From Condition Monitoring of Rotating Electrical Machines

2.6 Insulation Ageing Mechanisms

2.6.1 General

Electrical insulation faults are a significant contributor to the failure of rotating machines. Industry studies described in the next chapter indicate that up to one-third of rotating machine failures can be attributed to loss of function of the stator winding electrical insulation. Therefore they deserve special consideration before we consider failure modes in general. However, it should be borne in mind that although the final failure mode may be electrical breakdown of a dielectric component, the underlying mechanism driving the breakdown may be thermal, mechanical or environmental stress as well as electrical factors. This section will cover the basic stresses that affect the performance of stator winding, stator core and rotor winding insulation systems on operating machines as well as discussing the roles that design, operation and maintenance have on the life of the equipment.

Insulation in service is exposed to high temperature, high voltage, vibration and other mechanical forces, as well as some adverse environmental conditions. These stresses can act together or individually to degrade insulation materials or systems. Thermal ageing of insulating material due to high temperatures has been studied the most and is perhaps best understood. The mechanism may be treated as a chemical rate phenomenon, described by the Arrhenius relationship, and includes loss of volatiles, oxidation, depolymerisation, shrinkage and embrittlement. In actual service, loss of insulation system integrity is aggravated by cyclic and transient mechanical forces, which cause relative movement and abrasion of insulation. Furthermore, insulation subjected to high voltage...

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Products & Services
Electrical Winding Services
Companies that specialize in the fabrication of custom wound assemblies for a wide range of electrical applications and industries. Electrical winding services also includes the repair and refurbishing of individual wound components.
Motor Test Equipment
Motor test equipment is used to measure and evaluate various electrical characteristics and performance parameters of motors.
Linear Motors
Linear motors generate force only in the direction of travel. They are capable of extremely high speeds, quick acceleration, and accurate positioning.
AC Motors
AC motors include single, multiphase, universal, induction, synchronous, and gear motors. They also include servomotors.  
Insulation Jacketing
Insulation jacketing consists of a metal sheet or plastic film that is wrapped around tubing or pipe insulation to protect the insulation from moisture, wear and mechanical damage. Adhesive, clips, ties or other fasteners are used to hold the jacketing mat

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