The application of a pulse width modulation (PWM) adjustable frequency (AF) inverter drive, SMARTORQUE that was made to satisfy the special requirements of cranes, hoists, and other material handling equipment is discussed. The requirements that a motor control system must satisfy to be suitable for any crane and hoist applications with regard to load handling ability, thermal capacity, maintainability, endurance, environmental compatibility, size, and cost are examined. Features common to all AF drives that tend to give them a leading edge over all predecessors, as well as the particular advantages of the SMARTORQUE drive, including its intelligent software, are examined. Future trends in variable-frequency drives are considered.
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