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Anonymous asked in Science & MathematicsEngineering · 2 months ago

Theoretically, if a center tap on a transformer is not connected to ground, what would the voltages be for that wire.?

For a transformer where the secondary side is giving 240V, the two hot wires will each be carrying 120V and the center tapped neutral wire is carrying 0V because it cancels out with the ground wire.

But what if the neutral wire is not connected to ground; would there be some voltage coming from it?

If there is voltage, then what happens to the voltage in the hot wires?


I appreciate the responses, and I will now disappear into the abyss.

2 Answers

  • ?
    Lv 7
    2 months ago
    Favorite Answer

    I came here to give you a good response, but then I find you asked this very mundane question from behind chickenshit anonymity just like every other childish troll on this site.  Not worth my time.

  • 2 months ago

    If there is a load across the transformer, either 120V from centre tap to either end, or 240V between the winding ends (or any combination), it works the same regardless.

    Grounding the centre tap is for safety, and has no fundamental effect on the transformer or load. (With that grounded, an earth fault in one of the 120V outputs will blow a fuse rather than be undetected).

    The voltages measured from the centre tap will still be the same.

    Measuring voltages between the transformer circuit and anything else is then meaningless, just about any reading from nothing to hundreds of volts is possible at any point.

    The only valid information gained is that there is no ground connection.

    It's no different in principle to trying to measure the voltage on a battery that has no connections by putting one voltmeter probe on one battery terminal and one on a ground point - it's a "floating" circuit and any readings are due to static charges or capacitive coupling. 

    The readings from the transformer are likely a lot higher due to its (and the wiring) being larger and having much more capacitive coupling to other things.

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