Specifications

4
Insulation sleeves are used to cover the joints made at the coil ends and coil leads. It gives
physical protection to joints and also provides insulation. They come in rigid and flexible types.
They are available for standard wire sizes.
Insulation paper : A variety of insulating papers are available specifically designed for insulating
electrical circuits. In motors it is used to insulate the slots, in between coils. Following are the
most often used insulating materials: Leatheriod paper, Press pan paper, Manila or hemp paper,
Triflexil paper, Asbestos paper, Micanite paper
Insulation cloth : It is inserted between the coils after they are placed in slots. Sometimes it is
also used as slot liner. Empire cloth, Asbestos cloth, Glass cloth, Mica cloth, Micanite- cloth are
some of the types.
1.7. INSULATION MATERIALS:
Leathroid paper : These papers are pressed form of a non-woven fabric of fibres from good
and tough wood. It is available from 0.05mm thickness. It is sold as rolls in meters. Generally
used for low voltage machines. This A-grade insulating material is mainly used as insulation in
electrical appliances, machineries, and power equipments.
NOMEX : NOMEX is widely used in a majority of electrical equipments. It is used in almost
every known electrical sheet insulation application. Available in various thicknesses with a density
from 0.9 to 1.0, NOMEX is ideal choice to use as slot insulation in hand-wound motors and for
covering of coils, and is also used in other applications such as folded or punched parts. It is
also widely preferred as sheet insulation in fluid filled transformer applications due to its improved
impregnability. Dielectric strength of NOMEX ranges from 24 to 30 kV/mm. This is Insulation
class F (155 °C) materials.
The NOMEX sheet can be used with virtually all classes of electrical varnishes and adhesives
(polyimides, silicones, epoxies, polyesters, acrylics, phenolics, synthetic rubbers), Resins quickly
penetrate and pass through the sheet to form a cohesive bond between motor end turns. Due to
its stiff structure it can be quickly and easily inserted between coils. Mechanical toughness of
the sheet helps to keep the shape of the insulation intact during motor assembly. NOMEX is able
to maintain its insulation properties over a long period even if it is subjected to temperature
variations. This assures proper insulation between phases and gives good reliability for the
motors. NOMEX sheets can also be used with transformer fluids (mineral and silicone oils and
other synthetics) and with lubricating oils and refrigerants used in hermetic systems. Common
industrial solvents (alcohols, ketones, acetone, toluene, xylene) have a slight softening and
swelling effect on NOMEX paper, similar to that of water. These effects are largely reversible
when the solvent is removed. The Limiting Oxygen Index,LOI, (ASTM D-2863) of NOMEX paper
at room temperature ranges between 27 and 32% (depending on thickness and density).
Materials with LOI above 21% (ambient air) will not support combustion.
Triflexil : Combined flexible insulating material, this is Insulation class F (155 °C) material
conforms to IEC 626-1. The material consists of two or three layers: Inner layer: Polyester film,
Outer layers: Polyester non-woven fabric, esterimide-impregnated. Good adhesion between