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isolated AC voltage measurment

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Davood Amerion

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isolated ac voltage divider

How we can meaure AC voltage of 220V (3 phase) without use of transformer?
I want to make a project which measure voltage and phase sequence, for control purpose. and it must be isolated.
Any idea?

Thanks in advance.
Davood
 

Nimer

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voltage divider isolated

hi
i dont have a clear idea but i think that you should a kind of position sensors that is called the synchro which is a three phase transformer , search the web for more


best regards
 

IanP

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If you don't want to use transformers, and I think three small 230V-5V (something like 1VA) transformers for a three-phase system are the cheapest solution, then you have to consider isolation amplifiers ..
For basics on iso-amplifiers try: http://www.innovatia.com/Isoamps.htm
The amplifiers you will be looking at are: AD202, AD210, .., ISO124 ( http://www.rose-hulman.edu/~herniter/Data_Sheets/ISO124.pdf ) , and so no ..
Other option would be to get an isolated optocoupler and design a linear amplifier by yourself, but I don't think it is worth the hassle ..
Whichever option you choose, you will need a voltage divider to lover the voltage from 230 (if you have three phase + Neutral configuration), or from 380/440 if you don't have neutral available ..
In both cases you can consider the use of capacitors, instead of resistors, to reduce the voltage; for example, 1µF at 50Hz represents impedance (resistance) of 3.18kΩ, but will not generate heat ..
Regards,
IanP
 

xxargs

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Davood Amerion said:
How we can meaure AC voltage of 220V (3 phase) without use of transformer?
I want to make a project which measure voltage and phase sequence, for control purpose. and it must be isolated.
Any idea?

Thanks in advance.
Davood

Is most easy use transformer if want isolated connection...

is not easy to bulid equivalent function with optical coupler etc. - interface need power from measure point or from separat transformer, using op-amp and more or less advanced feedback network for linearity etc. etc.

For voltage transform you can using small simple 220/9 Volt tranformer - current transformer is more tricky if not want break line for mounting... but I thinking principe of tongs current meter with opening magnetic current sensor...
 

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