Leaking electricity from transformers.
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  1. #1
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    Default Leaking electricity from transformers.

    Hello,
    We have been super slow recently, so when I got our last utility bill, I was shocked to see the bill. With no machines being turned on, the bill was still huge so I turned off everything in the shop and clamped an amp meter to the main line coming to the shop and was surprised that we are loosing 8.5 amps @480v. We have two transformers ( 35kva & 45kva ) supplying the shop but one also supplies the 120v single phase to the wall outlets. Ill be shutting down one transformer but how do I go about shutting both without loosing the 120v outlets? The current coming in is at 480 and all the machines are wired for 240 or 208.

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    You dont, 8.5 amps seems high, check the transformers one at a time for load...Phil

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    First transformer is drawing 5amps and the second is around 3.5amps.

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    You don't.

    Look at your bill. You have a demand charge that is there if you use an power or not. Then there is the delivery charge and the taxes, etc.

    No matter how little you use, you will still have an electric bill that will be sizeable in relation to the power used.

    As far as your reading with the clamp on amp meter, that does not tell you much depending on your power factor.

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    You are wasting 4.08 kw x 24 hrs a day x 31 days/mo, adds up to a big bill, Is your transformers copper or aluminum? You might need to replace transformer with newer ones or add kvr caps to drop the idle current....Phil

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    Quote Originally Posted by Phil in Montana View Post
    You are wasting 4.08 kw x 24 hrs a day x 31 days/mo, adds up to a big bill, Is your transformers copper or aluminum? You might need to replace transformer with newer ones or add kvr caps to drop the idle current....Phil
    And to top it off he is in So Cal, if he isn't in a co-op and is under the wrath of SCE or SDG&E that leak alone would make a car payment. I had no idea transformers could leak like that.

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    They can and do, bad core design or aluminum winds don't help, Transformers also lose efficiency with age (the varnish between the steel lams. go to hell and the loss get high), and I as sure the cans are hot to the touch...Phil

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    Quote Originally Posted by Phil in Montana View Post
    You are wasting 4.08 kw x 24 hrs a day x 31 days/mo, adds up to a big bill, Is your transformers copper or aluminum? You might need to replace transformer with newer ones or add kvr caps to drop the idle current....Phil
    No - as Ziggy2 noted, the amps don't mean anything without knowing the power factor. You have no idea what the kilowatts is other than it can be as high as 4.08 kilowatts. Probably a lot less.

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    The real issue is all the electricity leaking out of the uncapped wall outlets!

    ;-)

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    Quote Originally Posted by markz528 View Post
    No - as Ziggy2 noted, the amps don't mean anything without knowing the power factor. You have no idea what the kilowatts is other than it can be as high as 4.08 kilowatts. Probably a lot less.
    Depending on location and your contract you might pay nearly same price for apparent power. Home users don't usually pay for apparent power but industrial user is opposite.
    Can be 500 Watts of real power, 5000 VA of apparent power and billed same as 5500 W real usage.

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    All transformers will use some energy to flip the magnetisation of the core (hysteresis losses) it is not 'leakage' .

    As an example I have a 1000VA (240vac uk mains volts) transformer driving my 120vac US made toaster.
    The transformer uses 18watts continuously* without any output , just from hysteresis losses.

    Generally speaking the larger the transformer the larger the losses - simple test , if it gets warm , it is using power !

    Bill


    *This more power, over a year , than I'd use making toast, so I have an additional switch mode psu that is used to sense when the power is required and that enables the transformer . Small (usually old) , non-switch mode, mains transformers (wall warts) with light loads are seriously inefficient and could be drawing a 100 times the load current (winding up your home electricity bill ) than they supply to the phone/laptop battery charger etc. .

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    "No - as Ziggy2 noted, the amps don't mean anything without knowing the power factor. You have no idea what the kilowatts is other than it can be as high as 4.08 kilowatts. Probably a lot less."

    BS, the power co will bill you for the kva used , the meter does not know or care what the PF is,...Phil

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    I would check how fast the meter is going with only the transformer(s) on That is what you pay for anyhow

    Peter

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    Quote Originally Posted by markz528 View Post
    No - as Ziggy2 noted, the amps don't mean anything without knowing the power factor. You have no idea what the kilowatts is other than it can be as high as 4.08 kilowatts. Probably a lot less.
    Unless it's a residential service, the power company *does* care about imaginary power - that is, they care about reactive currents. Commercial sites typically are charged for VARs (volt amp reactive) as well as
    in phase current. No doubt a lot of that bill is for reactive current.

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    Quote Originally Posted by Phil in Montana View Post
    "No - as Ziggy2 noted, the amps don't mean anything without knowing the power factor. You have no idea what the kilowatts is other than it can be as high as 4.08 kilowatts. Probably a lot less."

    BS, the power co will bill you for the kva used , the meter does not know or care what the PF is,...Phil
    BS^2

    In here residential users pay for real power (kW), not kva. For (large) industrial users reactive power is free as long as it is less than 20...40%(depends on power co) of real power.

    US is mostly similar I believe.

    edit: PG&E (kalifornia) for example seem to charge for reactive power for >400kW customers based on this: https://www.pge.com/pge_global/commo...tric_Power.pdf
    Residential and smaller businesses don't pay for reactive power.

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    Add capacitors to the primary side until the number that worries you goes down. Little will have changed, but you'll feel better.

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    if your contract states that you will be charged for kVArh as well as kWh, then get power factor correction capacirors for the transformers permanently and whatever loads you frequently use switched in with them. If your contract doesn't charge for kVArh, then do deeper investigation as to where the load is being drawn and see what you can do to reduce it. The utility's meter will definitely measure kWh. There may be an additional meter measuring kVArh.

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    The transformers are drawing kVA at a lousy power factor, possibly as low as 0.1, because there is a lot of VA and likely not much wattage. It is the "magnetizing current" and since it is flowing in an inductor, it is lagging current.

    You will be paying for the wattage, and getting dinged for the bad power factor as well.

    The 8.5A amounts to something around 7 kVA. How big are these transformers? It seems as if they may amount to somewhere around 220 kVA of transformer, possibly a bit more.

    You may be stuck with the one that supplies your 120, which will be the 208 unit. If it is an ongoing issue, you could install a separate smaller unit for 120V only, which would have a cost, but would allow you to shut off the larger transformers when the place is not operating any machines.

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    I second JST's suggestion. Get a SMALL 480:240/120 transformer to leave on all the time, use it for your basic 120 loads AND...

    A detection/control circuit for your big transformers. When your biz is shut down, drop out the contactors to the big transformers.

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    Whatever power is being used has to go somewhere. Is the transformer hot? 4kW is a lot. If it was really using that it would be too hot to touch. I suppose it takes a little power to make the buzzing noise but that is super minimal most all gets converted to heat.


    Sent from my iPhone using Tapatalk


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