Transformer Nameplates and H/X Terminal Markings
Read transformer kVA, voltage, taps, winding connection, and H/X markings, then identify the exact connection diagram and product-specific limits.
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Nameplate field lookup
Start with the transformer’s complete model, nameplate, and connection diagram. The winding ratings, tap arrangement, and application are product-specific. This page helps identify the information before it is used in a calculation or connection review.
| Field | What to read | Do not infer |
|---|---|---|
| kVA | Rated apparent power under the stated conditions | Not an automatic real-power capacity at any power factor or load condition. |
| Primary / secondary or winding voltages | The stated winding configurations and voltage ratings | A slash or multiple voltage list is not a complete jumper diagram. |
| Phase / frequency | Rated phase arrangement and frequency | A different source frequency or supply arrangement needs product review. |
| Winding connection / diagram code | The manufacturer’s specific connection information | Do not replace it with another transformer’s drawing having the same kVA. |
| Taps | Available winding taps and their defined use | Tap numbering alone does not identify which connection raises or lowers a measured output. |
| Impedance / percent Z | The published impedance with its rating basis | Not a measured output-voltage regulation value for every load. |
| Temperature / insulation / enclosure | Thermal and construction information | An enclosure description is not every environmental or classified-location approval. |
| Catalog / serial / drawing revision | The exact product identity | Physical similarity does not establish an identical winding or tap arrangement. |
H and X terminal markings
In the convention explained by Schneider, H and X identify the higher-voltage and lower-voltage winding terminal families. Many application diagrams use them for the documented primary and secondary arrangement. Do not interpret an H or X number as a universal supply, neutral, grounding, or polarity instruction.
| Marking context | Reference interpretation | Required document |
|---|---|---|
| H1, H2, and any additional H leads | Terminals associated with the documented H winding arrangement | Exact winding/jumper/tap diagram for the catalog number. |
| X1, X2, and any additional X leads | Terminals associated with the documented X winding arrangement | Exact output connection and any center-point identification. |
| Additional numbers or tap identifiers | Separate connection positions whose meaning is defined by the drawing | Manufacturer tap and reconnection instructions. |
| Case / protective bonding terminal | A separate equipment bonding connection where marked | Applicable equipment instructions and installation requirements. |
The H/X FAQ explains the winding convention. The second manufacturer FAQ illustrates additional application limits for back-feeding; neither supplies a universal reconnection permission.
Find the exact connection diagram
- Copy the full catalog and diagram code, including voltage and phase information.
- Locate the manufacturer drawing for that exact configuration and revision.
- Identify winding groups, polarity notation, taps, center connections, and protective bonding separately.
- Check any special application, including buck-boost or reverse-feed use, against its own documented conditions.
- Retain the verified configuration with the project record.
This page intentionally provides no universal H1–H4 or X1–X4 jumper recipe. Missing labels or an unreadable winding diagram require manufacturer clarification.
For rated winding currents use the existing transformer-current tool; for ideal ratios use the turns-ratio calculator. Those results do not validate a physical connection.