11 Electric Motors 1.2 Fundamentals 1.2.1 Stator and Rotor The construction of all rotating electric motors consists in principle of two main components. 2 1 Fig. 1.2 Construction of the asynchronous motor Stator The stator (1) is the stationary part of the motor which holds packages of laminations where the electrical windings are placed. Rotor The rotor (2) is the rotating part of the motor which is mounted on the motor shaft. Like the stator, the rotor is made of thin iron laminations which hold the rotor windings. One variation is the outer rotor motor. Unlike the inner rotor design, the stator is placed in the middle of the motor and the rotor rotates around the stator.
This construction is used in some fan applications where the fan blades are directly mounted on the rotor. Unless otherwise mentioned, all the following explanations are related to inner rotor design. The connection dimensions of typical industrial motors are defi ned in IEC standards. However not all motors fulfi ll these requirements. For example, NEMA frame motor dimensions diff er from IEC standards, due to the conversion from the metric to the imperial system.