Thread: 2K bulb in 1K?

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    #31
    Indie Arms Member Doc Bernard's Avatar
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    LOL, okay, you've done your homework.......... It is hard sometimes to explain electrical theory if someone is new to it.

    Yes, you have shown a "Delta" transformer, but those are not commonly used for residential applications.

    What you have should be:



    Now, there are other configurations for transformers Delta/Delta, Open Delta, Delta Wye, Wye Delta, and Wye Wye. But the most common is Wye, and if you see a 208 voltage.........you can be confident it is coming from a wye transformer.

    Okay, lets talk about legs and phases. In residential electrical, we don't call them phases, but in actuality, they are phases, but you only get to see two of them. In the distribution net, the power is sent out as three phase, but it is divided across the grid. Each neighborhood will only see AB, BC, or CA phases, unless they pull the third phase into the neighborhood. A good way to see if you have 3 phase to your area is to look at the power poles. If you see 4 wires across the top, that means all three phases are there with a neutral, but again........that is not common in a residential area.

    Balancing the power draw across all phases is the job of your local utility. By making sure the different leg divisions (AB, BC, CA) are balanced for load, the system will remain stable. But if they get imbalanced one set drawing too much, you start to see power outages in you area.


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    #32
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    So because of the configurations to carefully balance the load.. Some homes end up with 120v for each leg, but 208v when both are measured across?

    I live in an 'electrically diverse' area you might say but fortunately many homes here have the same 30a 240v outlet. I read that it would be possible to read the voltages across one of the poles using a cheap voltmeter, but reading them both requires a more expensive tool...


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    #33
    Indie Arms Member Doc Bernard's Avatar
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    Yes, the leg to leg voltage should read around 208. Leg to neutral should be around 120.

    A "240" outlet is probably 208. Its like calling all florescent set lights Kino's. It's just what they are commonly called. Or tripods = sticks

    As for reading your voltage........those cheap mutlimeters are not good. Home depot sells a decent DMM (digital multimeter), even radio shack has a couple. But if you are not familiar with electrical safety, don't attempt it. It is easy to mess up and get a nasty shock.


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