Biaxially oriented polyester films are widely used to provide insulation between conductor wires and the stator in electrical motor driving domestic and industrial equipment .It is mainly used in motor for domestic application like grinder, mixer, fans, air-condition, washing machine & refrigerator. It is also used in industrial application like drivers & generators. Polyester film has breakdown voltage of 22 KV at a thickness of 350 Mic.

Using polyester film, designer are able to gain substantial benefit by reducing volume and weight, increasing temperature rating, improving designs and automating production cycles.

The white opaque color of this film is ideal for its use as a slot liner and interphase separator in electrical motor and transformer, apart from the toughness, flexibility, and the high folding endurance. The film is cut, folded into cuff, which is then inserted into the slot.

The high breakdown voltage (B.D.V) of polyester film is an important for this application, a corollary is that the film should be free pinholes and other surface defects which can affect the B.D.V. The film also should be flat and the winding should be uniformly tight to give flat curl free laminate.

Polyester film is strong, tough material which is suitable for mechanical forming and allows easy roll to roll laminates. From solvents and resins commonly used in the production of electrical laminates. Polyester film makes it suitable for motor operating at elevated tempratures.

Polyester film is also coupled which one or two layer of high quality electrical grade paper such as pressphan paper or nomex aramid paper by using appropriate adhesive to produce flexible laminates of class 'E' up to 120'C or class 'F' up to 155'C.

Now a days these operations are carried out on automated lines which requires consistent film behavior. A slight difference in the flexibility of the film can not only blunt the edges of the punches but also result in burrs on the cutting edge. This can also result in stoppage of the lines.