%Z ?

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chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Using Bussmann fault current calculator for a 100kva 240/120 1Ø 2.2Z tranny a box pops up selecting "%Z TOL -10% max fault".

What does that mean?

Thanks
 
jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
Z is impedance, given on the nameplate of the transformers.

transformer%2BNameplate.jpg
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Chris is asking about %Z Tolerance with three choices:

-10% Max Fault,
0% no Change
+10%Min Fault.

I have the Android app.
 
ron

ron

Senior Member
Location
New York, 40.7514,-73.9925
During transformer construction, the manufacturer has a design goal for impedance. ANSI allows for some tolerance in the final result from the design goal # and I think it is 10% plus/minus.

They would put the tested impedance value on the nameplate, but there are times when you only know the goal value, or only an estimated value (many will guess at 2% for small utility XFMRS and 5.75% for larger), so you take a worst case estimate, which would include a -10% impedance adjustment too.
 
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