Why must the drawing retain two different inputs?
The manufacturer's July 2009 technical document describes transformer impedance as a current-limiting characteristic used alongside X/R information in system analysis. Its distinction supports keeping both input roles visible; it does not make old product tables a current design basis.
Critical Power Drafting is independent and is not affiliated with Schneider Electric. This article does not prescribe typical values, fault current, protective-device ratings or a study method. Use the actual approved transformer submittal and engineering study references.
What should the transfer sheet contain?
Preserve the source labels even when the office drawing template has one generic impedance column. A blank X/R field is a visible request for engineering information, not permission to copy the percent number.
| Field | Controlled input | Review question |
|---|---|---|
| Transformer | Tag, rating and variant | Same equipment as the study? |
| Percent impedance | Exact value and percent designation | Correct supplied basis? |
| X/R ratio | Separate approved ratio | Actually supplied or assumed? |
| Conditions | Applicable source notes | Which basis belongs to the value? |
| Revision | Submittal and study references | Same accepted issue? |
| Disposition | Engineer-approved resolution | Where was the drawing updated? |
What does a copied number fail to establish?
Illustrative example. A fictional submittal lists 5 percent impedance, while the X/R input has not been provided. A drawing editor fills both fields with 5. Matching digits do not establish matching quantities: 5 percent is a fraction of 0.05, while an X/R ratio of 5 would describe a different relationship.
The reviewer preserves the supplied percent value, marks X/R unresolved and asks the responsible engineer for the correct source. This example provides no real transformer data and does not calculate fault duty. Even a correctly transcribed input is not proof that a protection study has been completed.
How should a later submittal change be handled?
Trace the changed transformer reference through the schedule, SLD annotations and relevant study-input register. Record what changed and who accepted it. Do not silently replace study assumptions with a number from a different transformer family.
Drafting coordination checks consistency; the project engineer determines technical suitability. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Can percent impedance alone supply the X/R ratio?
No. Obtain the actual approved ratio or engineering disposition.
Does an old manufacturer table establish today's equipment values?
No. Use the selected equipment and approved project evidence.
Does this article calculate interrupting duty?
No. That requires the responsible engineering analysis.