Electrical Insulating Tape Applications: In spite of the acknowledged differences in transformer types and design, tapes are generally used for the same reasons regardless of type or design. They are used for holding and insulating leads and start and end-turn wires; for interlayer insulation; for single layer winding hold-down, for terminal strip anchoring; for terminal insulation; for splice protection; for outer coil wrapping; for coil-end ground insulation and for strengthening wire windings.

Functional Requirements: Transformer end-use determines the design, construction and choice of materials, as well as it's functional requirements. The following are listed in relative decreasing order of importance as relating to the common single-phase, small power transformer. Certain functional requirements assume great importance in some transformer design and will be so noted as exceptions.

Thermal Resistance: Any tape employed must at least equal the design parameters for thermal classification (105 C, 130 C, 155 C, or 180 C.). To be placed in these classes, the tape must withstand a 10,000 - 20,000 hour service life with no more than 50% loss of its important properties such as dielectric strength, insulation resistance, tensile strength, adhesion, etc. The transformer engineer practically never over designs because of economic factors. In general, the higher the temperature class, the more costly the transformer design and materials of construction.

Electrical Insulating Tape Applications: In spite of the acknowledged differences in transformer types and design, tapes are generally used for the same reasons regardless of type or design. They are used for holding and insulating leads and start and end-turn wires; for interlayer insulation; for single layer winding hold-down, for terminal strip anchoring; for terminal insulation; for splice protection; for outer coil wrapping; for coil-end ground insulation and for strengthening wire windings.

Functional Requirements: Transformer end-use determines the design, construction and choice of materials, as well as it's functional requirements. The following are listed in relative decreasing order of importance as relating to the common single-phase, small power transformer. Certain functional requirements assume great importance in some transformer design and will be so noted as exceptions.

Thermal Resistance: Any tape employed must at least equal the design parameters for thermal classification (105 C, 130 C, 155 C, or 180 C.). To be placed in these classes, the tape must withstand a 10,000 - 20,000 hour service life with no more than 50% loss of its important properties such as dielectric strength, insulation resistance, tensile strength, adhesion, etc. The transformer engineer practically never over designs because of economic factors. In general, the higher the temperature class, the more costly the transformer design and materials of construction.

The range of temperature classes account for the variety of tape backings and adhesives employed. There are four main types of adhesives:

a) Thermosetting Rubber-based adhesives provide up to class B properties (130 C). This kind of adhesive has good adhesion power. Under certain temperatures, they react and form three dimensional molecular structure which have increased strength of adhesion, bonding and solvent resistance.

b) Acrylic based adhesives provide up to class F properties (155 C). Acrylic adhesives are synthetic polymers and can offer excellent resistance to heat, oxidation, solvents and oils. The #239 tape which is a Polyester Film/Polyester Filament tape offers an acrylic adhesive that has exceptional resistance to transformer oil when fully thermoset. The extra strong backing makes this product ideal for use in large size oil immense transformers and solenoid coils

c) Thermosetting Silicone based adhesives provide up to Class H (180 C) properties. This type of adhesive also cures under elevated temperatures like the thermosetting rubbers, but with higher thermosetting temperatures up to 260 C. The silicone adhesive offers excellent heat resistance. Also, silicone adhesives combats the incompatibility and reversion problems caused by rubber resin adhesives used with silicone impregnating resins, potting and encapsulating compounds.

d) Non-thermosetting rubber adhesives will not cure when exposed to elevated temperatures. The majority of adhesives used in the electrical insulating tapes are selected to conform to the specifications of the backings in an effort to meet exact requirements. As a result, you may need only to select a suitable backing for your application.

Electrical Insulating Tapes UL File No. E126174 stipulates the range of temperature classes that account for the variety of tape backings and adhesives employed. Electrical Insulating tapes are made from a wide array of different backings to suit the requirements of different applications:

1. Polyester: Thin, conformable, tough and highly tear resistant. These type of tapes are best suited for use on small coils where dimensional restrictions limit insulation build up. FCR offers the #149, 1 mil Polyester Film Tape which is engineered for fine wire applications requiring a non-corrosive tape. Polyester backings can accommodate temperatures up to 130 C and can also offer flame retardancy. Examples of flame retardant polyesters would be the FCR FR-9 series.

2. Glass Cloth: Offer excellent conformability and superior solvent resistance. Glass cloth tapes offer very high temperature ratings and tensile strength. Glass cloth tapes are recommended for use in high temperature cable harnesses and connection insulating applications. The #269 and #451 Glass Cloth Tapes from FCR provide very high dielectric strength, and good puncture r.. resistance. The #269 Glass Cloth/Silicone Adhesive is our highest thermal rated glass cloth tape which is ideal for high temperature applications wherever superior solvent resistance and flame retardancy is required. Approved for temperatures up to 180 C.

3. Polyester Reinforced tapes: Provide ultra-high tensile strength with outstanding resistance to solvents and mineral coils. The FCR #239 and #320 Polyester Film with Reinforced Glass Filament tapes are engineered for use as a construction tape to make for easy winding of oil filled distribution and power transformers that use thick fiber and pressboard insulation, heavy-gauge aluminum strip low-voltage winding, and heavy magnet wire. Reinforced tapes offer high dielectric strength of polyester film and high tensile strength of glass cloth, with lower cost than glass cloth tapes. Application temperatures up to 130 C.

4. Polyimide Tapes: The ultimate in electrical insulating tapes. Kapton film is ideally suited to continuous high temperature operating conditions. FCR offers the #95, 1 mil Kapton Tape with a high temperature silicone adhesive that is recommended for use as ground, barrier, and phase insulation in small, high-performance torridal coils and high frequency motors. Also used in cross-over insulation and outer protective wraps on small bobbin wound coils. Kapton tapes are thin and conformable, with outstanding puncture, tear and abrasion resistance at elevated tempertures. Approved temperatures up to 180 C and flame retardant.

5. Paper tapes are versatile and low cost. These tapes are ideal for coil wrap and bundling. FRC offers the 3T Paper Tape which offers a smooth strong crepe backing for good abrasion and puncture resistance. Approved for temperatures up to 105 C.

6. Composite tapes: Blend polyester films with paper and non-woven polyesters to offer the industry an all purpose, economical electrical insulating tape used for the widest range of applications. As an example, FCR offers the #445 tape, which is a Polyester Film/Polyester Non-Woven tape that offers outstanding tear and puncture resistance, superior resistance to flagging, high tensile strength, excellent dielectric strength and low uniform unwind. These tapes are economically priced and are approved for temperatures up to 130 C.

7. Copper Foils: Specifically designed for use as electro magnetic interferance (EMI) and radio frequency interference (RFI) shielding on small electro-magnetic components - transformers and reactor coils, instrument and control motors. FRC offers the #18 and #19 Copper Foil tapes in both conductive and non-conductive adhesives.

8. Other types of tapes and their corresponding backings would include Teflon, Acetate, Cotton, Nomex, Epoxy, etc.