Losses in coils for any space and time-variations of electromagnetic conditions

Using a circuit model, loss calculations have been carried out for coils made of twisted filamentary composites which undergo any space and time-variations of the magnetic induction and of the transport current. This model has been tested by measuring losses in solenoids and in "special coils" which look like small Tokomaks, where the composite which carries a time-dependent current is submitted to simultaneous transverse and longitudinal magnetic induction changes. Experimental and theoretical values are in good agreement within about 5% to 15% for hysteretic losses and within 10% to 20% for eddy current losses.