-resonant Constant Voltage Transformer (CVT) will do a pretty good job of producing a stable output voltage if given a stable input frequency. If you try connecting it to a generator or to a grid that does not keep good frequency stability, you will find that a 1% difference in frequency will produce a 2% difference in output voltage.
    (When I did not have a good frequency meter, I would adjust a variable load on a generator to produce the right reference voltage from the CVT in order to get the accurate frequency I needed for other equipment. It was a 10 KW stationary diesel generator with a not-so-good speed governor.)
    SMA SB 3000, old BP panels.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #5
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?

    If voltage is not too low, I wouldn't worry. I lived with low voltage (115-117V at the entrance, slightly lower in the house) and I haven't noticed any bad effects.
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  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    #6
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?
    BB. wrote: »
    ...
    And, I have seen (in decades past) UPS Systems that also contain switching auto transformers too (running on a switched transformer is more efficient than running on UPS). ...

    Modern online UPSs don't use the transformers anymore (switched power supplies instead) and are about the same efficiency as the auto transformers.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
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  • KeithWHare
    KeithWHare Solar Expert Posts: 140 ✭✭✭
    #7
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?

    The power was actually on yesterday afternoon when I was at the clinic. I was getting about 75 volts between hot and neutral and 105 to 110 volts between hot and the new ground we installed yesterday morning.

    Today, the guy who connects stuff to the utility replaced the #12 with #4. He ran a neutral and two hot legs. This afternoon when the power was on, I tested each leg and picked the best one. With the ground bonded to neutral, we were getting 95 to 100 volts.

    As a side track, the guy who connects wires leaned a fiberglass ladder against the pole. At the top, he ran a strap around the poll to hold him as he stood on the top rung. This would not pass US safety requirements.

    My current plan is to set the Magnum MS4024 to quit charging and start inverting at about 85 or 90 volts. This will charge more slowly than 120 volts, but the power is generally needed when the utility is out, and not needed when the utility is on, so this should work well.

    Keith
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  • newl
    newl Solar Expert Posts: 53 ✭✭✭✭
    #8
    Re: Voltage regulator to buck sub-240 volt down to 120 volt?

    You might find that it actually would pass OH&S standards. So long as my ladder (extended or not) was tied off to the pole at the base (and at the top if fully extended) and I was belted in at the top, all was good. Never mind the difference between that and tossing on the climbing hooks and handing it up to a point where I'd belt in and relax. hehe
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