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Application and Protection of Medium-Voltage Motors
Published in Shoaib Khan, Industrial Power Systems, 2018
The Class 155(F) insulation system has become the industry standard. It is a good practice to purchase motors with Class 155(F) insulating systems but with a temperature rise of Class B (80°C) above an ambient of 40°C. This will reduce the losses, increase the motor insulation life, and permit overloads (up to 15%) without exceeding the temperature limits. The recommended temperature rise above an ambient temperature of 40°C shall not exceed the following:Motors rated 500 hp (375 kW) and less: 80°C by resistanceMotors rated above 500 hp (375 kW): 80°C by an embedded resistance-temperature detector (RTD)
Principles of Energy Conversion
Published in Hamid A. Toliyat, Gerald B. Kliman, Handbook of Electric Motors, 2018
Hamid A. Toliyat, Gerald B. Kliman
electrical machine. The failure of electrical insulation of motors is frequently associated with serious thermal aging except where there is physical damage from some external source or serious contamination of the insulation with foreign matter. Thermal aging is generally evidenced by loss of resistance to moisture and subsequent looseness of the winding and loss of adhesion of the insulation components. The following are major causes of in-service motor insulation failure Unusual surge voltages that may be caused by lightning, switching surges, or system malfunction.Mechanical damage due to some foreign matter being introduced into the machine, or some failure of the mechanical supports or ties as a result of short circuits.An accumulation of dirt, oil, and other chemical contaminants due to improper operating conditions or faulty maintenance.Damage caused by improper handling or coils and insulation during winding.Corona deterioration at points of high voltage stress.Faulty design with insufficient safety margin or unsuitable stress.Moisture absorption, which reduces insulation resistance and dielectric strength levels.Thermal aging caused by excessive operating temperatures that result in the insulation system being vulnerable to many other causes of failure.
Insulation, Coatings, and Adhesives in Transmission and Distribution Electrical Equipment
Published in Bella H. Chudnovsky, Electrical Power Transmission and Distribution, 2017
IEEE Standard 1-2001, “IEEE Recommended Practice—General Principles for Temperature Limits in the Rating of Electrical Equipment and for the Evaluation of Electrical Insulation” [8], is intended to help in the preparation of standards that are principally concerned with the thermal endurance of EIM and simple combinations of such materials, with the establishment of limiting temperatures of electrical insulation system (EIS), and with the provision of general principles for thermal classification of EIS.
Life Model for PWM Controlled Induction Motor Insulation using Design of Experiments Method
Published in Electric Power Components and Systems, 2019
Triloksingh G. Arora, Mohan V. Aware
The stresses which mostly age and cause failure of electrical insulation system are voltage and thermal stresses. For single stress, the life model based on inverse power law (IPL) has been proposed [17] and is given as;