Applying adjustable frequency controllers to high-starting-torque loads

Effectively applying adjustable frequency controllers (AFCs) to high-starting-torque loads present challenges to the application engineer. A detailed understanding of AFC operation is essential. The authors use a recent experience to review the essential system concepts and outline a practical method to minimize potential pitfalls and facilitate installation and start-up. A method is presented to assist in: understanding the types of loads and their effect on motor performance; understanding how motor torque capability changes at the low starting frequencies; sizing of the AFC by taking into account its performance capabilities and current limitations; and achieving up to the maximum starting torque possible, if necessary, for a given installation