Sensorless AC Drives Fill Price/Performance Niche

Controversial right from their name, "sensorless" ac drives actually use current and voltage sensors to achieve motor control. Sensorless ac drives fill the middleground between high-performance closed-loop control and simpler open-loop (or V/Hz) control of ac induction motors. Pricing is commensurate with performance delivered. Most sensorless ac drives are based on one of various flux vector methods, hence loosely called sensorless vector (SV) control. In short, sensorless control achieves near-closed-loop performance, without a motor feedback device, and lower life-cycle cost. Baldor Electric Co. sees several benefits in SV control versus V/Hz control. Among them are improved low-speed operation, better speed regulation with varying loads, and more starting torque for loads with high friction or inertia.