TABLE OF CONTENTS The total installed power capacity within the Eastern, Western, and Texan power pools of the United States is 900 GW with about 70 GW of spinning reserve. Approximately 60% of the 900 GW is consumed by induction motors and 100% passes through transformers. Similar percentages exist in most countries around the world. For this reason transformers and induction motors are important components of the electric power system.
The lifetime of any device is limited by the aging of the insulation material due to temperature: the higher the activation energy of any material, the faster the aging proceeds. Iron and copper/aluminum have low activation energies and for this reason their aging is negligible. Insulation material either of the organic or inorganic type is most susceptible to aging caused by temperature. If a device is properly designed then the rated temperature results in the rated lifetime. Temperature rises above rated temperature result in a decrease of lifetime below its rated value. There are a few mechanisms by which the rated lifetime can be reduced:
Temperature rises above the rated temperature can come about due to overload and voltage or current harmonics.
Lifetime can be also decreased by intermittent operation. It is well known that generators of pumped storage plants must be rewound every 15 years as compared to 40 years for generators which operate at a constant temperature.
Vibration within a machine due to load variations (e.g., piston compressor) can destroy the mechanical...
