Enamelled Copper Wire Specification Guide

The wire diameter determines the current-carrying capacity and the number of turns that fit in the stator slots or winding window. Use the original equipment manufacturer's gauge specification. If the original gauge is worn or unreadable, measure the diameter with a micrometer (not a ruler) and specify in mm. For Indian motors and transformers, the gauge is almost always SWG.

Enamel coating thickness is classified as Grade 1 (single build) and Grade 2 (double build). This is one of the most critical specifications in winding wire.

The thermal class indicates the maximum continuous operating temperature that the enamel insulation system can withstand without degradation.

Class F (155�C) is the standard for most induction motors in India. If your motor nameplate says "Class F insulation system," this is what you need. Class H (180�C) is required for motors that operate in high-ambient environments � steel plants, foundries, kilns, close-coupled pumps in boiler rooms. Using Class F wire in a Class H motor will cause premature enamel breakdown. Using Class H wire in a Class F motor is safe but costs more than necessary.

The conductor must be Electrolytic Tough Pitch (ETP) copper with minimum 99.9% copper content and conductivity =100% IACS. Oxygen-free high-conductivity (OFHC) copper is available for specialist applications on request.

If the original motor used copper winding wire, rewind with copper. Aluminium windings require different slot fill calculations, different termination methods (aluminium cannot be soldered directly), and different thermal expansion characteristics. Rewinding an aluminium-wound motor with copper is possible but requires recalculating the turns count � do not substitute without engineering input. See our aluminium vs copper winding wire comparison for details.

Indian Standard IS 13730 and IEC 60317 specify the requirements for enamelled round winding wire. When ordering, confirm that the wire complies with IS 13730 or the applicable part of IEC 60317. This ensures the enamel build, dielectric strength, elongation, springback, and thermal endurance are tested and certified.

What is the difference between Grade 1 and Grade 2 enamelled copper wire?

Grade 2 has approximately double the enamel build thickness of Grade 1. This provides higher dielectric strength (=5000 V vs ~2500 V breakdown) and better mechanical abrasion resistance during winding. For motor rewinding and transformer winding, always specify Grade 2.

What SWG is used for motor rewinding?

SWG 18 (1.22 mm) is the most common gauge for general motor rewinding (150W�10kW motors). SWG 20�22 for smaller motors, SWG 26 for ceiling fan motors, and SWG 12�16 for large industrial motors. Always measure the original wire with a micrometer before ordering. See our SWG to mm conversion table.

Can I use Class F wire in a Class H motor?

No. The motor nameplate specifies the insulation class of the complete system. Using Class F wire in a Class H motor will cause premature enamel breakdown at the higher operating temperature, leading to winding failure. Always match or exceed the motor's specified thermal class.

What is the difference between IS 13730 and IEC 60317?

IS 13730 is the Indian Standard that is technically equivalent to IEC 60317 (the international standard for enamelled winding wires). Both specify the same requirements for enamel build, dielectric strength, elongation, springback, and thermal endurance. Compliance with either standard is acceptable.

How do I measure the gauge of existing winding wire?

Use a digital micrometer to measure the bare conductor diameter after stripping the enamel (remove the enamel with heat or solvent). Do not include the enamel build in your measurement. Compare the bare diameter to our SWG to mm table to find the nearest standard gauge. For accurate results, take three measurements along the wire and average them.