Contents I. Introduction
To guarantee excellence in the manufacturing of an electric motor, it is important to evaluate both electric and dielectric materials and designs. As regards the stator, the use of electric steels of superior quality is indispensable to achieve high efficiency and outstanding machine performance, whereas the high quality of the insulation system is required to assure operation reliability and long-term durability of the machine. On the other hand, around 10% of the failures occurred with induction machines in industrial applications are related with rotor defects [1], so techniques for fault detection in rotors are becoming increasingly important for the diagnosis of the machine condition. With these preoccupations, machine manufacturers have invested both financial and human resources in the implementation and the development of new methods to qualify materials and their final products, aiming at efficient and long-lasting operation with reduced unexpected down-times, so to avoid financial losses for their customers. The techniques discussed in this paper to assess the stator quality comprise iron losses measurements (by means of an innovative testing scheme) to evaluate the quality of the steel and multi-stress accelerated ageing tests to evaluate the machine insulation system. The techniques discussed in this paper to assess the rotor quality (which can be performed directly in the production line or in the field) comprise tests for imperfection detection in rotor bars and short circuit rings, motor current signature analysis (MCSA), and ultrasound.
