Enamelled Wire Thermal Classes and Film Build Explained
Class F, H and C, what the 120 to 200 grade numbers mean, and how thin and thick film change the coil you end up with.
What the thermal class tells you
The thermal class indicates the maximum allowed operating temperature of the wire. It is written as a letter: F is 155 C, H is 180 C, C is 220 C. The wire is rated on its ability to run at that temperature without the insulation deteriorating.
The grade numbers
The product range covers 130 polyester enamelled wires, 155 modified polyester enamelled rectangular wires, 180 polyester imide enamelled copper or aluminium rectangular wires, 200 polyester imide and polyamide-imide composite enamelled rectangular wires, and 120 acetal enamelled rectangular wires.
Film build
According to the insulation requirement you can choose thin film from 0.06 to 0.11 mm or thick film from 0.12 to 0.17 mm. Thicker film buys dielectric margin and costs fill factor, so it is a coil geometry decision as much as an insulation one.
Bonded wire
For self-supporting coils, hot adhesive enamelled rectangular wire carries a self-adhesive layer generally 0.03 to 0.06 mm thick on top of the enamel.
How the film is controlled
Enamel thickness is monitored with a dielectric loss meter during production. Film builds outside the standard bands can be manufactured to a customer specification.
Voltage rating
Enamelled wires carry different voltage ratings depending on the application. Higher ratings are required for transformers used in power distribution systems, so the rating should follow the service the transformer sees, not the previous job.
Applying this to a live design?
Send the dimensions and the target figures and the sales desk will quote the grade that matches.