Three Phase Measurements

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roket
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Joined: Fri Sep 24, 2010 1:05 am

Three Phase Measurements

Post by roket » Fri Sep 24, 2010 1:14 am

We need to look at the 3 phase voltages from a three phase variac, probably 50VAC. What would be the connections, especially the ground banana plugs to allow this measurement. Dont want to blow the Picoscope 3425 up! Works well using current clamps.
Thanks

PeterF
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Joined: Thu Jun 07, 2007 10:53 am
Location: Cambridgeshire

Re: Three Phase Measurements

Post by PeterF » Thu Oct 07, 2010 1:10 pm

Hi,
As long as the Variac is wired in "Star" configuration, ie: one earth connection (Star Point) and three "Phase" outputs, then you are OK to connect the scope Ground pin and the -Ve terminals of three channels to the star point. The +Ve inputs of the scope go to the three Variac outputs.
If the Variac has no isolation between the inputs & outputs (auto-transformer) then to comply with safety regulations you will need an isolating transformer. (The 3425 is only a CAT I rated device.)
Regards,
PeterF.

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