Sealed Coil Construction

CMl’s Sealed insulation systems completely seal coils for motors operating in wet or corrosive atmospheres.

Applications requiring insulation systems with sealed windings get optimum protection from severe environmental conditions. This readily available rugged insulation system for replacement coils lets your motors operate in tough environmental conditions and helps your coils shrug off moisture, oil, solvents, and other aggressive and conducting contaminants. The sealed system is especially suited for on-site rewinds where a finished, sealed coil is required. Superior dielectric and mechanical strength improves motor operation and durability.

The CMI Sealed Construction Process

Turn-and-strand insulation is selected so that each insulation system design will provide maximum motor uptime. Coils are wound using rectangular copper conductors insulated with a minimum of quad enamel coatings whenever possible. Some applications may require the use of single or double glass over film combinations or mica turn-taped construction.

Conductors are pressure bonded and sized to align the turns to provide a highly flexible but mechanically stable coil loop. The coils are then shaped to precise dimensions in a coil spreader.The coil leads are then sleeved or taped with multiple layers of micamat tape and a layer of B-Stage epoxy armor tape and varnish. A layer of Dacron glass tape is then applied.

Coil ground insulation may consist entirely of micamat tapes or a combination of tapes and slot wrappers followed by a layer of the B-Stage epoxy tape and finally a layer of Dacron glass tape. A compatible B-stage epoxy lead seal is used to provide the extra sealing for coil leads in the area where the leads exit the coil. Multiple layers of these tapes and wrappers are used depending on voltage, motor application, or specific customer requirements.

After the coils have been insulated, they are then dipped in varnish and baked to cure the B-Stage epoxy tape and to develop the properties of high dielectric and mechanical strength as well as resistance to moisture and chemicals. Semiconducting paint is applied to the coil slot portions on all coils rated 6,600 volts and above.

Sealed coil testing assures the highest quality rewinds. Form-wound replacement coils using CMI sealed coil insulation systems are built to strict quality standards and are required to pass numerous quality checks. Single coils are surge tested at values well above IEEE standards. The completed coils can also be tested to the IEEE high-potential standard for new motors of twice the rated voltage plus 1,000 volts.