Balancing Inductor

Discussion in 'The Projects Forum' started by Crank, Feb 13, 2011.

  1. Crank

    Thread Starter New Member

    Feb 13, 2011
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    I have a generator that outputs 240V using two 120V windings in series. Loading one 120V side more than the other creates an inbalance and causes droop on the loaded side. The voltage regulation performs best with both winding equally loaded. Some ppl wire a 120V/240V primary input transformer onto the generator output to provide a current path across the windings to allow the system to balance. These transformers in the 3kw range are pricey whereas magnet wire and iron are a fraction of the price. I was thinking of just creating the primary side of a transformer. Basically it's half of a center tapped transformer that can handle 20A.
    How many turns of what size wire onto what material will produce what I need?

    Thanks
     
  2. wayneh

    Expert

    Sep 9, 2010
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    Why not just put the windings in parallel at 120V?
     
  3. Crank

    Thread Starter New Member

    Feb 13, 2011
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    Because I power my home with it and I require both 240 and 120.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Because you are mentioning 120VAC it is probably safe to assume you are in the USA. If you are wanting to balance your split phase power pole this would likely be something we would recommend using a licensed electrician to do, mistakes with something like this could be costly.

    Assuming this is the power pole (or in this case, generator) you need to figure the loads from each leg, and do some simple arithmatic. I am assuming that you are still using your breaker box with the generator when it is switched in instead of the line voltage. If so the breaker box needs reconfigured.

    Am I even close to what you're talking about?
     
  5. Crank

    Thread Starter New Member

    Feb 13, 2011
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    Schematic below:

    balance.JPG

    What I want to add is circled in RED
    The problem is if I have various 120V loads on throughout the house and the total load on one side is more than the other the generator head has an imbalance on it causing one winding to get hotter than the other and with a larger imbalance such as using the microwave or washing machine the voltage on that side drops. I'm not using my generator efficiently. I have measured all my loads with a Kill A Watt meter and know what they are but I don't want to manage or dictate what someone can turn on when or what they have to turn off before we turn something else on. Adding the inductors across the generator windings should allow the winding not loaded to aid in providing current to the loaded winding, balancing them out. This can be done with a transformer like this:
    http://www.grainger.com/Grainger/ACME-ELECTRIC-Transformer-4LEH8?Pid=search

    Wire the primary as illustrated in my sketch and leave the secondary open or use it for what ever purpose you may have. The 2KVA transformer is $650. My interest is to create the primary circuit of this transformer to meet my needs without spending $650. Used ones I have found, none locally are $150 and up.

    What I'm asking is can someone calculate how many turns of a given magnet wire is required to create this? Also what commonly available material can I wrap it on as the iron core.
     
    Last edited: Feb 14, 2011
  6. wayneh

    Expert

    Sep 9, 2010
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    I understand your problem but not so much the proposed solution. (My fault, not yours.)

    But help me understand: Aren't the two 120v legs actually 180° out of phase with each other? So 240V comes from the trough of one wave versus the peak of the other
     
  7. wayneh

    Expert

    Sep 9, 2010
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    I don't think the number of turns matters too much, as long as they're the same on both portions. The gauge of the wire should be the smallest that will safely carry the current load without melting the insulation. Estimating heat loss from a transformer coil can be challenging though. Why smallest? So that you can bend and wind it, and so you can get more turns for a given weight. The length of wire you use will determine the resistance of the winding, which needs to be high enough to avoid overloading your generator windings. The core should be laminated transformer steel. There are many sources of such cores. You don't don't need to worry about high frequency - you want high magnetic permeability and high saturation levels so that the magnetic field is max possible.

    Transformer design is half art, half science and there is much written on it.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    OK, so it is a house. Again, the solution is measure the loads on the various breakers, possibly using a gadget called a AC clamp meter. You add the loads on one side, then add the loads on the other side, and try to get the numbers as close as possible. This was (or should have been) done when the house was built, you just need to revisit the math.

    I'm not sure what you think and inductor will do for you. The transformer is fixed and sealed, though I think they may have the ability to do fine tweaks for adjusting loads. This is something a licensed electrician would know. You can't adjust a transformer with a large inductor, the coils that do the work are inside the transformer.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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    I believe that the transformer you link to may be a harmonic type. There are additional capacitors and inductors internally that will tend to keep the low voltage output constant despite variations on the input. The effect is only going to be useful at the low voltage output of that transformer. Attaching one across your generator output will only add an additional load. It will not be able to take power from one phase and add it to the other.

    In the case of using an external generator, load balancing is just that - the electrical loads on both phases must be adjusted so they are as nearly equal as possible.
     
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