CT current conversion
Convert a primary current to an ideal CT secondary current. This tool does not recommend protection settings.
Enable JavaScript for live calculations. Read the method and default example below.
Method and assumptions
- Isecondary = Iprimary × rated secondary / rated primary.
- Ideal ratio only; no allowance for saturation, phase error, accuracy class or burden.
Before using the result
- Never open-circuit an energised CT secondary. Protection settings require a coordination study and approved testing.
Worked example
Illustrative default inputs. Enter your project values above.
- CT rated primary
- 400 A
- CT rated secondary
- 5 A
- Primary current
- 240 A
Default results
- CT ratio
- 80:1
- Ideal secondary current
- 3 A
- Primary rating utilisation
- 60 %
Choose a reference or send your BOQ
Compare relevant product families, then confirm the exact rating, control supply and duty. Price and availability are confirmed with your enquiry.
Technical references
These references support planning. The exact model documentation and a project-specific engineering review govern the final specification.