Description
The introduction of the INVERTER in the industrial automation has started an epochal turning point, giving the possibility to regulate the speed of the induction motors and, in particular, of the asynchronous ones with short-circuited rotor (squirrel cage), at low cost and with relative simplicity of use. The drive by an inverter requires, however, a special prearrangement of the motor, both concerning the materials used and the electrical and mechanical finishes. In addition to this, some specific accessory components, such as axial servo ventilation, can be installed on the motor, which can guarantee the correct motor cooling even in case of prolonged operation at speeds below the nominal level, also reducing noise at the maximum rpm. By mounting an encoder to the shaft, the position and speed of the rotor can be detected, making possible the implementation of vector control techniques, with dynamic performances similar to DC motors. In addition to the encoder, other types of rotary transducers such as resolvers or Hall sensors are available. In the presence of variable work cycles, the winding temperature can be monitored by installing thermal sensors.
