A1-13 Common Insulating Materials

• What is the purpose of conductor insulation?

  Prevent unwanted flow of electrical current
• What conditions must insulation satisfy?

  -must have a voltage rating suitable for circuit application

  -must have a temperature rating to satisfy circuit application

  -must be appropriate for its location

  -must be protected against mechanical damage
• What is dielectric strength?

  Ability of a material to resist breakdown
• For every 10 degrees celsius beyond normal rating, the insulation life is reduced by ___


  one-half
• What is enamel?

  Insulated magnet wire that keeps it well insulated and doesn't take up too much space. The magnet wire is dipped in varnish or enamel to insulate it. It is used in meter coils, small transformers, relays, motor windings and other electromagnetic applications
• What are advantages of enamel?

  -moisture and chemical resistant

  -non-corrosive to copper

  -high in heat transferability (able to dissipate heat well)

  -not too costly
• What is varnished cambric?

  Insulating tape used for high-voltage generators/motors and can be used on bus bars
• When is rubber used?

  When flexibility and abrasion resistance are of prime importance (extension cords). Old cab tires used to be used but it breaks down/corrodes more than plastic
• What are some issues with thermoplastics?

  They can deform easily (ex. weight or weather cause it to deform). The warmer the plastic, the faster the current will flow
• What is a widely used thermoplastic?

  PVC - polyvinylchloride. It self extinguishes when flame is removed from the material
• What are the types of PVC?

  -T Type: for dry locations

  -TW Type: suitable for wet and dry locations

  -TWU Type: suitable for direct burial in the ground
• What are disadvantages of PVC?

  -max temperature allowed is 60 degrees

  -it stiffens and hardens at low temperatures, making it difficult to handle
• What are minerals?

  compounds of definite chemical composition, found in a natural state in the ground (not vegetable or animal origin). They are used for insulation in extremely hostile or corrosive environments. Some include mica and magnesium oxide
• What is magnesium oxide?

  Type of mineral powder with a high resistance when dry. It's used in a strong, moisture-proof sheath, such as copper
• Which colours are included in the colour code?

  -white/natural grey is reserved for identified conductors/neutral conductors, identified common conductors

  -green is reserved for bonding conductor
• When is a white wire allowed to be used where it is not neutral?

  -when an identified conductor is used for single-pole, three-way or four-way switch loops
• Which colours are live/hot?

  Any other colours (black, red, blue) should be considered dangerous
• How do you recognize cross-linked insulation?

  marked with a XLPE or X-LINK on its surface (combines thermoplastic with thermosetting material)