The introduction of new worldwide legislations, demanding motors with higher efficiency, is a challenge for motor designers and companies, which look for new materials and production processes. Thus, rotor cage production is a topic of great interest. Indeed, in recent years some motor manufacturers have changed from high-pressure die cast to low-pressure or centrifugal cast and also from traditional annealing (in a furnace) to inductive annealing. Since any process needs to be well known and well evaluated, a study was made with small induction motors (2 pole, 50Hz and 100 W) in order to quantify the impact on its performance when different rotor laminates coatings and also different cast methods are used. The use of furnace and inductive high frequency annealing processes were also investigated in order to compare its effectiveness. Several cares were, taken to reduce experimental errors like the use of rotor laminates obtained from the same electrical steel coil and from the same punch tooling. Rotors, having the same process steps were always, processed in the same tools (e.g., all rotors made by high-pressure cast process were produced in the same cast machine and using the same molten aluminum). For each parameter analyzed, the number of rotors in the sample set was compatible to dynamometer accuracy and typical process variations. All rotors were, tested with the same stator. These fine cares were necessary to have a good evaluation of different process of study. The most important developments in motor process take place at industry and they are, most of the time, treated as secret information. Even though most of results presented in this paper are not new for experienced engineers that work for motor manufacturers, they are important for the fresh ones that look for information normally not available in the literature.
II. ROTOR LAMINATION COATINGS
The cores of electrical motors and transformers need to be, laminated to restrain the effects of eddy currents and to reduce the core losses. The steel laminates are insulated from each other by use of an insulating coating. Some motor manufacturers use grain non-oriented (GNO) fully processed electrical steel that can be supplied with standard organic or inorganic coatings. The semi-processed steel is supplied without coating, which is formed in the final stage at decarburizing furnace, in motor manufacturer facilities. In the literature is possible to find relevant papers that analyze the
The introduction of new worldwide legislations, demanding motors with higher efficiency, is a challenge for motor designers and companies, which look for new materials and production processes. Thus, rotor cage production is a topic of great interest. Indeed, in recent years some motor manufacturers have changed from high-pressure die cast to low-pressure or centrifugal cast and also from traditional annealing (in a furnace) to inductive annealing. Since any process needs to be well known and well evaluated, a study was made with small induction motors (2 pole, 50Hz and 100 W) in order to quantify the impact on its performance when different rotor laminates coatings and also different cast methods are used. The use of furnace and inductive high frequency annealing processes were also investigated in order to compare its effectiveness. Several cares were, taken to reduce experimental errors like the use of rotor laminates obtained from the same electrical steel coil and from the same punch tooling. Rotors, having the same process steps were always, processed in the same tools (e.g., all rotors made by high-pressure cast process were produced in the same cast machine and using the same molten aluminum). For each parameter analyzed, the number of rotors in the sample set was compatible to dynamometer accuracy and typical process variations. All rotors were, tested with the same stator. These fine cares were necessary to have a good evaluation of different process of study. The most important developments in motor process take place at industry and they are, most of the time, treated as secret information. Even though most of results presented in this paper are not new for experienced engineers that work for motor manufacturers, they are important for the fresh ones that look for information normally not available in the literature. II. ROTOR LAMINATION COATINGS The cores of electrical motors and transformers need to be, laminated to restrain the effects of eddy currents and to reduce the core losses. The steel laminates are insulated from each other by use of an insulating coating. Some motor manufacturers use grain non-oriented (GNO) fully processed electrical steel that can be supplied with standard organic or inorganic coatings. The semi-processed steel is supplied without coating, which is formed in the final stage at decarburizing furnace, in motor manufacturer facilities. In the literature is possible to find relevant papers that analyze the
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