Current density
The amps per mm² in the conductor, key to sizing the windings.
Definition
Current density, expressed in amperes per square millimetre (A/mm²), is the current flowing in a conductor divided by its cross-section. It is a central parameter in sizing a transformer’s windings.
A high density uses less copper — hence a more compact, cheaper unit — but increases Joule losses and heating. A low density improves efficiency and thermal endurance at the cost of greater size and price. Usual values lie between 2 and 4 A/mm² depending on the cooling method.
The choice of current density is therefore a trade-off between compactness, losses and permissible heating.
The ABL tip
For transformers in closed enclosures or at high load factor, a conservative current density avoids hot spots. ABL Transfo adjusts the copper cross-section to your real thermal constraint, not to a generic standard.
