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Electrical Insulation

Electrical Insulating Material, also called a dielectric, is a material that resists the flow of electric charge. In insulating materials valence electrons are tightly bonded to their atoms. These materials are used in electrical equipment as  insulation. Their function is to support or separate electrical conductors without allowing current through themselves.

Class Of Insulation

  • Y-90 Deg.C
  • A-105 Deg.C
  • E-120 Deg.C
  • B-130 Deg.C
  • F-155 Deg.C
  • H-180 Deg.C
  • N-200 Deg.C
  • R-220 Deg.C
  • S-240 Deg.C
  • C-Over 240 Deg.C

Features Of Electrical Insulating Materials

The electrical insulating materials process the following properties depending upon the end application.
Thermal: Conductivity, Emissive, Operating Temperature

Physical: Apperance, Tensile Strength, Elongation, Tearing Strength, Flexibility, Dimensional Stability and Density

Chemical: Compatibility, Solvent Content, Ph Value, Curing Time, Fire reterdancy

Electrical: Dielectrical Strength, Arc Resistance, Dielectrical Constant (Tan-delta), Insulation Resistance, Surface and Volume  Resistance, Tracking, Arc Resistance.  

Basic Materials Used for Manufacture of Electrical Insulating Materials

Resins/Varnish and Enamels:

Alkyd, Unsaturated Polyster, Epoxy, Parylene, Phenolics, Polyurathane, Silicon, Polyimide, Polyamide, Polyamide-imide, Amino, Polyestermide

Coating Methods:

Vacuum Pressure Impregnation, Trickle Impregnation, Radiation Curing, Conformal Coating, Dip

Rubber and Compounds:

  • Fluoropolymers: Ptfe, Pfa, Fep, Etfe, Pvdf, Ectfe, Pctfe.
  • Ethylene Polymers (PE)
  • Proplylene Polymers (PP)
  • Polyvinly Chloride (Pvc)
  • Organic Elastomers
  • Natural Insulating Rubber, Styrene Butadiene Synthetic Rubber, Butyl Rubber, Silicon Elastomer

Woven and Non Woven Fabrics:

Woven: Polyster, Polyster Glass, Glass, Kevlar, Carbon Fiber, Kevlar Carbon Matrix

Non Woven:
Polyster, Aramid and Glass

Cellulose, Valcanised, Aramid, Mica, Ceramic and Glass

Dielectrical FILMS:

  • Cellulose Acetate (CA)
  • Fluropolymers (Ptfe, Pfa, Fep, Etfe, Pvdf, Ectfe, Pctfe)
  • Polycarbonate (Pc)
  • Polyster (PET)
  • Low Density Polyethylene (LDPE)
  • Polyimide (PI)
  • Polyarabanic Acid (PPA)
  • Polyproplene (PP)
  • Polystyrene (PS)
  • Polyvinly Chloride (Pvc)
  • Polysulfone, Polyethersulfone

Factors Causes Material Ageing and Deteriotion of Electrical Insulating Materials:

Electrical Insulation system has to undergo stress and exposure at environmental conditions: 
  • Thermal Stress
  • Electrical Stress
  • Mechnical Stress
  • Envoirmental Conditions
  • Moisture
  • Voids and Contamination
  • Corona Discharge

Selecting Insulating Materials

Enviromental Conditions:

All possible environmental conditions to which the material could be exposed should be determined such as temperature, humidity, chemicals and radiation.

Screening:Thermal Class

A list  of  candidate materials for application should be reviewed eliminating from further consideration all materials.

Example: An application which requires continous operation at 155 Deg.C all materials with lower thermal class should be screened out.

Design of the equipment:

Considering the equipment or part design and the manufacturing process to be used, only materials which posses the required mechanical and electrical properties should be selected for further reviews.

Example: Unreinforced mica paper tape would not withstand typical coil winding tensions. Glass Fabrics reinforced mica tape would withstand the winding process but at the cost of added bulk and expenses. Conformability, deformability and impact strength are important factors to be considered.

Compatibility :
Compatibility with other compounds in an insulation system is a critical factor and should serve as a screen materials.

Manufacturing Process
Manufacturing ease, time and cost should be considered together with material cost and technology to determine final suitability for end application.

Building and testing a prototype should be the final step with redesign and retesting where necessary.



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