208 WYE Electric Service is it possible to chang taps to get 480 WYE? - Page 2
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  1. #21
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    Just a couple of comments in case you are not already aware of it.

    The reason 208 wye is used in commercial applications is because you have 120 volts to the neutral. So you have an electrical panel fed with 3 phase 208 and now you have 120 single phase, 208 single phase and 208 3 phase all available in the one panel. Very clean and cheap to do.

    In a residential single phase panel, you have 120 volts or 240 volts single phase available. Most equipment will run ok with either 208 or 240 volts.

    So if you now change the incoming feed to 3 phase 480 volt, you want a 3 phase 480 volt to 3 phase 208/120 volt transformer that would then fed the existing 208 panel. You would need to add a 3 phase 480 volt panel to feed the 480 volt equipment.

  2. #22
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    Some utility transformers do indeed have different tappings, some don't. Most larger ones have a large connection box on the side of them, nearly all have a pretty clear rateing plate though, at least over here. Like most things its all down to what is paid for at day one, more options cost more. That said over here to do what your after most would just change how the secondary is connected, from delta to star. Hence why i would expect if its supplying 400 amps at 200 ish volts it to drop to supplying 200 amps at 400 ish volts with out replaceing that transformer with a larger one.

    Im not saying you have to figure anything out, but there's some seriously large potential saving's power bill and AC wise to be had setting this up properly and most suitably from the get go. What you don't dump as waste heat you don't have to install and power in AC to remove. Every machine having its own step down - up transformer means your have a lot of losses. Transformers have to be sized to the max load, hence on something like a cnc, you may be surprised - disappointed by how much power its dumping as heat most of the time. Knowing current real world power draws also lets you make serious plans as to how much spare capacity you should be considering if your having to pay to upgrade that transformer. If your doubling - tripling your floor space with plans to grow, you can take a pretty good stab then at what your likely worst case future power needs will be in that building.

  3. #23
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    None of the utility transformers I have worked with have tap settings on the secondary side that would go from 208 to 480 some have taps for boosting the voltage or dropping it they are called straddle taps they raise or lower voltage by 1.5% I think and must be moved de-energized. But some have a primary tap for changing the primary voltage (12KV to 21KV or 7200 to 12 KV) having been in the industry for over 30 years retired now that doesn't mean they don't exist I just have never seen one on the utility side.I am not an expert on the customers side of the meter although I do know they usually install a dry transformer to lower the 480 volts to 120 volts for those loads. On the utility side you will see 2 different 480 volt hook ups 240/480 Delta or 277/480 Y. The 120/208 is also Y and you have 120/240 delta 3Ø. On the delta 3Ø hook ups you have a wild leg that is not useful in a phase to neutral that is one reason 120/208 Y is better than 120/240 delta because you get 3 legs of 120 volts to split up the single Ø loads as opposed to 2 legs of 120 and one leg of 208 the wild leg in the delta connection. In the 240/480 delta the wild leg is 277 volts to ground or neutral. In the case of the open delta they are usually for small 3Ø loads they still have the wild leg.

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