question

andreas-siebenmorgen avatar image
andreas-siebenmorgen asked

Energy Meter VM-3P75CT: AC wiring 3-phase

Hello everybody,

can somebody explain the technical reason, why in a 3-phase system all 3 phases have to be connected to the device physically?

The manual states that the device is powered over L1, so what is the reason for connecting L2+L3 also?


Best regards

Andreas

Energy Meter
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stefan-jaeger avatar image stefan-jaeger commented ·

The CT only carries out a current measurement. To also get the power of each phase in watts, you need a voltage. Of course you can use static 230 V or the voltage from L1. However, since the line voltage can vary from line to line and depend from the load by up to +/- 10-20V, it is necessary to also measure the voltage of each line to get a more accurat result.

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1 Answer
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

To measure all the voltages?!

L1-N
L2-N
L3-N
L1-PE
L2-PE
L3-PE
L1-L2
L1-L3
L2-L3
N-PE

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andreas-siebenmorgen avatar image andreas-siebenmorgen commented ·

That sounds obvious ;-)

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