Get in touch with Toplit Transformer Co., Ltd Company
Impedance Category Screen
Checks a rating and its short-circuit impedance against the normal impedance ranges published in 10 CFR 431.192 for liquid-immersed transformers. A unit built to operate outside the normal range for its rating meets the special-impedance definition, which is one of the thirteen types excluded from the federal distribution-transformer category.
Enter a rating and an impedance, then press Screen.
Normal impedance ranges, liquid-immersed
| Single-phase band | Range | Three-phase band | Range |
|---|---|---|---|
| 10 to under 50 kVA | 1.0–4.5% | 15 to under 75 kVA | 1.0–4.5% |
| 50 to under 250 kVA | 1.5–4.5% | 75 to under 112.5 kVA | 1.0–5.0% |
| 250 to under 500 kVA | 1.5–6.0% | 112.5 to under 500 kVA | 1.2–6.0% |
| 500 to under 667 kVA | 1.5–7.0% | 500 to under 750 kVA | 1.5–7.0% |
| 667 to 833 kVA | 5.0–7.5% | 750 to 5000 kVA | 5.0–7.5% |
Impedance is one of five criteria. Input voltage, output voltage, frequency and capacity are assessed alongside it before any coverage conclusion is drawn.
![110kV Power Transformer Guide: Specs & Standards [2026]](https://toplit-transformer.com/wp-content/uploads/2026/07/110kv-power-transformer-guide-featured-150x150.png)
