ACIM is the most popular motor for industrial and consumer applications. This is due to many factors such as the lack of commutator/brushes (high reliability), high efficiency at high loads and the ability to connect directly to the AC line. ACIMs have a classic three-phase stator and commonly have a “squirrel cage” rotor in which the conductors are shorted together at both ends. The operation principle of ACIM is very similar to a transformer. A rotor current is induced in the rotor circuit from the stator windings. This current produces rotor flux, which interacts with the stator electromagnets to produce torque.
ADVANTAGES OF AC INDUCTION MOTOR
• Low cost per horsepower (no permanent magnets).
• Inherent AC operation (direct connection to AC line).
• Very low maintenance (no brushes) and rugged construction.
• Available in wide range of power ratings.
• Low-cost speed control with tachogenerator.
• Simple control (volt per hertz + PFC can handle 8-bit MCU).
DRAWBACKS OF AC INDUCTION MOTOR
• Inefficient at light loads.
• Rotor temperature change complicates sensorless control.
• Speed control requires varying stator frequency.
• Position control difficult (field orientation required).