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Virtual Neutral from 3 Phase supply

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gravi

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Hi,

How to generate an virtual Neutral from a 3 Phase circuit. i.e from a 3 wire supply and No Neutral.

Thanking You,
Ravi
 

FvM

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It's possible with a transformer with special windings configuration. E.g. Delta-Wye, transformer, using the unconnected delta winding to compensate the asymmetrical load.
 

gravi

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Hi,

I have seen in few boards deriving Neutral from 3 Phase with Resistor/Capacitors as shown in attachment. but in attachment resistor alone is used.

3P-N.png

Thanking You,
Ravi
 

FvM

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Unfortuantely your question isn't very clear. A "virtual neutral" for measurement puposes can be made with resistors (or RC circuit). But the connected measurement circuit must have high impedance, you can't load the vrtual ground.
 

gravi

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Hi FvM,

Yes, I need Virtual Neutral for measurement purpose only, I want to measure 3 Phase voltages and current of an 3 wired application I don,t have neutral so I thought Virtual neutral will be an good idea.

As you said there will not be any load on that virtual Neutral but this is used for Monitoring AC Voltages and Current only.
Can I use the circuit I attached in my first post or is there any better solution.

Thanking You,
Ravi.
 

gravi

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Hi,

Can I use the circuit for virtual Neutral shown in Post #3 for monitoring 3 Phase voltages and current
 

D.A.(Tony)Stewart

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Hi,

Can I use the circuit for virtual Neutral shown in Post #3 for monitoring 3 Phase voltages and current

The high impedance cables must be well shielded from stray currents. CM Chokes will help with shielded cable. Reactors are used to create a real Neutral. Perhaps an impedance divider will work better using film caps rated for line BIL voltage just like R divider but impedance ratio of Zc to feed cable with lower impedance.
but all methods fail if one line faults alone so differential measurements on each phase are also important.
 

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